WSO2 IS - Promethus Servelet

IdentityMetricsServlet.java

package org.wso2.carbon.identity.sample.prometheus.servlet;

import io.prometheus.client.CollectorRegistry;
import io.prometheus.client.exporter.common.TextFormat;

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.Writer;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;

public class IdentityMetricsServlet extends HttpServlet {

    public static final String CONTEXT = "/prometheus_metrics";

    @Override
    protected void doGet(final HttpServletRequest req, final HttpServletResponse resp)
            throws IOException {
        resp.setStatus(HttpServletResponse.SC_OK);
        resp.setContentType(TextFormat.CONTENT_TYPE_004);

        try (Writer writer = new BufferedWriter(resp.getWriter())) {
            TextFormat.write004(writer, CollectorRegistry.defaultRegistry.filteredMetricFamilySamples(parse(req)));
            writer.flush();
        }
    }

    private Set<String> parse(HttpServletRequest req) {
        String[] includedParam = req.getParameterValues("name[]");
        if (includedParam == null) {
            return Collections.emptySet();
        } else {
            return new HashSet<>(Arrays.asList(includedParam));
        }
    }

    @Override
    protected void doPost(final HttpServletRequest req, final HttpServletResponse resp)
            throws IOException {
        doGet(req, resp);
    }
}