LogDog: Update protobufs, add support library.

common/logdog/protocol/butler.proto

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package protocol;
 
 import "log.proto";
 import "types.proto";
 
 /*
+ * ButlerMetadata appears as a frame at the beginning of Butler published data
+ * to describe the remainder of the contents.

[tandrii(chromium), 2015/08/11 17:41:37]

I'm not sure that's the best way to achieve what you want. Maybe ask
protobuf-gurus on our team? I'll let someone else approve this change.

[dnj, 2015/08/11 18:20:37]

What do you mean?

+ */
+message ButlerMetadata {
+        /*
+         * This enumerates the possible contents of published Butler data.
+         */
+        enum ContentType {
+                /* The published data is a ButlerLogBundle protobuf message. */
+                ButlerLogBundle = 1;
+        }
+        /* This is the type of data in the subsequent frame. */
+        optional ContentType type = 1;
+
+        /* If true, the content data is compressed. */
+        optional bool compressed = 2;
+}
+
+
+/*
  * A message containing log data in transit from the Butler.
  *
  * The Butler is capable of conserving bandwidth by bundling collected log
  * messages together into this protocol buffer. Based on Butler bundling
  * settings, this message can represent anything from a single LogRecord to
  * multiple LogRecords belonging to several different streams.
  *
  * Entries in a Log Bundle are fully self-descriptive: no additional information
  * is needed to fully associate the contained data with its proper place in
  * the source log stream.
@@ skipping 50 matching lines @@
      * registered with the Coordinator. The largest stream prefix in this Entry
      * will be bound the stream's LogEntry records to [0:largest_prefix]. Once
      * all messages in that range have been received, the log may be archived.
      *
      * Further log entries belonging to this stream with stream indices
      * exceeding the terminal log's index will be discarded.
      */
     optional bool terminal = 3;
 
     /*
+     * If terminal is true, this is the terminal stream index; that is, the last
+     * message index in the stream.
+     */
+    optional uint64 terminal_index = 4;
+
+    /*
      * Log entries attached to this record. These must be sequential and in
      * order.
      *
      * This is the main log entry content.
      */
-    repeated protocol.LogEntry logs = 4;
+    repeated protocol.LogEntry logs = 5;
   }
 
   /**
    * Each Entry is an individual set of log records for a given log stream.
    */
   repeated Entry entries = 5;
 }