backdoor – Python interactive interpreter within a running process

The backdoor module is convenient for inspecting the state of a long-running process. It supplies the normal Python interactive interpreter in a way that does not block the normal operation of the application. This can be useful for debugging, performance tuning, or simply learning about how things behave in situ.

In the application, spawn a greenthread running backdoor_server on a listening socket:

eventlet.spawn(backdoor.backdoor_server, eventlet.listen(('localhost', 3000)), locals())

When this is running, the backdoor is accessible via telnet to the specified port.

$ telnet localhost 3000
(python version, build info)
Type "help", "copyright", "credits" or "license" for more information.
>>> import myapp
>>> dir(myapp)
['__all__', '__doc__', '__name__', 'myfunc']

The backdoor cooperatively yields to the rest of the application between commands, so on a running server continuously serving requests, you can observe the internal state changing between interpreter commands.

class eventlet.backdoor.SocketConsole(desc, hostport, locals)
switch(*args, **kwargs)

Switch execution to this greenlet.

If this greenlet has never been run, then this greenlet will be switched to using the body of*args, **kwargs).

If the greenlet is active (has been run, but was switch()’ed out before leaving its run function), then this greenlet will be resumed and the return value to its switch call will be None if no arguments are given, the given argument if one argument is given, or the args tuple and keyword args dict if multiple arguments are given.

If the greenlet is dead, or is the current greenlet then this function will simply return the arguments using the same rules as above.

eventlet.backdoor.backdoor(conn_info, locals=None)

Sets up an interactive console on a socket with a single connected client. This does not block the caller, as it spawns a new greenlet to handle the console. This is meant to be called from within an accept loop (such as backdoor_server).

eventlet.backdoor.backdoor_server(sock, locals=None)

Blocking function that runs a backdoor server on the socket sock, accepting connections and running backdoor consoles for each client that connects.

The locals argument is a dictionary that will be included in the locals() of the interpreters. It can be convenient to stick important application variables in here.