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database: reduce pruneLocks/Unlock transaction.

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pruneLocks could create deadlocked transactions on PostgreSQL if multiple locks expired and pruneLocks is called by multiple instances. Also adds some logging.
This commit is contained in:
Quentin Machu 2015-11-14 20:14:27 -05:00
parent 8bb6c50f80
commit b0142e1982
2 changed files with 26 additions and 7 deletions
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29
database/lock.go
View File

@ -68,20 +68,32 @@ func Lock(name string, duration time.Duration, owner string) (bool, time.Time) {
func Unlock(name, owner string) {
pruneLocks()
t := cayley.NewTransaction()
unlocked := 0
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 := cayley.NewTransaction()
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, ""))
err := store.ApplyTransaction(t)
if err != nil {
log.Errorf("failed transaction (Unlock): %s", err)
}
store.ApplyTransaction(t)
unlocked++
}
if it.Err() != nil {
log.Errorf("failed query in Unlock: %s", it.Err())
}
if unlocked > 1 {
// We should never see this, it would mean that our database doesn't ensure quad uniqueness
// and that the entire lock system is jeopardized.
log.Errorf("found inconsistency in Unlock: matched %d times a locked named: %s", unlocked, name)
}
}
// LockInfo returns the owner of a lock specified by its name and its
@ -109,7 +121,6 @@ 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) {
@ -123,12 +134,20 @@ func pruneLocks() {
if now.Unix() > tt {
log.Debugf("Lock %s owned by %s has expired.", n, o)
tr := cayley.NewTransaction()
tr.RemoveQuad(cayley.Quad(n, "locked", "locked", ""))
tr.RemoveQuad(cayley.Quad(n, "locked_until", t, ""))
tr.RemoveQuad(cayley.Quad(n, "locked_by", o, ""))
err := store.ApplyTransaction(tr)
if err != nil {
log.Errorf("failed transaction (pruneLocks): %s", err)
}
}
store.ApplyTransaction(tr)
}
if it.Err() != nil {
log.Errorf("failed query in Unlock: %s", it.Err())
}
}
// getLockedNodes returns every nodes that are currently locked

2
database/lock_test.go
View File

@ -35,7 +35,7 @@ func TestLock(t *testing.T) {
l, _ = Lock("test1", time.Minute, "owner2")
assert.False(t, l)
// Renew the lock
l, _ = Lock("test1", time.Minute, "owner1")
l, _ = Lock("test1", 2*time.Minute, "owner1")
assert.True(t, l)
// Unlock and then relock by someone else
Unlock("test1", "owner1")