// Copyright 2018 The Bazel Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

syntax = "proto3";

package build.bazel.remote.execution.v2;

import "build/bazel/semver/semver.proto";
import "google/api/annotations.proto";
import "google/longrunning/operations.proto";
import "google/protobuf/duration.proto";
import "google/protobuf/timestamp.proto";
import "google/rpc/status.proto";

option csharp_namespace = "Build.Bazel.Remote.Execution.V2";
option go_package = "remoteexecution";
option java_multiple_files = true;
option java_outer_classname = "RemoteExecutionProto";
option java_package = "build.bazel.remote.execution.v2";
option objc_class_prefix = "REX";


// The Remote Execution API is used to execute an
// [Action][build.bazel.remote.execution.v2.Action] on the remote
// workers.
//
// As with other services in the Remote Execution API, any call may return an
// error with a [RetryInfo][google.rpc.RetryInfo] error detail providing
// information about when the client should retry the request; clients SHOULD
// respect the information provided.
service Execution {
  // Execute an action remotely.
  //
  // In order to execute an action, the client must first upload all of the
  // inputs, the
  // [Command][build.bazel.remote.execution.v2.Command] to run, and the
  // [Action][build.bazel.remote.execution.v2.Action] into the
  // [ContentAddressableStorage][build.bazel.remote.execution.v2.ContentAddressableStorage].
  // It then calls `Execute` with an `action_digest` referring to them. The
  // server will run the action and eventually return the result.
  //
  // The input `Action`'s fields MUST meet the various canonicalization
  // requirements specified in the documentation for their types so that it has
  // the same digest as other logically equivalent `Action`s. The server MAY
  // enforce the requirements and return errors if a non-canonical input is
  // received. It MAY also proceed without verifying some or all of the
  // requirements, such as for performance reasons. If the server does not
  // verify the requirement, then it will treat the `Action` as distinct from
  // another logically equivalent action if they hash differently.
  //
  // Returns a stream of
  // [google.longrunning.Operation][google.longrunning.Operation] messages
  // describing the resulting execution, with eventual `response`
  // [ExecuteResponse][build.bazel.remote.execution.v2.ExecuteResponse]. The
  // `metadata` on the operation is of type
  // [ExecuteOperationMetadata][build.bazel.remote.execution.v2.ExecuteOperationMetadata].
  //
  // If the client remains connected after the first response is returned after
  // the server, then updates are streamed as if the client had called
  // [WaitExecution][build.bazel.remote.execution.v2.Execution.WaitExecution]
  // until the execution completes or the request reaches an error. The
  // operation can also be queried using [Operations
  // API][google.longrunning.Operations.GetOperation].
  //
  // The server NEED NOT implement other methods or functionality of the
  // Operations API.
  //
  // Errors discovered during creation of the `Operation` will be reported
  // as gRPC Status errors, while errors that occurred while running the
  // action will be reported in the `status` field of the `ExecuteResponse`. The
  // server MUST NOT set the `error` field of the `Operation` proto.
  // The possible errors include:
  //
  // * `INVALID_ARGUMENT`: One or more arguments are invalid.
  // * `FAILED_PRECONDITION`: One or more errors occurred in setting up the
  //   action requested, such as a missing input or command or no worker being
  //   available. The client may be able to fix the errors and retry.
  // * `RESOURCE_EXHAUSTED`: There is insufficient quota of some resource to run
  //   the action.
  // * `UNAVAILABLE`: Due to a transient condition, such as all workers being
  //   occupied (and the server does not support a queue), the action could not
  //   be started. The client should retry.
  // * `INTERNAL`: An internal error occurred in the execution engine or the
  //   worker.
  // * `DEADLINE_EXCEEDED`: The execution timed out.
  // * `CANCELLED`: The operation was cancelled by the client. This status is
  //   only possible if the server implements the Operations API CancelOperation
  //   method, and it was called for the current execution.
  //
  // In the case of a missing input or command, the server SHOULD additionally
  // send a [PreconditionFailure][google.rpc.PreconditionFailure] error detail
  // where, for each requested blob not present in the CAS, there is a
  // `Violation` with a `type` of `MISSING` and a `subject` of
  // `"blobs/{hash}/{size}"` indicating the digest of the missing blob.
  rpc Execute(ExecuteRequest) returns (stream google.longrunning.Operation) {
    option (google.api.http) = { post: "/v2/{instance_name=**}/actions:execute" body: "*" };
  }

  // Wait for an execution operation to complete. When the client initially
  // makes the request, the server immediately responds with the current status
  // of the execution. The server will leave the request stream open until the
  // operation completes, and then respond with the completed operation. The
  // server MAY choose to stream additional updates as execution progresses,
  // such as to provide an update as to the state of the execution.
  rpc WaitExecution(WaitExecutionRequest) returns (stream google.longrunning.Operation) {
    option (google.api.http) = { post: "/v2/{name=operations/**}:waitExecution" body: "*" };
  }
}

// The action cache API is used to query whether a given action has already been
// performed and, if so, retrieve its result. Unlike the
// [ContentAddressableStorage][build.bazel.remote.execution.v2.ContentAddressableStorage],
// which addresses blobs by their own content, the action cache addresses the
// [ActionResult][build.bazel.remote.execution.v2.ActionResult] by a
// digest of the encoded [Action][build.bazel.remote.execution.v2.Action]
// which produced them.
//
// The lifetime of entries in the action cache is implementation-specific, but
// the server SHOULD assume that more recently used entries are more likely to
// be used again.
//
// As with other services in the Remote Execution API, any call may return an
// error with a [RetryInfo][google.rpc.RetryInfo] error detail providing
// information about when the client should retry the request; clients SHOULD
// respect the information provided.
service ActionCache {
  // Retrieve a cached execution result.
  //
  // Implementations SHOULD ensure that any blobs referenced from the
  // [ContentAddressableStorage][build.bazel.remote.execution.v2.ContentAddressableStorage]
  // are available at the time of returning the
  // [ActionResult][build.bazel.remote.execution.v2.ActionResult] and will be
  // for some period of time afterwards. The TTLs of the referenced blobs SHOULD be increased
  // if necessary and applicable.
  //
  // Errors:
  //
  // * `NOT_FOUND`: The requested `ActionResult` is not in the cache.
  rpc GetActionResult(GetActionResultRequest) returns (ActionResult) {
    option (google.api.http) = { get: "/v2/{instance_name=**}/actionResults/{action_digest.hash}/{action_digest.size_bytes}" };
  }

  // Upload a new execution result.
  //
  // In order to allow the server to perform access control based on the type of
  // action, and to assist with client debugging, the client MUST first upload
  // the [Action][build.bazel.remote.execution.v2.Execution] that produced the
  // result, along with its
  // [Command][build.bazel.remote.execution.v2.Command], into the
  // `ContentAddressableStorage`.
  //
  // Errors:
  //
  // * `INVALID_ARGUMENT`: One or more arguments are invalid.
  // * `FAILED_PRECONDITION`: One or more errors occurred in updating the
  //   action result, such as a missing command or action.
  // * `RESOURCE_EXHAUSTED`: There is insufficient storage space to add the
  //   entry to the cache.
  rpc UpdateActionResult(UpdateActionResultRequest) returns (ActionResult) {
    option (google.api.http) = { put: "/v2/{instance_name=**}/actionResults/{action_digest.hash}/{action_digest.size_bytes}" body: "action_result" };
  }
}

// The CAS (content-addressable storage) is used to store the inputs to and
// outputs from the execution service. Each piece of content is addressed by the
// digest of its binary data.
//
// Most of the binary data stored in the CAS is opaque to the execution engine,
// and is only used as a communication medium. In order to build an
// [Action][build.bazel.remote.execution.v2.Action],
// however, the client will need to also upload the
// [Command][build.bazel.remote.execution.v2.Command] and input root
// [Directory][build.bazel.remote.execution.v2.Directory] for the Action.
// The Command and Directory messages must be marshalled to wire format and then
// uploaded under the hash as with any other piece of content. In practice, the
// input root directory is likely to refer to other Directories in its
// hierarchy, which must also each be uploaded on their own.
//
// For small file uploads the client should group them together and call
// [BatchUpdateBlobs][build.bazel.remote.execution.v2.ContentAddressableStorage.BatchUpdateBlobs].
// For large uploads, the client must use the
// [Write method][google.bytestream.ByteStream.Write] of the ByteStream API. The
// `resource_name` is `{instance_name}/uploads/{uuid}/blobs/{hash}/{size}`,
// where `instance_name` is as described in the next paragraph, `uuid` is a
// version 4 UUID generated by the client, and `hash` and `size` are the
// [Digest][build.bazel.remote.execution.v2.Digest] of the blob. The
// `uuid` is used only to avoid collisions when multiple clients try to upload
// the same file (or the same client tries to upload the file multiple times at
// once on different threads), so the client MAY reuse the `uuid` for uploading
// different blobs. The `resource_name` may optionally have a trailing filename
// (or other metadata) for a client to use if it is storing URLs, as in
// `{instance}/uploads/{uuid}/blobs/{hash}/{size}/foo/bar/baz.cc`. Anything
// after the `size` is ignored.
//
// A single server MAY support multiple instances of the execution system, each
// with their own workers, storage, cache, etc. The exact relationship between
// instances is up to the server. If the server does, then the `instance_name`
// is an identifier, possibly containing multiple path segments, used to
// distinguish between the various instances on the server, in a manner defined
// by the server. For servers which do not support multiple instances, then the
// `instance_name` is the empty path and the leading slash is omitted, so that
// the `resource_name` becomes `uploads/{uuid}/blobs/{hash}/{size}`.
// To simplify parsing, a path segment cannot equal any of the following
// keywords: `blobs`, `uploads`, `actions`, `actionResults`, `operations` and
// `capabilities`.
//
// When attempting an upload, if another client has already completed the upload
// (which may occur in the middle of a single upload if another client uploads
// the same blob concurrently), the request will terminate immediately with
// a response whose `committed_size` is the full size of the uploaded file
// (regardless of how much data was transmitted by the client). If the client
// completes the upload but the
// [Digest][build.bazel.remote.execution.v2.Digest] does not match, an
// `INVALID_ARGUMENT` error will be returned. In either case, the client should
// not attempt to retry the upload.
//
// For downloading blobs, the client must use the
// [Read method][google.bytestream.ByteStream.Read] of the ByteStream API, with
// a `resource_name` of `"{instance_name}/blobs/{hash}/{size}"`, where
// `instance_name` is the instance name (see above), and `hash` and `size` are
// the [Digest][build.bazel.remote.execution.v2.Digest] of the blob.
//
// The lifetime of entries in the CAS is implementation specific, but it SHOULD
// be long enough to allow for newly-added and recently looked-up entries to be
// used in subsequent calls (e.g. to
// [Execute][build.bazel.remote.execution.v2.Execution.Execute]).
//
// As with other services in the Remote Execution API, any call may return an
// error with a [RetryInfo][google.rpc.RetryInfo] error detail providing
// information about when the client should retry the request; clients SHOULD
// respect the information provided.
service ContentAddressableStorage {
  // Determine if blobs are present in the CAS.
  //
  // Clients can use this API before uploading blobs to determine which ones are
  // already present in the CAS and do not need to be uploaded again.
  //
  // There are no method-specific errors.
  rpc FindMissingBlobs(FindMissingBlobsRequest) returns (FindMissingBlobsResponse) {
    option (google.api.http) = { post: "/v2/{instance_name=**}/blobs:findMissing" body: "*" };
  }

  // Upload many blobs at once.
  //
  // The server may enforce a limit of the combined total size of blobs
  // to be uploaded using this API. This limit may be obtained using the
  // [Capabilities][build.bazel.remote.execution.v2.Capabilities] API.
  // Requests exceeding the limit should either be split into smaller
  // chunks or uploaded using the
  // [ByteStream API][google.bytestream.ByteStream], as appropriate.
  //
  // This request is equivalent to calling a Bytestream `Write` request
  // on each individual blob, in parallel. The requests may succeed or fail
  // independently.
  //
  // Errors:
  //
  // * `INVALID_ARGUMENT`: The client attempted to upload more than the
  //   server supported limit.
  //
  // Individual requests may return the following errors, additionally:
  //
  // * `RESOURCE_EXHAUSTED`: There is insufficient disk quota to store the blob.
  // * `INVALID_ARGUMENT`: The
  // [Digest][build.bazel.remote.execution.v2.Digest] does not match the
  // provided data.
  rpc BatchUpdateBlobs(BatchUpdateBlobsRequest) returns (BatchUpdateBlobsResponse) {
    option (google.api.http) = { post: "/v2/{instance_name=**}/blobs:batchUpdate" body: "*" };
  }

  // Download many blobs at once.
  //
  // The server may enforce a limit of the combined total size of blobs
  // to be downloaded using this API. This limit may be obtained using the
  // [Capabilities][build.bazel.remote.execution.v2.Capabilities] API.
  // Requests exceeding the limit should either be split into smaller
  // chunks or downloaded using the
  // [ByteStream API][google.bytestream.ByteStream], as appropriate.
  //
  // This request is equivalent to calling a Bytestream `Read` request
  // on each individual blob, in parallel. The requests may succeed or fail
  // independently.
  //
  // Errors:
  //
  // * `INVALID_ARGUMENT`: The client attempted to read more than the
  //   server supported limit.
  //
  // Every error on individual read will be returned in the corresponding digest
  // status.
  rpc BatchReadBlobs(BatchReadBlobsRequest) returns (BatchReadBlobsResponse) {
    option (google.api.http) = { post: "/v2/{instance_name=**}/blobs:batchRead" body: "*" };
  }

  // Fetch the entire directory tree rooted at a node.
  //
  // This request must be targeted at a
  // [Directory][build.bazel.remote.execution.v2.Directory] stored in the
  // [ContentAddressableStorage][build.bazel.remote.execution.v2.ContentAddressableStorage]
  // (CAS). The server will enumerate the `Directory` tree recursively and
  // return every node descended from the root.
  //
  // The GetTreeRequest.page_token parameter can be used to skip ahead in
  // the stream (e.g. when retrying a partially completed and aborted request),
  // by setting it to a value taken from GetTreeResponse.next_page_token of the
  // last successfully processed GetTreeResponse).
  //
  // The exact traversal order is unspecified and, unless retrieving subsequent
  // pages from an earlier request, is not guaranteed to be stable across
  // multiple invocations of `GetTree`.
  //
  // If part of the tree is missing from the CAS, the server will return the
  // portion present and omit the rest.
  //
  // * `NOT_FOUND`: The requested tree root is not present in the CAS.
  rpc GetTree(GetTreeRequest) returns (stream GetTreeResponse) {
    option (google.api.http) = { get: "/v2/{instance_name=**}/blobs/{root_digest.hash}/{root_digest.size_bytes}:getTree" };
  }
}

// The Capabilities service may be used by remote execution clients to query
// various server properties, in order to self-configure or return meaningful
// error messages.
//
// The query may include a particular `instance_name`, in which case the values
// returned will pertain to that instance.
service Capabilities {
  // GetCapabilities returns the server capabilities configuration of the
  // remote endpoint.
  // Only the capabilities of the services supported by the endpoint will
  // be returned:
  // * Execution + CAS + Action Cache endpoints should return both
  //   CacheCapabilities and ExecutionCapabilities.
  // * Execution only endpoints should return ExecutionCapabilities.
  // * CAS + Action Cache only endpoints should return CacheCapabilities.
  rpc GetCapabilities(GetCapabilitiesRequest) returns (ServerCapabilities) {
    option (google.api.http) = {
      get: "/v2/{instance_name=**}/capabilities"
    };
  }
}

// An `Action` captures all the information about an execution which is required
// to reproduce it.
//
// `Action`s are the core component of the [Execution] service. A single
// `Action` represents a repeatable action that can be performed by the
// execution service. `Action`s can be succinctly identified by the digest of
// their wire format encoding and, once an `Action` has been executed, will be
// cached in the action cache. Future requests can then use the cached result
// rather than needing to run afresh.
//
// When a server completes execution of an
// [Action][build.bazel.remote.execution.v2.Action], it MAY choose to
// cache the [result][build.bazel.remote.execution.v2.ActionResult] in
// the [ActionCache][build.bazel.remote.execution.v2.ActionCache] unless
// `do_not_cache` is `true`. Clients SHOULD expect the server to do so. By
// default, future calls to
// [Execute][build.bazel.remote.execution.v2.Execution.Execute] the same
// `Action` will also serve their results from the cache. Clients must take care
// to understand the caching behaviour. Ideally, all `Action`s will be
// reproducible so that serving a result from cache is always desirable and
// correct.
message Action {
  // The digest of the [Command][build.bazel.remote.execution.v2.Command]
  // to run, which MUST be present in the
  // [ContentAddressableStorage][build.bazel.remote.execution.v2.ContentAddressableStorage].
  Digest command_digest = 1;

  // The digest of the root
  // [Directory][build.bazel.remote.execution.v2.Directory] for the input
  // files. The files in the directory tree are available in the correct
  // location on the build machine before the command is executed. The root
  // directory, as well as every subdirectory and content blob referred to, MUST
  // be in the
  // [ContentAddressableStorage][build.bazel.remote.execution.v2.ContentAddressableStorage].
  Digest input_root_digest = 2;

  reserved 3 to 5; // Used for fields moved to [Command][build.bazel.remote.execution.v2.Command].

  // A timeout after which the execution should be killed. If the timeout is
  // absent, then the client is specifying that the execution should continue
  // as long as the server will let it. The server SHOULD impose a timeout if
  // the client does not specify one, however, if the client does specify a
  // timeout that is longer than the server's maximum timeout, the server MUST
  // reject the request.
  //
  // The timeout is a part of the
  // [Action][build.bazel.remote.execution.v2.Action] message, and
  // therefore two `Actions` with different timeouts are different, even if they
  // are otherwise identical. This is because, if they were not, running an
  // `Action` with a lower timeout than is required might result in a cache hit
  // from an execution run with a longer timeout, hiding the fact that the
  // timeout is too short. By encoding it directly in the `Action`, a lower
  // timeout will result in a cache miss and the execution timeout will fail
  // immediately, rather than whenever the cache entry gets evicted.
  google.protobuf.Duration timeout = 6;

  // If true, then the `Action`'s result cannot be cached, and in-flight
  // requests for the same `Action` may not be merged.
  bool do_not_cache = 7;
}

// A `Command` is the actual command executed by a worker running an
// [Action][build.bazel.remote.execution.v2.Action] and specifications of its
// environment.
//
// Except as otherwise required, the environment (such as which system
// libraries or binaries are available, and what filesystems are mounted where)
// is defined by and specific to the implementation of the remote execution API.
message Command {
  // An `EnvironmentVariable` is one variable to set in the running program's
  // environment.
  message EnvironmentVariable {
    // The variable name.
    string name = 1;

    // The variable value.
    string value = 2;
  }

  // The arguments to the command. The first argument must be the path to the
  // executable, which must be either a relative path, in which case it is
  // evaluated with respect to the input root, or an absolute path.
  repeated string arguments = 1;

  // The environment variables to set when running the program. The worker may
  // provide its own default environment variables; these defaults can be
  // overridden using this field. Additional variables can also be specified.
  //
  // In order to ensure that equivalent
  // [Command][build.bazel.remote.execution.v2.Command]s always hash to the same
  // value, the environment variables MUST be lexicographically sorted by name.
  // Sorting of strings is done by code point, equivalently, by the UTF-8 bytes.
  repeated EnvironmentVariable environment_variables = 2;

  // A list of the output files that the client expects to retrieve from the
  // action. Only the listed files, as well as directories listed in
  // `output_directories`, will be returned to the client as output.
  // Other files or directories that may be created during command execution
  // are discarded.
  //
  // The paths are relative to the working directory of the action execution.
  // The paths are specified using a single forward slash (`/`) as a path
  // separator, even if the execution platform natively uses a different
  // separator. The path MUST NOT include a trailing slash, nor a leading slash,
  // being a relative path.
  //
  // In order to ensure consistent hashing of the same Action, the output paths
  // MUST be sorted lexicographically by code point (or, equivalently, by UTF-8
  // bytes).
  //
  // An output file cannot be duplicated, be a parent of another output file, or
  // have the same path as any of the listed output directories.
  //
  // Directories leading up to the output files are created by the worker prior
  // to execution, even if they are not explicitly part of the input root.
  repeated string output_files = 3;

  // A list of the output directories that the client expects to retrieve from
  // the action. Only the listed directories will be returned (an entire
  // directory structure will be returned as a
  // [Tree][build.bazel.remote.execution.v2.Tree] message digest, see
  // [OutputDirectory][build.bazel.remote.execution.v2.OutputDirectory]), as
  // well as files listed in `output_files`. Other files or directories that
  // may be created during command execution are discarded.
  //
  // The paths are relative to the working directory of the action execution.
  // The paths are specified using a single forward slash (`/`) as a path
  // separator, even if the execution platform natively uses a different
  // separator. The path MUST NOT include a trailing slash, nor a leading slash,
  // being a relative path. The special value of empty string is allowed,
  // although not recommended, and can be used to capture the entire working
  // directory tree, including inputs.
  //
  // In order to ensure consistent hashing of the same Action, the output paths
  // MUST be sorted lexicographically by code point (or, equivalently, by UTF-8
  // bytes).
  //
  // An output directory cannot be duplicated or have the same path as any of
  // the listed output files. An output directory is allowed to be a parent of
  // another output directory.
  //
  // Directories leading up to the output directories (but not the output
  // directories themselves) are created by the worker prior to execution, even
  // if they are not explicitly part of the input root.
  repeated string output_directories = 4;

  // The platform requirements for the execution environment. The server MAY
  // choose to execute the action on any worker satisfying the requirements, so
  // the client SHOULD ensure that running the action on any such worker will
  // have the same result.
  // A detailed lexicon for this can be found in the accompanying platform.md.
  Platform platform = 5;

  // The working directory, relative to the input root, for the command to run
  // in. It must be a directory which exists in the input tree. If it is left
  // empty, then the action is run in the input root.
  string working_directory = 6;
}

// A `Platform` is a set of requirements, such as hardware, operating system, or
// compiler toolchain, for an
// [Action][build.bazel.remote.execution.v2.Action]'s execution
// environment. A `Platform` is represented as a series of key-value pairs
// representing the properties that are required of the platform.
message Platform {
  // A single property for the environment. The server is responsible for
  // specifying the property `name`s that it accepts. If an unknown `name` is
  // provided in the requirements for an
  // [Action][build.bazel.remote.execution.v2.Action], the server SHOULD
  // reject the execution request. If permitted by the server, the same `name`
  // may occur multiple times.
  //
  // The server is also responsible for specifying the interpretation of
  // property `value`s. For instance, a property describing how much RAM must be
  // available may be interpreted as allowing a worker with 16GB to fulfill a
  // request for 8GB, while a property describing the OS environment on which
  // the action must be performed may require an exact match with the worker's
  // OS.
  //
  // The server MAY use the `value` of one or more properties to determine how
  // it sets up the execution environment, such as by making specific system
  // files available to the worker.
  message Property {
    // The property name.
    string name = 1;

    // The property value.
    string value = 2;
  }

  // The properties that make up this platform. In order to ensure that
  // equivalent `Platform`s always hash to the same value, the properties MUST
  // be lexicographically sorted by name, and then by value. Sorting of strings
  // is done by code point, equivalently, by the UTF-8 bytes.
  repeated Property properties = 1;
}

// A `Directory` represents a directory node in a file tree, containing zero or
// more children [FileNodes][build.bazel.remote.execution.v2.FileNode],
// [DirectoryNodes][build.bazel.remote.execution.v2.DirectoryNode] and
// [SymlinkNodes][build.bazel.remote.execution.v2.SymlinkNode].
// Each `Node` contains its name in the directory, either the digest of its
// content (either a file blob or a `Directory` proto) or a symlink target, as
// well as possibly some metadata about the file or directory.
//
// In order to ensure that two equivalent directory trees hash to the same
// value, the following restrictions MUST be obeyed when constructing a
// a `Directory`:
//
// * Every child in the directory must have a path of exactly one segment.
//   Multiple levels of directory hierarchy may not be collapsed.
// * Each child in the directory must have a unique path segment (file name).
//   Note that while the API itself is case-sensitive, the environment where
//   the Action is executed may or may not be case-sensitive. That is, it is
//   legal to call the API with a Directory that has both "Foo" and "foo" as
//   children, but the Action may be rejected by the remote system upon
//   execution.
// * The files, directories and symlinks in the directory must each be sorted
//   in lexicographical order by path. The path strings must be sorted by code
//   point, equivalently, by UTF-8 bytes.
//
// A `Directory` that obeys the restrictions is said to be in canonical form.
//
// As an example, the following could be used for a file named `bar` and a
// directory named `foo` with an executable file named `baz` (hashes shortened
// for readability):
//
// ```json
// // (Directory proto)
// {
//   files: [
//     {
//       name: "bar",
//       digest: {
//         hash: "4a73bc9d03...",
//         size: 65534
//       }
//     }
//   ],
//   directories: [
//     {
//       name: "foo",
//       digest: {
//         hash: "4cf2eda940...",
//         size: 43
//       }
//     }
//   ]
// }
//
// // (Directory proto with hash "4cf2eda940..." and size 43)
// {
//   files: [
//     {
//       name: "baz",
//       digest: {
//         hash: "b2c941073e...",
//         size: 1294,
//       },
//       is_executable: true
//     }
//   ]
// }
// ```
message Directory {
  // The files in the directory.
  repeated FileNode files = 1;

  // The subdirectories in the directory.
  repeated DirectoryNode directories = 2;

  // The symlinks in the directory.
  repeated SymlinkNode symlinks = 3;
}

// A `FileNode` represents a single file and associated metadata.
message FileNode {
  // The name of the file.
  string name = 1;

  // The digest of the file's content.
  Digest digest = 2;

  reserved 3; // Reserved to ensure wire-compatibility with `OutputFile`.

  // True if file is executable, false otherwise.
  bool is_executable = 4;
}

// A `DirectoryNode` represents a child of a
// [Directory][build.bazel.remote.execution.v2.Directory] which is itself
// a `Directory` and its associated metadata.
message DirectoryNode {
  // The name of the directory.
  string name = 1;

  // The digest of the
  // [Directory][build.bazel.remote.execution.v2.Directory] object
  // represented. See [Digest][build.bazel.remote.execution.v2.Digest]
  // for information about how to take the digest of a proto message.
  Digest digest = 2;
}

// A `SymlinkNode` represents a symbolic link.
message SymlinkNode {
  // The name of the symlink.
  string name = 1;

  // The target path of the symlink. The path separator is a forward slash `/`.
  // The target path can be relative to the parent directory of the symlink or
  // it can be an absolute path starting with `/`. Support for absolute paths
  // can be checked using the [Capabilities][build.bazel.remote.execution.v2.Capabilities]
  // API. The canonical form forbids the substrings `/./` and `//` in the target
  // path. `..` components are allowed anywhere in the target path.
  string target = 2;
}

// A content digest. A digest for a given blob consists of the size of the blob
// and its hash. The hash algorithm to use is defined by the server, but servers
// SHOULD use SHA-256.
//
// The size is considered to be an integral part of the digest and cannot be
// separated. That is, even if the `hash` field is correctly specified but
// `size_bytes` is not, the server MUST reject the request.
//
// The reason for including the size in the digest is as follows: in a great
// many cases, the server needs to know the size of the blob it is about to work
// with prior to starting an operation with it, such as flattening Merkle tree
// structures or streaming it to a worker. Technically, the server could
// implement a separate metadata store, but this results in a significantly more
// complicated implementation as opposed to having the client specify the size
// up-front (or storing the size along with the digest in every message where
// digests are embedded). This does mean that the API leaks some implementation
// details of (what we consider to be) a reasonable server implementation, but
// we consider this to be a worthwhile tradeoff.
//
// When a `Digest` is used to refer to a proto message, it always refers to the
// message in binary encoded form. To ensure consistent hashing, clients and
// servers MUST ensure that they serialize messages according to the following
// rules, even if there are alternate valid encodings for the same message:
//
// * Fields are serialized in tag order.
// * There are no unknown fields.
// * There are no duplicate fields.
// * Fields are serialized according to the default semantics for their type.
//
// Most protocol buffer implementations will always follow these rules when
// serializing, but care should be taken to avoid shortcuts. For instance,
// concatenating two messages to merge them may produce duplicate fields.
message Digest {
  // The hash. In the case of SHA-256, it will always be a lowercase hex string
  // exactly 64 characters long.
  string hash = 1;

  // The size of the blob, in bytes.
  int64 size_bytes = 2;
}

// ExecutedActionMetadata contains details about a completed execution.
message ExecutedActionMetadata {
  // The name of the worker which ran the execution.
  string worker = 1;

  // When was the action added to the queue.
  google.protobuf.Timestamp queued_timestamp = 2;

  // When the worker received the action.
  google.protobuf.Timestamp worker_start_timestamp = 3;

  // When the worker completed the action, including all stages.
  google.protobuf.Timestamp worker_completed_timestamp = 4;

  // When the worker started fetching action inputs.
  google.protobuf.Timestamp input_fetch_start_timestamp = 5;

  // When the worker finished fetching action inputs.
  google.protobuf.Timestamp input_fetch_completed_timestamp = 6;

  // When the worker started executing the action command.
  google.protobuf.Timestamp execution_start_timestamp = 7;

  // When the worker completed executing the action command.
  google.protobuf.Timestamp execution_completed_timestamp = 8;

  // When the worker started uploading action outputs.
  google.protobuf.Timestamp output_upload_start_timestamp = 9;

  // When the worker finished uploading action outputs.
  google.protobuf.Timestamp output_upload_completed_timestamp = 10;
}

// An ActionResult represents the result of an
// [Action][build.bazel.remote.execution.v2.Action] being run.
message ActionResult {
  reserved 1; // Reserved for use as the resource name.

  // The output files of the action. For each output file requested in the
  // `output_files` field of the Action, if the corresponding file existed after
  // the action completed, a single entry will be present either in this field,
  // or the `output_file_symlinks` field if the file was a symbolic link to
  // another file.
  //
  // If an output of the same name was found, but was a directory rather
  // than a regular file, the server will return a FAILED_PRECONDITION.
  // If the action does not produce the requested output, then that output
  // will be omitted from the list. The server is free to arrange the output
  // list as desired; clients MUST NOT assume that the output list is sorted.
  repeated OutputFile output_files = 2;

  // The output files of the action that are symbolic links to other files. Those
  // may be links to other output files, or input files, or even absolute paths
  // outside of the working directory, if the server supports
  // [SymlinkAbsolutePathStrategy.ALLOWED][build.bazel.remote.execution.v2.CacheCapabilities.SymlinkAbsolutePathStrategy].
  // For each output file requested in the `output_files` field of the Action,
  // if the corresponding file existed after
  // the action completed, a single entry will be present either in this field,
  // or in the `output_files` field, if the file was not a symbolic link.
  //
  // If an output symbolic link of the same name was found, but its target
  // type was not a regular file, the server will return a FAILED_PRECONDITION.
  // If the action does not produce the requested output, then that output
  // will be omitted from the list. The server is free to arrange the output
  // list as desired; clients MUST NOT assume that the output list is sorted.
  repeated OutputSymlink output_file_symlinks = 10;

  // The output directories of the action. For each output directory requested
  // in the `output_directories` field of the Action, if the corresponding
  // directory existed after the action completed, a single entry will be
  // present in the output list, which will contain the digest of a
  // [Tree][build.bazel.remote.execution.v2.Tree] message containing the
  // directory tree, and the path equal exactly to the corresponding Action
  // output_directories member.
  //
  // As an example, suppose the Action had an output directory `a/b/dir` and the
  // execution produced the following contents in `a/b/dir`: a file named `bar`
  // and a directory named `foo` with an executable file named `baz`. Then,
  // output_directory will contain (hashes shortened for readability):
  //
  // ```json
  // // OutputDirectory proto:
  // {
  //   path: "a/b/dir"
  //   tree_digest: {
  //     hash: "4a73bc9d03...",
  //     size: 55
  //   }
  // }
  // // Tree proto with hash "4a73bc9d03..." and size 55:
  // {
  //   root: {
  //     files: [
  //       {
  //         name: "bar",
  //         digest: {
  //           hash: "4a73bc9d03...",
  //           size: 65534
  //         }
  //       }
  //     ],
  //     directories: [
  //       {
  //         name: "foo",
  //         digest: {
  //           hash: "4cf2eda940...",
  //           size: 43
  //         }
  //       }
  //     ]
  //   }
  //   children : {
  //     // (Directory proto with hash "4cf2eda940..." and size 43)
  //     files: [
  //       {
  //         name: "baz",
  //         digest: {
  //           hash: "b2c941073e...",
  //           size: 1294,
  //         },
  //         is_executable: true
  //       }
  //     ]
  //   }
  // }
  // ```
  // If an output of the same name was found, but was not a directory, the
  // server will return a FAILED_PRECONDITION.
  repeated OutputDirectory output_directories = 3;

  // The output directories of the action that are symbolic links to other
  // directories. Those may be links to other output directories, or input
  // directories, or even absolute paths outside of the working directory,
  // if the server supports
  // [SymlinkAbsolutePathStrategy.ALLOWED][build.bazel.remote.execution.v2.CacheCapabilities.SymlinkAbsolutePathStrategy].
  // For each output directory requested in the `output_directories` field of
  // the Action, if the directory existed after the action completed, a
  // single entry will be present either in this field, or in the
  // `output_directories` field, if the directory was not a symbolic link.
  //
  // If an output of the same name was found, but was a symbolic link to a file
  // instead of a directory, the server will return a FAILED_PRECONDITION.
  // If the action does not produce the requested output, then that output
  // will be omitted from the list. The server is free to arrange the output
  // list as desired; clients MUST NOT assume that the output list is sorted.
  repeated OutputSymlink output_directory_symlinks = 11;

  // The exit code of the command.
  int32 exit_code = 4;

  // The standard output buffer of the action. The server SHOULD NOT inline
  // stdout unless requested by the client in the
  // [GetActionResultRequest][build.bazel.remote.execution.v2.GetActionResultRequest]
  // message. The server MAY omit inlining, even if requested, and MUST do so if inlining
  // would cause the response to exceed message size limits.
  bytes stdout_raw = 5;

  // The digest for a blob containing the standard output of the action, which
  // can be retrieved from the
  // [ContentAddressableStorage][build.bazel.remote.execution.v2.ContentAddressableStorage].
  Digest stdout_digest = 6;

  // The standard error buffer of the action. The server SHOULD NOT inline
  // stderr unless requested by the client in the
  // [GetActionResultRequest][build.bazel.remote.execution.v2.GetActionResultRequest]
  // message. The server MAY omit inlining, even if requested, and MUST do so if inlining
  // would cause the response to exceed message size limits.
  bytes stderr_raw = 7;

  // The digest for a blob containing the standard error of the action, which
  // can be retrieved from the
  // [ContentAddressableStorage][build.bazel.remote.execution.v2.ContentAddressableStorage].
  Digest stderr_digest = 8;

  // The details of the execution that originally produced this result.
  ExecutedActionMetadata execution_metadata = 9;
}

// An `OutputFile` is similar to a
// [FileNode][build.bazel.remote.execution.v2.FileNode], but it is used as an
// output in an `ActionResult`. It allows a full file path rather than
// only a name.
message OutputFile {
  // The full path of the file relative to the working directory, including the
  // filename. The path separator is a forward slash `/`. Since this is a
  // relative path, it MUST NOT begin with a leading forward slash.
  string path = 1;

  // The digest of the file's content.
  Digest digest = 2;

  reserved 3; // Used for a removed field in an earlier version of the API.

  // True if file is executable, false otherwise.
  bool is_executable = 4;

  // The contents of the file if inlining was requested. The server SHOULD NOT inline
  // file contents unless requested by the client in the
  // [GetActionResultRequest][build.bazel.remote.execution.v2.GetActionResultRequest]
  // message. The server MAY omit inlining, even if requested, and MUST do so if inlining
  // would cause the response to exceed message size limits.
  bytes contents = 5;
}

// A `Tree` contains all the
// [Directory][build.bazel.remote.execution.v2.Directory] protos in a
// single directory Merkle tree, compressed into one message.
message Tree {
  // The root directory in the tree.
  Directory root = 1;

  // All the child directories: the directories referred to by the root and,
  // recursively, all its children. In order to reconstruct the directory tree,
  // the client must take the digests of each of the child directories and then
  // build up a tree starting from the `root`.
  repeated Directory children = 2;
}

// An `OutputDirectory` is the output in an `ActionResult` corresponding to a
// directory's full contents rather than a single file.
message OutputDirectory {
  // The full path of the directory relative to the working directory. The path
  // separator is a forward slash `/`. Since this is a relative path, it MUST
  // NOT begin with a leading forward slash. The empty string value is allowed,
  // and it denotes the entire working directory.
  string path = 1;

  reserved 2; // Used for a removed field in an earlier version of the API.

  // The digest of the encoded
  // [Tree][build.bazel.remote.execution.v2.Tree] proto containing the
  // directory's contents.
  Digest tree_digest = 3;
}

// An `OutputSymlink` is similar to a
// [Symlink][build.bazel.remote.execution.v2.SymlinkNode], but it is used as an
// output in an `ActionResult`.
//
// `OutputSymlink` is binary-compatible with `SymlinkNode`.
message OutputSymlink {
  // The full path of the symlink relative to the working directory, including the
  // filename. The path separator is a forward slash `/`. Since this is a
  // relative path, it MUST NOT begin with a leading forward slash.
  string path = 1;

  // The target path of the symlink. The path separator is a forward slash `/`.
  // The target path can be relative to the parent directory of the symlink or
  // it can be an absolute path starting with `/`. Support for absolute paths
  // can be checked using the [Capabilities][build.bazel.remote.execution.v2.Capabilities]
  // API. The canonical form forbids the substrings `/./` and `//` in the target
  // path. `..` components are allowed anywhere in the target path.
  string target = 2;
}

// An `ExecutionPolicy` can be used to control the scheduling of the action.
message ExecutionPolicy {
  // The priority (relative importance) of this action. Generally, a lower value
  // means that the action should be run sooner than actions having a greater
  // priority value, but the interpretation of a given value is server-
  // dependent. A priority of 0 means the *default* priority. Priorities may be
  // positive or negative, and such actions should run later or sooner than
  // actions having the default priority, respectively. The particular semantics
  // of this field is up to the server. In particular, every server will have
  // their own supported range of priorities, and will decide how these map into
  // scheduling policy.
  int32 priority = 1;
}

// A `ResultsCachePolicy` is used for fine-grained control over how action
// outputs are stored in the CAS and Action Cache.
message ResultsCachePolicy {
  // The priority (relative importance) of this content in the overall cache.
  // Generally, a lower value means a longer retention time or other advantage,
  // but the interpretation of a given value is server-dependent. A priority of
  // 0 means a *default* value, decided by the server.
  //
  // The particular semantics of this field is up to the server. In particular,
  // every server will have their own supported range of priorities, and will
  // decide how these map into retention/eviction policy.
  int32 priority = 1;
}

// A request message for
// [Execution.Execute][build.bazel.remote.execution.v2.Execution.Execute].
message ExecuteRequest {
  // The instance of the execution system to operate against. A server may
  // support multiple instances of the execution system (with their own workers,
  // storage, caches, etc.). The server MAY require use of this field to select
  // between them in an implementation-defined fashion, otherwise it can be
  // omitted.
  string instance_name = 1;

  // If true, the action will be executed even if its result is already
  // present in the [ActionCache][build.bazel.remote.execution.v2.ActionCache].
  // The execution is still allowed to be merged with other in-flight executions
  // of the same action, however - semantically, the service MUST only guarantee
  // that the results of an execution with this field set were not visible
  // before the corresponding execution request was sent.
  // Note that actions from execution requests setting this field set are still
  // eligible to be entered into the action cache upon completion, and services
  // SHOULD overwrite any existing entries that may exist. This allows
  // skip_cache_lookup requests to be used as a mechanism for replacing action
  // cache entries that reference outputs no longer available or that are
  // poisoned in any way.
  // If false, the result may be served from the action cache.
  bool skip_cache_lookup = 3;

  reserved 2, 4, 5; // Used for removed fields in an earlier version of the API.

  // The digest of the [Action][build.bazel.remote.execution.v2.Action] to
  // execute.
  Digest action_digest = 6;

  // An optional policy for execution of the action.
  // The server will have a default policy if this is not provided.
  ExecutionPolicy execution_policy = 7;

  // An optional policy for the results of this execution in the remote cache.
  // The server will have a default policy if this is not provided.
  // This may be applied to both the ActionResult and the associated blobs.
  ResultsCachePolicy results_cache_policy = 8;
}

// A `LogFile` is a log stored in the CAS.
message LogFile {
  // The digest of the log contents.
  Digest digest = 1;

  // This is a hint as to the purpose of the log, and is set to true if the log
  // is human-readable text that can be usefully displayed to a user, and false
  // otherwise. For instance, if a command-line client wishes to print the
  // server logs to the terminal for a failed action, this allows it to avoid
  // displaying a binary file.
  bool human_readable = 2;
}

// The response message for
// [Execution.Execute][build.bazel.remote.execution.v2.Execution.Execute],
// which will be contained in the [response
// field][google.longrunning.Operation.response] of the
// [Operation][google.longrunning.Operation].
message ExecuteResponse {
  // The result of the action.
  ActionResult result = 1;

  // True if the result was served from cache, false if it was executed.
  bool cached_result = 2;

  // If the status has a code other than `OK`, it indicates that the action did
  // not finish execution. For example, if the operation times out during
  // execution, the status will have a `DEADLINE_EXCEEDED` code. Servers MUST
  // use this field for errors in execution, rather than the error field on the
  // `Operation` object.
  //
  // If the status code is other than `OK`, then the result MUST NOT be cached.
  // For an error status, the `result` field is optional; the server may
  // populate the output-, stdout-, and stderr-related fields if it has any
  // information available, such as the stdout and stderr of a timed-out action.
  google.rpc.Status status = 3;

  // An optional list of additional log outputs the server wishes to provide. A
  // server can use this to return execution-specific logs however it wishes.
  // This is intended primarily to make it easier for users to debug issues that
  // may be outside of the actual job execution, such as by identifying the
  // worker executing the action or by providing logs from the worker's setup
  // phase. The keys SHOULD be human readable so that a client can display them
  // to a user.
  map<string, LogFile> server_logs = 4;

  // Freeform informational message with details on the execution of the action
  // that may be displayed to the user upon failure or when requested explicitly.
  string message = 5;
}

// The current stage of action execution.
message ExecutionStage {
  enum Value {
    // Invalid value.
    UNKNOWN = 0;

    // Checking the result against the cache.
    CACHE_CHECK = 1;

    // Currently idle, awaiting a free machine to execute.
    QUEUED = 2;

    // Currently being executed by a worker.
    EXECUTING = 3;

    // Finished execution.
    COMPLETED = 4;
  }
}

// Metadata about an ongoing
// [execution][build.bazel.remote.execution.v2.Execution.Execute], which
// will be contained in the [metadata
// field][google.longrunning.Operation.response] of the
// [Operation][google.longrunning.Operation].
message ExecuteOperationMetadata {
  // The current stage of execution.
  ExecutionStage.Value stage = 1;

  // The digest of the [Action][build.bazel.remote.execution.v2.Action]
  // being executed.
  Digest action_digest = 2;

  // If set, the client can use this name with
  // [ByteStream.Read][google.bytestream.ByteStream.Read] to stream the
  // standard output.
  string stdout_stream_name = 3;

  // If set, the client can use this name with
  // [ByteStream.Read][google.bytestream.ByteStream.Read] to stream the
  // standard error.
  string stderr_stream_name = 4;
}

// A request message for
// [WaitExecution][build.bazel.remote.execution.v2.Execution.WaitExecution].
message WaitExecutionRequest {
  // The name of the [Operation][google.longrunning.Operation]
  // returned by [Execute][build.bazel.remote.execution.v2.Execution.Execute].
  string name = 1;
}

// A request message for
// [ActionCache.GetActionResult][build.bazel.remote.execution.v2.ActionCache.GetActionResult].
message GetActionResultRequest {
  // The instance of the execution system to operate against. A server may
  // support multiple instances of the execution system (with their own workers,
  // storage, caches, etc.). The server MAY require use of this field to select
  // between them in an implementation-defined fashion, otherwise it can be
  // omitted.
  string instance_name = 1;

  // The digest of the [Action][build.bazel.remote.execution.v2.Action]
  // whose result is requested.
  Digest action_digest = 2;

  // A hint to the server to request inlining stdout in the
  // [ActionResult][build.bazel.remote.execution.v2.ActionResult] message.
  bool inline_stdout = 3;

  // A hint to the server to request inlining stderr in the
  // [ActionResult][build.bazel.remote.execution.v2.ActionResult] message.
  bool inline_stderr = 4;

  // A hint to the server to inline the contents of the listed output files.
  // Each path needs to exactly match one path in `output_files` in the
  // [Command][build.bazel.remote.execution.v2.Command] message.
  repeated string inline_output_files = 5;
}

// A request message for
// [ActionCache.UpdateActionResult][build.bazel.remote.execution.v2.ActionCache.UpdateActionResult].
message UpdateActionResultRequest {
  // The instance of the execution system to operate against. A server may
  // support multiple instances of the execution system (with their own workers,
  // storage, caches, etc.). The server MAY require use of this field to select
  // between them in an implementation-defined fashion, otherwise it can be
  // omitted.
  string instance_name = 1;

  // The digest of the [Action][build.bazel.remote.execution.v2.Action]
  // whose result is being uploaded.
  Digest action_digest = 2;

  // The [ActionResult][build.bazel.remote.execution.v2.ActionResult]
  // to store in the cache.
  ActionResult action_result = 3;

  // An optional policy for the results of this execution in the remote cache.
  // The server will have a default policy if this is not provided.
  // This may be applied to both the ActionResult and the associated blobs.
  ResultsCachePolicy results_cache_policy = 4;
}

// A request message for
// [ContentAddressableStorage.FindMissingBlobs][build.bazel.remote.execution.v2.ContentAddressableStorage.FindMissingBlobs].
message FindMissingBlobsRequest {
  // The instance of the execution system to operate against. A server may
  // support multiple instances of the execution system (with their own workers,
  // storage, caches, etc.). The server MAY require use of this field to select
  // between them in an implementation-defined fashion, otherwise it can be
  // omitted.
  string instance_name = 1;

  // A list of the blobs to check.
  repeated Digest blob_digests = 2;
}

// A response message for
// [ContentAddressableStorage.FindMissingBlobs][build.bazel.remote.execution.v2.ContentAddressableStorage.FindMissingBlobs].
message FindMissingBlobsResponse {
  // A list of the blobs requested *not* present in the storage.
  repeated Digest missing_blob_digests = 2;
}

// A request message for
// [ContentAddressableStorage.BatchUpdateBlobs][build.bazel.remote.execution.v2.ContentAddressableStorage.BatchUpdateBlobs].
message BatchUpdateBlobsRequest {
  // A request corresponding to a single blob that the client wants to upload.
  message Request {
    // The digest of the blob. This MUST be the digest of `data`.
    Digest digest = 1;

    // The raw binary data.
    bytes data = 2;
  }

  // The instance of the execution system to operate against. A server may
  // support multiple instances of the execution system (with their own workers,
  // storage, caches, etc.). The server MAY require use of this field to select
  // between them in an implementation-defined fashion, otherwise it can be
  // omitted.
  string instance_name = 1;

  // The individual upload requests.
  repeated Request requests = 2;
}

// A response message for
// [ContentAddressableStorage.BatchUpdateBlobs][build.bazel.remote.execution.v2.ContentAddressableStorage.BatchUpdateBlobs].
message BatchUpdateBlobsResponse {
  // A response corresponding to a single blob that the client tried to upload.
  message Response {
    // The blob digest to which this response corresponds.
    Digest digest = 1;

    // The result of attempting to upload that blob.
    google.rpc.Status status = 2;
  }

  // The responses to the requests.
  repeated Response responses = 1;
}

// A request message for
// [ContentAddressableStorage.BatchReadBlobs][build.bazel.remote.execution.v2.ContentAddressableStorage.BatchReadBlobs].
message BatchReadBlobsRequest {
  // The instance of the execution system to operate against. A server may
  // support multiple instances of the execution system (with their own workers,
  // storage, caches, etc.). The server MAY require use of this field to select
  // between them in an implementation-defined fashion, otherwise it can be
  // omitted.
  string instance_name = 1;

  // The individual blob digests.
  repeated Digest digests = 2;
}

// A response message for
// [ContentAddressableStorage.BatchReadBlobs][build.bazel.remote.execution.v2.ContentAddressableStorage.BatchReadBlobs].
message BatchReadBlobsResponse {
  // A response corresponding to a single blob that the client tried to download.
  message Response {
    // The digest to which this response corresponds.
    Digest digest = 1;

    // The raw binary data.
    bytes data = 2;

    // The result of attempting to download that blob.
    google.rpc.Status status = 3;
  }

  // The responses to the requests.
  repeated Response responses = 1;
}

// A request message for
// [ContentAddressableStorage.GetTree][build.bazel.remote.execution.v2.ContentAddressableStorage.GetTree].
message GetTreeRequest {
  // The instance of the execution system to operate against. A server may
  // support multiple instances of the execution system (with their own workers,
  // storage, caches, etc.). The server MAY require use of this field to select
  // between them in an implementation-defined fashion, otherwise it can be
  // omitted.
  string instance_name = 1;

  // The digest of the root, which must be an encoded
  // [Directory][build.bazel.remote.execution.v2.Directory] message
  // stored in the
  // [ContentAddressableStorage][build.bazel.remote.execution.v2.ContentAddressableStorage].
  Digest root_digest = 2;

  // A maximum page size to request. If present, the server will request no more
  // than this many items. Regardless of whether a page size is specified, the
  // server may place its own limit on the number of items to be returned and
  // require the client to retrieve more items using a subsequent request.
  int32 page_size = 3;

  // A page token, which must be a value received in a previous
  // [GetTreeResponse][build.bazel.remote.execution.v2.GetTreeResponse].
  // If present, the server will use it to return the following page of results.
  string page_token = 4;
}

// A response message for
// [ContentAddressableStorage.GetTree][build.bazel.remote.execution.v2.ContentAddressableStorage.GetTree].
message GetTreeResponse {
  // The directories descended from the requested root.
  repeated Directory directories = 1;

  // If present, signifies that there are more results which the client can
  // retrieve by passing this as the page_token in a subsequent
  // [request][build.bazel.remote.execution.v2.GetTreeRequest].
  // If empty, signifies that this is the last page of results.
  string next_page_token = 2;
}

// A request message for
// [Capabilities.GetCapabilities][build.bazel.remote.execution.v2.Capabilities.GetCapabilities].
message GetCapabilitiesRequest {
  // The instance of the execution system to operate against. A server may
  // support multiple instances of the execution system (with their own workers,
  // storage, caches, etc.). The server MAY require use of this field to select
  // between them in an implementation-defined fashion, otherwise it can be
  // omitted.
  string instance_name = 1;
}

// A response message for
// [Capabilities.GetCapabilities][build.bazel.remote.execution.v2.Capabilities.GetCapabilities].
message ServerCapabilities {
  // Capabilities of the remote cache system.
  CacheCapabilities cache_capabilities = 1;

  // Capabilities of the remote execution system.
  ExecutionCapabilities execution_capabilities = 2;

  // Earliest RE API version supported, including deprecated versions.
  build.bazel.semver.SemVer deprecated_api_version = 3;

  // Earliest non-deprecated RE API version supported.
  build.bazel.semver.SemVer low_api_version = 4;

  // Latest RE API version supported.
  build.bazel.semver.SemVer high_api_version = 5;
}

// The digest function used for converting values into keys for CAS and Action
// Cache.
message DigestFunction {
  enum Value {
    // It is an error for the server to return this value.
    UNKNOWN = 0;

    // The Sha-256 digest function.
    SHA256 = 1;

    // The Sha-1 digest function.
    SHA1 = 2;

    // The MD5 digest function.
    MD5 = 3;

    // The Microsoft "VSO-Hash" paged SHA256 digest function.
    // See https://github.com/microsoft/BuildXL/blob/master/Documentation/Specs/PagedHash.md .
    VSO = 4;
  }
}

// Describes the server/instance capabilities for updating the action cache.
message ActionCacheUpdateCapabilities {
  bool update_enabled = 1;
}

// Allowed values for priority in
// [ResultsCachePolicy][google.devtools.remoteexecution.v2.ResultsCachePolicy]
// Used for querying both cache and execution valid priority ranges.
message PriorityCapabilities {
  // Supported range of priorities, including boundaries.
  message PriorityRange {
    int32 min_priority = 1;
    int32 max_priority = 2;
  }
  repeated PriorityRange priorities = 1;
}

// Describes how the server treats absolute symlink targets.
message SymlinkAbsolutePathStrategy {
  enum Value {
    // Invalid value.
    UNKNOWN = 0;

    // Server will return an `INVALID_ARGUMENT` on input symlinks with absolute
    // targets.
    // If an action tries to create an output symlink with an absolute target, a
    // `FAILED_PRECONDITION` will be returned.
    DISALLOWED = 1;

    // Server will allow symlink targets to escape the input root tree, possibly
    // resulting in non-hermetic builds.
    ALLOWED = 2;
  }
}

// Capabilities of the remote cache system.
message CacheCapabilities {
  // All the digest functions supported by the remote cache.
  // Remote cache may support multiple digest functions simultaneously.
  repeated DigestFunction.Value digest_function = 1;

  // Capabilities for updating the action cache.
  ActionCacheUpdateCapabilities action_cache_update_capabilities = 2;

  // Supported cache priority range for both CAS and ActionCache.
  PriorityCapabilities cache_priority_capabilities = 3;

  // Maximum total size of blobs to be uploaded/downloaded using
  // batch methods. A value of 0 means no limit is set, although
  // in practice there will always be a message size limitation
  // of the protocol in use, e.g. GRPC.
  int64 max_batch_total_size_bytes = 4;

  // Whether absolute symlink targets are supported.
  SymlinkAbsolutePathStrategy.Value symlink_absolute_path_strategy = 5;
}

// Capabilities of the remote execution system.
message ExecutionCapabilities {
  // Remote execution may only support a single digest function.
  DigestFunction.Value digest_function = 1;

  // Whether remote execution is enabled for the particular server/instance.
  bool exec_enabled = 2;

  // Supported execution priority range.
  PriorityCapabilities execution_priority_capabilities = 3;
}

// Details for the tool used to call the API.
message ToolDetails {
  // Name of the tool, e.g. bazel.
  string tool_name = 1;

  // Version of the tool used for the request, e.g. 5.0.3.
  string tool_version = 2;
}

// An optional Metadata to attach to any RPC request to tell the server about an
// external context of the request. The server may use this for logging or other
// purposes. To use it, the client attaches the header to the call using the
// canonical proto serialization:
//
// * name: `build.bazel.remote.execution.v2.requestmetadata-bin`
// * contents: the base64 encoded binary `RequestMetadata` message.
// Note: the gRPC library serializes binary headers encoded in base 64 by
// default (https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md#requests).
// Therefore, if the gRPC library is used to pass/retrieve this
// metadata, the user may ignore the base64 encoding and assume it is simply
// serialized as a binary message.
message RequestMetadata {
  // The details for the tool invoking the requests.
  ToolDetails tool_details = 1;

  // An identifier that ties multiple requests to the same action.
  // For example, multiple requests to the CAS, Action Cache, and Execution
  // API are used in order to compile foo.cc.
  string action_id = 2;

  // An identifier that ties multiple actions together to a final result.
  // For example, multiple actions are required to build and run foo_test.
  string tool_invocation_id = 3;

  // An identifier to tie multiple tool invocations together. For example,
  // runs of foo_test, bar_test and baz_test on a post-submit of a given patch.
  string correlated_invocations_id = 4;
}