Add an on-disk storage option for the remote worker

I'm planning to switch the remote worker over to the on-disk storage system,
and delete the in-memory option. Currently, running a Bazel build with the
in-memory storage system uses up over 50% of the total available memory on my
machine (I only have 32 GB total), and grinds it to a complete halt (unless I
close most of my apps) on a simple build of //src:bazel.

PiperOrigin-RevId: 160877546

3 files changed, 80 insertions, 2 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/remote/blobstore/OnDiskBlobStore.java b/src/main/java/com/google/devtools/build/lib/remote/blobstore/OnDiskBlobStore.java
new file mode 100644
index 0000000000..8f2ee0790e
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/remote/blobstore/OnDiskBlobStore.java
@@ -0,0 +1,57 @@
+// Copyright 2017 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.remote.blobstore;
+
+import com.google.devtools.build.lib.vfs.FileSystemUtils;
+import com.google.devtools.build.lib.vfs.Path;
+import java.io.IOException;
+import java.io.OutputStream;
+import java.util.UUID;
+
+/** A on-disk store for the remote action cache. */
+public final class OnDiskBlobStore implements SimpleBlobStore {
+  private final Path root;
+
+  public OnDiskBlobStore(Path root) {
+    this.root = root;
+  }
+
+  @Override
+  public boolean containsKey(String key) {
+    return toPath(key).exists();
+  }
+
+  @Override
+  public byte[] get(String key) throws IOException {
+    Path f = toPath(key);
+    return f.exists() ? FileSystemUtils.readContent(f) : null;
+  }
+
+  @Override
+  public void put(String key, byte[] value) throws IOException {
+    Path temp = toPath(UUID.randomUUID().toString());
+    try (OutputStream out = temp.getOutputStream()) {
+      out.write(value);
+    }
+    Path f = toPath(key);
+    temp.renameTo(f);
+  }
+
+  @Override
+  public void close() {}
+
+  private Path toPath(String key) {
+    return root.getChild(key);
+  }
+}
\ No newline at end of file
diff --git a/src/tools/remote_worker/src/main/java/com/google/devtools/build/remote/RemoteWorker.java b/src/tools/remote_worker/src/main/java/com/google/devtools/build/remote/RemoteWorker.java
index d9056e9932..49e63d7915 100644
--- a/src/tools/remote_worker/src/main/java/com/google/devtools/build/remote/RemoteWorker.java
+++ b/src/tools/remote_worker/src/main/java/com/google/devtools/build/remote/RemoteWorker.java
@@ -27,6 +27,7 @@ import com.google.devtools.build.lib.remote.RemoteOptions;
 import com.google.devtools.build.lib.remote.SimpleBlobStoreActionCache;
 import com.google.devtools.build.lib.remote.SimpleBlobStoreFactory;
 import com.google.devtools.build.lib.remote.blobstore.ConcurrentMapBlobStore;
+import com.google.devtools.build.lib.remote.blobstore.OnDiskBlobStore;
 import com.google.devtools.build.lib.remote.blobstore.SimpleBlobStore;
 import com.google.devtools.build.lib.shell.Command;
 import com.google.devtools.build.lib.shell.CommandException;
@@ -39,6 +40,7 @@ import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.FileSystemUtils;
 import com.google.devtools.build.lib.vfs.JavaIoFileSystem;
 import com.google.devtools.build.lib.vfs.Path;
+import com.google.devtools.build.lib.vfs.PathFragment;
 import com.google.devtools.common.options.OptionsParser;
 import com.google.devtools.remoteexecution.v1test.ActionCacheGrpc.ActionCacheImplBase;
 import com.google.devtools.remoteexecution.v1test.ContentAddressableStorageGrpc.ContentAddressableStorageImplBase;
@@ -165,12 +167,20 @@ public final class RemoteWorker {
     if (!usingRemoteCache) {
       logger.warning("Not using remote cache. This should be used for testing only!");
     }
+    if ((remoteWorkerOptions.casPath != null)
+        && (!PathFragment.create(remoteWorkerOptions.casPath).isAbsolute()
+            || !getFileSystem().getPath(remoteWorkerOptions.casPath).exists())) {
+      logger.severe("--cas_path must refer to an existing, absolute path!");
+      System.exit(1);
+      return;
+    }
 
     SimpleBlobStore blobStore =
         usingRemoteCache
             ? SimpleBlobStoreFactory.create(remoteOptions)
-            : new ConcurrentMapBlobStore(
-                new ConcurrentHashMap<String, byte[]>());
+            : remoteWorkerOptions.casPath != null
+                ? new OnDiskBlobStore(getFileSystem().getPath(remoteWorkerOptions.casPath))
+                : new ConcurrentMapBlobStore(new ConcurrentHashMap<String, byte[]>());
 
     RemoteWorker worker =
         new RemoteWorker(
diff --git a/src/tools/remote_worker/src/main/java/com/google/devtools/build/remote/RemoteWorkerOptions.java b/src/tools/remote_worker/src/main/java/com/google/devtools/build/remote/RemoteWorkerOptions.java
index 686761f9ed..e8bc12a781 100644
--- a/src/tools/remote_worker/src/main/java/com/google/devtools/build/remote/RemoteWorkerOptions.java
+++ b/src/tools/remote_worker/src/main/java/com/google/devtools/build/remote/RemoteWorkerOptions.java
@@ -43,6 +43,17 @@ public class RemoteWorkerOptions extends OptionsBase {
   public String workPath;
 
   @Option(
+    name = "cas_path",
+    defaultValue = "null",
+    category = "build_worker",
+    documentationCategory = OptionDocumentationCategory.UNCATEGORIZED,
+    effectTags = {OptionEffectTag.UNKNOWN},
+    help = "A directory for the build worker to store it's files in. If left unset, and if no "
+        + "other store is set, the worker falls back to an in-memory store."
+  )
+  public String casPath;
+
+  @Option(
     name = "debug",
     defaultValue = "false",
     category = "build_worker",