diff options
| -rw-r--r-- | src/vpp-api/python/vpp_papi/vpp_papi.py | 303 |
1 files changed, 219 insertions, 84 deletions
diff --git a/src/vpp-api/python/vpp_papi/vpp_papi.py b/src/vpp-api/python/vpp_papi/vpp_papi.py index 45774723..8de1e4b4 100644 --- a/src/vpp-api/python/vpp_papi/vpp_papi.py +++ b/src/vpp-api/python/vpp_papi/vpp_papi.py @@ -16,30 +16,58 @@ from __future__ import print_function import sys, os, logging, collections, struct, json, threading, glob +import atexit + logging.basicConfig(level=logging.DEBUG) import vpp_api def eprint(*args, **kwargs): + """Print critical diagnostics to stderr.""" print(*args, file=sys.stderr, **kwargs) +def vpp_atexit(self): + """Clean up VPP connection on shutdown.""" + if self.connected: + eprint ('Cleaning up VPP on exit') + self.disconnect() + class VPP(): + """VPP interface. + + This class provides the APIs to VPP. The APIs are loaded + from provided .api.json files and makes functions accordingly. + These functions are documented in the VPP .api files, as they + are dynamically created. + + Additionally, VPP can send callback messages; this class + provides a means to register a callback function to receive + these messages in a background thread. + """ def __init__(self, apifiles = None, testmode = False): + """Create a VPP API object. + + apifiles is a list of files containing API + descriptions that will be loaded - methods will be + dynamically created reflecting these APIs. If not + provided this will load the API files from VPP's + default install location. + """ self.messages = {} self.id_names = [] self.id_msgdef = [] self.buffersize = 10000 self.connected = False self.header = struct.Struct('>HI') + self.results_lock = threading.Lock() self.results = {} self.timeout = 5 - self.apifile = [] + self.apifiles = [] if not apifiles: # Pick up API definitions from default directory apifiles = glob.glob('/usr/share/vpp/api/*.api.json') for file in apifiles: - self.apifile.append(file) with open(file) as apidef_file: api = json.load(apidef_file) for t in api['types']: @@ -47,25 +75,34 @@ class VPP(): for m in api['messages']: self.add_message(m[0], m[1:]) + self.apifiles = apifiles # Basic sanity check if len(self.messages) == 0 and not testmode: raise ValueError(1, 'Missing JSON message definitions') + # Make sure we allow VPP to clean up the message rings. + atexit.register(vpp_atexit, self) class ContextId(object): + """Thread-safe provider of unique context IDs.""" def __init__(self): self.context = 0 + self.lock = threading.Lock() def __call__(self): - self.context += 1 - return self.context + """Get a new unique (or, at least, not recently used) context.""" + with self.lock: + self.context += 1 + return self.context get_context = ContextId() def status(self): + """Debug function: report current VPP API status to stdout.""" print('Connected') if self.connected else print('Not Connected') - print('Read API definitions from', self.apifile) + print('Read API definitions from', ', '.join(self.apifiles)) def __struct (self, t, n = None, e = -1, vl = None): + """Create a packing structure for a message.""" base_types = { 'u8' : 'B', 'u16' : 'H', 'u32' : 'I', @@ -113,6 +150,7 @@ class VPP(): raise ValueError(1, 'Invalid message type: ' + t) def __struct_type(self, encode, msgdef, buf, offset, kwargs): + """Get a message packer or unpacker.""" if encode: return self.__struct_type_encode(msgdef, buf, offset, kwargs) else: @@ -261,7 +299,7 @@ class VPP(): def make_function(self, name, i, msgdef, multipart, async): if (async): - f = lambda **kwargs: (self._call_vpp_async(i, msgdef, multipart, **kwargs)) + f = lambda **kwargs: (self._call_vpp_async(i, msgdef, **kwargs)) else: f = lambda **kwargs: (self._call_vpp(i, msgdef, multipart, **kwargs)) args = self.messages[name]['args'] @@ -286,6 +324,7 @@ class VPP(): setattr(self, name, self.make_function(name, i, msgdef, multipart, async)) def _write (self, buf): + """Send a binary-packed message to VPP.""" if not self.connected: raise IOError(1, 'Not connected') return vpp_api.write(str(buf)) @@ -304,11 +343,19 @@ class VPP(): self.vpp_dictionary_maxid = max(self.vpp_dictionary_maxid, i) def connect(self, name, chroot_prefix = None, async = False, rx_qlen = 32): - msg_handler = self.msg_handler if not async else self.msg_handler_async - if not chroot_prefix: - rv = vpp_api.connect(name, msg_handler, rx_qlen) + """Attach to VPP. + + name - the name of the client. + chroot_prefix - if VPP is chroot'ed, the prefix of the jail + async - if true, messages are sent without waiting for a reply + rx_qlen - the length of the VPP message receive queue between + client and server. + """ + msg_handler = self.msg_handler_sync if not async else self.msg_handler_async + if chroot_prefix is not None: + rv = vpp_api.connect(name, msg_handler, rx_qlen, chroot_prefix) else: - rv = vpp_api.connect(name, msg_handler, rx_qlen, chroot_prefix) + rv = vpp_api.connect(name, msg_handler, rx_qlen) if rv != 0: raise IOError(2, 'Connect failed') @@ -322,29 +369,115 @@ class VPP(): self.control_ping_msgdef = self.messages['control_ping'] def disconnect(self): + """Detach from VPP.""" rv = vpp_api.disconnect() + self.connected = False return rv def results_wait(self, context): - return (self.results[context]['e'].wait(self.timeout)) + """In a sync call, wait for the reply + + The context ID is used to pair reply to request. + """ + + # Results is filled by the background callback. It will + # raise the event when the context receives a response. + # Given there are two threads we have to be careful with the + # use of results and the structures under it, hence the lock. + with self.results_lock: + result = self.results[context] + ev = result['e'] + + timed_out = not ev.wait(self.timeout) + + if timed_out: + raise IOError(3, 'Waiting for reply timed out') + else: + with self.results_lock: + result = self.results[context] + del self.results[context] + return result['r'] + + def results_prepare(self, context, multi=False): + """Prep for receiving a result in response to a request msg + + context - unique context number sent in request and + returned in reply or replies + multi - true if we expect multiple messages from this + reply. + """ + + # The event is used to indicate that all results are in + new_result = { + 'e': threading.Event(), + } + if multi: + # Make it clear to the BG thread it's going to see several + # messages; messages are stored in a results array + new_result['m'] = True + new_result['r'] = [] + + new_result['e'].clear() + + # Put the prepped result structure into results, at which point + # the bg thread can also access it (hence the thread lock) + with self.results_lock: + self.results[context] = new_result + + def msg_handler_sync(self, msg): + """Process an incoming message from VPP in sync mode. + + The message may be a reply or it may be an async notification. + """ + r = self.decode_incoming_msg(msg) + if r is None: + return + + # If we have a context, then use the context to find any + # request waiting for a reply + context = 0 + if hasattr(r, 'context') and r.context > 0: + context = r.context - def results_prepare(self, context): - self.results[context] = {} - self.results[context]['e'] = threading.Event() - self.results[context]['e'].clear() - self.results[context]['r'] = [] + msgname = type(r).__name__ - def results_clean(self, context): - del self.results[context] + if context == 0: + # No context -> async notification that we feed to the callback + if self.event_callback: + self.event_callback(msgname, r) + else: + # Context -> use the results structure (carefully) to find + # who we're responding to and return the message to that + # thread + with self.results_lock: + if context not in self.results: + eprint('Not expecting results for this context', context, r) + else: + result = self.results[context] + + # + # Collect results until control ping + # + + if msgname == 'control_ping_reply': + # End of a multipart + result['e'].set() + elif 'm' in self.results[context]: + # One element in a multipart + result['r'].append(r) + else: + # All of a single result + result['r'] = r + result['e'].set() - def msg_handler(self, msg): + def decode_incoming_msg(self, msg): if not msg: eprint('vpp_api.read failed') return i, ci = self.header.unpack_from(msg, 0) if self.id_names[i] == 'rx_thread_exit': - return; + return # # Decode message and returns a tuple. @@ -354,87 +487,75 @@ class VPP(): raise IOError(2, 'Reply message undefined') r = self.decode(msgdef, msg) - if 'context' in r._asdict(): - if r.context > 0: - context = r.context - - msgname = type(r).__name__ - # - # XXX: Call provided callback for event - # Are we guaranteed to not get an event during processing of other messages? - # How to differentiate what's a callback message and what not? Context = 0? - # - #if not is_waiting_for_reply(): - if r.context == 0 and self.event_callback: - self.event_callback(msgname, r) - return + return r - # - # Collect results until control ping - # - if msgname == 'control_ping_reply': - self.results[context]['e'].set() - return + def msg_handler_async(self, msg): + """Process a message from VPP in async mode. - if not context in self.results: - eprint('Not expecting results for this context', context, r) + In async mode, all messages are returned to the callback. + """ + r = self.decode_incoming_msg(msg) + if r is None: return - if 'm' in self.results[context]: - self.results[context]['r'].append(r) - return + msgname = type(r).__name__ - self.results[context]['r'] = r - self.results[context]['e'].set() + if self.event_callback: + self.event_callback(msgname, msg) - def msg_handler_async(self, msg): - if not msg: - eprint('vpp_api.read failed') - return + def _control_ping(self, context): + """Send a ping command.""" + self._call_vpp_async(self.control_ping_index, + self.control_ping_msgdef, + context=context) - i, ci = self.header.unpack_from(msg, 0) - if self.id_names[i] == 'rx_thread_exit': - return; + def _call_vpp(self, i, msgdef, multipart, **kwargs): + """Given a message, send the message and await a reply. - # - # Decode message and returns a tuple. - # - msgdef = self.id_msgdef[i] - if not msgdef: - raise IOError(2, 'Reply message undefined') + msgdef - the message packing definition + i - the message type index + multipart - True if the message returns multiple + messages in return. + context - context number - chosen at random if not + supplied. + The remainder of the kwargs are the arguments to the API call. - r = self.decode(msgdef, msg) - msgname = type(r).__name__ + The return value is the message or message array containing + the response. It will raise an IOError exception if there was + no response within the timeout window. + """ - self.event_callback(msgname, r) + # We need a context if not supplied, in order to get the + # response + context = kwargs.get('context', self.get_context()) + kwargs['context'] = context - def _control_ping(self, context): - self._write(self.encode(self.control_ping_msgdef, - { '_vl_msg_id' : self.control_ping_index, - 'context' : context})) + # Set up to receive a response + self.results_prepare(context, multi=multipart) - def _call_vpp(self, i, msgdef, multipart, **kwargs): - if not 'context' in kwargs: - context = self.get_context() - kwargs['context'] = context - else: - context = kwargs['context'] - kwargs['_vl_msg_id'] = i - b = self.encode(msgdef, kwargs) - - self.results_prepare(context) - self._write(b) + # Output the message + self._call_vpp_async(i, msgdef, **kwargs) if multipart: - self.results[context]['m'] = True + # Send a ping after the request - we use its response + # to detect that we have seen all results. self._control_ping(context) - self.results_wait(context) - r = self.results[context]['r'] - self.results_clean(context) + + # Block until we get a reply. + r = self.results_wait(context) + return r - def _call_vpp_async(self, i, msgdef, multipart, **kwargs): + def _call_vpp_async(self, i, msgdef, **kwargs): + """Given a message, send the message and await a reply. + + msgdef - the message packing definition + i - the message type index + context - context number - chosen at random if not + supplied. + The remainder of the kwargs are the arguments to the API call. + """ if not 'context' in kwargs: context = self.get_context() kwargs['context'] = context @@ -446,5 +567,19 @@ class VPP(): self._write(b) def register_event_callback(self, callback): + """Register a callback for async messages. + + This will be called for async notifications in sync mode, + and all messages in async mode. In sync mode, replies to + requests will not come here. + + callback is a fn(msg_type_name, msg_type) that will be + called when a message comes in. While this function is + executing, note that (a) you are in a background thread and + may wish to use threading.Lock to protect your datastructures, + and (b) message processing from VPP will stop (so if you take + a long while about it you may provoke reply timeouts or cause + VPP to fill the RX buffer). Passing None will disable the + callback. + """ self.event_callback = callback - |