CODEWITHSUNDEEP
javaspringspring-bootdropwizardmetrics
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Always Learning

Reputation: 2743

Dropwizard Metrics Get Average Items Per REST Request

I would like to use Dropwizard metrics to get the average number of items in a list for each request my spring boot REST controller services. My controller takes in a string which is serialized into a RequestCollection. RequestCollection has a single List<Integer> ids field that consists of a list of ids. I'd like to know what the average number of items in the ids field is across all requests.

Controller

@RestController
@RequestMapping("/api")
public class ApiController {

    private MetricRegistry metricRegistry;

    public ApiController(MetricRegistry metricRegistry) {
        this.metricRegistry = metricRegistry;
    }

    @GetMapping
    public String getFooBarred(
            @RequestParam(value = "params") String requestItem
    ) {
        RequestCollection request = request = new ObjectMapper()
                .registerModule(new JavaTimeModule())
                .readValue(requestItem, RequestCollection.class);

        // Add metric here to metricRegistry for average number of items 
        // in RequestCollection across all requests.
        // RequestCollection has a single property which is a List<Integer> ids

        return "foobar";
    }
}

Here is the RequestCollection class whose ids field I would like to measure across all requests.

RequestCollection

public class RequestCollection {
    private List<Integer> ids;

    public RequestCollection() {
        this.ids = new ArrayList<>();
    }

    public List<Integer> getIds() {
        return ids;
    }
}

Upvotes: 1

Views: 1305

Answers (1)

Paul Samsotha
Paul Samsotha

Reputation: 209082

Out of the 5 main metric types, Guages, Counters, Histograms, Meters, and Timers, the one that suits your need the best would probably be the Histogram, which "measures the distribution of values in a stream of data: e.g., the number of results returned by a search".

Histogram itemCount
    = metrics.histogram(MetricRegistry.name(RequestCollection.class, "id-count"));

The in each request, just update the histogram with the count for the collection.

itemCount.update(collection.getIds().size());

The reporting will give you a few different of statistics, along with the mean, which is what you want

-- Histograms ----------------------------
com.example.RequestCollection.id-count
             count = 100
               min = 0
               max = 99
              mean = 45.47
            stddev = 31.65
            median = 45.00
              75% <= 73.00
              95% <= 94.00
              98% <= 99.00
              99% <= 99.00
            99.9% <= 99.00

Upvotes: 1

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