From: Fredrik Tolf Date: Thu, 22 Dec 2011 18:29:25 +0000 (+0100) Subject: Started documentation. X-Git-Tag: 0.1~2^2~2 X-Git-Url: http://git.dolda2000.com/gitweb/?a=commitdiff_plain;h=6fde0e19d966a3d83f837a035d05e2afbc20e010;p=pdm.git Started documentation. --- diff --git a/pdm/__init__.py b/pdm/__init__.py index e69de29..383b2e1 100644 --- a/pdm/__init__.py +++ b/pdm/__init__.py @@ -0,0 +1,31 @@ +"""Python Daemon Management + +This package aids in inspecting and managing daemon processes. A +program intended for running as a daemon may create PDM listeners, to +which PDM clients may connect in order to interact with the +process. + +This package contains the following modules: + + * srv -- Server module + * cli -- Client module + * perf -- Library for implementing object for the PERF protocol + +The protocol allows multiple management subprotocols for different +modes of operation. Currently, the following two management protocols +are supported. + + * The REPL protocol implements a simple read-eval-print loop which + accepts arbitrary Python code, executes it in the daemon process, + and returns its replies, all in text form. The protocol is simple, + generic, and has few failure modes, but is hardly suitable for + programmatic interaction. See the documentation for pdm.srv.repl + and pdm.cli.replclient for further details. + + * The PERF protocol is intended for programmatic interaction with the + daemon process. Various Python modules may expose objects that + implement one or several of a few pre-defined interfaces that allow + for various forms of inspection and management of the program + state. See the documentation for pdm.srv.perf and + pdm.cli.perfclient for further details. +""" diff --git a/pdm/srv.py b/pdm/srv.py index 9f6869e..128c6d9 100644 --- a/pdm/srv.py +++ b/pdm/srv.py @@ -1,18 +1,40 @@ -"""Management for daemon processes +"""Python Daemon Management -- Server functions -This module contains a utility to listen for management commands on a -socket, lending itself to managing daemon processes. +This module implements the server part of the PDM protocols. The +primary object of interest herein is the listen() function, which is +the most generic way to create PDM listeners based on user +configuration, and the documentation for the repl and perf classes, +which describes the functioning of the REPL and PERF protocols. """ import os, sys, socket, threading, grp, select import types, pprint, traceback import pickle, struct -__all__ = ["listener", "unixlistener", "tcplistener", "listen"] +__all__ = ["repl", "perf", "listener", "unixlistener", "tcplistener", "listen"] protocols = {} class repl(object): + """REPL protocol handler + + Provides a read-eval-print loop. The primary client-side interface + is the pdm.cli.replclient class. Clients can send arbitrary code, + which is compiled and run on its own thread in the server process, + and output responses that are echoed back to the client. + + Each client is provided with its own module, in which the code + runs. The module is prepared with a function named `echo', which + takes a single object and pretty-prints it as part of the command + response. If a command can be parsed as an expression, the value + it evaluates to is automatically echoed to the client. If the + evalution of the command terminates with an exception, its + traceback is echoed to the client. + + The REPL protocol is only intended for interactive usage. In order + to interact programmatically with the server process, see the PERF + protocol instead. + """ def __init__(self, cl): self.cl = cl self.mod = types.ModuleType("repl") @@ -53,6 +75,97 @@ class repl(object): protocols["repl"] = repl class perf(object): + """PERF protocol handler + + The PERF protocol provides an interface for program interaction + with the server process. It allows limited remote interactions + with Python objects over a few defined interfaces. + + All objects that wish to be available for interaction need to + implement a method named `pdm_protocols' which, when called with + no arguments, should return a list of strings, each indicating a + PERF interface that the object implements. For each such + interface, the object must implement additional methods as + described below. + + A client can find PERF objects to interact with either by + specifying the name of such an object in an existing module, or by + using the `dir' interface, described below. Thus, to make a PERF + object available for clients, it needs only be bound to a global + variable in a module and implement the `pdm_protocols' + method. When requesting an object from a module, the module must + already be imported. PDM will not import new modules for clients; + rather, the daemon process needs to import all modules that + clients should be able to interact with. PDM itself always imports + the pdm.perf module, which contains a few basic PERF objects. See + its documentation for details. + + The following interfaces are currently known to PERF. + + * attr: + An object that implements the `attr' interface models an + attribute that can be read by clients. The attribute can be + anything, as long as its representation can be + pickled. Examples of attributes could be such things as the CPU + time consumed by the server process, or the number of active + connections to whatever clients the program serves. To + implement the `attr' interface, an object must implement + methods called `readattr' and `attrinfo'. `readattr' is called + with no arguments to read the current value of the attribute, + and `attrinfo' is called with no arguments to read a + description of the attribute. Both should be + idempotent. `readattr' can return any pickleable object, and + `attrinfo' should return either None to indicate that it has no + description, or an instance of the pdm.perf.attrinfo class. + + * dir: + The `dir' interface models a directory of other PERF + objects. An object implementing it must implement methods + called `lookup' and `listdir'. `lookup' is called with a single + string argument that names an object, and should either return + another PERF object based on the name, or raise KeyError if it + does not recognize the name. `listdir' is called with no + arguments, and should return a list of known names that can be + used as argument to `lookup', but the list is not required to + be exhaustive and may also be empty. + + * invoke: + The `invoke' interface allows a more arbitrary form of method + calls to objects implementing it. Such objects must implement a + method called `invoke', which is called with one positional + argument naming a method to be called (which it is free to + interpret however it wishes), and with any additional + positional and keyword arguments that the client wishes to pass + to it. Whatever `invoke' returns is pickled and sent back to + the client. In case the method name is not recognized, `invoke' + should raise an AttributeError. + + * event: + The `event' interface allows PERF objects to notify clients of + events asynchronously. Objects implementing it must implement + methods called `subscribe' and `unsubscribe'. `subscribe' will + be called with a single argument, which is a callable of one + argument, which should be registered to be called when an event + pertaining to the `event' object in question occurs. The + `event' object should then call all such registered callables + with a single argument describing the event. The argument could + be any object that can be pickled, but should be an instance of + a subclass of the pdm.perf.event class. If `subscribe' is + called with a callback object that it has already registered, + it should raise a ValueError. `unsubscribe' is called with a + single argument, which is a previously registered callback + object, which should then be unregistered to that it is no + longer called when an event occurs. If the given callback + object is not, in fact, registered, a ValueError should be + raised. + + The pdm.perf module contains a few convenience classes which + implements the interfaces, but PERF objects are not required to be + instances of them. Any object can implement a PERF interface, as + long as it does so as described above. + + The pdm.cli.perfclient class is the client-side implementation. + """ def __init__(self, cl): self.cl = cl self.odtab = {} @@ -292,11 +405,19 @@ class client(threading.Thread): class listener(threading.Thread): + """PDM listener + + This subclass of a thread listens to PDM connections and handles + client connections properly. It is intended to be subclassed by + providers of specific domains, such as unixlistener and + tcplistener. + """ def __init__(self): super(listener, self).__init__(name = "Management listener") self.setDaemon(True) def listen(self, sk): + """Listen for and accept connections.""" self.running = True while self.running: rfd, wfd, efd = select.select([sk], [], [sk], 1) @@ -306,6 +427,11 @@ class listener(threading.Thread): self.accept(nsk, addr) def stop(self): + """Stop listening for client connections + + Tells the listener thread to stop listening, and then waits + for it to terminate. + """ self.running = False self.join() @@ -314,7 +440,14 @@ class listener(threading.Thread): cl.start() class unixlistener(listener): + """Unix socket listener""" def __init__(self, name, mode = 0600, group = None): + """Create a listener that will bind to the Unix socket named + by `name'. The socket will not actually be bound until the + listener is started. The socket will be chmodded to `mode', + and if `group' is given, the named group will be set as the + owner of the socket. + """ super(unixlistener, self).__init__() self.name = name self.mode = mode @@ -339,7 +472,12 @@ class unixlistener(listener): os.unlink(self.name) class tcplistener(listener): + """TCP socket listener""" def __init__(self, port, bindaddr = "127.0.0.1"): + """Create a listener that will bind to the given TCP port, and + the given local interface. The socket will not actually be + bound until the listener is started. + """ super(tcplistener, self).__init__() self.port = port self.bindaddr = bindaddr @@ -354,6 +492,22 @@ class tcplistener(listener): sk.close() def listen(spec): + """Create and start a listener according to a string + specification. The string specifications can easily be passed from + command-line options, user configuration or the like. Currently, + the two following specification formats are recognized: + + PATH[:MODE[:GROUP]] -- PATH must contain at least one slash. A + Unix socket listener will be created listening to that path, and + the socket will be chmodded to MODE and owned by GROUP. If MODE is + not given, it defaults to 0600, and if GROUP is not given, the + process' default group is used. + + ADDRESS:PORT -- PORT must be entirely numeric. A TCP socket + listener will be created listening to that port, bound to the + given local interface address. Since PDM has no authentication + support, ADDRESS should probably be localhost. + """ if ":" in spec: first = spec[:spec.index(":")] last = spec[spec.rindex(":") + 1:]