Expose the JVB stress level as a stat (#1440)

* support division in JvbLoadMeasurement

* expose the current stress level in load manager

* always create load manager/sampler, only enable/disable reducer

* update jmc

* change semantics of load management enabled config to be reducer enabled, add tests

* expose stress level in stats

jvb/src/main/java/org/jitsi/videobridge/Videobridge.java

@@ -148,9 +148,6 @@ public class Videobridge
     public Videobridge()
     {
         videobridgeExpireThread = new VideobridgeExpireThread(this);
-        if (JvbLoadManager.isEnabled())
-        {
-            logger.info("Starting JVB load management task");
         jvbLoadManager = new JvbLoadManager<>(
             PacketRateMeasurement.getLoadedThreshold(),
             PacketRateMeasurement.getRecoveryThreshold(),
@@ -160,18 +157,21 @@ public class Videobridge
             )
         );
         loadSamplerTask = TaskPools.SCHEDULED_POOL.scheduleAtFixedRate(
-                new PacketRateLoadSampler(this, jvbLoadManager),
+            new PacketRateLoadSampler(
+                this,
+                (loadMeasurement) -> {
+                    // Update the load manager with the latest measurement
+                    jvbLoadManager.loadUpdate(loadMeasurement);
+                    // Update the stats with the latest stress level
+                    getStatistics().stressLevel = jvbLoadManager.getCurrentStressLevel();
+                    return Unit.INSTANCE;
+                }
+            ),
             0,
             10,
             TimeUnit.SECONDS
         );
     }
-        else
-        {
-            jvbLoadManager = null;
-            loadSamplerTask = null;
-        }
-    }
 
     /**
      * Initializes a new {@link Conference} instance with an ID unique to the
@@ -569,10 +569,7 @@ public class Videobridge
         debugState.put("time", System.currentTimeMillis());
 
         debugState.put("health", getHealthStatus());
-        if (jvbLoadManager != null)
-        {
         debugState.put("load-management", jvbLoadManager.getStats());
-        }
         debugState.put(Endpoint.overallAverageBridgeJitter.name, Endpoint.overallAverageBridgeJitter.get());
 
         JSONObject conferences = new JSONObject();
@@ -804,5 +801,10 @@ public class Videobridge
          * wasn't (at the time of expiration).
          */
         public AtomicInteger dtlsFailedEndpoints = new AtomicInteger();
+
+        /**
+         * The stress level for this bridge
+         */
+        public Double stressLevel = 0.0;
     }
 }

jvb/src/main/java/org/jitsi/videobridge/stats/VideobridgeStatistics.java

@@ -435,6 +435,10 @@ public class VideobridgeStatistics
                 EPS_NO_MSG_TRANSPORT_AFTER_DELAY,
                 jvbStats.numEndpointsNoMessageTransportAfterDelay.get()
             );
+            unlockedSetStat(
+                "stress_level",
+                jvbStats.stressLevel
+            );
             unlockedSetStat(CONFERENCES, conferences);
             unlockedSetStat(OCTO_CONFERENCES, octoConferences);
             unlockedSetStat(INACTIVE_CONFERENCES, inactiveConferences);

jvb/src/main/kotlin/org/jitsi/videobridge/load_management/JvbLoadManager.kt

@@ -36,46 +36,62 @@ class JvbLoadManager<T : JvbLoadMeasurement> @JvmOverloads constructor(
 ) {
     private val logger = createLogger(minLogLevel = Level.ALL)
 
+    val reducerEnabled: Boolean by config("videobridge.load-management.reducer-enabled".from(JitsiConfig.newConfig))
+
     private var lastReducerTime: Instant = NEVER
 
     private var state: State = State.NOT_OVERLOADED
 
+    private var mostRecentLoadMeasurement: T? = null
+
     fun loadUpdate(loadMeasurement: T) {
         logger.cdebug { "Got a load measurement of $loadMeasurement" }
+        mostRecentLoadMeasurement = loadMeasurement
         val now = clock.instant()
         if (loadMeasurement.getLoad() >= jvbLoadThreshold.getLoad()) {
             state = State.OVERLOADED
+            if (reducerEnabled) {
                 logger.info("Load measurement $loadMeasurement is above threshold of $jvbLoadThreshold")
                 if (canRunReducer(now)) {
                     logger.info("Running load reducer")
                     loadReducer.reduceLoad()
                     lastReducerTime = now
                 } else {
-                logger.info("Load reducer ran at $lastReducerTime, which is within ${loadReducer.impactTime()} " +
+                    logger.info("Load reducer ran at $lastReducerTime, which is within " +
-                    "of now, not running reduce")
+                        "${loadReducer.impactTime()} of now, not running reduce")
+                }
             }
         } else {
             state = State.NOT_OVERLOADED
+            if (reducerEnabled) {
                 if (loadMeasurement.getLoad() < jvbRecoveryThreshold.getLoad()) {
                     if (canRunReducer(now)) {
                         if (loadReducer.recover()) {
-                        logger.info("Recovery ran after a load measurement of $loadMeasurement (which was below " +
+                            logger.info("Recovery ran after a load measurement of $loadMeasurement (which was " +
-                            "threshold of $jvbRecoveryThreshold) was received")
+                                "below threshold of $jvbRecoveryThreshold) was received")
                             lastReducerTime = now
                         } else {
                             logger.cdebug { "Recovery had no work to do" }
                         }
                     } else {
-                    logger.cdebug { "Load measurement $loadMeasurement is below recovery threshold, but load reducer " +
+                        logger.cdebug {
-                        "ran at $lastReducerTime, which is within ${loadReducer.impactTime()} of now, not running " +
+                            "Load measurement $loadMeasurement is below recovery threshold, but load reducer " +
-                        "recover" }
+                                "ran at $lastReducerTime, which is within ${loadReducer.impactTime()} of now, " +
+                                "not running recover"
+                        }
+                    }
                 }
             }
         }
     }
 
+    fun getCurrentStressLevel(): Double =
+        mostRecentLoadMeasurement?.div(jvbLoadThreshold) ?: 0.0
+
     fun getStats() = OrderedJsonObject().apply {
         put("state", state.toString())
+        put("stress", getCurrentStressLevel().toString())
+        put("reducer_enabled", reducerEnabled.toString())
         put("reducer", loadReducer.getStats())
     }
 
@@ -86,11 +102,4 @@ class JvbLoadManager<T : JvbLoadMeasurement> @JvmOverloads constructor(
         OVERLOADED,
         NOT_OVERLOADED
     }
-
-    companion object {
-        val enabled: Boolean by config("videobridge.load-management.enabled".from(JitsiConfig.newConfig))
-
-        @JvmStatic
-        fun isEnabled() = enabled
-    }
 }

jvb/src/main/kotlin/org/jitsi/videobridge/load_management/JvbLoadMeasurement.kt

@@ -23,6 +23,8 @@ package org.jitsi.videobridge.load_management
 interface JvbLoadMeasurement {
     fun getLoad(): Double
 
+    operator fun div(other: JvbLoadMeasurement): Double
+
     companion object {
         const val CONFIG_BASE = "videobridge.load-management.load-measurements"
     }

jvb/src/main/kotlin/org/jitsi/videobridge/load_management/PacketRateLoadSampler.kt

@@ -20,7 +20,7 @@ import org.jitsi.videobridge.Videobridge
 
 class PacketRateLoadSampler(
     private val videobridge: Videobridge,
-    private val jvbLoadManager: JvbLoadManager<PacketRateMeasurement>
+    private val newMeasurementHandler: (PacketRateMeasurement) -> Unit
 ) : Runnable {
 
     override fun run() {
@@ -33,6 +33,6 @@ class PacketRateLoadSampler(
                 }
             }
         }
-        jvbLoadManager.loadUpdate(PacketRateMeasurement(totalPacketRate))
+        newMeasurementHandler(PacketRateMeasurement(totalPacketRate))
     }
 }

jvb/src/main/kotlin/org/jitsi/videobridge/load_management/PacketRateMeasurement.kt

@@ -22,6 +22,13 @@ import org.jitsi.metaconfig.config
 class PacketRateMeasurement(private val packetRate: Long) : JvbLoadMeasurement {
     override fun getLoad(): Double = packetRate.toDouble()
 
+    override fun div(other: JvbLoadMeasurement): Double {
+        if (other !is PacketRateMeasurement) {
+            throw UnsupportedOperationException("Can only divide load measurements of same type")
+        }
+        return packetRate / other.packetRate.toDouble()
+    }
+
     override fun toString(): String = "RTP packet rate (up + down) of $packetRate pps"
 
     companion object {

jvb/src/main/resources/reference.conf

@@ -139,7 +139,8 @@ videobridge {
     send-queue-size=1024
   }
   load-management {
-    enabled = false
+    # Whether or not the reducer will be enabled to take actions to mitigate load
+    reducer-enabled = false
     load-measurements {
       packet-rate {
         # The packet rate at which we'll consider the bridge overloaded

jvb/src/test/kotlin/org/jitsi/videobridge/load_management/JvbLoadManagerTest.kt

@@ -18,10 +18,13 @@ package org.jitsi.videobridge.load_management
 
 import io.kotest.core.spec.IsolationMode
 import io.kotest.core.spec.style.ShouldSpec
+import io.kotest.matchers.shouldBe
 import io.mockk.Called
 import io.mockk.every
 import io.mockk.mockk
 import io.mockk.verify
+import org.jitsi.config.setNewConfig
+import org.jitsi.metaconfig.MetaconfigSettings
 import org.jitsi.test.time.FakeClock
 import org.jitsi.utils.mins
 import org.jitsi.utils.secs
@@ -34,12 +37,17 @@ class JvbLoadManagerTest : ShouldSpec({
     }
     val clock = FakeClock()
 
-    val loadManager = JvbLoadManager<MockLoadMeasurement>(
+    val loadManager = createWithConfig("""
+        videobridge.load-management.reducer-enabled=true
+        """.trimIndent()
+    ) {
+        JvbLoadManager(
             MockLoadMeasurement(10.0),
             MockLoadMeasurement(7.0),
             reducer,
             clock
         )
+    }
 
     context("a load update") {
         context("with a load which isn't overloaded") {
@@ -100,10 +108,44 @@ class JvbLoadManagerTest : ShouldSpec({
             }
         }
     }
+    context("the stress level") {
+        should("be 0 if no measurement has been received") {
+            loadManager.getCurrentStressLevel() shouldBe 0.0
+        }
+        should("update with every load measurement") {
+            loadManager.loadUpdate(MockLoadMeasurement(1.0))
+            loadManager.getCurrentStressLevel() shouldBe .1
+            loadManager.loadUpdate(MockLoadMeasurement(3.0))
+            loadManager.getCurrentStressLevel() shouldBe .3
+            loadManager.loadUpdate(MockLoadMeasurement(11.0))
+            loadManager.getCurrentStressLevel() shouldBe 1.1
+        }
+    }
 })
 
 class MockLoadMeasurement(var loadMeasurement: Double) : JvbLoadMeasurement {
     override fun getLoad(): Double = loadMeasurement
 
+    override fun div(other: JvbLoadMeasurement): Double {
+        other as MockLoadMeasurement
+        return loadMeasurement / other.loadMeasurement
+    }
+
     override fun toString(): String = "Mock load measurement of $loadMeasurement"
 }
+
+/**
+ * A helper function to run the given [block] with the given [config] in place and
+ * return the result.
+ *
+ * This assumes that the result of [block] should be created with exactly the given
+ * [config] in place, and all config values will be retrieved immediately.
+ */
+private fun <T : Any> createWithConfig(config: String, block: () -> T): T {
+    setNewConfig(config, true, "name")
+    MetaconfigSettings.retrieveValuesImmediately = true
+    val result = block()
+    MetaconfigSettings.retrieveValuesImmediately = false
+    setNewConfig("", true, "name")
+    return result
+}

jvb/src/test/kotlin/org/jitsi/videobridge/load_management/PacketRateMeasurementTest.kt

@@ -0,0 +1,38 @@
+/*
+ * Copyright @ 2018 - 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.videobridge.load_management
+
+import io.kotest.assertions.throwables.shouldThrow
+import io.kotest.core.spec.style.ShouldSpec
+import io.kotest.matchers.shouldBe
+
+class PacketRateMeasurementTest : ShouldSpec({
+    context("division") {
+        context("between two PacketRateMeasurements") {
+            should("yield the correct result") {
+                PacketRateMeasurement(10) / PacketRateMeasurement(2) shouldBe 5.0
+            }
+        }
+        context("between a PacketRateMeasurement and another measurement type") {
+            should("throw an exception") {
+                shouldThrow<UnsupportedOperationException> {
+                    PacketRateMeasurement(10) / MockLoadMeasurement(1.1)
+                }
+            }
+        }
+    }
+})

pom.xml

@@ -64,7 +64,7 @@
             <dependency>
                 <groupId>${project.groupId}</groupId>
                 <artifactId>jitsi-metaconfig</artifactId>
-                <version>30cdd3e22b</version>
+                <version>315a3cec35</version>
             </dependency>
             <dependency>
                 <groupId>${project.groupId}</groupId>