Add a server.pid file for platforms where GetPeerProcessId is not supported

--
Change-Id: I36b096cfdf7b150121809ff5b07c74eac1cbf7ad
Reviewed-on: https://bazel-review.git.corp.google.com/#/c/1771
MOS_MIGRATED_REVID=100573875

1 files changed, 14 insertions, 0 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/server/RPCServer.java b/src/main/java/com/google/devtools/build/lib/server/RPCServer.java
index a1e9982a73..903ef567a7 100644
--- a/src/main/java/com/google/devtools/build/lib/server/RPCServer.java
+++ b/src/main/java/com/google/devtools/build/lib/server/RPCServer.java
@@ -26,10 +26,12 @@ import com.google.devtools.build.lib.unix.LocalClientSocket;
 import com.google.devtools.build.lib.unix.LocalServerSocket;
 import com.google.devtools.build.lib.unix.LocalSocketAddress;
 import com.google.devtools.build.lib.util.Clock;
+import com.google.devtools.build.lib.util.OsUtils;
 import com.google.devtools.build.lib.util.ThreadUtils;
 import com.google.devtools.build.lib.util.io.OutErr;
 import com.google.devtools.build.lib.util.io.StreamMultiplexer;
 import com.google.devtools.build.lib.vfs.Path;
+import com.google.devtools.build.lib.vfs.PathFragment;
 
 import java.io.IOException;
 import java.io.InputStream;
@@ -365,6 +367,18 @@ public final class RPCServer {
 
     ensureExclusiveAccess(socketFile);
 
+    // We create the server.pid file strictly before binding the socket.
+    // The client only accesses the pid file after connecting to the socket
+    // which ensures that it gets the correct pid value.
+    Path pidFile = serverDirectory.getRelative("server.pid");
+    deleteAtExit(pidFile, /*deleteParent=*/ false);
+    try {
+      pidFile.delete();
+    } catch (IOException e) {
+      // Ignore.
+    }
+    pidFile.createSymbolicLink(new PathFragment(String.valueOf(OsUtils.getpid())));
+
     LocalServerSocket serverSocket = new LocalServerSocket();
     serverSocket.bind(new LocalSocketAddress(socketFile.getPathFile()));
     FilesystemUtils.chmod(socketFile.getPathFile(), 0600);  // Lock it down.