Monkey comes with an optional Trace mode that can be only enabled on compile time. It aim to print to STDOUT different trace messages across different sections of the core when running.
Due to it's verbosity this Trace mode should only used under a development context as performance is affected. Never enable Trace mode on production.
A printed trace line is formed using the following format:
~ seconds:milliseconds [component|file:line] function() message
Description of each field below:
| field | description |
|---|---|
| seconds | elapsed time in seconds since the server started |
| milliseconds | number of milliseconds for the current seconds unit |
| component | Monkey component, can be core or a plugin name |
| file | Filename where the trace was generated |
| line | Line of the file where the trace was generated |
| function | Caller function() |
| message | Trace message |
As said, Monkey needs to be recompiled with Trace mode enabled, to accomplish that append the --trace argument to the configure script:
$ ./configure --trace
Now is suggested to clean up any old object file and recompile:
$ make clean
$ make
To verify that Trace mode was enabled, start Monkey server and check the output printed to STDOUT:
$ bin/monkey
~ 0.338244 [core|monkey.c:255] main() Monkey TRACE is enabled
Monkey HTTP Server 1.5.6
Built : Mar 2 2015 08:46:25 (gcc 4.8.2)
Home : http://monkey-project.com
~ 0.338750 [core|mk_vhost.c:394] mk_vhost_read() Map error page: status 404 -> 404.html
~ 0.338836 [core|mk_file.c:100] mk_file_get_info() warning: target has not execution permission
~ 0.339356 [core|mk_file.c:100] mk_file_get_info() warning: target has not execution permission
~ 0.339618 [core|mk_plugin.c:500] mk_plugin_read_config() Load Plugin 'liana@/home/edsiper/coding/monkey/plugins/liana/monkey-liana.so'
~ 0.339655 [core|mk_plugin.c:821] mk_plugin_preworker_calls() [liana] Set thread key
[+] Process ID is 6204
[+] Server socket listening on Port 2001
[+] 4 threads, 126 client connections per thread, total 504
[+] Transport layer by liana in http mode
[+] Linux Features: TCP_FASTOPEN SO_REUSEPORT
Now we can see in the top line after the server signature a message like this:
~ 0.338244 [core|monkey.c:255] main() Monkey TRACE is enabled
Once the server start receiving requests the Trace feature will print out messages about everything that is happening internally.
Sometimes when using Trace mode we want to only trace specific files of Monkey core or some specific plugin, for this purpose exists a filtering mechanism that allows to just print desired events that happens on a specific file name.
A filter is set using the environment variable MK_TRACE_FILTER, many file names can be added. As an example, if we would just be interested into get trace messages from the Monkey Scheduler we should set the filter as follows:
$ export MK_TRACE_FILTER="mk_scheduler.c"
$ bin/monkey
As described, the filter must be set before to start Monkey. If you want to also trace multiple files just append them in the same filter line, e.g: if we are also interested into the Event Loop traces we should do:
$ export MK_TRACE_FILTER="mk_scheduler.c mk_epoll.c"
$ bin/monkey
Remember that Monkey Trace should not be enabled on production, just for development purposes.