Add MetricsUpdater (moved from jicofo). (#195)

jicoco-metrics/src/main/kotlin/org/jitsi/metrics/MetricsUpdater.kt

@@ -0,0 +1,74 @@
+/*
+ * Copyright @ 2023 - present 8x8, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.jitsi.metrics
+
+import org.jitsi.utils.logging2.createLogger
+import java.time.Duration
+import java.util.concurrent.CopyOnWriteArrayList
+import java.util.concurrent.ScheduledExecutorService
+import java.util.concurrent.ScheduledFuture
+import java.util.concurrent.TimeUnit
+
+class MetricsUpdater(
+    private val executor: ScheduledExecutorService,
+    private val updateInterval: Duration
+) {
+    private val logger = createLogger()
+    private val subtasks: MutableList<() -> Unit> = CopyOnWriteArrayList()
+    private var updateTask: ScheduledFuture<*>? = null
+
+    // Allow updates to be disabled for tests
+    var disablePeriodicUpdates = false
+
+    fun addUpdateTask(subtask: () -> Unit) {
+        if (disablePeriodicUpdates) {
+            logger.warn("Periodic updates are disabled, will not execute update task.")
+            return
+        }
+
+        subtasks.add(subtask)
+        synchronized(this) {
+            if (updateTask == null) {
+                logger.info("Scheduling metrics update task with interval $updateInterval.")
+                updateTask = executor.scheduleAtFixedRate(
+                    { updateMetrics() },
+                    0,
+                    updateInterval.toMillis(),
+                    TimeUnit.MILLISECONDS
+                )
+            }
+        }
+    }
+
+    fun updateMetrics() {
+        synchronized(this) {
+            logger.debug("Running ${subtasks.size} subtasks.")
+            subtasks.forEach {
+                try {
+                    it.invoke()
+                } catch (e: Exception) {
+                    logger.warn("Exception while running subtask", e)
+                }
+            }
+        }
+    }
+
+    fun stop() = synchronized(this) {
+        updateTask?.cancel(false)
+        updateTask = null
+        subtasks.clear()
+    }
+}