LogDog: Add collector service implementation.

server/internal/logdog/collector/coordinator.go

+// Copyright 2016 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 collector
+
+import (
+        "time"
+
+        "github.com/luci/luci-go/common/logdog/types"
+        log "github.com/luci/luci-go/common/logging"
+        "github.com/luci/luci-go/common/retry"
+        cc "github.com/luci/luci-go/server/internal/logdog/coordinatorClient"
+        "golang.org/x/net/context"
+)
+
+// CoordinatorClient is an interface to the methods in the Coordinator service
+// that the Collector uses.
+//
+// cc.Client implements this interface.
+type CoordinatorClient interface {
+        // RegisterStream registers a stream's state with the Coordinator. On success,
+        // it will return the Coordinator's view of the stream state.
+        //
+        // This operation is idempotent. It may return an errors.Transient error if
+        // a transient failure happened.
+        RegisterStream(context.Context, cc.State) (*cc.State, error)
+
+        // TerminateStream registers the stream's terminal index with the Coordinator.
+        // If successful, the terminal index was successfully registered.
+        //
+        // This operation is idempotent. It may return an errors.Transient error if
+        // a transient failure happened.
+        TerminateStream(ctx context.Context, p types.StreamPath, s []byte, idx types.MessageIndex) error
+}
+
+// RetryCoordinatorClient wraps a CoordinatorClient, retrying transient errors.
+type RetryCoordinatorClient struct {
+        // Client is the CoordinatorClient that is being wrapped.
+        Client CoordinatorClient
+
+        // G is the retry.Generator to use to generate retry.Iterator instances. If
+        // nil, retry.Default will be used.
+        F retry.Factory
+}
+
+// RegisterStream implements CoordinatorClient.
+func (c *RetryCoordinatorClient) RegisterStream(ctx context.Context, st cc.State) (rst *cc.State, err error) {
+        err = retry.Retry(ctx, c.retryFactory(), func() (err error) {
+                rst, err = c.Client.RegisterStream(ctx, st)
+                return
+        }, func(err error, d time.Duration) {
+                log.Fields{
+                        log.ErrorKey: err,
+                        "delay":      d,
+                }.Warningf(ctx, "Transient error registering stream. Retrying...")
+        })
+        return
+}
+
+// TerminateStream implements CoordinatorClient.
+func (c *RetryCoordinatorClient) TerminateStream(ctx context.Context, p types.StreamPath, s []byte, idx types.MessageIndex) error {
+        return retry.Retry(ctx, c.retryFactory(), func() error {
+                return c.Client.TerminateStream(ctx, p, s, idx)
+        }, func(err error, d time.Duration) {
+                log.Fields{
+                        log.ErrorKey: err,
+                        "delay":      d,
+                }.Warningf(ctx, "Transient error terminating stream. Retrying...")
+        })
+}
+
+func (c *RetryCoordinatorClient) retryFactory() retry.Factory {
+        var f retry.Factory
+        if c.F != nil {
+                f = c.F
+        } else {
+                f = retry.Default
+        }
+        return retry.TransientOnly(f)
+}