forked from quay/clair
/
lock.go
137 lines (114 loc) · 4.7 KB
/
lock.go
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// Copyright 2015 clair 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 database
import (
"strconv"
"time"
"github.com/barakmich/glog"
cerrors "github.com/coreos/clair/utils/errors"
"github.com/google/cayley"
"github.com/google/cayley/graph"
"github.com/google/cayley/graph/path"
)
// Lock tries to set a temporary lock in the database.
// If a lock already exists with the given name/owner, then the lock is renewed
//
// Lock does not block, instead, it returns true and its expiration time
// is the lock has been successfully acquired or false otherwise
func Lock(name string, duration time.Duration, owner string) (bool, time.Time) {
pruneLocks()
until := time.Now().Add(duration)
untilString := strconv.FormatInt(until.Unix(), 10)
// Try to get the expiration time of a lock with the same name/owner
currentExpiration, err := toValue(cayley.StartPath(store, name).Has("locked_by", owner).Out("locked_until"))
if err == nil && currentExpiration != "" {
// Renew our lock
if currentExpiration == untilString {
return true, until
}
t := cayley.NewTransaction()
t.RemoveQuad(cayley.Quad(name, "locked_until", currentExpiration, ""))
t.AddQuad(cayley.Quad(name, "locked_until", untilString, ""))
// It is not necessary to verify if the lock is ours again in the transaction
// because if someone took it, the lock's current expiration probably changed and the transaction will fail
return store.ApplyTransaction(t) == nil, until
}
t := cayley.NewTransaction()
t.AddQuad(cayley.Quad(name, "locked", "locked", "")) // Necessary to make the transaction fails if the lock already exists (and has not been pruned)
t.AddQuad(cayley.Quad(name, "locked_until", untilString, ""))
t.AddQuad(cayley.Quad(name, "locked_by", owner, ""))
glog.SetStderrThreshold("FATAL")
success := store.ApplyTransaction(t) == nil
glog.SetStderrThreshold("ERROR")
return success, until
}
// Unlock unlocks a lock specified by its name if I own it
func Unlock(name, owner string) {
pruneLocks()
t := cayley.NewTransaction()
it, _ := cayley.StartPath(store, name).Has("locked", "locked").Has("locked_by", owner).Save("locked_until", "locked_until").BuildIterator().Optimize()
defer it.Close()
for cayley.RawNext(it) {
tags := make(map[string]graph.Value)
it.TagResults(tags)
t.RemoveQuad(cayley.Quad(name, "locked", "locked", ""))
t.RemoveQuad(cayley.Quad(name, "locked_until", store.NameOf(tags["locked_until"]), ""))
t.RemoveQuad(cayley.Quad(name, "locked_by", owner, ""))
}
store.ApplyTransaction(t)
}
// LockInfo returns the owner of a lock specified by its name and its
// expiration time
func LockInfo(name string) (string, time.Time, error) {
it, _ := cayley.StartPath(store, name).Has("locked", "locked").Save("locked_until", "locked_until").Save("locked_by", "locked_by").BuildIterator().Optimize()
defer it.Close()
for cayley.RawNext(it) {
tags := make(map[string]graph.Value)
it.TagResults(tags)
tt, _ := strconv.ParseInt(store.NameOf(tags["locked_until"]), 10, 64)
return store.NameOf(tags["locked_by"]), time.Unix(tt, 0), nil
}
if it.Err() != nil {
log.Errorf("failed query in LockInfo: %s", it.Err())
return "", time.Time{}, ErrBackendException
}
return "", time.Time{}, cerrors.ErrNotFound
}
// pruneLocks removes every expired locks from the database
func pruneLocks() {
now := time.Now()
// Delete every expired locks
tr := cayley.NewTransaction()
it, _ := cayley.StartPath(store, "locked").In("locked").Save("locked_until", "locked_until").Save("locked_by", "locked_by").BuildIterator().Optimize()
defer it.Close()
for cayley.RawNext(it) {
tags := make(map[string]graph.Value)
it.TagResults(tags)
n := store.NameOf(it.Result())
t := store.NameOf(tags["locked_until"])
o := store.NameOf(tags["locked_by"])
tt, _ := strconv.ParseInt(t, 10, 64)
if now.Unix() > tt {
log.Debugf("Lock %s owned by %s has expired.", n, o)
tr.RemoveQuad(cayley.Quad(n, "locked", "locked", ""))
tr.RemoveQuad(cayley.Quad(n, "locked_until", t, ""))
tr.RemoveQuad(cayley.Quad(n, "locked_by", o, ""))
}
}
store.ApplyTransaction(tr)
}
// getLockedNodes returns every nodes that are currently locked
func getLockedNodes() *path.Path {
return cayley.StartPath(store, "locked").In("locked")
}