Getting Started¶
The best way to get to know Pravega is to start it up and run a sample Pravega application.
Running Pravega is Simple¶
Verify the following prerequisite
Java 11
Download Pravega
Download the Pravega release from the Github Releases.
If you prefer to build Pravega yourself, you can download the code and run ./gradlew distribution. More
details are shown in the Pravega README.
$ tar xfvz pravega-<version>.tgz
Run Pravega in standalone mode
This launches all the components of Pravega on your local machine.
Note: This is for testing/demo purposes only, do not use this mode of deployment in Production!
In order to remotely troubleshoot Java application, JDWP port is being used. The default JDWP port in Pravega(8050) can be overridden using the below command before starting Pravega in standalone mode. 0 to 65535 are allowed range of port numbers.
$ export JDWP_PORT=8888
More options and additional ways to run Pravega can be found in Running Pravega guide.
$ cd pravega-<version>
$ ./bin/pravega-standalone
The command above runs Pravega locally for development and testing purposes. It does not persist in the storage tiers like we do with a real deployment of Pravega and as such you shouldn't expect it to recover from crashes, and further, not rely on it for production use. For production use, we strongly encourage a full deployment of Pravega.
Running a sample Pravega Application¶
We have developed a few samples to introduce the developer to coding with Pravega here: Pravega Samples.
Download and run the "Hello World" Pravega sample reader and writer applications. Pravega dependencies will be pulled from maven central.
Note: The samples can also use a locally compiled version of Pravega. For more information, please see the README note on maven publishing.
Download the Pravega-Samples git repo
$ git clone https://github.com/pravega/pravega-samples
$ cd pravega-samples
Generate the scripts to run the applications
$ ./gradlew installDist
Run the sample "HelloWorldWriter"
This runs a simple Java application that writes a "hello world" message as an event into a Pravega stream.
$ cd pravega-samples/pravega-client-examples/build/install/pravega-client-examples
$ ./bin/helloWorldWriter
...
Writing message: 'hello world' with routing-key: 'helloRoutingKey' to stream 'examples / helloStream'
...
Run the sample "HelloWorldReader"
$ cd pravega-samples/pravega-client-examples/build/install/pravega-client-examples
$ ./bin/helloWorldReader
Example HelloWorldReader output
...
Reading all the events from examples/helloStream
...
Read event 'hello world'
No more events from examples/helloStream
...
See the README file in the pravega-client-examples for more details on running the HelloWorldReader application.
Serializers
The Java client by has multiple built in serializers: UTF8StringSerializer, ByteArraySerializer, ByteBufferSerializer, and JavaSerializer.
Additional pre-made serializers are available in: https://github.com/pravega/pravega-serializer You can also write your own implementation of the interface.