CODEWITHSUNDEEP
javagroovy
dromodel
dromodel

Reputation: 10243

Why do I get "Too many open files" errors?

I find myself having to explicitly call System.gc() in my Groovy scripts to prevent errors like the one below. Why doesn't the garbage collector do this for me? Is there something I can do to cause it to garbage collect to prevent these errors (maybe JAVA_OPTS)?

Caught: java.util.concurrent.ExecutionException: org.codehaus.groovy.runtime.InvokerInvocationException: java.io.IOException: Cannot run program "ls": java.io.IOException: error=24, Too many open files
    at groovyx.gpars.GParsPool.runForkJoin(GParsPool.groovy:305)
    at UsageAnalyzer$_run_closure2_closure6.doCall(UsageAnalyzer.groovy:36)
    at groovyx.gpars.GParsPool$_withExistingPool_closure1.doCall(GParsPool.groovy:170)
    at groovyx.gpars.GParsPool$_withExistingPool_closure1.doCall(GParsPool.groovy)
    at groovyx.gpars.GParsPool.withExistingPool(GParsPool.groovy:169)
    at groovyx.gpars.GParsPool.withPool(GParsPool.groovy:141)
    at groovyx.gpars.GParsPool.withPool(GParsPool.groovy:117)
    at groovyx.gpars.GParsPool.withPool(GParsPool.groovy:96)
    at UsageAnalyzer$_run_closure2.doCall(<removed>)
    at UsageAnalyzer.run(<removed>)

This stack trace is from a parallel program but it happens in sequential programs as well.

Upvotes: 0

Views: 2747

Answers (2)

winstaan74
winstaan74

Reputation: 1131

As you're using groovy, you can use the convenient methods such as File.withReader(), File.withWriter(), File.withInputStream(), InputStream.withStream() to ensure resources get closed cleanly. This is less cumbersome than using Java's try .. finally idiom, as there's not need to explicitly call close(), or declare a variable outside the try block.

e.g. to read from a file.

File f = new File('/mumble/mumble/')
f.withReader{ r -> 
   // do stuff with reader here
}

Upvotes: 6

Vala
Vala

Reputation: 5674

Definitely look for any place you open files or streams and make sure you close them. It's often beneficial to wrap them like this:

final InputStream in = ...;
try
{
    // Do whatever.
}
finally
{
    // Will always close the stream, regardless of exceptions, return statements, etc.
    in.close();
}

Upvotes: 3

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