cipd: instance cache

client/cipd/internal/messages/messages.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.
 
 syntax = "proto3";
 
+import "google/protobuf/timestamp.proto";
+
 package messages;
 
 // BlobWithSHA1 is a wrapper around a binary blob with SHA1 hash to verify
 // its integrity.
 message BlobWithSHA1 {
   bytes blob = 1;
   bytes sha1 = 2;
 }
 
 // TagCache stores a mapping (package name, tag) -> instance ID to speed up
 // subsequence ResolveVersion calls when tags are used.
 message TagCache {
   message Entry {
     string package = 1;
     string tag = 2;
     string instance_id = 3;
   }
 
   // Capped list of entries, most recently resolved is last.
   repeated Entry entries = 1;
 }
+
+// InstanceCache stores a list of instances in cache
+// and their last access time.
+message InstanceCache {
+  // Entry stores info about an instance.
+  message Entry {
+    // LastAccess is last time this instance was retrieved from or put to the
+    // cache.
+    google.protobuf.Timestamp last_access = 2;
+  }
+
+  // Entries is a map of {instance id -> information about instance}.
+  map<string, Entry> entries = 1;
+  // LastSynced is timestamp when we synchronized Entries with actual
+  // instance files.
+  google.protobuf.Timestamp last_synced = 2;
+}