1 files changed, 73 insertions, 0 deletions
diff --git a/container-core/src/main/java/com/yahoo/container/jdisc/state/PrometheusHelper.java b/container-core/src/main/java/com/yahoo/container/jdisc/state/PrometheusHelper.java
new file mode 100644
index 00000000000..ca12e8161a9
--- /dev/null
+++ b/container-core/src/main/java/com/yahoo/container/jdisc/state/PrometheusHelper.java
@@ -0,0 +1,73 @@
+// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.container.jdisc.state;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.OutputStream;
+import java.util.Map;
+
+import static com.yahoo.container.jdisc.state.JsonUtil.sanitizeDouble;
+
+/**
+ * @author olaa
+ */
+public class PrometheusHelper {
+
+    private static final String HELP_LINE = "# HELP %s\n# TYPE %s untyped\n";
+    private static final String METRIC_LINE = "%s{%s} %s %d\n";
+
+    protected static byte[] buildPrometheusOutput(MetricSnapshot metricSnapshot, String application, long timestamp) throws IOException {
+        var outputStream = new ByteArrayOutputStream();
+
+        for (Map.Entry<MetricDimensions, MetricSet> snapshotEntry : metricSnapshot) {
+            var metricDimensions = snapshotEntry.getKey();
+            var metricSet = snapshotEntry.getValue();
+
+            var dimensionBuilder = new StringBuilder();
+            for (var dimension : metricDimensions) {
+                dimensionBuilder.append(dimension.getKey()).append("=\"").append(dimension.getValue()).append("\",");
+            }
+            dimensionBuilder.append("vespa_service=\"").append(application).append("\",");
+            var dimensions = dimensionBuilder.toString();
+
+            for (var metric : metricSet) {
+                var metricName = metric.getKey();
+                var metricValue = metric.getValue();
+
+                if (metricValue instanceof CountMetric) {
+                    var sanitizedMetricName = getSanitizedMetricName(metricName, "count");
+                    var value = ((CountMetric) metricValue).getCount();
+                    outputStream.write(getMetricLines(sanitizedMetricName, dimensions, value, timestamp));
+                } else if (metricValue instanceof GaugeMetric) {
+                    var gauge = (GaugeMetric) metricValue;
+                    writeGaugeMetrics(outputStream, metricName, gauge, dimensions, timestamp);
+                }
+            }
+        }
+        return outputStream.toByteArray();
+    }
+
+    private static void writeGaugeMetrics(OutputStream outputStream, String metricName, GaugeMetric gaugeMetric, String dimensions, long timestamp) throws IOException {
+        var sanitizedMetricName = getSanitizedMetricName(metricName, "last");
+        var value = sanitizeDouble(gaugeMetric.getLast());
+        outputStream.write(getMetricLines(sanitizedMetricName, dimensions, value, timestamp));
+
+        sanitizedMetricName = getSanitizedMetricName(metricName, "average");
+        value = sanitizeDouble(gaugeMetric.getAverage());
+        outputStream.write(getMetricLines(sanitizedMetricName, dimensions, value, timestamp));
+
+        sanitizedMetricName = getSanitizedMetricName(metricName, "max");
+        value = sanitizeDouble(gaugeMetric.getMax());
+        outputStream.write(getMetricLines(sanitizedMetricName, dimensions, value, timestamp));
+    }
+
+    private static byte[] getMetricLines(String metricName, String dimensions, Number value, long timestamp) {
+        return (String.format(HELP_LINE, metricName, metricName) +
+                String.format(METRIC_LINE, metricName, dimensions, value, timestamp)).getBytes();
+    }
+
+    private static String getSanitizedMetricName(String metricName, String suffix) {
+        return metricName.replaceAll("([-.])", "_") + "_" + suffix;
+    }
+
+}