manhole 0.5.1

Inpection manhole for python applications. Connection is done via unix domain sockets.

Manhole is a python daemon thread that will accept unix domain socket connections and present the stacktraces for all threads and an interactive prompt.

Access to the socket is restricted to the application’s effective user id or root.

This is just like Twisted’s manhole. It’s simpler (no dependencies) and it only runs on Unix domain sockets (in contrast to Twisted’s manhole which can run on telnet or ssh).

Usage

You can put this in your django settings, wsgi app file, some module that’s always imported early etc:

import manhole
manhole.install() # this will start the daemon thread

# and now you start your app, eg: server.serve_forever()

Now in a shell you can do either of these:

netcat -U /tmp/manhole-1234
socat - unix-connect:/tmp/manhole-1234
socat readline unix-connect:/tmp/manhole-1234

Sample output:

$ nc -U /tmp/manhole-1234

Python 2.7.3 (default, Apr 10 2013, 06:20:15)
[GCC 4.6.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
(InteractiveConsole)
>>> dir()
['__builtins__', 'dump_stacktraces', 'os', 'socket', 'sys', 'traceback']
>>> print 'foobar'
foobar

Features

• Uses unix domain sockets, only root or same effective user can connect.

• Can run the connection in a thread or in a signal handler (see oneshot_on option).

• Can start the thread listening for connections from a singla handler (see activate_on option)

• Compatible with apps that fork, reinstalls the Manhole thread after fork - had to monkeypatch os.fork/os.forkpty for this.

• The thread is compatible with apps that use signalfd (will mask all signals for the Manhole threads).

Options

manhole.install(verbose=True, patch_fork=True, activate_on=None, sigmask=manhole.ALL_SIGNALS, oneshot_on=None)

• verbose - set it to False to squelch the stderr ouput

• patch_fork - set it to False if you don’t want your os.fork and os.forkpy monkeypatched

• activate_on - set to "USR1", "USR2" or some other signal name, or a number if you want the Manhole thread to start when this signal is sent. This is desireable in case you don’t want the thread active all the time.

• oneshot_on - set to "USR1", "USR2" or some other signal name, or a number if you want the Manhole to listen for connection in the signal handler. This is desireable in case you don’t want threads at all.

• sigmask - will set the signal mask to the given list (using signalfd.sigprocmask). No action is done if signalfd is not importable. NOTE: This is done so that the Manhole thread doesn’t steal any signals; Normally that is fine cause Python will force all the signal handling to be run in the main thread but signalfd doesn’t.

What happens when you actually connect to the socket

1. Credentials are checked (if it’s same user or root)

2. sys.__std*__/sys.std* are be redirected to the UDS

3. Stacktraces for each thread are written to the UDS

4. REPL is started so you can fiddle with the process

Whishlist

• Be compatible with eventlet/stackless (provide alternative implementation without thread) - currently oneshot_on should be usable for those. The are not tests done on eventlet/stackless for now.

• More configurable (chose what sys.__std*__/sys.std* to patch on connect time)

• Support windows ?!

Requirements

Not sure yet … so far Python 2.6, 2.7, 3.2, 3.3 and pypy are tested in Travis:

Coverage is wrong, must be a bug in coveralls, it should be at least 80%-90% depending whether you count branches or not.

Similar projects

• Twisted’s old manhole and the newer implementation (colors, serverside history).

• wsgi-shell - spawns a thread.

• pyrasite - uses gdb to inject code.

• pydbattach - uses gdb to inject code.