Blogs Single lock owner: an important step forward

Single lock owner: an important step forward

The single lock owner is a highly requested Infinispan improvement. The basic idea behind it is that, when writing to a key, locks are no longer acquired on all the nodes that own that key, but only on a single designated node (named "main owner").

How does it help me?

Short version: if you use transactions that concurrently write to the same keys, this improvement significantly increases your system' throughput.

Long version: If you’re using Infinispan with transactions that modify the same key(s) concurrently then you can easily end up in a deadlock. A deadlock can also occur if two transaction modify the same key at the same time - which is both inefficient and counter-intuitive. Such a deadlock means that at one transaction(or both) eventually rollback but also the lock on the key is held for the duration of a lockAquistionTimout config option (defaults to 10 seconds). These deadlocks reduces the throughput significantly as transactions threads are held inactive during deadlock time. On top of that, other transactions that want to operate on that key are also delayed, potentially resulting in a cascade effect.

What’s the added performance penalty?

The only encountered performance penalty is during cluster topology changes. At that point the cluster needs to perform some additional computation (no RPC involved) to fail-over the acquired locks from previous to new owners. Another noticeable aspect is that locks are now being released asynchronously, after the transaction commits. This doesn’t add any burden to the transaction duration, but it means that locks are being held slightly longer. That’s not something to be concerned about if you’re not using transactions that compete for same locks though. We plan to benchmark this feature using Radargun benchmark tool - we’ll report back!

Want to know more?

You can read the single lock owner design wiki or/and follow the JIRA JIRA discussions.

Get it, Use it, Ask us!

We’re hard at work on new features, improvements and fixes, so watch this space for more announcements!

Please, download and test the latest release.

The source code is hosted on GitHub. If you need to report a bug or request a new feature, look for a similar one on our JIRA issues tracker. If you don’t find any, create a new issue.

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