[erlang-questions] Command-line for releases

Roberto Ostinelli roberto@REDACTED
Sun Dec 28 12:48:41 CET 2014

Thank you Jesper!
Yes indeed, the erlang:memory() call is just an example (I use folsom too
for real production system monitoring).

I use rebar for releases, and the ping command just dumps a "pong"
response. I'm assuming you refer to the RPC command instead, or maybe the
nodetool generated by relx is different?


On Sun, Dec 28, 2014 at 12:28 PM, Jesper Louis Andersen <
jesper.louis.andersen@REDACTED> wrote:

> I tend to do two things in this area (note relx):
> Alter the 'myapp' script such that it takes extra commands and execute
> this command like "ping" is implemented: call nodetool to do rpc towards
> the node (IIRC it creates a distributed node, connects it to the running
> node and runs its stuff).
> But for stats in general, my approach is very different. I use "folsom" to
> gather statistics[0]. Note that this is gathering, not persisting/storing.
> Then another application shovels the gathered statistics to a foreign
> system for historical data and you plot the data. Knowing that your system
> used 320 megabytes of space now is of little use unless you happen to know
> what the typical baseline of your system tend to be. So I gather that
> information for any production system if I can.
> I'm pretty aggressive in stats gathering. It is not uncommon to have 1000+
> probes in a system for me. This is because I firmly believe that you need
> to measure in order to improve a system.
> [0] In a newly deployed system, I would probably check out exometer.
> On Sun Dec 28 2014 at 12:16:26 PM Roberto Ostinelli <roberto@REDACTED>
> wrote:
>> Hi all,
>> Let's say that you have a running node, started from a release command:
>> $ myapp start
>> Now, I'd like to check some current stats of the node (for instance, with
>> erlang:memory/0), but would like to do it with an external script, i.e. a
>> command-line tool so that it gets printed in the console, like so:
>> $ myappctl memory
>> total:14303080
>> What is your recommended way to have a command-line tool connect to a
>> release-started erlang node to issue a command and return a value?
>> There are many ways, I'd like to hear some recommendations.
>> Best,
>> r.
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