Allow overriding the hostname and instance name in bytestream:// URIs

In cases where full network transparency doesn't exist, people may run
Bazel with custom values of --remote_executor and --remote_instance_name
to proxy gRPC traffic. Such proxies may do caching, tunneling and
authentication.

What's problematic about this is that the values of these command line
flags aren't just used to establish a gRPC connection to a remote
execution service. They also get logged by Bazel in build event streams
in the form of bytestream:// URIs. This means that a build event stream
generated on system A may contain bytestream:// URIs that are not valid
on system B.

Let's introduce a command line flag, --remote_bytestream_uri_prefix,
that can be used to force generation of bytestream:// URIs that are
canonical.

src/main/java/com/google/devtools/build/lib/remote/ByteStreamBuildEventArtifactUploader.java

@@ -63,16 +63,11 @@ class ByteStreamBuildEventArtifactUploader extends AbstractReferenceCounted
   ByteStreamBuildEventArtifactUploader(
       ByteStreamUploader uploader,
       MissingDigestsFinder missingDigestsFinder,
-      String remoteServerName,
+      String remoteServerInstanceName,
       String buildRequestId,
       String commandId,
-      @Nullable String remoteInstanceName,
       int maxUploadThreads) {
     this.uploader = Preconditions.checkNotNull(uploader);
-    String remoteServerInstanceName = Preconditions.checkNotNull(remoteServerName);
-    if (!Strings.isNullOrEmpty(remoteInstanceName)) {
-      remoteServerInstanceName += "/" + remoteInstanceName;
-    }
     this.buildRequestId = buildRequestId;
     this.commandId = commandId;
     this.remoteServerInstanceName = remoteServerInstanceName;

src/main/java/com/google/devtools/build/lib/remote/ByteStreamBuildEventArtifactUploaderFactory.java

@@ -27,36 +27,32 @@ class ByteStreamBuildEventArtifactUploaderFactory implements
     BuildEventArtifactUploaderFactory {
 
   private final ByteStreamUploader uploader;
-  private final String remoteServerName;
+  private final String remoteServerInstanceName;
   private final String buildRequestId;
   private final String commandId;
   private final MissingDigestsFinder missingDigestsFinder;
-  @Nullable private final String remoteInstanceName;
 
   ByteStreamBuildEventArtifactUploaderFactory(
       ByteStreamUploader uploader,
       MissingDigestsFinder missingDigestsFinder,
-      String remoteServerName,
+      String remoteServerInstanceName,
       String buildRequestId,
-      String commandId,
-      @Nullable String remoteInstanceName) {
+      String commandId) {
     this.uploader = uploader;
     this.missingDigestsFinder = missingDigestsFinder;
-    this.remoteServerName = remoteServerName;
+    this.remoteServerInstanceName = remoteServerInstanceName;
     this.buildRequestId = buildRequestId;
     this.commandId = commandId;
-    this.remoteInstanceName = remoteInstanceName;
   }
 
   @Override
   public BuildEventArtifactUploader create(CommandEnvironment env) {
     return new ByteStreamBuildEventArtifactUploader(
         uploader.retain(),
         missingDigestsFinder,
-        remoteServerName,
+        remoteServerInstanceName,
         buildRequestId,
         commandId,
-        remoteInstanceName,
         env.getOptions().getOptions(RemoteOptions.class).buildEventUploadMaxThreads);
   }
 }

src/main/java/com/google/devtools/build/lib/remote/RemoteModule.java

@@ -482,6 +482,14 @@ public void beforeCommand(CommandEnvironment env) throws AbruptExitException {
       }
     }
 
+    String remoteBytestreamUriPrefix = remoteOptions.remoteBytestreamUriPrefix;
+    if (Strings.isNullOrEmpty(remoteBytestreamUriPrefix)) {
+      remoteBytestreamUriPrefix = cacheChannel.authority();
+      if (!Strings.isNullOrEmpty(remoteOptions.remoteInstanceName)) {
+        remoteBytestreamUriPrefix += "/" + remoteOptions.remoteInstanceName;
+      }
+    }
+
     ByteStreamUploader uploader =
         new ByteStreamUploader(
             remoteOptions.remoteInstanceName,
@@ -504,10 +512,9 @@ public void beforeCommand(CommandEnvironment env) throws AbruptExitException {
         new ByteStreamBuildEventArtifactUploaderFactory(
             uploader,
             cacheClient,
-            cacheChannel.authority(),
+            remoteBytestreamUriPrefix,
             buildRequestId,
-            invocationId,
-            remoteOptions.remoteInstanceName));
+            invocationId));
 
     if (enableRemoteExecution) {
       RemoteExecutionClient remoteExecutor;

src/main/java/com/google/devtools/build/lib/remote/options/RemoteOptions.java

@@ -181,6 +181,19 @@ public final class RemoteOptions extends OptionsBase {
               + " the unit is omitted, the value is interpreted as seconds.")
   public Duration remoteTimeout;
 
+  @Option(
+      name = "remote_bytestream_uri_prefix",
+      defaultValue = "null",
+      documentationCategory = OptionDocumentationCategory.REMOTE,
+      effectTags = {OptionEffectTag.UNKNOWN},
+      help =
+          "The hostname and instance name to be used in bytestream:// URIs that are written into "
+              + "build event streams. This option can be set when builds are performed using a "
+              + "proxy, which causes the values of --remote_executor and --remote_instance_name "
+              + "to no longer correspond to the canonical name of the remote execution service. "
+              + "When not set, it will default to \"${hostname}/${instance_name}\".")
+  public String remoteBytestreamUriPrefix;
+
   /** Returns the specified duration. Assumes seconds if unitless. */
   public static class RemoteTimeoutConverter implements Converter<Duration> {
     private static final Pattern UNITLESS_REGEX = Pattern.compile("^[0-9]+$");

src/test/java/com/google/devtools/build/lib/remote/ByteStreamBuildEventArtifactUploaderTest.java

@@ -361,10 +361,9 @@ private ByteStreamBuildEventArtifactUploader newArtifactUploader(
     return new ByteStreamBuildEventArtifactUploader(
         uploader,
         missingDigestsFinder,
-        "localhost",
+        "localhost/instance",
         "none",
         "none",
-        "instance",
         /* maxUploadThreads= */ 100);
   }
 

src/test/shell/bazel/remote/remote_execution_test.sh

@@ -1440,6 +1440,41 @@ EOF
   expect_log "uri:.*bytestream://localhost"
 }
 
+function test_bytestream_uri_prefix() {
+  # Test that when --remote_bytestream_uri_prefix is set, bytestream://
+  # URIs do not contain the hostname that's part of --remote_executor.
+  # They should use a fixed value instead.
+  mkdir -p a
+  cat > a/success.sh <<'EOF'
+#!/bin/sh
+exit 0
+EOF
+  chmod 755 a/success.sh
+  cat > a/BUILD <<'EOF'
+sh_test(
+  name = "success_test",
+  srcs = ["success.sh"],
+)
+
+genrule(
+  name = "foo",
+  srcs = [],
+  outs = ["foo.txt"],
+  cmd = "echo \"foo\" > \"$@\"",
+)
+EOF
+
+  bazel test \
+    --remote_executor=grpc://localhost:${worker_port} \
+    --remote_download_minimal \
+    --remote_bytestream_uri_prefix=example.com/my-instance-name \
+    --build_event_text_file=$TEST_log \
+    //a:foo //a:success_test || fail "Failed to test //a:foo //a:success_test"
+
+  expect_not_log 'uri:.*file://'
+  expect_log "uri:.*bytestream://example.com/my-instance-name/blobs"
+}
+
 # This test is derivative of test_bep_output_groups in
 # build_event_stream_test.sh, which verifies that successful output groups'
 # artifacts appear in BEP when a top-level target fails to build.