Switch to github.com/golang/dep for vendoring

Signed-off-by: Mrunal Patel <mrunalp@gmail.com>

vendor/k8s.io/kubernetes/pkg/storage/etcd3/compact.go

@@ -0,0 +1,161 @@
+/*
+Copyright 2016 The Kubernetes 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 etcd3
+
+import (
+	"strconv"
+	"sync"
+	"time"
+
+	"github.com/coreos/etcd/clientv3"
+	"github.com/golang/glog"
+	"golang.org/x/net/context"
+)
+
+const (
+	compactInterval = 5 * time.Minute
+	compactRevKey   = "compact_rev_key"
+)
+
+var (
+	endpointsMapMu sync.Mutex
+	endpointsMap   map[string]struct{}
+)
+
+func init() {
+	endpointsMap = make(map[string]struct{})
+}
+
+// StartCompactor starts a compactor in the background to compact old version of keys that's not needed.
+// By default, we save the most recent 10 minutes data and compact versions > 10minutes ago.
+// It should be enough for slow watchers and to tolerate burst.
+// TODO: We might keep a longer history (12h) in the future once storage API can take advantage of past version of keys.
+func StartCompactor(ctx context.Context, client *clientv3.Client) {
+	endpointsMapMu.Lock()
+	defer endpointsMapMu.Unlock()
+
+	// In one process, we can have only one compactor for one cluster.
+	// Currently we rely on endpoints to differentiate clusters.
+	for _, ep := range client.Endpoints() {
+		if _, ok := endpointsMap[ep]; ok {
+			glog.V(4).Infof("compactor already exists for endpoints %v", client.Endpoints())
+			return
+		}
+	}
+	for _, ep := range client.Endpoints() {
+		endpointsMap[ep] = struct{}{}
+	}
+
+	go compactor(ctx, client, compactInterval)
+}
+
+// compactor periodically compacts historical versions of keys in etcd.
+// It will compact keys with versions older than given interval.
+// In other words, after compaction, it will only contain keys set during last interval.
+// Any API call for the older versions of keys will return error.
+// Interval is the time interval between each compaction. The first compaction happens after "interval".
+func compactor(ctx context.Context, client *clientv3.Client, interval time.Duration) {
+	// Technical definitions:
+	// We have a special key in etcd defined as *compactRevKey*.
+	// compactRevKey's value will be set to the string of last compacted revision.
+	// compactRevKey's version will be used as logical time for comparison. THe version is referred as compact time.
+	// Initially, because the key doesn't exist, the compact time (version) is 0.
+	//
+	// Algorithm:
+	// - Compare to see if (local compact_time) = (remote compact_time).
+	// - If yes, increment both local and remote compact_time, and do a compaction.
+	// - If not, set local to remote compact_time.
+	//
+	// Technical details/insights:
+	//
+	// The protocol here is lease based. If one compactor CAS successfully, the others would know it when they fail in
+	// CAS later and would try again in 10 minutes. If an APIServer crashed, another one would "take over" the lease.
+	//
+	// For example, in the following diagram, we have a compactor C1 doing compaction in t1, t2. Another compactor C2
+	// at t1' (t1 < t1' < t2) would CAS fail, set its known oldRev to rev at t1', and try again in t2' (t2' > t2).
+	// If C1 crashed and wouldn't compact at t2, C2 would CAS successfully at t2'.
+	//
+	//                 oldRev(t2)     curRev(t2)
+	//                                  +
+	//   oldRev        curRev           |
+	//     +             +              |
+	//     |             |              |
+	//     |             |    t1'       |     t2'
+	// +---v-------------v----^---------v------^---->
+	//     t0           t1             t2
+	//
+	// We have the guarantees:
+	// - in normal cases, the interval is 10 minutes.
+	// - in failover, the interval is >10m and <20m
+	//
+	// FAQ:
+	// - What if time is not accurate? We don't care as long as someone did the compaction. Atomicity is ensured using
+	//   etcd API.
+	// - What happened under heavy load scenarios? Initially, each apiserver will do only one compaction
+	//   every 10 minutes. This is very unlikely affecting or affected w.r.t. server load.
+
+	var compactTime int64
+	var rev int64
+	var err error
+	for {
+		select {
+		case <-time.After(interval):
+		case <-ctx.Done():
+			return
+		}
+
+		compactTime, rev, err = compact(ctx, client, compactTime, rev)
+		if err != nil {
+			glog.Errorf("etcd: endpoint (%v) compact failed: %v", client.Endpoints(), err)
+			continue
+		}
+	}
+}
+
+// compact compacts etcd store and returns current rev.
+// It will return the current compact time and global revision if no error occurred.
+// Note that CAS fail will not incur any error.
+func compact(ctx context.Context, client *clientv3.Client, t, rev int64) (int64, int64, error) {
+	resp, err := client.KV.Txn(ctx).If(
+		clientv3.Compare(clientv3.Version(compactRevKey), "=", t),
+	).Then(
+		clientv3.OpPut(compactRevKey, strconv.FormatInt(rev, 10)), // Expect side effect: increment Version
+	).Else(
+		clientv3.OpGet(compactRevKey),
+	).Commit()
+	if err != nil {
+		return t, rev, err
+	}
+
+	curRev := resp.Header.Revision
+
+	if !resp.Succeeded {
+		curTime := resp.Responses[0].GetResponseRange().Kvs[0].Version
+		return curTime, curRev, nil
+	}
+	curTime := t + 1
+
+	if rev == 0 {
+		// We don't compact on bootstrap.
+		return curTime, curRev, nil
+	}
+	if _, err = client.Compact(ctx, rev); err != nil {
+		return curTime, curRev, err
+	}
+	glog.Infof("etcd: compacted rev (%d), endpoints (%v)", rev, client.Endpoints())
+	return curTime, curRev, nil
+}