adamw / elasticmq

Message queueing system with an actor-based Scala and Amazon SQS-compatible interfaces. Runs stand-alone or embedded.

Version Matrix



  • message queue system
  • runs stand-alone (download) or embedded
  • Amazon SQS-compatible interface
  • fully asynchronous implementation, no blocking calls

Created and maintained by SoftwareMill logo


ElasticMQ is a message queue system, offering an actor-based Scala and an SQS-compatible REST (query) interface.

ElasticMQ follows the semantics of SQS. Messages are received by polling the queue. When a message is received, it is blocked for a specified amount of time (the visibility timeout). If the message isn't deleted during that time, it will be again available for delivery. Moreover, queues and messages can be configured to always deliver messages with a delay.

The focus in SQS (and ElasticMQ) is to make sure that the messages are delivered. It may happen, however, that a message is delivered twice (if, for example, a client dies after receiving a message and processing it, but before deleting). That's why clients of ElasticMQ (and Amazon SQS) should be idempotent.

As ElasticMQ implements a subset of the SQS query (REST) interface, it is a great SQS alternative both for testing purposes (ElasticMQ is easily embeddable) and for creating systems which work both within and outside of the Amazon infrastructure.

The future will most probably bring even more exciting features :).


Installation: stand-alone

You can download the stand-alone distribution here: https://s3/.../elasticmq-server-0.13.9.jar

Java 8 or above is required for running the server.

Simply run the jar and you should get a working server, which binds to localhost:9324:

java -jar elasticmq-server-0.13.9.jar

ElasticMQ uses Typesafe Config for configuration. To specify custom configuration values, create a file (e.g. custom.conf), fill it in with the desired values, and pass it to the server:

java -Dconfig.file=custom.conf -jar elasticmq-server-0.13.9.jar

The config file may contain any configuration for Akka and ElasticMQ. Current ElasticMQ configuration values are:

include classpath("application.conf")

// What is the outside visible address of this ElasticMQ node
// Used to create the queue URL (may be different from bind address!)
node-address {
    protocol = http
    host = localhost
    port = 9324
    context-path = ""

rest-sqs {
    enabled = true
    bind-port = 9324
    bind-hostname = ""
    // Possible values: relaxed, strict
    sqs-limits = strict

// Should the node-address be generated from the bind port/hostname
// Set this to true e.g. when assigning port automatically by using port 0.
generate-node-address = false

queues {
    // See next section

You can also provide an alternative Logback configuration file (the default is configured to log INFO logs and above to the console):

java -Dlogback.configurationFile=my_logback.xml -jar elasticmq-server-0.13.9.jar

How are queue URLs created

Some of the responses include a queue URL. By default the urls will use http://localhost:9324 as the base URL. To customize, you should properly set the protocol/host/port/context in the node-address setting (see above).

You can also set to a special value, "*", which will cause any queue URLs created during a request to use the path of the incoming request. This might be useful e.g. in containerized (Docker) deployments.

Note that changing the bind-port and bind-hostname settings does not affect the queue URLs in any way unless generate-node-address is true. In that case, the bind host/port are used to create the node address. This is useful when the port should be automatically assigned (use port 0 in such case, the selected port will be visible in the logs).

Automatically creating queues on startup

Queues can be automatically created on startup by providing appropriate configuration:

The queues are specified in a custom configuration file. For example, create a custom.conf file with the following:

include classpath("application.conf")

queues {
    queue1 {
        defaultVisibilityTimeout = 10 seconds
        delay = 5 seconds
        receiveMessageWait = 0 seconds
        deadLettersQueue {
            name = "queue1-dead-letters"
            maxReceiveCount = 3 // from 1 to 1000
    queue1-dead-letters { }

All attributes are optional (except name and maxReceiveCount when a deadLettersQueue is defined).

Starting an embedded ElasticMQ server with an SQS interface

val server = SQSRestServerBuilder.start()
// ... use ...

If you need to bind to a different host/port, there are configuration methods on the builder:

val server = SQSRestServerBuilder.withPort(9325).withInterface("localhost").start()
// ... use ...

You can also set a dynamic port with a port value of 0 or by using the method withDynamicPort. To retrieve the port (and other configuration) when using a dynamic port value you can access the server via waitUntilStarted for example:

val server = SQSRestServerBuilder.withDynamicPort().start()

You can also provide a custom ActorSystem; for details see the javadocs.

Embedded ElasticMQ can be used from any JVM-based language (Java, Scala, etc.).

Using the Amazon Java SDK to access an ElasticMQ Server

To use Amazon Java SDK as an interface to an ElasticMQ server you just need to change the endpoint:

client = new AmazonSQSClient(new BasicAWSCredentials("x", "x"))

The endpoint value should be the same address as the NodeAddress provided as an argument to SQSRestServerBuilder or in the configuration file.

The rest-sqs-testing-amazon-java-sdk module contains some more usage examples.

Using the Amazon boto (Python) to access an ElasticMQ Server

To use Amazon boto as an interface to an ElasticMQ server you set up the connection using:

region = boto.sqs.regioninfo.RegionInfo(name='elasticmq',
conn = boto.connect_sqs(aws_access_key_id='x',

where sqs_endpoint and sqs_port are the host and port.

The boto3 interface is different:

client = boto3.resource('sqs',
queue = client.get_queue_by_name(QueueName='queue1')

ElasticMQ dependencies in SBT

// Scala 2.12 and 2.11
val elasticmqSqs        = "org.elasticmq" %% "elasticmq-rest-sqs"         % "0.13.9"

// Scala 2.10
val elasticmqSqs        = "org.elasticmq" %% "elasticmq-rest-sqs"         % "0.7.1"

If you don't want the SQS interface, but just use the actors directly, you can add a dependency only to the core module:

val elasticmqCore       = "org.elasticmq" %% "elasticmq-core"             % "0.13.9"

If you want to use a snapshot version, you will need to add the repository to your configuration.

ElasticMQ dependencies in Maven



If you want to use a snapshot version, you will need to add the repository to your configuration.

Replication, journaling, SQL backend

Until version 0.7.0, ElasticMQ included optional replication, journaling and an SQL message storage. These modules have been discontinued.

Current versions

Stable: 0.13.9, 0.8.12

Development: 0.13.9-SNAPSHOT


ElasticMQ uses Slf4j for logging. By default no logger backend is included as a dependency, however Logback is recommended.


Tests done on a 2012 MBP, 2.6GHz, 16GB RAM, no replication. Throughput is in messages per second (messages are small).

Directly accessing the client:

Running test for [in-memory], iterations: 10, msgs in iteration: 100000, thread count: 1.
Overall in-memory throughput: 21326.054040

Running test for [in-memory], iterations: 10, msgs in iteration: 100000, thread count: 2.
Overall in-memory throughput: 26292.956117

Running test for [in-memory], iterations: 10, msgs in iteration: 100000, thread count: 10.
Overall in-memory throughput: 25591.155697

Through the SQS REST interface:

Running test for [rest-sqs + in-memory], iterations: 10, msgs in iteration: 1000, thread count: 20.
Overall rest-sqs + in-memory throughput: 2540.553587

Running test for [rest-sqs + in-memory], iterations: 10, msgs in iteration: 1000, thread count: 40.
Overall rest-sqs + in-memory throughput: 2600.002600

Note that both the client and the server were on the same machine.

Test class: org.elasticmq.performance.LocalPerformanceTest.

Building, running, and packaging

To build and run with debug (this will listen for a remote debugger on port 5005):

~/workspace/elasticmq $ sbt -jvm-debug 5005
> project elasticmq-server
> run

To build a jar-with-dependencies:

~/workspace/elasticmq $ sbt
> project elasticmq-server
> assembly

Tests and coverage

To run the tests:

~/workspace/elasticmq $ sbt test

To check the coverage reports:

~/workspace/elasticmq $ sbt
> coverage
> tests
> coverageReport
> coverageAggregate

Although it's mostly only the core project that is relevant for coverage testing, each project's report can be found in their target directory:

  • core/target/scala-2.12/scoverage-report/index.html
  • common-test/target/scala-2.12/scoverage-report/index.html
  • rest/rest-sqs/target/scala-2.12/scoverage-report/index.html
  • server/target/scala-2.12/scoverage-report/index.html

The aggregate report can be found at target/scala-2.12/scoverage-report/index.html


  • Core: Scala and Akka.
  • Rest server: Akka HTTP, a high-performance, asynchronous, REST/HTTP toolkit.
  • Testing the SQS interface: Amazon Java SDK; see the rest-sqs-testing-amazon-java-sdk module for the testsuite.

Change log

Version 0.13.9 (13 March 2018)

  • bug fixes

Version 0.13.9 (25 June 2017)

  • bug fixes

Version 0.13.7 (24 June 2017)

  • bug fixes

Version 0.13.6 (22 June 2017)

  • bug fixes

Version 0.13.5 (26 May 2017)

  • bug fixes

Version 0.13.4 (16 May 2017)

  • fix akka dependencies
  • properly returned only requrested attributes

Version 0.13.3 (5 May 2017)

  • fix queue creation order in presence of DLQs
  • update dependencies, akka & akka-http

Version 0.13.2 (7 Feb 2017)

  • bug fix

Version 0.13.1 (26 Jan 2017)

  • add dummy add permission endpoint

Version 0.13.0 (25 Jan 2017)

  • add dead letter queue support (thx @mkorolyov)

Version 0.12.1 (13 Dec 2016)

  • remove TODOs which caused problems with .NET client

Version 0.12.0 (7 Dec 2016)

  • support for dynamic port allocation
  • node address is generated from bind address if not specified

Version 0.11.1 (30 Nov 2016)

  • bug fix

Version 0.11.0 (23 Nov 2016)

  • updating dependencies, using Akka HTTP 10, builds for Scala 2.11 and 2.12

Version 0.10.1 (31 Oct 2016)

  • fixing a bug with changing message visibility and long pooling

Version 0.10.0 (22 Sep 2016)

  • updating Akka and other dependencies

Version 0.9.3 (13 Apr 2016)

  • bug fix

Version 0.9.2 (8 Apr 2016)

  • fixes handling of wait time seconds equal to 0 when receiving messages

Version 0.9.1 (4 Apr 2016)

  • fixed bug to allow connecting using Perl client

Version 0.9.0 (23 Mar 2016)

  • replace Spray with Akka
  • increase message body size limits
  • provide an option to create queues on startup
  • add a special node-address setting: *, which uses the incoming request url to create queue urls

Version 0.8.12 (30 Sep 2015)

  • checking queue length if limits are strict

Version 0.8.11 (3 Sep 2015)

  • downgrading typesafe-config to keep Java6 compatibility

Version 0.8.10 (3 Sep 2015)

  • numeric attributes support (thx @sf-git)

Version 0.8.9 (10 Aug 2015)

  • binary attributes support (thx @brainoutsource)
  • dependency updates

Version 0.8.8 (10 Apr 2015)

  • dependency updates, bug fixes

Version 0.8.6, 0.8.7 (7 Feb 2015, 13 Feb 2015)

  • adding support for the QueueArn attribute

Version 0.8.5 (11 Dec 2014)

  • supporting PurgeQueue action instead of a custom one

Version 0.8.4 (2 Dec 2014)

  • custom action for clearing all messages from a queue

Version 0.8.3 (22 Oct 2014)

  • bug fixes
  • updating dependencies
  • publishing to Maven Central

Version 0.8.2 (6 Jun 2014)

  • increasing the bind timeout
  • initial support for String-valued message attributes (thx @hayesgm)

Version 0.8.1 (29 May 2014)

  • fixing Node.JS compatibility
  • fixing a bug when calculating queue attributes
  • updating to Scala 2.11.1, Akka 2.3.3

Version 0.8.0 (29 April 2014)

  • updating to Scala 2.11, Akka 2.3.2
  • updating libraries to latest versions

Version 0.7.1 (22 August 2013)

  • bug fixes

Version 0.7.0 (5 June 2013)

  • reimplemented using Akka and Spray (actor-based, no blocking)
  • long polling support
  • bug fixes

Version 0.6.3 (21 January 2013)

  • Scala 2.10 support
  • Changing the way the stand-alone server is configured

Version 0.6.2 (13 December 2012)

  • bug fixes
  • properly handling SQS receipt handles - message can be deleted only when passing the most recent receipt handle

Version 0.6.1 (18 November 2012)

  • using Sonatype's OSS repositories for releases
  • library upgrades

Version 0.6 (19 October 2012)

  • batch operations in SQS (send, receive, delete, change visibility)
  • changed SQSRestServerFactory to SQSRestServerBuilder
  • "strict" and "relaxed" modes when creating an SQS server: the limits enforced by SQS are optionally checked, e.g. for batch operations (max 10 messages), maximum message size (64KB). Strict by default.

Version 0.5 (26 May 2012)

  • stand-alone distribution (download)
  • file log for message storage (journal)
  • factoring out storage-database module, to decrease the dependencies of the core modules

Version 0.4 (27 Mar 2012)

  • replication

Version 0.3 (6 Feb 2012)

  • in-memory storage
  • new native API
  • bug fixes

Version 0.2 (12 Jan 2012)

  • new SQS functions support
  • testing with Amazon Java SDK
  • bug fixes

Version 0.1 (12 Oct 2011)

  • initial release
  • DB storage
  • SQS interface support