Move ResourceSnapshot out of PsInfoCollector (we'll be using creating this snapshot with cgroups which has nothing to do with ps) and also only collect resources from alive workers.

PiperOrigin-RevId: 601125773
Change-Id: I3dc2c2d62fd15caf3d58b13ac1a96ddd6471aee6
diff --git a/src/main/java/com/google/devtools/build/lib/metrics/BUILD b/src/main/java/com/google/devtools/build/lib/metrics/BUILD
index cd0efda..02c0450 100644
--- a/src/main/java/com/google/devtools/build/lib/metrics/BUILD
+++ b/src/main/java/com/google/devtools/build/lib/metrics/BUILD
@@ -88,7 +88,10 @@
 
 java_library(
     name = "ps_info_collector",
-    srcs = ["PsInfoCollector.java"],
+    srcs = [
+        "PsInfoCollector.java",
+        "ResourceSnapshot.java",
+    ],
     deps = [
         "//src/main/java/com/google/devtools/build/lib/clock",
         "//third_party:auto_value",
diff --git a/src/main/java/com/google/devtools/build/lib/metrics/PsInfoCollector.java b/src/main/java/com/google/devtools/build/lib/metrics/PsInfoCollector.java
index 952c256..00cd48f 100644
--- a/src/main/java/com/google/devtools/build/lib/metrics/PsInfoCollector.java
+++ b/src/main/java/com/google/devtools/build/lib/metrics/PsInfoCollector.java
@@ -190,19 +190,4 @@
           pidToPsInfo, pidToChildrenPsInfo, collectionTime);
     }
   }
-
-  /** Contains resource consumption info per process tree. */
-  @AutoValue
-  public abstract static class ResourceSnapshot {
-    /** Overall memory consumption by all descendant processes including initial process. */
-    public abstract ImmutableMap<Long, Integer> getPidToMemoryInKb();
-
-    /** Time when this snapshot was collected. */
-    public abstract Instant getCollectionTime();
-
-    public static ResourceSnapshot create(
-        ImmutableMap<Long, Integer> pidToMemoryInKb, Instant collectionTime) {
-      return new AutoValue_PsInfoCollector_ResourceSnapshot(pidToMemoryInKb, collectionTime);
-    }
-  }
 }
diff --git a/src/main/java/com/google/devtools/build/lib/metrics/ResourceSnapshot.java b/src/main/java/com/google/devtools/build/lib/metrics/ResourceSnapshot.java
new file mode 100644
index 0000000..99009f7
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/metrics/ResourceSnapshot.java
@@ -0,0 +1,38 @@
+// Copyright 2024 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.metrics;
+
+import com.google.auto.value.AutoValue;
+import com.google.common.collect.ImmutableMap;
+import java.time.Instant;
+
+/** Contains a snapshot of the resource usage of multiple processes. */
+@AutoValue
+public abstract class ResourceSnapshot {
+  /** Overall memory consumption by all descendant processes including initial process. */
+  public abstract ImmutableMap<Long, Integer> getPidToMemoryInKb();
+
+  /** Time when this snapshot was collected. */
+  public abstract Instant getCollectionTime();
+
+  public static ResourceSnapshot create(
+      ImmutableMap<Long, Integer> pidToMemoryInKb, Instant collectionTime) {
+    return new AutoValue_ResourceSnapshot(pidToMemoryInKb, collectionTime);
+  }
+
+  public static ResourceSnapshot createEmpty() {
+    return new AutoValue_ResourceSnapshot(ImmutableMap.of(), Instant.now());
+  }
+}
diff --git a/src/main/java/com/google/devtools/build/lib/worker/WorkerProcessMetricsCollector.java b/src/main/java/com/google/devtools/build/lib/worker/WorkerProcessMetricsCollector.java
index 3636cff..ba998a2 100644
--- a/src/main/java/com/google/devtools/build/lib/worker/WorkerProcessMetricsCollector.java
+++ b/src/main/java/com/google/devtools/build/lib/worker/WorkerProcessMetricsCollector.java
@@ -15,6 +15,7 @@
 package com.google.devtools.build.lib.worker;
 
 import static com.google.common.collect.ImmutableList.toImmutableList;
+import static com.google.common.collect.ImmutableSet.toImmutableSet;
 
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.collect.ImmutableList;
@@ -24,6 +25,7 @@
 import com.google.devtools.build.lib.buildeventstream.BuildEventStreamProtos.BuildMetrics.WorkerMetrics.WorkerStatus;
 import com.google.devtools.build.lib.clock.Clock;
 import com.google.devtools.build.lib.metrics.PsInfoCollector;
+import com.google.devtools.build.lib.metrics.ResourceSnapshot;
 import com.google.devtools.build.lib.util.OS;
 import java.time.Instant;
 import java.util.ArrayList;
@@ -57,18 +59,29 @@
     this.clock = clock;
   }
 
+  ResourceSnapshot collectResourceUsage() {
+    // Only collect for process we know are alive.
+    ImmutableSet<Long> alivePids =
+        processIdToWorkerProcessMetrics.entrySet().stream()
+            .filter(e -> !e.getValue().getStatus().isKilled())
+            .map(e -> e.getKey())
+            .collect(toImmutableSet());
+    return collectResourceUsage(OS.getCurrent(), alivePids);
+  }
+
   /**
    * Collects memory usage of all ancestors of processes by pid. If a pid does not allow collecting
    * memory usage, it is silently ignored.
    */
-  PsInfoCollector.ResourceSnapshot collectMemoryUsageByPid(OS os, ImmutableSet<Long> processIds) {
+  ResourceSnapshot collectResourceUsage(OS os, ImmutableSet<Long> processIds) {
     // TODO(b/181317827): Support Windows.
-    if (processIds.isEmpty() || (os != OS.LINUX && os != OS.DARWIN)) {
-      return PsInfoCollector.ResourceSnapshot.create(
-          /* pidToMemoryInKb= */ ImmutableMap.of(), /* collectionTime= */ Instant.now());
+    if (processIds.isEmpty()) {
+      return ResourceSnapshot.createEmpty();
     }
-
-    return PsInfoCollector.instance().collectResourceUsage(processIds);
+    if (os == OS.LINUX || os == OS.DARWIN) {
+      return PsInfoCollector.instance().collectResourceUsage(processIds);
+    }
+    return ResourceSnapshot.createEmpty();
   }
 
   public ImmutableList<WorkerProcessMetrics> getLiveWorkerProcessMetrics() {
@@ -78,9 +91,7 @@
   }
 
   public ImmutableList<WorkerProcessMetrics> collectMetrics() {
-    PsInfoCollector.ResourceSnapshot resourceSnapshot =
-        collectMemoryUsageByPid(
-            OS.getCurrent(), ImmutableSet.copyOf(processIdToWorkerProcessMetrics.keySet()));
+    ResourceSnapshot resourceSnapshot = collectResourceUsage();
 
     ImmutableMap<Long, Integer> pidToMemoryInKb = resourceSnapshot.getPidToMemoryInKb();
     Instant collectionTime = resourceSnapshot.getCollectionTime();