How to launch local DynamoDB programmatically?

Question

I am able to launch a local DynamoDB server from bash through this command:

java -Djava.library.path=./DynamoDBLocal_lib -jar DynamoDBLocal.jar -sharedD         


        

Answer 1

EDIT: September 23rd 2015

There was an announcement on Aug 3, 2015 that now adds the ability to have an embedded DynamoDB local running in the same process. You can add a Maven test dependency and use one of the ways below to run it.

<!--Dependency:-->
<dependencies>
    <dependency>
       <groupId>com.amazonaws</groupId>
       <artifactId>DynamoDBLocal</artifactId>
       <version>[1.11,2.0)</version>
    </dependency>
</dependencies>
<!--Custom repository:-->
<repositories>
    <repository>
       <id>dynamodb-local-oregon</id>
       <name>DynamoDB Local Release Repository</name>
       <url>https://s3-us-west-2.amazonaws.com/dynamodb-local/release</url>
    </repository>
</repositories>

And here is an example taken from the awslabs/aws-dynamodb-examples Github repository:

AmazonDynamoDB dynamodb = null;
try {
    // Create an in-memory and in-process instance of DynamoDB Local that skips HTTP
    dynamodb = DynamoDBEmbedded.create().amazonDynamoDB();
    // use the DynamoDB API with DynamoDBEmbedded
    listTables(dynamodb.listTables(), "DynamoDB Embedded");
} finally {
    // Shutdown the thread pools in DynamoDB Local / Embedded
    if(dynamodb != null) {
        dynamodb.shutdown();
    }
}

// Create an in-memory and in-process instance of DynamoDB Local that runs over HTTP
final String[] localArgs = { "-inMemory" };
DynamoDBProxyServer server = null;
try {
    server = ServerRunner.createServerFromCommandLineArgs(localArgs);
    server.start();

    dynamodb = AmazonDynamoDBClientBuilder.standard().withEndpointConfiguration(
        // we can use any region here
        new AwsClientBuilder.EndpointConfiguration("http://localhost:8000", "us-west-2"))
        .build();

    // use the DynamoDB API over HTTP
    listTables(dynamodb.listTables(), "DynamoDB Local over HTTP");
} finally {
    // Stop the DynamoDB Local endpoint
    if(server != null) {
        server.stop();
    }
}

---

Old answer

Like you said, there is currently no built-in way from DynamoDBLocal or the SDK to do this right now. It would be nice if there was an embedded DynamoDBLocal that you could start up in the same process.

Here is a simple workaround/solution using java.lang.Process to start it up and shut it down programmatically in case others are interested.

Documentation for DynamoDBLocal can be found here and here are the current definition of the arguments:

• -inMemory — Run in memory, no file dump
• -port 4000 — Communicate using port 4000.
• -sharedDb — Use a single database file, instead of separate files for each credential and region

Note that this is using the most recent version of DynamoDBLocal as of August 5th, 2015.

final ProcessBuilder processBuilder = new ProcessBuilder("java",
        "-Djava.library.path=./DynamoDBLocal_lib",
        "-jar",
        "DynamoDBLocal.jar",
        "-sharedDb",
        "-inMemory",
        "-port",
        "4000")
        .inheritIO()
        .directory(new File("/path/to/dynamo/db/local"));

final Process process = processBuilder.start();

Runtime.getRuntime().addShutdownHook(new Thread() {
    @Override
    public void run() {
        System.out.println("Shutdown DynamoDBLocal");
        process.destroy();
        try {
            process.waitFor(3, TimeUnit.SECONDS);
        } catch (InterruptedException e) {
            System.out.println("Process did not terminate after 3 seconds.");
        }
        System.out.println("DynamoDBLocal isAlive=" + process.isAlive());
    }
});
// Do some stuff

Answer 2

Write a gradle task to extract the Dynamodb-Local zip and now you can use https://github.com/marcoVermeulen/gradle-spawn-plugin gradle plugin to launch the dynamodb local. It is very easy to use and no need to do any process builder magic.

Sample code -

// to start dynamodb-local
task launch(type: SpawnProcessTask) {
    println("Launching....")
    command "java -Djava.library.path=/location/to/dynamodb-local/DynamoDBLocal_lib -jar /location/to/dynamodb-local/DynamoDBLocal.jar -inMemory -delayTransientStatuses"
    ready "Initializing DynamoDB Local"
}

// to stop dynamodb-local process
task stop(type: KillProcessTask)