dropwizard metrics and API timing - dropwizard

Question

I'm trying to do very simple performance measurement of some of my APIs to determine how long they take.
I've added a test resource:
private static final MetricRegistry metrics = new MetricRegistry();
private final Timer responses = metrics.timer("test_responses");
#GET
public void test() {
final Timer.Context context = responses.time();
try {
log.info("sleeping...");
Thread.sleep(10*1000);
} catch (InterruptedException e) {
} finally {
context.stop();//2
}
}
and added the folllowing to my main Application class:
ConsoleReporter reporter = ConsoleReporter.forRegistry(metrics).convertRatesTo(TimeUnit.SECONDS).convertDurationsTo(TimeUnit.MILLISECONDS).build();
reporter.start(10, TimeUnit.SECONDS);
Every ten seconds I see:
6/13/16 11:38:51 AM ============================================================
6/13/16 11:39:01 AM ============================================================
But nothing provided about the "test_responses" metric I created. Any help is greatly appreciated!

Answer 1

Your issue is that you use 2 instances of the metric registry. Look at this example:
public class Application extends io.dropwizard.Application<Configuration>{
#Override
public void run(Configuration configuration, Environment environment) throws Exception {
MetricRegistry metrics = environment.metrics();
environment.jersey().register(new HelloResource(metrics));
ConsoleReporter.forRegistry(metrics).build().start(1, TimeUnit.SECONDS);;
}
public static void main(String[] args) throws Exception {
new Application().run("server", "/home/artur/dev/repo/sandbox/src/main/resources/config/test.yaml");
}
}
I am using the metrics registry that DW creates for you. This MR also includes the Jetty stats.
My resource:
#Path("/test")
#Produces(MediaType.APPLICATION_JSON)
#Consumes(MediaType.APPLICATION_JSON)
public class HelloResource {
private MetricRegistry service;
public HelloResource(MetricRegistry service) {
this.service = service;
}
#GET
public String hello() {
Timer timer = service.timer("test");
try(Context t = timer.time()) {
return "Hello World";
}
}
}
And the output:
test
count = 3
mean rate = 0.89 calls/second
1-minute rate = 0.00 calls/second
5-minute rate = 0.00 calls/second
15-minute rate = 0.00 calls/second
min = 0.00 milliseconds
max = 0.01 milliseconds
mean = 0.00 milliseconds
stddev = 0.00 milliseconds
median = 0.00 milliseconds
75% <= 0.01 milliseconds
95% <= 0.01 milliseconds
98% <= 0.01 milliseconds
99% <= 0.01 milliseconds
99.9% <= 0.01 milliseconds
I have invoked the test method 3 times, and you can see the stats recorded by the MetricRegistry.
I hope that solves your issue.
Regards,
artur