blob: e60d319cb6c4c7abfd326ffaae90b5cf114ba94f [file] [log] [blame]
// Copyright 2016 The LUCI Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package coordinator implements a minimal interface to the Coordinator service
// that is sufficient for Collector usage.
//
// The interface also serves as an API abstraction boundary between the current
// Coordinator service definition and the Collector's logic.
//
// Cache
//
// Coordinator methods are called very heavily during Collector operation. In
// production, the Coordinator instance should be wrapped in a Cache structure
// to locally cache Coordinator's known state.
//
// The cache is responsible for two things: Firstly, it coalesces multiple
// pending requests for the same stream state into a single Coordinator request.
// Secondly, it maintains a cache of completed responses to short-circuit the
// Coordinator.
//
// Stream state is stored internally as a Promise. This Promise is evaluated by
// querying the Coordinator. This interface is hidden to callers.
package coordinator