├── LICENSE ├── README.md ├── boot.properties ├── build.boot └── src └── jvm_alloc_rate_meter ├── MeterThread.java └── core.clj /LICENSE: -------------------------------------------------------------------------------- 1 | THE ACCOMPANYING PROGRAM IS PROVIDED UNDER THE TERMS OF THIS ECLIPSE PUBLIC 2 | LICENSE ("AGREEMENT"). ANY USE, REPRODUCTION OR DISTRIBUTION OF THE PROGRAM 3 | CONSTITUTES RECIPIENT'S ACCEPTANCE OF THIS AGREEMENT. 4 | 5 | 1. DEFINITIONS 6 | 7 | "Contribution" means: 8 | 9 | a) in the case of the initial Contributor, the initial code and 10 | documentation distributed under this Agreement, and 11 | 12 | b) in the case of each subsequent Contributor: 13 | 14 | i) changes to the Program, and 15 | 16 | ii) additions to the Program; 17 | 18 | where such changes and/or additions to the Program originate from and are 19 | distributed by that particular Contributor. 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No party to this 212 | Agreement will bring a legal action under this Agreement more than one year 213 | after the cause of action arose. Each party waives its rights to a jury trial 214 | in any resulting litigation. 215 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # jvm-alloc-rate-meter 2 | 3 | A trivial Java library for continuous monitoring of JVM heap allocation rate. 4 | Many GCs can report this metric in their logs, but it's hard to extract that in 5 | real time. This library solves that. 6 | 7 | jvm-alloc-rate-meter starts a background thread that measures how heap usage 8 | changes between the specified intervals and reports the result into a callback. 9 | You get to choose where the data will go — log it, send to a monitoring solution 10 | (Metrics, StatsD, etc.), or aggregate some other way. 11 | 12 | ## Usage 13 | 14 | First, add it to your dependencies: 15 | 16 | [![](https://clojars.org/com.clojure-goes-fast/jvm-alloc-rate-meter/latest-version.svg)](https://clojars.org/com.clojure-goes-fast/jvm-alloc-rate-meter) 17 | 18 | ### Java 19 | 20 | You are safe to use this library in any Java project, it doesn't explicitly 21 | depend on Clojure (or anything else). You can also forgo the dependency and just 22 | paste [MeterThread](src/jvm_alloc_rate_meter/MeterThread.java) class directly 23 | into your project. 24 | 25 | ```java 26 | import jvm_alloc_rate_meter.MeterThread; 27 | 28 | // ... 29 | 30 | MeterThread t = new MeterThread((r) -> System.out.println("Rate is: " + (r / 1e6) + " MB/sec")); 31 | t.start(); 32 | 33 | // To stop the meter thread 34 | t.terminate(); 35 | ``` 36 | 37 | The first argument to MeterThread's constructor is a LongConsumer callback that 38 | will be called with every new measurement of allocation rate in bytes/sec. 39 | 40 | The second (optional) argument is the measurement interval in milliseconds (1000 41 | by default). Regardless of the interval length, the reported rate will be 42 | normalized to per-second value. Note that the callback might not be called on 43 | each interval, because under certain conditions we can't reliably measure the 44 | allocation rate (if both the garbage collection happened and a few of the 45 | heavy-allocating threads died). 46 | 47 | Here's an example of combining jvm-alloc-rate-meter with [Dropwizard 48 | Metrics](https://github.com/dropwizard/metrics): 49 | 50 | ```java 51 | import jvm_alloc_rate_meter.MeterThread; 52 | import com.codahale.metrics.Histogram; 53 | import com.codahale.metrics.SlidingTimeWindowArrayReservoir; 54 | import java.util.concurrent.TimeUnit; 55 | 56 | // ... 57 | 58 | Histogram hist = new Histogram(new SlidingTimeWindowArrayReservoir(10, TimeUnit.SECONDS)); 59 | MeterThread mt = new MeterThread(hist::update); 60 | mt.start(); 61 | 62 | // Now, you can forward this histogram to Graphite, or check the values manually, e.g.: 63 | hist.getSnaphot.getMean(); 64 | ``` 65 | 66 | ### Clojure 67 | 68 | ```clj 69 | (require '[jvm-alloc-rate-meter.core :as ameter]) 70 | (def am (ameter/start-alloc-rate-meter #(println "Rate is:" (/ % 1e6) "MB/sec"))) 71 | 72 | ;; Test it out 73 | (while true 74 | (byte-array 1e7) 75 | (Thread/sleep 100)) 76 | 77 | ;; The meter should report ~100 MB/sec allocation rate into the console. 78 | 79 | ;; To stop the meter thread 80 | (am) 81 | ``` 82 | 83 | The only function `start-alloc-rate-meter` accepts an unary function as an 84 | argument and starts the measuring thread. See the section above using the 85 | library from Java for the details. 86 | 87 | ## License 88 | 89 | jvm-hiccup-meter is distributed under the Eclipse Public License. See 90 | [LICENSE](LICENSE). 91 | 92 | Copyright 2018-2024 Alexander Yakushev 93 | -------------------------------------------------------------------------------- /boot.properties: -------------------------------------------------------------------------------- 1 | #http://boot-clj.com 2 | #Tue Jun 26 19:08:05 EEST 2018 3 | BOOT_CLOJURE_NAME=org.clojure/clojure 4 | BOOT_CLOJURE_VERSION=1.10.0 5 | BOOT_VERSION=2.8.2 6 | -------------------------------------------------------------------------------- /build.boot: -------------------------------------------------------------------------------- 1 | (task-options! 2 | pom {:project 'com.clojure-goes-fast/jvm-alloc-rate-meter 3 | :version "0.1.4" 4 | :description "Measure JVM heap allocation rate in real time" 5 | :url "http://github.com/clojure-goes-fast/jvm-alloc-rate-meter" 6 | :scm {:url "http://github.com/clojure-goes-fast/jvm-alloc-rate-meter"} 7 | :license {"Eclipse Public License" 8 | "http://www.eclipse.org/legal/epl-v10.html"}} 9 | push {:repo "clojars"}) 10 | 11 | (set-env! :source-paths #{"src"}) 12 | 13 | (deftask build [] 14 | (comp (javac) 15 | (sift :to-resource [#"jvm_alloc_rate_meter/.+\.clj$"]) 16 | (pom) (jar))) 17 | 18 | (comment ;; Development 19 | (set-env! :dependencies #(conj % '[virgil "LATEST"])) 20 | (require '[virgil.boot :as virgil]) 21 | (boot (virgil/javac* :verbose true))) 22 | -------------------------------------------------------------------------------- /src/jvm_alloc_rate_meter/MeterThread.java: -------------------------------------------------------------------------------- 1 | package jvm_alloc_rate_meter; 2 | 3 | import com.sun.management.ThreadMXBean; 4 | import java.math.BigInteger; 5 | import java.util.List; 6 | import java.util.function.LongConsumer; 7 | import java.lang.management.MemoryMXBean; 8 | import java.lang.management.GarbageCollectorMXBean; 9 | import java.lang.management.ManagementFactory; 10 | 11 | public class MeterThread extends Thread { 12 | 13 | private final MemoryMXBean memoryBean; 14 | private final ThreadMXBean threadBean; 15 | private final List gcBeans; 16 | 17 | private final LongConsumer callback; 18 | private final int intervalMs; 19 | 20 | private volatile boolean doRun = true; 21 | 22 | public MeterThread(LongConsumer callback) { 23 | this(callback, 1000); 24 | } 25 | 26 | public MeterThread(LongConsumer callback, int intervalMs) { 27 | super("jvm-alloc-rate-meter-thread"); 28 | 29 | this.memoryBean = ManagementFactory.getMemoryMXBean(); 30 | this.threadBean = (ThreadMXBean)ManagementFactory.getThreadMXBean(); 31 | this.gcBeans = ManagementFactory.getGarbageCollectorMXBeans(); 32 | 33 | this.callback = callback; 34 | this.intervalMs = intervalMs; 35 | setDaemon(true); 36 | } 37 | 38 | // Basically, we have two ways of measuring the allocation rate. 39 | // The first relies on checking heap usage between two points in time and 40 | // subtracting. This is accurate but works only if the GC didn't trigger in 41 | // the meantime. 42 | // The second works by taking allocation stats by each alive thread. This is 43 | // more reliable but potentially less accurate (because threads can go away, 44 | // and we lose their allocation stats). 45 | // The idea is to use the first approach if GC didn't happen, and the second 46 | // one if it did. 47 | 48 | public void run() { 49 | long lastTime = 0, lastHeapUsage = -1, lastGcCounts = -1; 50 | BigInteger lastThreadAllocated = BigInteger.valueOf(-1); 51 | try { 52 | while (doRun) { 53 | long time = System.currentTimeMillis(); 54 | double multiplier = 1000.0 / (time - lastTime); 55 | 56 | long heapUsage = usedHeap(); 57 | long gcCounts = gcCounts(); 58 | long deltaUsage = heapUsage - lastHeapUsage; 59 | 60 | BigInteger threadAllocated = allocatedByAllThreads(); 61 | BigInteger deltaAllocated = threadAllocated.subtract(lastThreadAllocated); 62 | 63 | if (lastTime != 0) { 64 | if ((gcCounts == lastGcCounts) && (deltaUsage >= 0)) { 65 | long rate = Math.round(deltaUsage * multiplier); 66 | callback.accept(rate); 67 | } else if (threadAllocated.compareTo(BigInteger.ZERO) >= 0 && 68 | lastThreadAllocated.compareTo(BigInteger.ZERO) >= 0 && 69 | deltaAllocated.compareTo(BigInteger.ZERO) >= 0) { 70 | long rate = Math.round(deltaAllocated.longValue() * multiplier); 71 | callback.accept(rate); 72 | } else { 73 | // Apparently, neither approach did well, just skip this 74 | // iteration. 75 | } 76 | } 77 | 78 | Thread.sleep(intervalMs); 79 | 80 | lastTime = time; 81 | lastHeapUsage = heapUsage; 82 | lastGcCounts = gcCounts; 83 | lastThreadAllocated = threadAllocated; 84 | } 85 | } catch (InterruptedException e) { 86 | System.err.println("MeterThread terminating..."); 87 | } 88 | } 89 | 90 | public void terminate() { 91 | doRun = false; 92 | } 93 | 94 | private long usedHeap() { 95 | return memoryBean.getHeapMemoryUsage().getUsed(); 96 | } 97 | 98 | /** Returns total number of GC cycles since the start of the VM. **/ 99 | private long gcCounts() { 100 | long total = 0; 101 | for (GarbageCollectorMXBean bean : gcBeans) { 102 | total += bean.getCollectionCount(); 103 | } 104 | return total; 105 | } 106 | 107 | /** Total allocation can overflow a long, so using BigInt here. **/ 108 | private BigInteger allocatedByAllThreads() { 109 | long[] ids = threadBean.getAllThreadIds(); 110 | long[] allocatedBytes = threadBean.getThreadAllocatedBytes(ids); 111 | BigInteger result = BigInteger.ZERO; 112 | // This approach is not entirely correct because it doesn't see the 113 | // allocation data from threads that died since the last iteration. Oh 114 | // well, just making the best effort. 115 | for (long abytes : allocatedBytes) 116 | result = result.add(BigInteger.valueOf(abytes)); 117 | return result; 118 | } 119 | } 120 | -------------------------------------------------------------------------------- /src/jvm_alloc_rate_meter/core.clj: -------------------------------------------------------------------------------- 1 | (ns jvm-alloc-rate-meter.core 2 | (:import jvm_alloc_rate_meter.MeterThread 3 | java.util.function.LongConsumer)) 4 | 5 | (defn start-alloc-rate-meter 6 | "Start the allocation meter thread. It will measure the heap object allocation 7 | rate every `interval-ms` (1000 by default) and call `callback-fn` with the 8 | allocation rate in bytes/sec. Note that the rate might not be reported every 9 | `interval-ms` as some iterations may not produce reliable data. 10 | 11 | Returns a nullary function which terminates the measuring thread when invoked." 12 | [callback-fn & {:keys [interval-ms]}] 13 | (let [iw (MeterThread. (reify LongConsumer 14 | (accept [_ v] 15 | (callback-fn v))) 16 | (or interval-ms 1000))] 17 | (.start iw) 18 | #(.terminate iw))) 19 | 20 | #_(def -t (start-alloc-rate-meter #(println (/ % 1e6) "MB/sec"))) 21 | --------------------------------------------------------------------------------