io.prometheus.metrics.exporter.httpserver.DefaultHandler Maven / Gradle / Ivy

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package io.prometheus.metrics.exporter.httpserver;

import com.sun.net.httpserver.HttpExchange;
import com.sun.net.httpserver.HttpHandler;

import java.io.IOException;
import java.nio.charset.StandardCharsets;

/**
 * Handler for the / endpoint
 */
public class DefaultHandler implements HttpHandler {

    private final byte[] responseBytes;
    private final String contentType;

    public DefaultHandler() {
        String responseString = "" +
                "\n" +
                "Prometheus Java Client\n" +
                "\n" +
                "Prometheus Java Client\n" +
                "Metrics Path\n" +
                "The metrics path is /metrics.\n" +
                "Name Filter\n" +
                "If you want to scrape only specific metrics, use the name[] parameter like this:\n" +
                "\n" +
                "/metrics?name[]=my_metric\n" +
                "\n" +
                "You can also use multiple name[] parameters to query multiple metrics:\n" +
                "\n" +
                "/metrics?name[]=my_metric_a&name=[]=my_metric_b\n" +
                "\n" +
                "The name[] parameter can be used by the Prometheus server for scraping. Add the following snippet to your scrape job configuration in prometheus.yaml:\n" +
                "\n" +
                "params:\n" +
                "    name[]:\n" +
                "        - my_metric_a\n" +
                "        - my_metric_b\n" +
                "\n" +
                "Debug Parameter\n" +
                "The Prometheus Java metrics library supports multiple exposition formats.\n" +
                "The Prometheus server sends the Accept header to indicate which format it accepts.\n" +
                "By default, the Prometheus server accepts OpenMetrics text format, unless the Prometheus server is started with feature flag --enable-feature=native-histograms,\n" +
                "in which case the default is Prometheus protobuf.\n" +
                "The Prometheus Java metrics library supports a debug query parameter for viewing the different formats in a Web browser:\n" +
                "\n" +
                "/metrics?debug=openmetrics: View OpenMetrics text format.\n" +
                "/metrics?debug=text: View Prometheus text format (this is the default when accessing the /metrics endpoint with a Web browser).\n" +
                "/metrics?debug=prometheus-protobuf: View a text representation of the Prometheus protobuf format.\n" +
                "\n" +
                "Note that the debug parameter is only for viewing different formats in a Web browser, it should not be used by the Prometheus server for scraping. The Prometheus server uses the Accept header for indicating which format it accepts.\n" +
                "\n" +
                "\n";
        this.responseBytes = responseString.getBytes(StandardCharsets.UTF_8);
        this.contentType = "text/html; charset=utf-8";
    }

    @Override
    public void handle(HttpExchange exchange) throws IOException {
        exchange.getResponseHeaders().set("Content-Type", contentType);
        exchange.getResponseHeaders().set("Content-Length", Integer.toString(responseBytes.length));
        exchange.sendResponseHeaders(200, responseBytes.length);
        exchange.getResponseBody().write(responseBytes);
        exchange.close();
    }
}