**Reported in Launchpad by David last update 28-08-2015 07:48:01

This is more likely a feature request than a bug, but the before_collect triggers do not fire when threshold + cycles = fire , but only if the collect process itself is invoked , which could be interpreted to contradict to what is specified in the documentation:

"before_collect

Called when the trigger occurs, before running a --collect subprocesses in the background."

I would like to leverage pt-stalk to do some ad-hoc specific monitoring of custom counts (via the --function option) and then collect some custom data (via --plugins) without dumping all of the data collected by pt-stalk

Details -

plugin :

From the example page :

before_collect() {
touch /tmp/foo
}

Log output for failed trigger fire:

2015_08_26_10_06_44 Starting /mysql/software/pt/bin/pt-stalk --function=./pt_stalk_user --variable=Threads_running --threshold=1 --match= --cycles=5 --interval=10 --iterations= --run-time=30 --sleep=5 --dest=/var/lib/pt-stalk --prefix= --notify-by-email= --log=./pt-stalk.log --pid=./pid --plugin=./pt_stalk_collect
2015_08_26_10_06_44 Not running with root privileges!
2015_08_26_10_06_44 Check results: ./pt_stalk_user(Threads_running)=2, matched=yes, cycles_true=1
2015_08_26_10_06_54 Check results: ./pt_stalk_user(Threads_running)=2, matched=yes, cycles_true=2
2015_08_26_10_07_04 Check results: ./pt_stalk_user(Threads_running)=2, matched=yes, cycles_true=3
2015_08_26_10_07_14 Check results: ./pt_stalk_user(Threads_running)=2, matched=yes, cycles_true=4
2015_08_26_10_07_24 Check results: ./pt_stalk_user(Threads_running)=2, matched=yes, cycles_true=5
2015_08_26_10_07_24 Collect 1 triggered
2015_08_26_10_07_24 Collect 1 done

Log output for successful trigger-fire:

2015_08_26_10_10_21 Starting /mysql/software/pt/bin/pt-stalk --function=./pt_stalk_user --variable=Threads_running --threshold=1 --match= --cycles=5 --interval=10 --iterations= --run-time=30 --sleep=5 --dest=. --prefix= --notify-by-email= --log=./pt-stalk.log --pid=./pid --plugin=./pt_stalk_collect
2015_08_26_10_10_21 Not running with root privileges!
2015_08_26_10_10_21 Check results: ./pt_stalk_user(Threads_running)=2, matched=yes, cycles_true=1
2015_08_26_10_10_31 Check results: ./pt_stalk_user(Threads_running)=2, matched=yes, cycles_true=2
2015_08_26_10_10_41 Check results: ./pt_stalk_user(Threads_running)=2, matched=yes, cycles_true=3
2015_08_26_10_10_51 Check results: ./pt_stalk_user(Threads_running)=2, matched=yes, cycles_true=4
2015_08_26_10_11_01 Check results: ./pt_stalk_user(Threads_running)=2, matched=yes, cycles_true=5
2015_08_26_10_11_01 Collect 1 triggered
2015_08_26_10_11_01 Collect 1 PID 26643
2015_08_26_10_11_01 Collect 1 done

The log in example one says that the 'Collect 1 " event is triggered, but must then branch when encountering the "--no-collect' option, before parsing any plugin files

It is a small thing, but it would be useful!

Thanks!