Running a Worker Until Condition is met

Introduction - Custom Poll Worker

We can use a worker and keep it running until a condition is met. This is similar to the HTTP Poll task, where you can poll an HTTP endpoint until a specific condition is met. Having a worker do the same is useful when you don't have an endpoint to call directly from Conductor.

Code Sample

Complete source file on Github: ../workers/PollUntilConditionMeetsWorker.java

    @Override
    public TaskResult execute(Task task) {
        TaskResult taskResult = new TaskResult(task);
        if (!task.getInputData().containsKey(POLL_COUNTER)) {
            taskResult.addOutputData("message", "pollCounter param not found in input, will use default of " + defaultPollCount + " polls");
        }

        int pollCounter = Math.min(10, castToInt(task.getInputData().getOrDefault(POLL_COUNTER, defaultPollCount)));
        int pollIntervalSeconds = Math.min(10, castToInt(task.getInputData().getOrDefault(POLL_INTERVAL_SECONDS, 5)));

        // Add these to the output for context
        taskResult.addOutputData(POLL_INTERVAL_SECONDS, pollIntervalSeconds + " (this test task has a max limit of 10 seconds)");
        taskResult.addOutputData(POLL_COUNTER, pollCounter + " (this test task has a max limit of 10 iterations)");

        // We can read current iteration from the task output as the data will be retained on the worker when polled
        int currentIteration = castToInt(taskResult.getOutputData().getOrDefault(CURRENT_ITERATION, 0));

        // Increment the current iteration and set to the task output
        taskResult.addOutputData(CURRENT_ITERATION, ++currentIteration);
        taskResult.addOutputData("updatedTime", new Date().toString());

        // While condition is not met, keep task in progress
        if (currentIteration < pollCounter) {
            taskResult.setStatus(TaskResult.Status.IN_PROGRESS);
            // Set to configured seconds to callback, and you can set this to any value as per the requirements
            taskResult.setCallbackAfterSeconds(pollIntervalSeconds);
            return taskResult;
        }

        // Set task as completed now that the poll count condition is met
        taskResult.setStatus(TaskResult.Status.COMPLETED);
        return taskResult;
    }

In this example worker, we use the callbackAfterSeconds attribute to keep the worker in progress until a condition is met. This can be any arbitrary condition that our code defines.

Specifically, this example waits for the poll count to reach the input parameter pollCounter.

When you return a task as IN_PROGRESS with a callbackAfterSeconds value set, Conductor will schedule the same task instance to be polled exactly after the callbackAfterSeconds value.

We are leveraging the output data to hold the context across polls, and once it reaches the desired state, we exit IN_PROGRESS and mark the task as COMPLETED.

Go ahead and try this worker in a workflow in our playground environment. We have already configured this in our sandbox, so it should run when you test.

Language agnostic

Such workers can be implemented in any of the languages.