Merge "Use subscribe pattern to avoid eager stream-events materialization"

Documentation/cmd-stream-events.txt

@@ -26,6 +26,14 @@ link:access-control.html#capability_streamEvents[the 'Stream Events' global capa
 == SCRIPTING
 This command is intended to be used in scripts.
 
+== OPTIONS
+--subscribe|-s::
+	Type of the event to subscribe to.  Multiple --subscribe options
+	may be specified to subscribe to multiple events. When this option
+	is provided, only subscribed events are emitted and all other
+	events are ignored. When this option is omitted, all events are
+	emitted.
+
 == EXAMPLES
 
 ====
@@ -34,6 +42,13 @@ This command is intended to be used in scripts.
   {"type":"comment-added",change:{"project":"tools/gerrit", ...}, ...}
 ====
 
+Only subscribe to specific event types:
+
+====
+  $ ssh -p 29418 review.example.com gerrit stream-events \
+      -s draft-published -s patchset-created -s ref-replicated
+====
+
 == SCHEMA
 The JSON messages consist of nested objects referencing the *change*,
 *patchSet*, *account* involved, and other attributes as appropriate.

gerrit-sshd/src/main/java/com/google/gerrit/sshd/commands/StreamEvents.java

@@ -38,10 +38,13 @@ import com.google.gson.JsonSerializer;
 import com.google.inject.Inject;
 
 import org.apache.sshd.server.Environment;
+import org.kohsuke.args4j.Option;
 
 import java.io.IOException;
 import java.io.PrintWriter;
 import java.lang.reflect.Type;
+import java.util.ArrayList;
+import java.util.List;
 import java.util.concurrent.Future;
 import java.util.concurrent.LinkedBlockingQueue;
 
@@ -55,6 +58,10 @@ final class StreamEvents extends BaseCommand {
   /** Number of events to write before yielding off the thread. */
   private static final int BATCH_SIZE = 32;
 
+  @Option(name = "--subscribe", aliases = {"-s"}, metaVar = "SUBSCRIBE",
+      usage = "subscribe to specific stream-events")
+  private List<String> subscribedToEvents = new ArrayList<>();
+
   @Inject
   private IdentifiedUser currentUser;
 
@@ -87,8 +94,11 @@ final class StreamEvents extends BaseCommand {
   private final EventListener listener = new EventListener() {
     @Override
     public void onEvent(final Event event) {
+      if (subscribedToEvents.isEmpty()
+          || subscribedToEvents.contains(event.getType())) {
         offer(event);
       }
+    }
   };
 
   private final CancelableRunnable writer = new CancelableRunnable() {