├── LICENSE ├── README.md ├── build.boot └── src └── jvm_hiccup_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-hiccup-meter 2 | 3 | A miniature library for measuring JVM and OS hiccups that affect your program. 4 | It is inspired by Gil Tene's [jHiccup](https://github.com/giltene/jHiccup). In 5 | fact, this is a maximally trimmed jHiccup with the implementation taken straight 6 | out of the ancestor library. 7 | 8 | jHiccup is a great tool that focuses on very precise on-demand measurement of 9 | platform-induced lags. It uses 10 | [HdrHistogram](https://github.com/HdrHistogram/HdrHistogram) to record 11 | high-fidelity measurement data which can later be queried for real percentile 12 | values on arbitrary time spans. However, jHiccup's API is not convenient for 13 | ongoing always-on measuring and reporting. 14 | 15 | jvm-hiccup-meter contains the exact measuring code from jHiccup and exposes it 16 | via the most primitive callback API. This gives developers the utmost 17 | flexibility in consuming the measurements, be it writing them to a monitoring 18 | solution (Metrics, StatsD, etc.) or aggregating in any other way. 19 | 20 | ## How it works 21 | 22 | The idea behind jHiccup (and, as a consequence, this library) is trivially 23 | brilliant: if an idle thread that does nothing but sleeping is denied the CPU 24 | time by the system, then the real worker threads are likely to observe the 25 | similar effect. jvm-hiccup-meter starts a thread that sleeps for a defined 26 | interval (by default, 10 milliseconds) and measures how much of actual time has 27 | passed. The difference between the desired and actual sleep time becomes the 28 | length of the system "hiccup" for this cycle. 29 | 30 | Of course, you can't expect `Thread.sleep(10)` to wake up strictly in 10 31 | milliseconds even under ideal conditions when no hiccups are happening. But 32 | obsessing about small fluctuations is not the point, the point is to discover 33 | long pauses of hundreds of milliseconds or even seconds. Those can be caused by 34 | stop-the-world GC phases, stolen CPU cycles in virtualized environments, 35 | unpredicted hardware effects, and other application-independent reasons. 36 | 37 | jvm-hiccup-meter is non-invasive — an extra thread that does a few arithmetic 38 | operations and goes to sleep a hundred times per second should not bring a 39 | noticeable overhead to your application. 40 | 41 | ## Usage 42 | 43 | [![](https://clojars.org/com.clojure-goes-fast/jvm-hiccup-meter/latest-version.svg)](https://clojars.org/com.clojure-goes-fast/jvm-hiccup-meter) 44 | 45 | ```clj 46 | (require '[jvm-hiccup-meter.core :as hmeter]) 47 | (def hm (hmeter/start-hiccup-meter callback-fn :resolution-ms 10)) 48 | 49 | ;; To stop the meter thread 50 | (hm) 51 | ``` 52 | 53 | The only function `start-hiccup-meter` accepts an unary function as an argument 54 | and starts the measuring thread. On each measurement iteration, the callback 55 | will be called with the measured delay in nanoseconds. Optional resolution can 56 | be passed to change the default sleep period. `start-hiccup-meter` returns a 57 | nullary function calling which stops the thread. 58 | 59 | Here's an example of combining jvm-hiccup-meter with [Dropwizard 60 | Metrics](https://github.com/dropwizard/metrics): 61 | 62 | ```clj 63 | (import 'com.codahale.metrics.Histogram 64 | 'com.codahale.metrics.SlidingTimeWindowArrayReservoir 65 | 'java.util.concurrent.TimeUnit) 66 | 67 | (def hist (Histogram. (SlidingTimeWindowArrayReservoir. 10 TimeUnit/SECONDS))) 68 | (def hm (hmeter/start-hiccup-meter #(.update ^Histogram hist %))) 69 | 70 | ;; Now, you can forward this histogram to Graphite, or check the values 71 | ;; manually, e.g: 72 | (.getMax (.getSnapshot hist)) 73 | ``` 74 | 75 | ## License 76 | 77 | jHiccup was written by Gil Tene of Azul Systems, and released to the public 78 | domain, as explained at http://creativecommons.org/publicdomain/zero/1.0/ 79 | 80 | --- 81 | 82 | jvm-hiccup-meter is distributed under the Eclipse Public License. See 83 | [LICENSE](LICENSE). 84 | 85 | Copyright 2018 Alexander Yakushev 86 | -------------------------------------------------------------------------------- /build.boot: -------------------------------------------------------------------------------- 1 | (task-options! 2 | pom {:project 'com.clojure-goes-fast/jvm-hiccup-meter 3 | :version "0.1.1" 4 | :description "Measure JVM and OS hiccups influencing your program" 5 | :url "http://github.com/clojure-goes-fast/jvm-hiccup-meter" 6 | :scm {:url "http://github.com/clojure-goes-fast/jvm-hiccup-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_hiccup_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_hiccup_meter/MeterThread.java: -------------------------------------------------------------------------------- 1 | /** 2 | * Originally written by Gil Tene of Azul Systems, and released to the public 3 | * domain, as explained at http://creativecommons.org/publicdomain/zero/1.0/ 4 | */ 5 | 6 | package jvm_hiccup_meter; 7 | 8 | import java.util.function.LongConsumer; 9 | import java.util.concurrent.TimeUnit; 10 | 11 | public class MeterThread extends Thread { 12 | 13 | private static boolean allocateObjects = true; 14 | public volatile Long lastSleepTimeObj; // public volatile to make sure allocs are not optimized away 15 | 16 | private LongConsumer callback; 17 | private int resolutionMs; 18 | 19 | private volatile boolean doRun = true; 20 | 21 | public MeterThread(LongConsumer callback) { 22 | this(callback, 10); 23 | } 24 | 25 | public MeterThread(LongConsumer callback, int resolutionMs) { 26 | super("jvm-hiccup-metter-thread"); 27 | this.callback = callback; 28 | this.resolutionMs = resolutionMs; 29 | setDaemon(true); 30 | } 31 | 32 | public void run() { 33 | final long resolutionNsec = (long)(resolutionMs * 1000L * 1000L); 34 | try { 35 | long shortestObservedDeltaTimeNsec = Long.MAX_VALUE; 36 | long timeBeforeMeasurement = Long.MAX_VALUE; 37 | while (doRun) { 38 | TimeUnit.NANOSECONDS.sleep(resolutionNsec); 39 | if (allocateObjects) { 40 | // Allocate an object to make sure potential allocation stalls are measured. 41 | lastSleepTimeObj = new Long(timeBeforeMeasurement); 42 | } 43 | final long timeAfterMeasurement = System.nanoTime(); 44 | final long deltaTimeNsec = timeAfterMeasurement - timeBeforeMeasurement; 45 | timeBeforeMeasurement = timeAfterMeasurement; 46 | 47 | if (deltaTimeNsec < 0) { 48 | // On the very first iteration (which will not time the loop in it's entirety) 49 | // the delta will be negative, and we'll skip recording. 50 | continue; 51 | } 52 | 53 | if (deltaTimeNsec < shortestObservedDeltaTimeNsec) { 54 | shortestObservedDeltaTimeNsec = deltaTimeNsec; 55 | } 56 | 57 | long hiccupTimeNsec = deltaTimeNsec - shortestObservedDeltaTimeNsec; 58 | 59 | callback.accept(hiccupTimeNsec); 60 | } 61 | } catch (InterruptedException e) { 62 | System.err.println("MeterThread terminating..."); 63 | } 64 | } 65 | 66 | public void terminate() { 67 | doRun = false; 68 | } 69 | } 70 | -------------------------------------------------------------------------------- /src/jvm_hiccup_meter/core.clj: -------------------------------------------------------------------------------- 1 | (ns jvm-hiccup-meter.core 2 | (:import jvm_hiccup_meter.MeterThread 3 | java.util.function.LongConsumer)) 4 | 5 | (defn start-hiccup-meter 6 | "Start the hiccup meter thread. It will continuosly sleep every `resolution-ms` 7 | milliseconds (10 by default) and call `callback-fn` with the presumed hiccup 8 | time in nanoseconds. 9 | 10 | Returns a nullary function which when called terminates the measuring thread." 11 | [callback-fn & {:keys [resolution-ms]}] 12 | (let [iw (MeterThread. (reify LongConsumer 13 | (accept [_ v] 14 | (callback-fn v))) 15 | (or resolution-ms 10))] 16 | (.start iw) 17 | #(.terminate iw))) 18 | --------------------------------------------------------------------------------