Tuesday, July 24, 2012

Datomic Free Edition

We're happy to announce today the release of Datomic Free Edition. This edition is oriented around making Datomic easier to get, and use, for open source and smaller production deployments.
  • Datomic Free Edition is ... free!
  • The system supports transactor-local storage
  • The peer library includes a memory database and Datomic Datalog
  • The Free transactor and peers are freely redistributable 
  • The transactor supports 2 simultaneous peers
Of particular note here is that Datomic Free Edition comes with a redistributable license, and does not require a personal/business-specific license from us. That means you can download Datomic Free, build e.g. an open source application with it, and ship/include Datomic Free binaries with your software. You can also put the Datomic Free bits into public repositories and package managers (as long as you retain the licenses and copyright notices).

There is a ton of capability included in the Free Edition, including the Datomic in-process memory database (great for testing), and the Datomic datalog engine, which works on both Datomic databases and in-memory collections. That's right, free datalog for everyone.

You can use Datomic Free Edition in production, and you can use it in commercial applications.

Datomic Free edition is completely API-compatible with what we are now calling Datomic Pro edition (the one that pays the bills). Datomic Pro adds the ability to use additional storages like SQL and DynamoDB, support for more peers, as well as high-availabilty mode for transactors and our new memcache support.

You can read about the editions here. 

Memcache Support

We're happy to announce today transparent integrated support for memcached in Datomic Pro Edition.

One of the nice things about the Datomic architecture is that the index segments kept in storage are immutable. That enables them to be cached extensively. Currently that caching happens inside the peers, which keep segments they have needed thus far in the application process heap.

While this is great for process-local working sets, there is only so much a single machine can cache. So, we've added support for an optional second tier of distributed, shared cache, leveraging a memcached cluster. This tier of cache can be as large as you wish, and is shared between all the peers.

The entire use of memcached is automatic and integrated - just provide the endpoints of your memcached cluster in configuration. The peer protocols will automatically both look in it, and populate it on cache misses. Being based upon immutability, there are no cache coherence problems nor expiration policy woes.

The architecture incorporating memcached looks like this:



The benefits of this are many:


  • You can get a shared cache of arbitrary size - many deployments will be able to fit their entire database in memcached if desired. 
  • If you are using a storage that is not otherwise distributed (e.g. unclustered PostgreSQL), the memcached tier can both almost entirely remove the read load on the single server and distribute it.
  • Even when using a distributed storage like DynamoDB, the memcached tier can reduce your read provisioning and increase speed.
  • Developers can set up a small memcached daemon locally so their DB will always feel 'hot' across process restarts.
  • The memcached tier will enable hybrid strategies where the peers, transactors and memcached are all local but the storage is remote (e.g. DynamoDB).

Datomic is a good citizen in its use of memcached - it doesn't need to 'own' the cluster, and all of the Datomic keys incorporate UUIDs so they won't conflict with other application-level use of the same memcached cluster.

We hope you enjoy this feature, which is included in the Pro Edition at no extra charge.

Datomic Editions and Pricing

Over the past few months we've gotten feedback and input regarding our pricing and licensing, and we've revamped them to make things simpler and clearer. The subscription pricing made people feel as if the offering was a service (it's not), as well as brought about misgivings about termination etc, so we've dropped it. 


Here's the new offering:


  • We've added Datomic Free Edition - it's free and redistributable
  • Datomic Pro is licensed software.
  • It is offered with a perpetual license.
  • Maintenance (updates and support) for the first 12 months is included.
  • Maintenance in subsequent years is ~50% of the license fee.
  • Pricing is yearly, and up front on web site.
  • Pricing is based upon the number of processes (transactors + peers) using the software in production in your organization.
  • Development and testing usage doesn't count against your license limits


We've priced it such that the expenditure for maintenance roughly correlates to our older subscription pricing.


Evaluation has changed a bit as well. In all modes, Datomic Pro will require a license key. You can get a free 30-day eval key via the web site. There is no longer a 'runs for a week without a key' mode.


Note that Datomic is not just for cloud deployments - our SQL and other storage support lets you run it on-premise or in the cloud.


You can get more information on the editions and pricing here.