support twistd's --profiler= and --debug options when starting a node

[davidsarah]

tahoe start and tahoe run should take a --profile option, like the twistd command, so that you don't have to run twistd directly when profiling.

twistd's --debug option might also be useful.

[davidsarah]

From the output of twistd --help:

  -p, --profile=         Run in profile mode, dumping results to specified file
      --profiler=        Name of the profiler to use (profile, cprofile,
                         hotshot). [default: hotshot]
[...]
  -b, --debug            run the application in the Python Debugger (implies
                         nodaemon), sending SIGUSR2 will drop into debugger

[davidsarah]

Oh, it already does support the --profile option, but not overriding the profiler:

$ bin/tahoe start --help

Usage:  tahoe <command> [command options] start [options]
Options:
[...]
  -p, --profile           Run under the Python profiler, putting results in
                          'profiling_results.prof'.

src/allmydata/scripts/startstop_node.py@4765#L57:

    if opts["profile"]:
        args.extend(["--profile=profiling_results.prof", "--savestats",])

[davidsarah]

According to francois in ticket:1264#comment:7, the -n or --nodaemon option to twistd is necessary in order to save profile output.

[warner]

What if we accepted a syntax like "tahoe start DIR -- ARG1 ARG2" or "tahoe start -- ARG1 ARG2", and passed all the extra ARG1/ARG2 strings into twistd.run()? I'd really like if it we had a way to pass arbitrary twistd arguments, rather than having to hand-code support for each one.

[zooko]

Replying to warner:

What if we accepted a syntax like "tahoe start DIR -- ARG1 ARG2" or "tahoe start -- ARG1 ARG2", and passed all the extra ARG1/ARG2 strings into twistd.run()? I'd really like if it we had a way to pass arbitrary twistd arguments, rather than having to hand-code support for each one.

Created #1546 for this.

[exarkun]

ticket:1546 would seem to completely supersede this one since it suggests allowing any options to be passed through to twistd and the profiler and debugger options fall into the set of "any options".

Not sure why this was left open or why that other ticket was created instead of this one being resolved. Resolving this one as a duplicate now.