A replicated Akka Persistence journal backed by MongoDB Casbah.
| Technology | Version |
|---|---|
| Scala | 2.10.4, 2.11.1 - Cross Compiled |
| Akka | 2.3.4 or higher |
| Mongo | 2.4.8 or higher |
The mongo journal driver is now available on the Maven Central Snapshot Repo.
resolvers += "Sonatype OSS Snapshots" at "https://oss.sonatype.org/content/repositories/snapshots"
libraryDependencies ++= Seq(
"com.github.ddevore" %% "akka-persistence-mongo-casbah" % "0.7.3-SNAPSHOT" % "compile")
<dependency>
<groupId>com.github.ddevore</groupId>
<artifactId>akka-persistence-mongo-casbah_2.10</artifactId>
<version>0.7.3-SNAPSHOT</version>
</dependency>
<dependency>
<groupId>com.github.ddevore</groupId>
<artifactId>akka-persistence-mongo-casbah_2.11</artifactId>
<version>0.7.3-SNAPSHOT</version>
</dependency>
Build and install the journal plugin to your local Ivy cache with sbt publishLocal (requires sbt 0.13.2). It can then be included as dependency:
libraryDependencies += "com.github.ddevore" %% "akka-persistence-mongo-casbah" % "0.7.3-SNAPSHOT"
To activate the Mongo journal plugin, add the following line to your Akka application.conf:
akka.persistence.journal.plugin = "casbah-journal"
This will run the journal with its default settings. The default settings can be changed with the following configuration keys:
A comma-separated list of Mongo hosts. You can specify as many hosts as necessary, for example, connections to replica sets. The default value is mongodb://localhost:27017/store.messages. For more information on configuring the mongo-url see Connection String Uri Format.
A journal must support the following akka-persistence property:
When a processor's receive method is called with a Persistent message it can safely assume that this message has been successfully written to the journal.
As a result only the following write concerns are supported:
acknowledged[Safe] - Exceptions are raised for network issues and server errors; waits on a server for the write operation.journaled[JournalSafe] - Exceptions are raised for network issues, and server errors; the write operation waits for the server to group commit to the journal file on disk.replicas-acknowledged[ReplicasSafe] - Exceptions are raised for network issues and server errors; waits for at least 2 servers for the write operation.
The default write concern is journaled [JournalSafe]. To better understand MongoDB WriteConcern see Write Concern.
This is an Int value that sets the timeout for the journal write concern. The default is 10000 millis [10 Seconds].
To activate the Mongo snapshot plugin, add the following line to your Akka application.conf:
akka.persistence.snapshot-store.plugin = "casbah-snapshot-store"
This will run the snapshot-store with its default settings. The default settings can be changed with the following configuration keys:
A comma-separated list of Mongo hosts. You can specify as many hosts as necessary, for example, connections to replica sets. The default value is mongodb://localhost:27017/store.snapshots. For more information on configuring the mongo-url see Connection String Uri Format.
A snapshot-store must support the following akka-persistence property:
When a processor's receive method is called to persist a snapshot it can safely assume that snapshot has been successfully written.
As a result only the following write concerns are supported:
acknowledged[Safe] - Exceptions are raised for network issues and server errors; waits on a server for the write operation.journaled[JournalSafe] - Exceptions are raised for network issues, and server errors; the write operation waits for the server to group commit to the journal file on disk.replicas-acknowledged[ReplicasSafe] - Exceptions are raised for network issues and server errors; waits for at least 2 servers for the write operation.
The default write concern is journaled [JournalSafe]. To better understand MongoDB WriteConcern see Write Concern.
This is an Int value that sets the timeout for the snapshot-store write concern. The default is 10000 millis [10 Seconds].
Allows for the selection of the youngest of {n} snapshots that match the upper bound. This helps where a snapshot may not have persisted correctly because of a JVM crash. As a result an attempt to load the snapshot may fail but an older may succeed. This is an Int value that defaults to 3.
- All operations required by the Akka Persistence journal plugin API are supported.
- Message writes are batched to optimize throughput.
- When using channels, confirmation writes are batched to optimize throughput.
- Deletes (marked & permanent) are batched to optimize throughput.
- Sharding is not yet supported.
- Akka-Persistence is still considered experimental and as such the underlying api may change based on changes to Akka Persistence or user feedback.
Minimal performance testing is included against a native instance. In general the journal will persist around 7000 to 8000 messages per second.
There is an example application that implements Akka-Persistence command sourcing. In this example, the journal acts as a write-ahead-log for whatever persisted messages it recieves.
There is also an example application that implements Akka-Persistence event sourcing.