"hostname" program is called every time the config is read

[raskig]

We are using Nomad for retrieving config every time an endpoint is called of a web service. As we see from the logs, every time the config is read the "hostname" in shell is also called. This results in the following error after a while:
"java.io.IOException: Cannot run program "hostname": error=24, Too many open files"
Please confirm that this is a valid bug.
Thanks,
Gabor

[jarohen]

Hi @raskig, thanks for the report.

I don't think this is an issue with Nomad - it doesn't hold any open files after the call to hostname. Have you got a trace that shows whether there are multiple lingering hostname processes?

James

[raskig]

Hi @jarohen,
I think it is enough if it calls the "hostname" every time. My understanding is that the operation system will run out of file descriptors after a while when the load is high..

This is the exception we face after a while:

@40000000584fb9a93503e44c java.io.IOException: Cannot run program "hostname": error=24, Too many open files
@40000000584fb9a93503f7d4 	at java.lang.ProcessBuilder.start(ProcessBuilder.java:1047) ~[na:1.7.0_111]
@40000000584fb9a93503f7d4 	at java.lang.Runtime.exec(Runtime.java:617) ~[na:1.7.0_111]
@40000000584fb9a93503fbbc 	at clojure.java.shell$sh.doInvoke(shell.clj:116) ~[cljrc-web-120-standalone.jar:na]
@40000000584fb9a93503fbbc 	at clojure.lang.RestFn.invoke(RestFn.java:408) ~[cljrc-web-120-standalone.jar:na]
    @40000000584fb9a93504038c 	at nomad$get_hostname.invoke(nomad.clj:43) ~[cljrc-web-  120-standalone.jar:na]
    @40000000584fb9a93504038c 	at nomad$update_config.invoke(nomad.clj:168) ~[cljrc-web-120-standalone.jar:na]
@40000000584fb9a93504038c 	at nomad$read_config.doInvoke(nomad.clj:181) ~[cljrc-web-120-standalone.jar:na]

I was able to reproduce the problem by using a load test. By applying a quick fix (wrapping the (config) call in a (memoize config) ) it fixes the problem, but of course we loose the ability to change the config on the fly.

Hope this all makes sense.

[jarohen]

Hi @raskig - as luck would have it, I've just received a PR changing the implementation to use Java interop rather than shelling out (#32). Have released 0.7.3 with that change - does that work for you?