src/main/java/com/google/devtools/build/lib/sandbox/RealSandboxfs02Process.java - bazel - Git at Google

 // Copyright 2019 The Bazel Authors. All rights reserved.
 //
 // 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.

 package com.google.devtools.build.lib.sandbox;

 import static com.google.common.base.Preconditions.checkArgument;
 import static com.google.common.base.Preconditions.checkState;
 import static java.nio.charset.StandardCharsets.UTF_8;

 import com.google.common.util.concurrent.SettableFuture;
 import com.google.devtools.build.lib.shell.Subprocess;
 import com.google.devtools.build.lib.vfs.Path;
 import com.google.devtools.build.lib.vfs.PathFragment;
 import com.google.gson.stream.JsonReader;
 import com.google.gson.stream.JsonToken;
 import com.google.gson.stream.JsonWriter;
 import java.io.BufferedReader;
 import java.io.BufferedWriter;
 import java.io.EOFException;
 import java.io.IOException;
 import java.io.InputStreamReader;
 import java.io.OutputStreamWriter;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
 import java.util.concurrent.ExecutionException;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 import javax.annotation.Nullable;
 import javax.annotation.concurrent.GuardedBy;

 /**
  * A sandboxfs implementation that uses an external sandboxfs binary to manage the mount point.
  *
  * <p>This implementation provides support for the reconfiguration protocol introduced in 0.2.0.
  */
 final class RealSandboxfs02Process extends RealSandboxfsProcess {

   private static final Logger log = Logger.getLogger(RealSandboxfsProcess.class.getName());

   /**
    * Writer with which to send data to the sandboxfs instance. Null only after {@link #destroy()}
    * has been invoked.
    */
   @GuardedBy("this")
   private JsonWriter processStdIn;

   /**
    * Collection of active reconfiguration requests.
    *
    * <p>Each entry in this map is keyed by the identifier of the sandbox being affected by a
    * reconfiguration request and points to a future that is set when the request completes.
    *
    * <p>New entries can be added to this map at any time, but only before {@link #destroy} is
    * called. Once the sandboxfs instance has been destroyed, we do not expect any new requests to
    * come in. However, existing requests will be drained by the {@link ResponsesReader} thread.
    */
   private final ConcurrentMap<String, SettableFuture<Void>> inFlightRequests =
       new ConcurrentHashMap<>();

   /**
    * Thread that reads responses from sandboxfs and dispatches them to the futures maintained by
    * {@link #inFlightRequests}.
    */
   private final Thread responsesReader;

   /** Representation of a response returned by sandboxfs. */
   private static class Response {
     /** Identifier given in the request. Null if this carries a fatal error. */
     @Nullable final String id;

     /**
      * Error message returned by sandboxfs if not null. If {@link #id} is not null, then this error
      * corresponds to a specific request and is recoverable. Otherwise corresponds to a fatal
      * condition, in which case sandboxfs will have stopped listening for requests.
      */
     @Nullable final String error;

     /** Constructs a new response with the given values. */
     Response(@Nullable String id, @Nullable String error) {
       this.id = id;
       this.error = error;
     }
   }

   /**
    * A thread that reads responses from the sandboxfs output stream and dispatches them to the
    * futures awaiting for them.
    */
   private static class ResponsesReader extends Thread {

     private final JsonReader reader;
     private final ConcurrentMap<String, SettableFuture<Void>> inFlightRequests;

     ResponsesReader(
         JsonReader reader, ConcurrentMap<String, SettableFuture<Void>> inFlightRequests) {
       this.reader = reader;
       this.inFlightRequests = inFlightRequests;
     }

     /** Waits for responses and dispatches them. */
     private void processResponses() throws IOException {
       while (!Thread.interrupted() && reader.peek() != JsonToken.END_DOCUMENT) {
         Response response = readResponse(reader);
         if (response.id == null) {
           // Non-recoverable error: abort.
           throw new IOException(response.error != null ? response.error : "No error reported");
         }

         SettableFuture<Void> future = inFlightRequests.remove(response.id);
         if (future == null) {
           throw new IOException("sandboxfs returned response for unknown id " + response.id);
         }
         if (response.error == null) {
           future.set(null);
         } else {
           future.setException(new IOException(response.error));
         }
       }
     }

     @Override
     public void run() {
       try {
         processResponses();
       } catch (EOFException e) {
         // OK, nothing to do.
       } catch (IOException e) {
         log.log(Level.WARNING, "Failed to read responses from sandboxfs", e);
       }

       // sandboxfs has either replied with an unrecoverable error or has stopped providing
       // responses. Either way, we have to clean up any pending in-flight requests to unblock the
       // threads waiting for them.
       //
       // Given that we only get here once destroy() has been called, we do not expect any new
       // requests to show up in the inFlightRequests map. This is why we do not synchronize
       // accesses to the map during the iteration.
       while (!inFlightRequests.isEmpty()) {
         Iterator<Map.Entry<String, SettableFuture<Void>>> iter =
             inFlightRequests.entrySet().iterator();
         while (iter.hasNext()) {
           Map.Entry<String, SettableFuture<Void>> entry = iter.next();
           entry.getValue().cancel(true);
           iter.remove();
         }
       }
     }
   }

   /**
    * Initializes a new sandboxfs process instance.
    *
    * @param process process handle for the already-running sandboxfs instance
    */
   RealSandboxfs02Process(Path mountPoint, Subprocess process) {
     super(mountPoint, process);

     this.processStdIn =
         new JsonWriter(
             new BufferedWriter(new OutputStreamWriter(process.getOutputStream(), UTF_8)));
     JsonReader processStdOut =
         new JsonReader(new BufferedReader(new InputStreamReader(process.getInputStream(), UTF_8)));

     // Must use lenient writing and parsing to accept a stream of separate top-level JSON objects.
     this.processStdIn.setLenient(true);
     processStdOut.setLenient(true);

     responsesReader = new ResponsesReader(processStdOut, inFlightRequests);
     responsesReader.start();
   }

   @Override
   public synchronized void destroy() {
     super.destroy();

     responsesReader.interrupt();
     try {
       responsesReader.join();
     } catch (InterruptedException e) {
       log.warning("Interrupted while waiting for responses processor thread");
       Thread.currentThread().interrupt();
     }

     processStdIn = null;
   }

   /**
    * Waits for a single response from sandboxfs and returns it.
    *
    * @param input the stream connected to sandboxfs's stdout
    * @return the response obtained from the stream
    * @throws IOException if sandboxfs fails to read from the stream for any reason, including EOF
    */
   private static Response readResponse(JsonReader input) throws IOException {
     input.beginObject();
     String id = null;
     String error = null;
     while (input.hasNext()) {
       String name = input.nextName();
       switch (name) {
         case "error":
           if (input.peek() == JsonToken.NULL) {
             input.nextNull();
           } else {
             checkState(error == null);
             error = input.nextString();
           }
           break;

         case "id":
           if (input.peek() == JsonToken.NULL) {
             input.nextNull();
           } else {
             checkState(id == null);
             id = input.nextString();
           }
           break;

         default:
           throw new IOException("Invalid field name in response: " + name);
       }
     }
     input.endObject();
     return new Response(id, error);
   }

   /**
    * Registers a new in-flight operation for the given sandbox identifier.
    *
    * <p>The caller must wait for the returned operation using {@link #waitForRequest}.
    *
    * @param id the identifier of the sandbox for which the request will be issued. There can only be
    *     one in-flight request per identifier.
    * @return the future used to wait for the request's completion
    */
   private SettableFuture<Void> newRequest(String id) {
     SettableFuture<Void> future = SettableFuture.create();
     SettableFuture<Void> other = inFlightRequests.put(id, future);
     checkState(other == null, "Cannot have two in-flight requests for sandbox '%s'", id);
     return future;
   }

   /**
    * Waits for a request to complete and unregisters its in-flight operation.
    *
    * @param future the value returned by {@link #newRequest}.
    * @throws IOException if the request cannot be waited for or if it raised an error
    */
   private static void waitForRequest(SettableFuture<Void> future) throws IOException {
     try {
       future.get();
     } catch (ExecutionException e) {
       Throwable cause = e.getCause();
       if (cause instanceof IOException) {
         throw (IOException) cause;
       } else {
         throw new AssertionError("Unexpected exception type thrown by readResponse()", cause);
       }
     } catch (InterruptedException e) {
       Thread.currentThread().interrupt();
       throw new IOException("Interrupted while waiting for sandboxfs response");
     }
   }

   /** Encodes a mapping into JSON. */
   @SuppressWarnings("UnnecessaryParentheses")
   private static void writeMapping(JsonWriter writer, Mapping mapping) throws IOException {
     writer.beginObject();
     {
       writer.name("path");
       writer.value(mapping.path().getPathString());
       writer.name("underlying_path");
       writer.value(mapping.target().getPathString());
       writer.name("writable");
       writer.value(mapping.writable());
     }
     writer.endObject();
   }

   @Override
   @SuppressWarnings("UnnecessaryParentheses")
   public void createSandbox(String id, List<Mapping> mappings) throws IOException {
     checkArgument(!PathFragment.containsSeparator(id));

     SettableFuture<Void> future = newRequest(id);
     synchronized (this) {
       processStdIn.beginObject();
       {
         processStdIn.name("CreateSandbox");
         processStdIn.beginObject();
         {
           processStdIn.name("id");
           processStdIn.value(id);
           processStdIn.name("mappings");
           processStdIn.beginArray();
           for (Mapping mapping : mappings) {
             writeMapping(processStdIn, mapping);
           }
           processStdIn.endArray();
         }
         processStdIn.endObject();
       }
       processStdIn.endObject();

       processStdIn.flush();
     }
     waitForRequest(future);
   }

   @Override
   @SuppressWarnings("UnnecessaryParentheses")
   public void destroySandbox(String id) throws IOException {
     checkArgument(!PathFragment.containsSeparator(id));

     SettableFuture<Void> future = newRequest(id);
     synchronized (this) {
       processStdIn.beginObject();
       {
         processStdIn.name("DestroySandbox");
         processStdIn.value(id);
       }
       processStdIn.endObject();

       processStdIn.flush();
     }
     waitForRequest(future);
   }
 }
	// Copyright 2019 The Bazel Authors. All rights reserved.
	//
	// 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.

	package com.google.devtools.build.lib.sandbox;

	import static com.google.common.base.Preconditions.checkArgument;
	import static com.google.common.base.Preconditions.checkState;
	import static java.nio.charset.StandardCharsets.UTF_8;

	import com.google.common.util.concurrent.SettableFuture;
	import com.google.devtools.build.lib.shell.Subprocess;
	import com.google.devtools.build.lib.vfs.Path;
	import com.google.devtools.build.lib.vfs.PathFragment;
	import com.google.gson.stream.JsonReader;
	import com.google.gson.stream.JsonToken;
	import com.google.gson.stream.JsonWriter;
	import java.io.BufferedReader;
	import java.io.BufferedWriter;
	import java.io.EOFException;
	import java.io.IOException;
	import java.io.InputStreamReader;
	import java.io.OutputStreamWriter;
	import java.util.Iterator;
	import java.util.List;
	import java.util.Map;
	import java.util.concurrent.ConcurrentHashMap;
	import java.util.concurrent.ConcurrentMap;
	import java.util.concurrent.ExecutionException;
	import java.util.logging.Level;
	import java.util.logging.Logger;
	import javax.annotation.Nullable;
	import javax.annotation.concurrent.GuardedBy;

	/**
	* A sandboxfs implementation that uses an external sandboxfs binary to manage the mount point.
	*
	* <p>This implementation provides support for the reconfiguration protocol introduced in 0.2.0.
	*/
	final class RealSandboxfs02Process extends RealSandboxfsProcess {

	private static final Logger log = Logger.getLogger(RealSandboxfsProcess.class.getName());

	/**
	* Writer with which to send data to the sandboxfs instance. Null only after {@link #destroy()}
	* has been invoked.
	*/
	@GuardedBy("this")
	private JsonWriter processStdIn;

	/**
	* Collection of active reconfiguration requests.
	*
	* <p>Each entry in this map is keyed by the identifier of the sandbox being affected by a
	* reconfiguration request and points to a future that is set when the request completes.
	*
	* <p>New entries can be added to this map at any time, but only before {@link #destroy} is
	* called. Once the sandboxfs instance has been destroyed, we do not expect any new requests to
	* come in. However, existing requests will be drained by the {@link ResponsesReader} thread.
	*/
	private final ConcurrentMap<String, SettableFuture<Void>> inFlightRequests =
	new ConcurrentHashMap<>();

	/**
	* Thread that reads responses from sandboxfs and dispatches them to the futures maintained by
	* {@link #inFlightRequests}.
	*/
	private final Thread responsesReader;

	/** Representation of a response returned by sandboxfs. */
	private static class Response {
	/** Identifier given in the request. Null if this carries a fatal error. */
	@Nullable final String id;

	/**
	* Error message returned by sandboxfs if not null. If {@link #id} is not null, then this error
	* corresponds to a specific request and is recoverable. Otherwise corresponds to a fatal
	* condition, in which case sandboxfs will have stopped listening for requests.
	*/
	@Nullable final String error;

	/** Constructs a new response with the given values. */
	Response(@Nullable String id, @Nullable String error) {
	this.id = id;
	this.error = error;
	}
	}

	/**
	* A thread that reads responses from the sandboxfs output stream and dispatches them to the
	* futures awaiting for them.
	*/
	private static class ResponsesReader extends Thread {

	private final JsonReader reader;
	private final ConcurrentMap<String, SettableFuture<Void>> inFlightRequests;

	ResponsesReader(
	JsonReader reader, ConcurrentMap<String, SettableFuture<Void>> inFlightRequests) {
	this.reader = reader;
	this.inFlightRequests = inFlightRequests;
	}

	/** Waits for responses and dispatches them. */
	private void processResponses() throws IOException {
	while (!Thread.interrupted() && reader.peek() != JsonToken.END_DOCUMENT) {
	Response response = readResponse(reader);
	if (response.id == null) {
	// Non-recoverable error: abort.
	throw new IOException(response.error != null ? response.error : "No error reported");
	}

	SettableFuture<Void> future = inFlightRequests.remove(response.id);
	if (future == null) {
	throw new IOException("sandboxfs returned response for unknown id " + response.id);
	}
	if (response.error == null) {
	future.set(null);
	} else {
	future.setException(new IOException(response.error));
	}
	}
	}

	@Override
	public void run() {
	try {
	processResponses();
	} catch (EOFException e) {
	// OK, nothing to do.
	} catch (IOException e) {
	log.log(Level.WARNING, "Failed to read responses from sandboxfs", e);
	}

	// sandboxfs has either replied with an unrecoverable error or has stopped providing
	// responses. Either way, we have to clean up any pending in-flight requests to unblock the
	// threads waiting for them.
	//
	// Given that we only get here once destroy() has been called, we do not expect any new
	// requests to show up in the inFlightRequests map. This is why we do not synchronize
	// accesses to the map during the iteration.
	while (!inFlightRequests.isEmpty()) {
	Iterator<Map.Entry<String, SettableFuture<Void>>> iter =
	inFlightRequests.entrySet().iterator();
	while (iter.hasNext()) {
	Map.Entry<String, SettableFuture<Void>> entry = iter.next();
	entry.getValue().cancel(true);
	iter.remove();
	}
	}
	}
	}

	/**
	* Initializes a new sandboxfs process instance.
	*
	* @param process process handle for the already-running sandboxfs instance
	*/
	RealSandboxfs02Process(Path mountPoint, Subprocess process) {
	super(mountPoint, process);

	this.processStdIn =
	new JsonWriter(
	new BufferedWriter(new OutputStreamWriter(process.getOutputStream(), UTF_8)));
	JsonReader processStdOut =
	new JsonReader(new BufferedReader(new InputStreamReader(process.getInputStream(), UTF_8)));

	// Must use lenient writing and parsing to accept a stream of separate top-level JSON objects.
	this.processStdIn.setLenient(true);
	processStdOut.setLenient(true);

	responsesReader = new ResponsesReader(processStdOut, inFlightRequests);
	responsesReader.start();
	}

	@Override
	public synchronized void destroy() {
	super.destroy();

	responsesReader.interrupt();
	try {
	responsesReader.join();
	} catch (InterruptedException e) {
	log.warning("Interrupted while waiting for responses processor thread");
	Thread.currentThread().interrupt();
	}

	processStdIn = null;
	}

	/**
	* Waits for a single response from sandboxfs and returns it.
	*
	* @param input the stream connected to sandboxfs's stdout
	* @return the response obtained from the stream
	* @throws IOException if sandboxfs fails to read from the stream for any reason, including EOF
	*/
	private static Response readResponse(JsonReader input) throws IOException {
	input.beginObject();
	String id = null;
	String error = null;
	while (input.hasNext()) {
	String name = input.nextName();
	switch (name) {
	case "error":
	if (input.peek() == JsonToken.NULL) {
	input.nextNull();
	} else {
	checkState(error == null);
	error = input.nextString();
	}
	break;

	case "id":
	if (input.peek() == JsonToken.NULL) {
	input.nextNull();
	} else {
	checkState(id == null);
	id = input.nextString();
	}
	break;

	default:
	throw new IOException("Invalid field name in response: " + name);
	}
	}
	input.endObject();
	return new Response(id, error);
	}

	/**
	* Registers a new in-flight operation for the given sandbox identifier.
	*
	* <p>The caller must wait for the returned operation using {@link #waitForRequest}.
	*
	* @param id the identifier of the sandbox for which the request will be issued. There can only be
	* one in-flight request per identifier.
	* @return the future used to wait for the request's completion
	*/
	private SettableFuture<Void> newRequest(String id) {
	SettableFuture<Void> future = SettableFuture.create();
	SettableFuture<Void> other = inFlightRequests.put(id, future);
	checkState(other == null, "Cannot have two in-flight requests for sandbox '%s'", id);
	return future;
	}

	/**
	* Waits for a request to complete and unregisters its in-flight operation.
	*
	* @param future the value returned by {@link #newRequest}.
	* @throws IOException if the request cannot be waited for or if it raised an error
	*/
	private static void waitForRequest(SettableFuture<Void> future) throws IOException {
	try {
	future.get();
	} catch (ExecutionException e) {
	Throwable cause = e.getCause();
	if (cause instanceof IOException) {
	throw (IOException) cause;
	} else {
	throw new AssertionError("Unexpected exception type thrown by readResponse()", cause);
	}
	} catch (InterruptedException e) {
	Thread.currentThread().interrupt();
	throw new IOException("Interrupted while waiting for sandboxfs response");
	}
	}

	/** Encodes a mapping into JSON. */
	@SuppressWarnings("UnnecessaryParentheses")
	private static void writeMapping(JsonWriter writer, Mapping mapping) throws IOException {
	writer.beginObject();
	{
	writer.name("path");
	writer.value(mapping.path().getPathString());
	writer.name("underlying_path");
	writer.value(mapping.target().getPathString());
	writer.name("writable");
	writer.value(mapping.writable());
	}
	writer.endObject();
	}

	@Override
	@SuppressWarnings("UnnecessaryParentheses")
	public void createSandbox(String id, List<Mapping> mappings) throws IOException {
	checkArgument(!PathFragment.containsSeparator(id));

	SettableFuture<Void> future = newRequest(id);
	synchronized (this) {
	processStdIn.beginObject();
	{
	processStdIn.name("CreateSandbox");
	processStdIn.beginObject();
	{
	processStdIn.name("id");
	processStdIn.value(id);
	processStdIn.name("mappings");
	processStdIn.beginArray();
	for (Mapping mapping : mappings) {
	writeMapping(processStdIn, mapping);
	}
	processStdIn.endArray();
	}
	processStdIn.endObject();
	}
	processStdIn.endObject();

	processStdIn.flush();
	}
	waitForRequest(future);
	}

	@Override
	@SuppressWarnings("UnnecessaryParentheses")
	public void destroySandbox(String id) throws IOException {
	checkArgument(!PathFragment.containsSeparator(id));

	SettableFuture<Void> future = newRequest(id);
	synchronized (this) {
	processStdIn.beginObject();
	{
	processStdIn.name("DestroySandbox");
	processStdIn.value(id);
	}
	processStdIn.endObject();

	processStdIn.flush();
	}
	waitForRequest(future);
	}
	}