ConfX created HADOOP-18822:
------------------------------
Summary: Out of Memory when mistakenly set
decay-scheduler.metrics.top.user.count to a large number
Key: HADOOP-18822
URL: https://issues.apache.org/jira/browse/HADOOP-18822
Project: Hadoop Common
Issue Type: Bug
Reporter: ConfX
Attachments: reproduce.sh
h2. What happened:
When setting {{decay-scheduler.metrics.top.user.count}} to a large number,
{{DecayRpcScheduler}} in Hcommon throws an out-of-memory exception due to
inappropriate checking and handling.
Hcommon only checks the value should be larger than 0.
h2. Buggy code:
In DecayRpcScheduler.java
{noformat}
public DecayRpcScheduler(int numLevels, String ns, Configuration conf) {
...
topUsersCount =
conf.getInt(DECAYSCHEDULER_METRICS_TOP_USER_COUNT,
DECAYSCHEDULER_METRICS_TOP_USER_COUNT_DEFAULT); <<---- topUsersCount
gets the config value
Preconditions.checkArgument(topUsersCount > 0, <<--- Only checks for
positivity
"the number of top users for scheduler metrics must be at least 1");
...
}
private void addTopNCallerSummary(MetricsRecordBuilder rb) {
TopN topNCallers = getTopCallers(topUsersCount); <<--- calls getTopCallers
with n equals topUsersCount
...
}
private TopN getTopCallers(int n) {
TopN topNCallers = new TopN(n); <<--- starts an priorityQ with initial
capacity n, causing out of memory
...
}{noformat}
h2. StackTrace:
{noformat}
java.lang.OutOfMemoryError: Java heap space
at java.base/java.util.PriorityQueue.<init>(PriorityQueue.java:172)
at java.base/java.util.PriorityQueue.<init>(PriorityQueue.java:139)
at
org.apache.hadoop.metrics2.util.Metrics2Util$TopN.<init>(Metrics2Util.java:80)
at
org.apache.hadoop.ipc.DecayRpcScheduler.getTopCallers(DecayRpcScheduler.java:1002)
at
org.apache.hadoop.ipc.DecayRpcScheduler.addTopNCallerSummary(DecayRpcScheduler.java:982)
at
org.apache.hadoop.ipc.DecayRpcScheduler.getMetrics(DecayRpcScheduler.java:935)
at
org.apache.hadoop.ipc.DecayRpcScheduler$MetricsProxy.getMetrics(DecayRpcScheduler.java:893)
at
org.apache.hadoop.metrics2.impl.MetricsSourceAdapter.getMetrics(MetricsSourceAdapter.java:200)
at
org.apache.hadoop.metrics2.impl.MetricsSourceAdapter.updateJmxCache(MetricsSourceAdapter.java:183)
at
org.apache.hadoop.metrics2.impl.MetricsSourceAdapter.getMBeanInfo(MetricsSourceAdapter.java:156)
at
java.management/com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.getNewMBeanClassName(DefaultMB
eanServerInterceptor.java:329)
at
java.management/com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.registerMBean(DefaultMBeanServ
erInterceptor.java:315)
at
java.management/com.sun.jmx.mbeanserver.JmxMBeanServer.registerMBean(JmxMBeanServer.java:522)
at org.apache.hadoop.metrics2.util.MBeans.register(MBeans.java:100)
at org.apache.hadoop.metrics2.util.MBeans.register(MBeans.java:73)
at
org.apache.hadoop.metrics2.impl.MetricsSourceAdapter.startMBeans(MetricsSourceAdapter.java:222)
at
org.apache.hadoop.metrics2.impl.MetricsSourceAdapter.start(MetricsSourceAdapter.java:101)
at
org.apache.hadoop.metrics2.impl.MetricsSystemImpl.registerSource(MetricsSystemImpl.java:268)
at
org.apache.hadoop.metrics2.impl.MetricsSystemImpl.register(MetricsSystemImpl.java:233)
at
org.apache.hadoop.ipc.DecayRpcScheduler$MetricsProxy.registerMetrics2Source(DecayRpcScheduler.java:8
19)
at
org.apache.hadoop.ipc.DecayRpcScheduler$MetricsProxy.<init>(DecayRpcScheduler.java:792)
at
org.apache.hadoop.ipc.DecayRpcScheduler$MetricsProxy.getInstance(DecayRpcScheduler.java:800)
at
org.apache.hadoop.ipc.DecayRpcScheduler.<init>(DecayRpcScheduler.java:260){noformat}
h2. Reproduce:
(1) Set {{decay-scheduler.metrics.top.user.count}} to a large value, e.g.,
1419140791
(2) Run a simple test that exercises this parameter, e.g.
{{org.apache.hadoop.ipc.TestDecayRpcScheduler#testNPEatInitialization}}
For an easy reproduction, run the reproduce.sh in the attachment.
We are happy to provide a patch if this issue is confirmed.
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