I'm writing my first dropwizard service. Typically I've used guava,
jetty/grizzly, jersey, etc. on my own and created Guava Services for each
and then a ServiceManager. In the dropwizard world, what is the best way to
create background processing services each with a health check?
Normally I would do this with something like a guava
AbstractExecutionThreadService for each. Maybe one reads an SQS queue and
puts things into a Database Batching blocking queue (that might be two
services). Then I'd take my Jetty Service, and two background services and
put them into a ServiceManager that I start in my main.
What's the best way to write these background services with dropwizard?
Should I do them the same way and then wrap them in Managed register each
managed and its healthcheck in main? Or does dropwizard have something else
I should use instead of the Guava AbstractExecutionThreadService?
That might look like this. But I feel like if that was the standard way to
do it I wouldn't have to write ManagedGuavaService and
GuavaServiceHealthCheck. So I'm thinking perhaps there is a better way to
do this, perhaps not even using Guava Services?
@Override
public void run(final MyConfiguration config, final Environment env) {
SqsQueue queue = new SqsQueue(config.getRegion(),
config.getQueueFullName());
AbstractExecutionThreadService queueConsumer =
queue.createConsumerService(System.out::println);
// Rest resource writes messages to the queue
ProviderResource resource = new ProviderResource(queue::send);
env.jersey().register(resource);
env.healthChecks().register("providers-api", new
ProviderResourceHealthCheck());
// Queue consumer thread to process the SQS queue
env.lifecycle().manage(new ManagedGuavaService(queueConsumer));
env.healthChecks().register("queue-consumer", new
GuavaServiceHealthCheck(queueConsumer));
}
static class ManagedGuavaService implements Managed {
private final Service service;
public ManagedGuavaService(Service service) {
this.service = service;
}
@Override
public void start() throws Exception {
service.startAsync();
}
@Override
public void stop() throws Exception {
service.stopAsync();
}
}
private static class GuavaServiceHealthCheck extends HealthCheck {
private final Service service;
public GuavaServiceHealthCheck(Service service) {
this.service = service;
}
@Override
protected Result check() throws Exception {
return service.isRunning()
? Result.healthy()
: Result.unhealthy(service.state().toString());
}
}
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