Mercurial > hg > release > thermostat-1.0
view vm-gc/agent/src/main/java/com/redhat/thermostat/vm/gc/agent/internal/VmGcDataExtractor.java @ 1405:9a29868e2610
Better error handling for missing jvmstat counters
When running Thermostat with OpenJDK 8, jvmstat falsely reports the
number of GC generations. This causes us to query performance counters
for a non-existent generation. This patch adds error handling so the
agent doesn't crash with a NullPointerException on these non-existent
counters. The patch also includes test cases for these error conditions.
Reviewed-by: omajid
Review-thread: http://icedtea.classpath.org/pipermail/thermostat/2014-March/009355.html
PR1800
author | Elliott Baron <ebaron@redhat.com> |
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date | Mon, 10 Mar 2014 18:35:14 -0400 |
parents | b269be10beb4 |
children | a0592d702416 |
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/* * Copyright 2012, 2013 Red Hat, Inc. * * This file is part of Thermostat. * * Thermostat is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published * by the Free Software Foundation; either version 2, or (at your * option) any later version. * * Thermostat is distributed in the hope that it will be useful, but * WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * General Public License for more details. * * You should have received a copy of the GNU General Public License * along with Thermostat; see the file COPYING. If not see * <http://www.gnu.org/licenses/>. * * Linking this code with other modules is making a combined work * based on this code. Thus, the terms and conditions of the GNU * General Public License cover the whole combination. * * As a special exception, the copyright holders of this code give * you permission to link this code with independent modules to * produce an executable, regardless of the license terms of these * independent modules, and to copy and distribute the resulting * executable under terms of your choice, provided that you also * meet, for each linked independent module, the terms and conditions * of the license of that module. An independent module is a module * which is not derived from or based on this code. If you modify * this code, you may extend this exception to your version of the * library, but you are not obligated to do so. If you do not wish * to do so, delete this exception statement from your version. */ package com.redhat.thermostat.vm.gc.agent.internal; import com.redhat.thermostat.backend.VmUpdate; import com.redhat.thermostat.backend.VmUpdateException; /** * A helper class to provide type-safe access to commonly used jvmstat monitors * <p> * Implementation details: For local vms, jvmstat uses a ByteBuffer * corresponding to mmap()ed hsperfdata file. The hsperfdata file is updated * asynchronously by the vm that created the file. The polling that jvmstat api * provides is merely an abstraction over this (possibly always up-to-date) * ByteBuffer. So the data this class extracts is as current as possible, and * does not correspond to when the jvmstat update events fired. */ public class VmGcDataExtractor { /* * Note, there may be a performance issue to consider here. We have a lot of * string constants. When we start adding some of the more heavyweight * features, and running into CPU issues this may need to be reconsidered in * order to avoid the String pool overhead. See also: * http://docs.oracle.com/javase/6/docs/api/java/lang/String.html#intern() */ private final VmUpdate update; public VmGcDataExtractor(VmUpdate update) { this.update = update; } public Long getTotalCollectors() throws VmUpdateException { return update.getPerformanceCounterLong("sun.gc.policy.collectors"); } public String getCollectorName(long collector) throws VmUpdateException { return update.getPerformanceCounterString("sun.gc.collector." + collector + ".name"); } public Long getCollectorTime(long collector) throws VmUpdateException { return update.getPerformanceCounterLong("sun.gc.collector." + collector + ".time"); } public Long getCollectorInvocations(long collector) throws VmUpdateException { return update.getPerformanceCounterLong("sun.gc.collector." + collector + ".invocations"); } }