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Description

JVMs use File Descriptors (FDs) to access files and sockets. Often, the default (1024) is not high enough to support a running Geode JVM.

Determination

A native memory issue will manifest itself in the Geode log file as a SocketException with the message Too many open files thrown either by a Geode thread or an application thread. An example of the exception is shown below.

[info 2009/05/02 00:33:26.480 UTC  <RMI TCP Connection(83)-168.109.18.47> tid=0x100f]
 Connection: failed to connect to peer server(12739):53311/47704 because: java.net.SocketException: Too many open files
 

lsof

One way to determine whether there is an FD issue is to use the operating system lsof command to list open files including sockets of any running process including JVMs. These include:

  • Java jar files
  • Geode stats and log files
  • Established and listening TCP sockets
  • UDP sockets

The example below shows a partial list of the open files for the JVM with pid 26896.

lsof -p26896
COMMAND   PID     USER   FD   TYPE             DEVICE SIZE/OFF     NODE NAME
java    26896 user1  cwd    DIR               0,26     4096  7577811 /path/to/server1
java    26896 user1  txt    REG               0,25     7718 12856054 /path/to/jre/bin/java
java    26896 user1  mem    REG               0,25 62559453 12855938 /path/to/jre/lib/rt.jar
java    26896 user1    5r   REG               0,25 13850425 43279281 /path/to/GemFire8.1.0/lib/gemfire.jar
java    26896 user1    6r   REG               0,25   133531 43279230 /path/to/GemFire8.1.0/lib/log4j-api-2.1.jar
java    26896 user1    7r   REG               0,25   824749 43279262 /path/to/GemFire8.1.0/lib/log4j-core-2.1.jar
java    26896 user1   32r   REG               0,26    71085  7494566 /path/to/server1/cacheserver.log
java    26896 user1   33w   REG               0,26    85549  7494568 /path/to/server1/cacheserver.gfs
java    26896 user1   37r  IPv6           26751251      0t0      TCP host1:25940 (LISTEN)
java    26896 user1   39r  IPv6           26751254      0t0      TCP host1:25940->host2:47695 (ESTABLISHED)
java    26896 user1   40r  IPv6           26751256      0t0      UDP host1:15684 
java    26896 user1   41r  IPv6           26751257      0t0      TCP host1:10429 (LISTEN)
java    26896 user1   42r  IPv6           26751335      0t0      TCP host1:25940->host2:47713 (ESTABLISHED)
java    26896 user1   43r  IPv6           26751272      0t0      TCP host1:25940->host2:47701 (ESTABLISHED)
java    26896 user1   44r  IPv6           26751273      0t0      TCP host1:36938->host2:24980 (ESTABLISHED)
java    26896 user1   49u  IPv6           26751283      0t0      TCP host1:10429->host2:47830 (ESTABLISHED)
java    26896 user1   51u  IPv6           26751347      0t0      TCP host1:56087->host2:30937 (ESTABLISHED)
java    26896 user1   53r  IPv6           26751373      0t0      TCP host1:56092->host2:30937 (ESTABLISHED)
java    26896 user1   54u  IPv6           26751375      0t0      TCP host1:36951->host2:24980 (ESTABLISHED)
java    26896 user1   55u  IPv6           26751377      0t0      TCP *:43514 (LISTEN)
java    26896 user1   56r  IPv6           26751521      0t0      TCP host1:43514->host2:59930 (ESTABLISHED)
java    26896 user1   57r  IPv6           26751565      0t0      TCP host1:43514->host2:59960 (ESTABLISHED)
java    26896 user1   58u  IPv6           26751566      0t0      TCP host1:43514->host2:59962 (ESTABLISHED)
java    26896 user1   59u  IPv6           26751579      0t0      TCP host1:43514->host2:59965 (ESTABLISHED)
java    26896 user1   60u  IPv6           26751594      0t0      TCP host1:43514->host2:59966 (ESTABLISHED)
java    26896 user1   61u  IPv6           26751600      0t0      TCP host1:43514->host2:59969 (ESTABLISHED)
java    26896 user1   62u  IPv6           26751603      0t0      TCP host1:43514->host2:59971 (ESTABLISHED)
java    26896 user1   63u  IPv6           26751605      0t0      TCP host1:43514->host2:59973 (ESTABLISHED)
java    26896 user1   64u  IPv6           26751622      0t0      TCP host1:43514->host2:59975 (ESTABLISHED)
java    26896 user1   65u  IPv6           26751623      0t0      TCP host1:43514->host2:59978 (ESTABLISHED)

The example below counts established TCP socket connections.

lsof -p26896 | grep ESTABLISHED | wc
     29     290    4037

vsd

Another way to determine whether there is an FD issue is to use vsd to display the open and maximum FD values contained in a given Geode statistics archive.

VMStats

The chart below shows VMStats fdLimit and fdsOpen values. In this case, the application ran out of FDs. 

VMStats

The JVM will also maintain references to FDs for files and (mainly) sockets that have been closed until a GC cleans them up. This condition is referred to as a soft FD leak. It results in a saw-tooth pattern in the VMStats.

VMStats

gfsh

The gfsh show metrics command can be used to show the FD limit (fileDescriptorLimit) and number of open FDs (totalFileDescriptorOpen) of a member. An example is:

show metrics --member=server1 --categories=jvm

Member Metrics

Category |         Metric          | Value
-------- | ----------------------- | -----
jvm      | jvmThreads              | 82
         | fileDescriptorLimit     | 81920
         | totalFileDescriptorOpen | 75
 

Action

There are several actions that can help prevent FD issues, including:

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