feat: add prometheus plugin scaffold

2026-01-22 22:05:03 -05:00
commit 01878de01e
13 changed files with 456 additions and 0 deletions
@@ -0,0 +1,155 @@
+package com.prometheus.spigot.metrics;
+
+import java.lang.management.ManagementFactory;
+import java.lang.management.MemoryUsage;
+import java.lang.management.ThreadMXBean;
+import java.util.Comparator;
+import java.util.Locale;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.LongAdder;
+import org.bukkit.Material;
+import org.bukkit.Server;
+import org.bukkit.event.entity.EntityDamageEvent;
+
+public final class MetricsRegistry {
+    private final Server server;
+    private final boolean enableJvm;
+    private final boolean enableProcess;
+    private final long startTimeMillis;
+
+    private final LongAdder chatMessages = new LongAdder();
+    private final LongAdder playerMovements = new LongAdder();
+    private final ConcurrentHashMap<String, LongAdder> blocksBrokenByMaterial = new ConcurrentHashMap<>();
+    private final ConcurrentHashMap<String, LongAdder> deathsByCause = new ConcurrentHashMap<>();
+
+    public MetricsRegistry(Server server, boolean enableJvm, boolean enableProcess) {
+        this.server = server;
+        this.enableJvm = enableJvm;
+        this.enableProcess = enableProcess;
+        this.startTimeMillis = System.currentTimeMillis();
+    }
+
+    public void incrementChatMessages() {
+        chatMessages.increment();
+    }
+
+    public void incrementPlayerMovements() {
+        playerMovements.increment();
+    }
+
+    public void incrementBlocksBroken(Material material) {
+        incrementLabeledCounter(blocksBrokenByMaterial, material.name());
+    }
+
+    public void incrementPlayerDeath(EntityDamageEvent.DamageCause cause) {
+        incrementLabeledCounter(deathsByCause, cause.name());
+    }
+
+    public void incrementPlayerDeath(String cause) {
+        incrementLabeledCounter(deathsByCause, cause);
+    }
+
+    public String render() {
+        StringBuilder builder = new StringBuilder();
+
+        appendCounter(builder, "spigot_chat_messages_total", "Total chat messages sent", chatMessages.sum());
+        appendCounter(builder, "spigot_player_movements_total", "Total player movement events", playerMovements.sum());
+
+        appendLabeledCounter(builder, "spigot_blocks_broken_total", "Blocks broken by material", "material", blocksBrokenByMaterial);
+        appendLabeledCounter(builder, "spigot_player_deaths_total", "Player deaths by cause", "cause", deathsByCause);
+
+        appendGauge(builder, "spigot_players_online", "Online player count", server.getOnlinePlayers().size());
+        appendGauge(builder, "spigot_players_max", "Max player slots", server.getMaxPlayers());
+        appendGauge(builder, "spigot_worlds_loaded", "Loaded world count", server.getWorlds().size());
+
+        if (enableProcess) {
+            appendProcessMetrics(builder);
+        }
+
+        if (enableJvm) {
+            appendJvmMetrics(builder);
+        }
+
+        return builder.toString();
+    }
+
+    private void appendProcessMetrics(StringBuilder builder) {
+        double uptimeSeconds = (System.currentTimeMillis() - startTimeMillis) / 1000.0;
+        appendGauge(builder, "process_uptime_seconds", "Process uptime in seconds", formatDouble(uptimeSeconds));
+    }
+
+    private void appendJvmMetrics(StringBuilder builder) {
+        MemoryUsage heap = ManagementFactory.getMemoryMXBean().getHeapMemoryUsage();
+        MemoryUsage nonHeap = ManagementFactory.getMemoryMXBean().getNonHeapMemoryUsage();
+        appendMemoryMetrics(builder, "heap", heap);
+        appendMemoryMetrics(builder, "nonheap", nonHeap);
+
+        ThreadMXBean threadBean = ManagementFactory.getThreadMXBean();
+        appendGauge(builder, "jvm_threads", "Current JVM thread count", threadBean.getThreadCount());
+    }
+
+    private void appendMemoryMetrics(StringBuilder builder, String area, MemoryUsage usage) {
+        appendLabeledGauge(builder, "jvm_memory_used_bytes", "JVM memory used in bytes", "area", area, usage.getUsed());
+        if (usage.getMax() >= 0) {
+            appendLabeledGauge(builder, "jvm_memory_max_bytes", "JVM memory max in bytes", "area", area, usage.getMax());
+        }
+    }
+
+    private void appendCounter(StringBuilder builder, String name, String help, long value) {
+        appendHelpAndType(builder, name, help, "counter");
+        builder.append(name).append(' ').append(value).append('\n');
+    }
+
+    private void appendGauge(StringBuilder builder, String name, String help, long value) {
+        appendHelpAndType(builder, name, help, "gauge");
+        builder.append(name).append(' ').append(value).append('\n');
+    }
+
+    private void appendGauge(StringBuilder builder, String name, String help, String value) {
+        appendHelpAndType(builder, name, help, "gauge");
+        builder.append(name).append(' ').append(value).append('\n');
+    }
+
+    private void appendLabeledCounter(StringBuilder builder, String name, String help, String label, Map<String, LongAdder> values) {
+        appendHelpAndType(builder, name, help, "counter");
+        values.entrySet().stream()
+            .sorted(Map.Entry.comparingByKey(Comparator.naturalOrder()))
+            .forEach(entry -> builder.append(name)
+                .append('{').append(label).append("=\"")
+                .append(escapeLabelValue(entry.getKey()))
+                .append("\"} ")
+                .append(entry.getValue().sum())
+                .append('\n'));
+    }
+
+    private void appendLabeledGauge(StringBuilder builder, String name, String help, String label, String labelValue, long value) {
+        appendHelpAndType(builder, name, help, "gauge");
+        builder.append(name)
+            .append('{').append(label).append("=\"")
+            .append(escapeLabelValue(labelValue))
+            .append("\"} ")
+            .append(value)
+            .append('\n');
+    }
+
+    private void appendHelpAndType(StringBuilder builder, String name, String help, String type) {
+        builder.append("# HELP ").append(name).append(' ').append(help).append('\n');
+        builder.append("# TYPE ").append(name).append(' ').append(type).append('\n');
+    }
+
+    private void incrementLabeledCounter(ConcurrentHashMap<String, LongAdder> map, String labelValue) {
+        String normalized = labelValue.toLowerCase(Locale.ROOT);
+        map.computeIfAbsent(normalized, key -> new LongAdder()).increment();
+    }
+
+    private String escapeLabelValue(String value) {
+        return value.replace("\\", "\\\\")
+            .replace("\n", "\\n")
+            .replace("\"", "\\\"");
+    }
+
+    private String formatDouble(double value) {
+        return String.format(Locale.ROOT, "%.3f", value);
+    }
+}