Fix sparse index handling, add index params.

logdog/api/logpb/log.proto

 // Copyright 2015 The LUCI Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 syntax = "proto3";
 
 package logpb;
 
 import "google/protobuf/timestamp.proto";
 import "google/protobuf/duration.proto";
@@ skipping 245 matching lines @@
    * A series of ascending-ordered Entry messages representing snapshots of an
    * archived log stream.
    *
    * Within this set of Entry messages, the "offset", "prefix_index",
    * "stream_index", and "time_offset" fields will be ascending.
    *
    * The frequency of Entry messages is not defined; it is up to the Archivist
    * process to choose a frequency.
    */
   repeated Entry entries = 2;
+
+  /**

[dnj, 2016/10/17 22:12:12]

New fields, backwards-compatible with old protobufs. All are good to have, only
"last_stream_index" is used ATM.

+   * The last prefix index in the log stream.
+   *
+   * This is optional. If zero, there is either no information about the last
+   * prefix index, or there are zero entries in the prefix.
+   */
+  uint64 last_prefix_index = 3;
+  /**
+   * The last stream index in the log stream.
+   *
+   * This is optional. If zero, there is either no information about the last
+   * stream index, or there are zero entries in the stream.
+   */
+  uint64 last_stream_index = 4;
+  /**
+   * The number of log entries in the stream.
+   *
+   * This is optional. If zero, there is either no information about the number
+   * of log entries, or there are zero entries in the stream.
+   */
+  uint64 log_entry_count = 5;
 }