LogDog: Update to archival V2.

server/cmd/logdog_archivist/task.go

Index: server/cmd/logdog_archivist/task.go
diff --git a/server/cmd/logdog_archivist/task.go b/server/cmd/logdog_archivist/task.go
new file mode 100644
index 0000000000000000000000000000000000000000..d5ed6bc00edd4ac835e53da61e0db0d6a75ebfc0
--- /dev/null
+++ b/server/cmd/logdog_archivist/task.go
@@ -0,0 +1,58 @@
+// 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 main
+
+import (
+	"time"
+
+	"github.com/luci/luci-go/common/gcloud/pubsub"
+	log "github.com/luci/luci-go/common/logging"
+	"github.com/luci/luci-go/common/retry"
+	"golang.org/x/net/context"
+	gcps "google.golang.org/cloud/pubsub"
+)
+
+// pubsubArchiveTask implements the archivist.Task interface for a ArchiveTask
+// Pub/Sub message.
+type pubSubArchivistTask struct {
+	// Context is a cloud package authenticated Context that can be used for raw
+	// Pub/Sub interaction. This is necessary because ModifyAckDeadline is not
+	// available to the "new API" Client.
+	context.Context
+
+	// subscriptionName is the name of the subscription that this task was pulled
+	// from. This is NOT the full subscription path.
+	subscriptionName string
+	// msg is the message that this task is bound to.
+	msg *gcps.Message
+}
+
+func (t *pubSubArchivistTask) UniqueID() string {
+	// The Message's AckID is guaranteed to be unique for a single lease.
+	return t.msg.AckID
+}
+
+func (t *pubSubArchivistTask) Data() []byte {
+	return t.msg.Data
+}
+
+func (t *pubSubArchivistTask) AssertLease(c context.Context) error {
+	return retry.Retry(c, retry.Default, func() error {
+		// Call ModifyAckDeadline directly, since we need immediate confirmation of
+		// our continued ownership of the ACK. This will change the ACK's state
+		// from that expected by the Message Iterator's keepalive system; however,
+		// since we're extending it to the maximum deadline, worst-case the
+		// keepalive will underestimate it and aggressively modify it.
+		//
+		// In practice, we tell the keepalive to use the maximum ACK deadline too,
+		// so the disconnect will be minor at best.
+		return gcps.ModifyAckDeadline(t, t.subscriptionName, t.msg.AckID, pubsub.MaxACKDeadline)
+	}, func(err error, d time.Duration) {
+		log.Fields{
+			log.ErrorKey: err,
+			"delay":      d,
+		}.Warningf(c, "Failed to modify ACK deadline. Retrying...")
+	})
+}