chpr-worker
v3.2.3
Published
AMQP worker library
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chpr-worker
chpr-worker allows you to easily create a worker that take tasks from an AMQP queue. It handles common concerns related to implementing a worker with AMQP:
- Number of tasks handled at the same time
- Timeout after which the task is considered as failed
- Handle disconnections from the AMQP server
- Validating the schema of the message specifying the task
Note: this package is a wrapper for the stakhanov open-source package. It only adds our logger via dependency injection. For up-to-date documentation, please consult the stakhanov project's repository.
BREAKING CHANGE with version >= 2.x
It is not possible anymore to create a single worker by calling createWorker
:
const worker = workerlib.createWorker({...});
You should use createWorkers
for all worker creations.
WARNING
The queueName
configuration must be unique for each worker, otherwise messages won't necessarily
be routed to the good consumer.
When listening, the lib will create a queue of the form queueName.routingKey
for each routing
key/handler. That is why the queueName config must really be unique, typically of the form
application.workername
. This will generate a unique queue name per routing key, of the form
application.workername.routingkey
.
Example:
function* handle(msg) { ... };
function* validate(msg) { ... };
const worker = workerlib.createWorkers([{
handle: handle,
validate: validate,
routingKey: 'test.something_happened'
}], {
workerName: 'my worker',
amqpUrl: 'amqp://guest:guest@localhost:5672',
exchangeName: 'bus',
queueName: 'test.test_watcher'
}, {
channelPrefetch: 50,
taskTimeout: 30000,
processExitTimeout: 3000,
channelCloseTimeout: 500
});
Basic use
To listen on channel:
yield worker.listen();
To shutdown worker:
worker.close();
Remark: for testing purpose, as the close function will execute a process.exit, you can add the following parameter to the close function:
worker.close(false);
By default, the close
method will be called on SIGTERM/SIGINT signals and operate a graceful shutdown.
If you want to override this behaviour (not recommended for production workers),
you should specify closeOnSignals: false
as an option.
Events
To organize your own tests, the worker instance allows you to wait for specific event
with the wait
method.
Example:
yield worker.wait(worker.TASK_COMPLETED);
Spec:
wait(event, timeout)
The wait method returns a Promise which will be completed when the expected event occurs for the first time, or rejected after a timeout.
event
: name of the event, required. Must be one of the available events:
worker.TASK_COMPLETED
: emitted when a task has been completed.worker.TASK_RETRIED
: emitted when a task is going to be retried because the handler has failed.worker.TASK_FAILED
: emitted when a task has failed because the handler has failed on a task which was already being retried.worker.WORKER_CLOSED
: emitted when the worker has been closed.
timeout
: timeout in milliseconds after which the promise will be rejected. Defaults
to 1000 ms.
Dev Requirements
Install Node 6.
For nvm users, just move to the project directory and run :
nvm i
If you already have installed Node 6 before, just type:
nvm use