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If you work for Uber use the internal cadence-java-client-samples repository.

Java Cadence Samples

These samples demonstrate various capabilities of Java Cadence client and server. You can learn more about Cadence at:

Overview of the Samples

  • HelloWorld Samples

    The following samples demonstrate:

    • HelloActivity: a single activity workflow
    • HelloActivityRetry: how to retry an activity
    • HelloAsync: how to call activities asynchronously and wait for them using Promises
    • HelloAsyncLambda: how to run part of a workflow asynchronously in a separate task (thread)
    • HelloAsyncActivityCompletion: an asynchronous activity implementation
    • HelloChild: a child workflow
    • HelloException: exception propagation and wrapping
    • HelloQuery: a query
    • HelloSignal: sending and handling a signal
    • HelloPeriodic: a sample workflow that executes an activity periodically forever
  • FileProcessing demonstrates task routing features. The sample workflow downloads a file, processes it, and uploads the result to a destination. The first activity can be picked up by any worker. However, the second and third activities must be executed on the same host as the first one.

Get the Samples

Run the following commands:

  git clone https://github.com/uber/cadence-java-samples
  cd cadence-java-samples

Import into IntelliJ

In the IntelliJ user interface, navigate to File->New->Project from Existing Sources.

Select the cloned directory. In the Import Project page, select Import project from external model, choose Gradle and then click Next->Finish.

Build the Samples

  ./gradlew build

Run Cadence Server

Run Cadence Server using Docker Compose:

curl -O https://raw.githubusercontent.com/uber/cadence/master/docker/docker-compose.yml
docker-compose up

If this does not work, see the instructions for running Cadence Server at https://github.com/uber/cadence/blob/master/README.md.

Register the Domain

To register the sample domain, run the following command once before running any samples:

./gradlew -q execute -PmainClass=com.uber.cadence.samples.common.RegisterDomain

See Cadence UI

The Cadence Server running in a docker container includes a Web UI.

Connect to http://localhost:8088.

Enter the sample domain. You'll see a "No Results" page. After running any sample, change the filter in the top right corner from "Open" to "Closed" to see the list of the completed workflows.

Click on a RUN ID of a workflow to see more details about it. Try different view formats to get a different level of details about the execution history.

Install Cadence CLI

Check out Cadence Service and run make bins. CLI executable named cadence will be in the root directory.

To not pass the domain on every command set the following environment variable:

export CADENCE_CLI_DOMAIN=sample

After the CADENCE_CLI_DOMAIN is set, to list closed workflow executions run:

cadence workflow list

To see a history of a particular workflow execution run:

cadence workflow showid <WorkflowID>

To see a stack trace of a currently running workflow execution run:

./cadence workflow stack -w <WorkflowID>

Run the samples

Each sample has specific requirements for running it. The following sections contain information about how to run each of the samples after you've built them using the preceding instructions.

Hello World

To run the hello world samples:

./gradlew -q execute -PmainClass=com.uber.cadence.samples.hello.HelloActivity
./gradlew -q execute -PmainClass=com.uber.cadence.samples.hello.HelloActivityRetry
./gradlew -q execute -PmainClass=com.uber.cadence.samples.hello.HelloAsync
./gradlew -q execute -PmainClass=com.uber.cadence.samples.hello.HelloAsyncActivityCompletion
./gradlew -q execute -PmainClass=com.uber.cadence.samples.hello.HelloAsyncLambda
./gradlew -q execute -PmainClass=com.uber.cadence.samples.hello.HelloChild
./gradlew -q execute -PmainClass=com.uber.cadence.samples.hello.HelloException
./gradlew -q execute -PmainClass=com.uber.cadence.samples.hello.HelloPeriodic
./gradlew -q execute -PmainClass=com.uber.cadence.samples.hello.HelloQuery
./gradlew -q execute -PmainClass=com.uber.cadence.samples.hello.HelloSignal

File Processing

This sample has two executables. Execute each command in a separate terminal window. The first command runs the worker that hosts the workflow and activities implementation. To demonstrate that activities execute together, we recommend that you run more than one instance of this worker.

./gradlew -q execute -PmainClass=com.uber.cadence.samples.fileprocessing.FileProcessingWorker

The second command starts workflows. Each invocation starts a new workflow execution.

./gradlew -q execute -PmainClass=com.uber.cadence.samples.fileprocessing.FileProcessingStarter
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