I/O exception (java.net.SocketException) caught when connecting to the target host: Too many open files

Question

I am using Apache Jmeter for testing our application but suddenly most of the errors that Jmeter displayed was

java.net.SocketException: Too many open files at java.net.Socket.createImpl(Socket.java:447) at java.net.Socket.getImpl(Socket.java:510) at java.net.Socket.setSoTimeout(Socket.java:1101)
at org.apache.http.conn.scheme.PlainSokcetFactory.connectSocket(PlainSocketFactory.java:126)

as I searched on the internet most of the comments about this error is because of the open limit of the machine, and then there was an answer that said Entities should be consume and when I tried on consuming the Entities the number of errors were reduced but not that many. are there any other ways to handle this kind of error?

Answer 1

Default maximum number of open files and or sockets on Linux machines is 1024.

If your test exceeds it although shouldn't you need to inspect your test and detect and fix leaks.

If it's expected and you just increase limits on files/sockets it should be possible to increase them to reasonably higher value. See ulimit command reference and information on limits.conf file.Alternatively you could try running JMeter as root user.

To get maximum number of allowed open files execute

ulimit -n 

in terminal

References:

• JMeter Performance and Tuning Tips - guide on JMeter tuning and best practices
• Linux ulimit command reference
• limits.conf file documentation

Hope this helps

Answer 2

The most likely cause is that you create a lot of Socket s but do not .close() them properly.

You don't show code so no one can fix that for you; anyway, there are classical idioms when dealing with Socket s, or indeed any class which implements Closeable ( which Socket does ).

With Java 6:

final Closeable closeable = whatever(); // or Socket, or InputStream, or...
try {
    doSomethingWith(closeable);
} finally {
    closeable.close();
}

With Java 7:

try (
    final Closeable closeable = whatever();
) {
    doSomethingWith(closeable);
}
// Automatically closed for you

NOTE: with Java 7, it is in fact anything which implements AutoCloseable ; and Closeable extends AutoCloseable .

NOTE 2: if Java 6 and you can afford Guava 14+, consider using Closer .