create_zmq_connection¶

aiozmq.create_zmq_connection(protocol_factory, zmq_type, *, bind=None, connect=None, zmq_sock=None, loop=None)¶

Create a ZeroMQ connection.

This method is a coroutine.

If you don’t use bind or connect params you can do it later by ZmqTransport.bind() and ZmqTransport.connect() calls.

Parameters:	protocol_factory (callable) – a factory that instantiates ZmqProtocol object. zmq_type (int) – a type of ZeroMQ socket (zmq.REQ, zmq.REP, zmq.PUB, zmq.SUB, zmq.PAIR*, zmq.DEALER, zmq.ROUTER, zmq.PULL, zmq.PUSH, etc.) bind (str or iterable of strings) – endpoints specification. Every endpoint generates call to ZmqTransport.bind() for accepting connections from specified endpoint. Other side should use connect parameter to connect to this transport. connect (str or iterable of strings) – endpoints specification. Every endpoint generates call to ZmqTransport.connect() for connecting transport to specified endpoint. Other side should use bind parameter to wait for incoming connections. zmq_sock (zmq.Socket) – a preexisting zmq socket that will be passed to returned transport. loop (asyncio.AbstractEventLoop) – optional event loop instance, None for default event loop.
Returns:	a pair of (transport, protocol) where transport supports ZmqTransport interface.
Return type:	tuple

New in version 0.5.

ZmqTransport¶

class aiozmq.ZmqTransport¶

Transport for ZeroMQ connections. Implements asyncio.BaseTransport interface.

End user should never create ZmqTransport objects directly, he gets it by yield from aiozmq.create_zmq_connection() call.

get_extra_info(key, default=None)¶

Return optional transport information if name is present otherwise return default.

ZmqTransport supports the only valid key: "zmq_socket". The value is zmq.Socket instance.

Parameters:	name (str) – name of info record. default – default value

close()¶

Close the transport.

Buffered data will be flushed asynchronously. No more data will be received. After all buffered data is flushed, the protocol’s connection_lost() method will (eventually) called with None as its argument.

write(data)¶

Write message to the transport.

Parameters:	data – iterable to send as multipart message.

This does not block; it buffers the data and arranges for it to be sent out asynchronously.

abort()¶

Close the transport immediately.

Buffered data will be lost. No more data will be received. The protocol’s connection_lost() method will (eventually) be called with None as it’s argument.

getsockopt(option)¶

Get ZeroMQ socket option.

Parameters:	option (int) – a constant like zmq.SUBSCRIBE, zmq.UNSUBSCRIBE, zmq.TYPE etc. For list of available options please see: http://api.zeromq.org/master:zmq-getsockopt
Returns:	option value
Raises OSError:	if call to ZeroMQ was unsuccessful.

setsockopt(option, value)¶

Set ZeroMQ socket option.

Parameters:	option (int) – a constant like zmq.SUBSCRIBE, zmq.UNSUBSCRIBE, zmq.TYPE etc. value – a new option value, it’s type depend of option name. For list of available options please see: http://api.zeromq.org/master:zmq-setsockopt

set_write_buffer_limits(high=None, low=None)¶

Set the high- and low-water limits for write flow control.

Parameters:	high (int or None) – high-water limit low (int or None) – low-water limit

These two values control when to call the protocol’s pause_writing() and resume_writing() methods. If specified, the low-water limit must be less than or equal to the high-water limit. Neither value can be negative.

The defaults are implementation-specific. If only the high-water limit is given, the low-water limit defaults to a implementation-specific value less than or equal to the high-water limit. Setting high to zero forces low to zero as well, and causes pause_writing() to be called whenever the buffer becomes non-empty. Setting low to zero causes resume_writing() to be called only once the buffer is empty. Use of zero for either limit is generally sub-optimal as it reduces opportunities for doing I/O and computation concurrently.

get_write_buffer_size()¶

Return the current size of the write buffer.

pause_reading()¶

Pause the receiving end.

No data will be passed to the protocol’s ZmqProtocol.msg_received() method until resume_reading() is called.

resume_reading()¶

Resume the receiving end.

Data received will once again be passed to the protocol’s ZmqProtocol.msg_received() method.

bind(endpoint)¶

Bind transpot to endpoint. See http://api.zeromq.org/master:zmq-bind for details.

This method is a coroutine.

Parameters:	endpoint – a string in format transport://address as ZeroMQ requires.
Returns:	bound endpoint, unwinding wildcards if needed.
Return type:	str
Raises:	OSError – on error from ZeroMQ layer TypeError – if endpoint is not a str

unbind(endpoint)¶

Unbind transpot from endpoint.

This method is a coroutine.

Parameters:	endpoint – a string in format transport://address as ZeroMQ requires.
Returns:	None
Raises:	OSError – on error from ZeroMQ layer TypeError – if endpoint is not a str

bindings()¶

Return immutable set of endpoints bound to transport.

Note

Returned endpoints include only ones that has been bound via ZmqTransport.bind() or create_zmq_connection() calls and do not include bindings that have been done on zmq_sock before create_zmq_connection() call.

connect(endpoint)¶

Connect transpot to endpoint. See http://api.zeromq.org/master:zmq-connect for details.

This method is a coroutine.

Parameters:	endpoint (str) – a string in format transport://address as ZeroMQ requires. For tcp connections the endpoint should specify IPv4 or IPv6 address, not DNS name. Use yield from get_event_loop().getaddrinfo(host, port) for translating DNS into IP address.
Returns:	endpoint
Return type:	str
Raises:	ValueError – if the endpoint is a tcp DNS address. OSError – on error from ZeroMQ layer TypeError – if endpoint is not a str

disconnect(endpoint)¶

Disconnect transpot from endpoint.

This method is a coroutine.

Parameters:	endpoint – a string in format transport://address as ZeroMQ requires.
Returns:	None
Raises:	OSError – on error from ZeroMQ layer TypeError – if endpoint is not a str

connections()¶

Return immutable set of endpoints connected to transport.

Note

Returned endpoints include only ones that has been connected via ZmqTransport.connect() or create_zmq_connection() calls and do not include connections that have been done to zmq_sock before create_zmq_connection() call.

subscribe(value)¶

Establish a new message filter on SUB transport.

Newly created SUB transports filters out all incoming messages, therefore you should call this method to establish an initial message filter.

An empty (b'') value subscribes to all incoming messages. A non-empty value subscribes to all messages beginning with the specified prefix. Multiple filters may be attached to a single SUB transport, in which case a message shall be accepted if it matches at least one filter.

Parameters:	value (bytes) – a filter value to add to SUB filters.
Raises:	NotImplementedError – the transport is not SUB. TypeError – when value is not bytes.

Warning

Unlike to ZeroMQ socket level the call first check for value in ZmqTransport.subscriptions() and does nothing if the transport already has been subscribed to the value.

unsubscribe(value)¶

Remove an existing message filter on a SUB transport.

The filter specified must match an existing filter previously established with the ZmqTransport.subscribe().

If the transport has several instances of the same filter attached the .unsubscribe() removes only one instance, leaving the rest in place and functional (if you use ZmqTransport.subscribe() to adding new filters that never happens, see difference between aiozmq and ZeroMQ raw sockets for details).

Parameters:	value (bytes) – a filter value to add to SUB filters.
Raises:	NotImplementedError – the transport is not SUB. TypeError – when value is not bytes.

subscriptions()¶

Return immutable set of subscriptions (set of bytes) subscribed on transport.

Note

Returned subscriptions include only ones that has been subscribed via ZmqTransport.subscribe() call and do not include subscribtions that have been done to zmq_sock before create_zmq_connection() call.

Raises NotImplementedError:
	the transport is not SUB.

ZmqProtocol¶

class aiozmq.ZmqProtocol¶

Protocol for ZeroMQ connections. Derives from asyncio.BaseProtocol.

connection_made(transport)¶

Called when a connection is made.

Parameters:	transport (ZmqTransport) – representing the pipe connection. To receive data, wait for msg_received() calls. When the connection is closed, connection_lost() is called.

connection_lost(exc)¶

Called when the connection is lost or closed.

Parameters:	exc (instance of Exception or derived class) – an exception object or None (the latter meaning the connection was aborted or closed).

pause_writing()¶

Called when the transport’s buffer goes over the high-water mark.

Pause and resume calls are paired – pause_writing() is called once when the buffer goes strictly over the high-water mark (even if subsequent writes increases the buffer size even more), and eventually resume_writing() is called once when the buffer size reaches the low-water mark.

Note that if the buffer size equals the high-water mark, pause_writing() is not called – it must go strictly over. Conversely, resume_writing() is called when the buffer size is equal or lower than the low-water mark. These end conditions are important to ensure that things go as expected when either mark is zero.

Note

This is the only Protocol callback that is not called through asyncio.AbstractEventLoop.call_soon() – if it were, it would have no effect when it’s most needed (when the app keeps writing without yielding until pause_writing() is called).

resume_writing()¶

Called when the transport’s buffer drains below the low-water mark.

See pause_writing() for details.

msg_received(data)¶

Called when some ZeroMQ message is received.

Parameters:	data (list) – the multipart list of bytes with at least one item.

Exception policy¶

Every call to zmq.Socket method can raise zmq.ZMQError exception. But all methods of ZmqEventLoop and ZmqTransport translate ZMQError into OSError (or descendat) with errno and strerror borrowed from underlying ZMQError values.

The reason for translation is that Python 3.3 implements PEP 3151 — Reworking the OS and IO Exception Hierarchy which gets rid of exceptions zoo and uses OSError and descendants for all exceptions generated by system function calls.

aiozmq implements the same pattern. Internally it looks like:

try:
    return self._zmq_sock.getsockopt(option)
except zmq.ZMQError as exc:
    raise OSError(exc.errno, exc.strerror)

Also public methods of aiozmq will never raise InterruptedError (aka EINTR), they process interruption internally.

Getting aiozmq version¶

aiozmq.version¶

a text version of the library:

'0.1.0 , Python 3.3.2+ (default, Feb 28 2014, 00:52:16) \n[GCC 4.8.1]'

aiozmq.version_info¶

a named tuple with version information, useful for comparison:

VersionInfo(major=0, minor=1, micro=0, releaselevel='alpha', serial=0)

The Python itself uses the same schema (sys.version_info).

Installing ZeroMQ event loop¶

To use ZeroMQ layer you should install proper event loop first.

The recommended way is to setup global event loop policy:

import asyncio
import aiozmq

asyncio.set_event_loop_policy(aiozmq.ZmqEventLoopPolicy())

That installs ZmqEventLoopPolicy globally. After installing you can get event loop instance from main thread by asyncio.get_event_loop() call:

loop = asyncio.get_event_loop()

If you need to execute event loop in your own (not main) thread you have to set it up first:

import threading

def thread_func():
    loop = asyncio.new_event_loop()
    asyncio.set_event_loop()

    loop.run_forever()

thread = threading.Thread(target=thread_func)
thread.start()

ZmqEventLoopPolicy¶

ZeroMQ policy implementation for accessing the event loop.

In this policy, each thread has its own event loop. However, we only automatically create an event loop by default for the main thread; other threads by default have no event loop.

ZmqEventLoopPolicy implements an asyncio.AbstractEventLoopPolicy interface.

class aiozmq.ZmqEventLoopPolicy¶

Create policy for ZeroMQ event loops.

Note

policy should be installed, see Installing ZeroMQ event loop.

get_event_loop()¶

Get the event loop.

If current thread is the main thread and there are no registered event loop for current thread then the call creates new event loop and registers it.

Returns:	Return an instance of ZmqEventLoop.
Raises RuntimeError:
	if there is no registered event loop for current thread.

new_event_loop()¶

Create a new event loop.

You must call ZmqEventLoopPolicy.set_event_loop() to make this the current event loop.

set_event_loop(loop)¶

Set the event loop.

As a side effect, if a child watcher was set before, then calling .set_event_loop() from the main thread will call asyncio.AbstractChildWatcher.attach_loop() on the child watcher.

Parameters:	loop – an asyncio.AbstractEventLoop instance or None
Raises TypeError:
	if loop is not instance of asyncio.AbstractEventLoop

get_child_watcher()¶

Get the child watcher

If not yet set, a asyncio.SafeChildWatcher object is automatically created.

Returns:	Return an instance of asyncio.AbstractChildWatcher.

set_child_watcher(watcher)¶

Set the child watcher.

Parameters:	watcher – an asyncio.AbstractChildWatcher instance or None
Raises TypeError:
	if watcher is not instance of asyncio.AbstractChildWatcher

ZmqEventLoop¶

Event loop with ZeroMQ support.

Follows asyncio.AbstractEventLoop specification and has create_zmq_connection() method for ZeroMQ sockets layer.

class aiozmq.ZmqEventLoop(*, zmq_context=None)¶

Parameters:	zmq_context (zmq.Context) – explicit context to use for ZeroMQ socket creation inside ZmqEventLoop.create_zmq_connection() calls. aiozmq shares global context returned by zmq.Context.instance() call if zmq_context parameter is None.

create_zmq_connection(protocol_factory, zmq_type, *, bind=None, connect=None, zmq_sock=None)¶

Create a ZeroMQ connection.

If you don’t use bind or connect params you can do it later by ZmqTransport.bind() and ZmqTransport.connect() calls.

Parameters:	protocol_factory (callable) – a factory that instantiates ZmqProtocol object. zmq_type (int) – a type of ZeroMQ socket (zmq.REQ, zmq.REP, zmq.PUB, zmq.SUB, zmq.PAIR*, zmq.DEALER, zmq.ROUTER, zmq.PULL, zmq.PUSH, etc.) bind (str or iterable of strings) – endpoints specification. Every endpoint generates call to ZmqTransport.bind() for accepting connections from specified endpoint. Other side should use connect parameter to connect to this transport. connect (str or iterable of strings) – endpoints specification. Every endpoint generates call to ZmqTransport.connect() for connecting transport to specified endpoint. Other side should use bind parameter to wait for incoming connections. zmq_sock (zmq.Socket) – a preexisting zmq socket that will be passed to returned transport.
Returns:	a pair of (transport, protocol) where transport supports ZmqTransport interface.
Return type:	tuple

Intro¶

While core API provides a core support for ZeroMQ transports, the End User may need some high-level API.

Thus we have the aiozmq.rpc module for Remote Procedure Calls.

The main goal of the module is to provide easy-to-use interface for calling some method from the remote process (which can be running on the other host).

ZeroMQ itself gives some handy sockets but says nothing about RPC.

On the other hand, this module provides human API, but it is not compatible with other implementations.

If you need to support a custom protocol over ZeroMQ layer, please feel free to build your own implementation on top of the core primitives.

The aiozmq.rpc supports three pairs of communications:

• Request-Reply
• Push-Pull
• Publish-Subscribe

pip3 install msgpack-python\>=0.4.0

Request-Reply¶

This is a Remote Procedure Call pattern itself. Client calls a remote function on server and waits for the returned value. If the remote function raises an exception, that exception instance is also raised on the client side.

Let’s assume we have N clients bound to M servers. Any client can connect to several servers and any server can listen to multiple endpoints.

When client sends a message, the message will be delivered to any server that is ready (doesn’t processes another message).

When the server sends a reply with the result of the remote call back, the result is routed to the client that has sent the request originally.

This pair uses DEALER/ROUTER ZeroMQ sockets.

The basic usage is:

import asyncio
from aiozmq import rpc

class Handler(rpc.AttrHandler):

    @rpc.method
    def remote(self, arg1, arg2):
        return arg1 + arg2

@asyncio.coroutine
def go():
    server =  yield from rpc.serve_rpc(Handler(),
                                       bind='tcp://127.0.0.1:5555')

    client = yield from rpc.connect_rpc(connect='tcp://127.0.0.1:5555')

    ret = yield from client.call.remote(1, 2)
    assert ret == 3

event_loop.run_until_complete(go())

aiozmq.rpc.connect_rpc(*, connect=None, bind=None, loop=None, error_table=None, timeout=None, translation_table=None)¶

A coroutine that creates and connects/binds RPC client.

Usually for this function you need to use connect parameter, but ZeroMQ does not forbid to use bind.

Parameters bind, connect and loop work like that of aiozmq.create_zmq_connection().

Parameters:

error_table (dict) – an optional table for custom exception translators. See also Exception translation at client side timeout (float) – an optional timeout for RPC calls. If timeout is not None and remote call takes longer than timeout seconds then asyncio.TimeoutError will be raised at client side. If the server will return an answer after timeout has been raised that answer is ignored. See also RPCClient.with_timeout() method. translation_table (dict) – an optional table for custom value translators. See also Value translators

Returns:

RPCClient instance.

aiozmq.rpc.serve_rpc(handler, *, bind=None, connect=None, loop=None, log_exceptions=False, exclude_log_exceptions=(), translation_table=None)¶

A coroutine that creates and connects/binds RPC server instance.

Usually for this function you need to use bind parameter, but ZeroMQ does not forbid to use connect.

Parameters bind, connect and loop work like that of aiozmq.create_zmq_connection().

Parameters:

handler (aiozmq.rpc.AbstractHander) – an object which processes incoming RPC calls. Usually you like to pass AttrHandler instance. log_exceptions (bool) – log exceptions from remote calls if True. See also Logging exceptions from remote calls at server side exclude_log_exceptions (sequence) – sequence of exception types that should not to be logged if log_exceptions is True. See also Logging exceptions from remote calls at server side translation_table (dict) – an optional table for custom value translators. See also Value translators

Returns:

Service instance.

Changed in version 0.2: Added log_exceptions parameter.

Push-Pull¶

This is a Notify aka Pipeline pattern. Client calls a remote function on the server and doesn’t wait for the result. If a remote function call raises an exception, this exception is only logged at the server side. Client cannot get any information about processing the remote call on server.

Thus this is one-way communication: fire and forget.

Let’s assume that we have N clients bound to M servers. Any client can connect to several servers and any server can listen to multiple endpoints.

When client sends a message, the message will be delivered to any server that is ready (doesn’t processes another message).

That’s all.

This pair uses PUSH/PULL ZeroMQ sockets.

The basic usage is:

import asyncio
from aiozmq import rpc

class Handler(rpc.AttrHandler):

    @rpc.method
    def remote(self):
        do_something(arg)

@asyncio.coroutine
def go():
    server =  yield from rpc.serve_pipeline(Handler(),
                                            bind='tcp://127.0.0.1:5555')

    client = yield from rpc.connect_pipeline(connect='tcp://127.0.0.1:5555')

    ret = yield from client.notify.remote(1)

event_loop.run_until_complete(go())

aiozmq.rpc.connect_pipeline(*, connect=None, bind=None, loop=None, error_table=None, translation_table=None)¶

A coroutine that creates and connects/binds pipeline client.

Parameters bind, connect and loop work like that of aiozmq.create_zmq_connection().

Usually for this function you need to use connect parameter, but ZeroMQ does not forbid to use bind.

Parameters:	translation_table (dict) – an optional table for custom value translators. See also Value translators
Returns:	PipelineClient instance.

aiozmq.rpc.serve_pipeline(handler, *, connect=None, bind=None, loop=None, log_exceptions=False, exclude_log_exceptions=(), translation_table=None)¶

A coroutine that creates and connects/binds pipeline server instance.

Usually for this function you need to use bind parameter, but ZeroMQ does not forbid to use connect.

Parameters bind, connect and loop work like that of aiozmq.create_zmq_connection().

Parameters:

handler (aiozmq.rpc.AbstractHander) – an object which processes incoming pipeline calls. Usually you like to pass AttrHandler instance. log_exceptions (bool) – log exceptions from remote calls if True. See also Logging exceptions from remote calls at server side exclude_log_exceptions (sequence) – sequence of exception types that should not to be logged if log_exceptions is True. See also Logging exceptions from remote calls at server side translation_table (dict) – an optional table for custom value translators. See also Value translators

Returns:

Service instance.

Changed in version 0.2: Added log_exceptions parameter.

Publish-Subscribe¶

This is PubSub pattern. It’s very close to Publish-Subscribe but has some difference:

• server subscribes to topics in order to receive messages only from that topics.
• client sends a message to concrete topic.

Let’s assume we have N clients bound to M servers. Any client can connect to several servers and any server can listen to multiple endpoints.

When client sends a message to topic, the message will be delivered to servers that only has been subscribed to this topic.

This pair uses PUB/SUB ZeroMQ sockets.

The basic usage is:

import asyncio
from aiozmq import rpc

class Handler(rpc.AttrHandler):

    @rpc.method
    def remote(self):
        do_something(arg)

@asyncio.coroutine
def go():
    server =  yield from rpc.serve_pubsub(Handler(),
                                          subscribe='topic',
                                          bind='tcp://127.0.0.1:5555')

    client = yield from rpc.connect_pubsub(connect='tcp://127.0.0.1:5555')

    ret = yield from client.publish('topic').remote(1)

event_loop.run_until_complete(go())

aiozmq.rpc.connect_pubsub(*, connect=None, bind=None, loop=None, error_table=None, translation_table=None)¶

A coroutine that creates and connects/binds pubsub client.

Usually for this function you need to use connect parameter, but ZeroMQ does not forbid to use bind.

Parameters bind, connect and loop work like that of aiozmq.create_zmq_connection().

Parameters:	translation_table (dict) – an optional table for custom value translators. See also Value translators
Returns:	PubSubClient instance.

aiozmq.rpc.serve_pubsub(handler, *, connect=None, bind=None, subscribe=None, loop=None, log_exceptions=False, exclude_log_exceptions=(), translation_table=None)¶

A coroutine that creates and connects/binds pubsub server instance.

Usually for this function you need to use bind parameter, but ZeroMQ does not forbid to use connect.

Parameters bind, connect and loop work like that of aiozmq.create_zmq_connection().

param aiozmq.rpc.AbstractHander handler:
	an object which processes incoming pipeline calls. Usually you like to pass AttrHandler instance.
param bool log_exceptions:
	log exceptions from remote calls if True. See also Logging exceptions from remote calls at server side
param sequence exclude_log_exceptions:
	sequence of exception types that should not to be logged if log_exceptions is True. See also Logging exceptions from remote calls at server side
param subscribe:
	subscription specification. Subscribe server to topics. Allowed parameters are str, bytes, iterable of str or bytes.
param dict translation_table:
	an optional table for custom value translators. See also Value translators
return:	PubSubService instance.
raise OSError:	on system error.
raise TypeError:
	if arguments have inappropriate type.

Changed in version 0.2: Added log_exceptions parameter.

Exception translation at client side¶

If a remote server method raises an exception, that exception is passed back to the client and raised on the client side, as follows:

try:
    yield from client.call.func_raises_value_error()
except ValueError as exc:
    log.exception(exc)

The rules for exception translation are:

• if remote method raises an exception — server answers with full exception class name (like package.subpackage.MyError) and exception constructor arguments (args).
• translator table is a mapping of {excpetion_name: exc_class} where keys are full names of exception class (str) and values are exception classes.
• if translation is found then client code gives exception raise exc_class(args).
• user defined translators are searched first.
• all builtin exceptions are translated by default.
• NotFoundError and ParameterError are translated by default also.
• if there is no registered traslation then GenericError(excpetion_name, args) is raised.

For example if custom RPC server handler can raise mod1.Error1 and pack.mod2.Error2 then error_table should be:

from mod1 import Error1
from pack.mod2 import Error2

error_table = {'mod1.Error1': Error1,
               'pack.mod2.Error2': Error2}

client = loop.run_until_complete(
    rpc.connect_rpc(connect='tcp://127.0.0.1:5555',
                    error_table=error_table))

You have to have the way to import exception classes from server-side. Or you can build your own translators without server-side code, use only string for full exception class name and tuple of args — that’s up to you.

Signature validation¶

The library supports optional validation of the remote call signatures.

If validation fails then ParameterError is raised on client side.

All validations are done on RPC server side, then errors are translated back to client.

Let’s take a look on example of user-defined RPC handler:

class Handler(rpc.AttrHandler):

    @rpc.method
    def func(self, arg1: int, arg2) -> float:
        return arg1 + arg2

Parameter arg1 and return value has annotaions, int and float correspondingly.

At the call time, if parameter has an annotaion, then actual value passed and RPC method is calculated as actual_value = annotation(value). If there is no annotaion for parameter, the value is passed as-is.

Annotaion should be any callable that accepts a value as single argument and returns actual value.

If annotation call raises exception, that exception is sent to the client wrapped in ParameterError.

Value, returned by RPC call, can be checked by optional return annotation.

Thus int can be a good annotation: it raises TypeError if arg1 cannot be converted to int.

Usually you need more complex check, say parameter can be int or None.

You always can write a custom validator:

def int_or_none(val):
   if isinstance(val, int) or val is None:
       return val
   else:
       raise ValueError('bad value')

class Handler(rpc.AttrHandler):
    @rpc.method
    def func(self, arg: int_or_none):
        return arg

Writing a tons of custom validators is inconvinient, so we recommend to use trafaret library (can be installed via pip3 install trafaret).

This is example of trararet annotation:

import trafaret as t

class Handler(rpc.AttrHandler):
    @rpc.method
    def func(self, arg: t.Int|t.Null):
        return arg

Trafaret has advanced types like List and Dict, so you can put your complex JSON-like structure as RPC method annotation. Also you can create custom trafarets if needed. It’s easy, trust me.

Value translators¶

aiozmq.rpc uses msgpack for transfering python objects from client to server and back.

You can think about msgpack as: this is a-like JSON but fast and compact.

Every object that can be passed to json.dump(), can be passed to msgpack.dump() also. The same for unpacking.

The only difference is: aiozmq.rpc converts all lists to tuples. The reasons is are:

• you never need to modify given list as it is your incoming value. If you still want to use list data type you can do it easy by list(val) call.

• tuples are a bit faster for unpacking.

• tuple can be a key in dict, so you can pack something like {(1,2): 'a'} and unpack it on other side without any error. Lists cannot be keys in dicts, they are unhashable.

  This point is the main reason for choosing tuples. Unfortunatelly msgpack gives no way to mix tuples and lists in the same pack.

But sometimes you want to call remote side with non-plain-json arguments. datetime.datetime is a good example. aiozmq.rpc supports all family of dates, times and timezones from datetime from-the-box (predefined translators).

If you need to transfer a custom object via RPC you should register translator at both server and client side. Say, you need to pass the instances of your custom class Point via RPC. There is an example:

import asyncio
import aiozmq, aiozmq.rpc
import msgpack

class Point:
    def __init__(self, x, y):
        self.x = x
        self.y = y

    def __eq__(self, other):
        if isinstance(other, Point):
            return (self.x, self.y) == (other.x, other.y)
        return NotImplemented

translation_table = {
    0: (Point,
        lambda value: msgpack.packb((value.x, value.y)),
        lambda binary: Point(*msgpack.unpackb(binary))),
}

class ServerHandler(aiozmq.rpc.AttrHandler):
    @aiozmq.rpc.method
    def remote(self, val):
        return val

@asyncio.coroutine
def go():
    server = yield from aiozmq.rpc.serve_rpc(
        ServerHandler(), bind='tcp://127.0.0.1:5555',
        translation_table=translation_table)
    client = yield from aiozmq.rpc.connect_rpc(
        connect='tcp://127.0.0.1:5555',
        translation_table=translation_table)

    ret = yield from client.call.remote(Point(1, 2))
    assert ret == Point(1, 2)

You should create a translation table and pass it to both connect_rpc() and serve_rpc(). That’s all, server and client now have all information about passing your Point via the wire.

• Translation table is the dict.
• Keys should be an integers in range [0, 127]. We recommend to use keys starting from 0 for custom translators, high numbers are reserved for library itself (it uses the same schema for passing datetime objects etc).
• Values are tuples of (translated_class, packer, unpacker).
  • translated_class is a class which you want to pass to peer.
  • packer is a callable which receives your class instance and returns bytes of instance data.
  • unpacker is a callable which receives bytes of instance data and returns your class instance.
• When the library tries to pack your class instance it searches the translation table in ascending order.
• If your object is an instance of translated_class then packer is called and resulting bytes will be sent to peer.
• On unpacking unpacker is called with the bytes received by peer. The result should to be your class instance.

Table of predefined translators:

Logging exceptions from remote calls at server side¶

By default aiozmq.rpc does no logging if remote call raises an exception.

That behavoir can be changed by passing log_exceptions=True to rpc servers: serve_rpc(), serve_pipeline() and serve_pubsub().

If, say, you make PubSub server as:

server =  yield from rpc.serve_pubsub(handler,
                                      subscribe='topic',
                                      bind='tcp://127.0.0.1:5555',
                                      log_exceptions=True)

then exceptions raised from handler remote calls will be logged by standard aiozmq.rpc.logger.

But sometimes you don’t want to log exceptions of some types.

Say, you use your own exceptions as part of public API to report about expected failures. In this case you probably want to pass that exceptions over the log, but record all other unexpected errors.

For that case you can use exclude_log_exceptions parameter:

server =  yield from rpc.serve_rpc(handler,
                                   bind='tcp://127.0.0.1:7777',
                                   log_exceptions=True,
                                   exclude_log_exceptions=(MyError,
                                                           OtherError))

Exceptions¶

exception aiozmq.rpc.Error¶

Base class for aiozmq.rpc exceptions. Derived from Exception.

exception aiozmq.rpc.GenericError¶

Subclass of Error, raised when a remote call produces exception that cannot be translated.

exc_type¶

A string contains full name of unknown exception("package.module.MyError").

arguments¶

A tuple of arguments passed to unknown exception constructor

See also

BaseException.args - parameters for exception constructor.

See also

Exception translation at client side

exception aiozmq.rpc.NotFoundError¶

Subclass of both Error and LookupError, raised when a remote call name is not found at RPC server.

exception aiozmq.rpc.ParameterError¶

Subclass of both Error and ValueError, raised by remote call when parameter substitution or remote method signature validation is failed.

exception aiozmq.rpc.ServiceClosedError¶

Subclass of Error, raised Service has been closed.

See also

Service.transport property.

Clases¶

@aiozmq.rpc.method¶

Marks a decorated function as RPC endpoint handler.

The func object may provide arguments and/or return annotations. If so annotations should be callable objects and they will be used to validate received arguments and/or return value.

Example:

@aiozmq.rpc.method
def remote(a: int, b: int) -> int:
    return a + b

Methods are objects that returned by AbstractHander.__getitem__() lookup at RPC method search stage.

class aiozmq.rpc.AbstractHander¶

The base class for all RPC handlers.

Every handler should be AbstractHandler by direct inheritance or indirect subclassing (method __getitem__ should be defined).

Therefore AttrHandler and dict are both good citizens.

Returned value eighter should implement AbstractHandler interface itself for looking up forward or must be callable decorated by method().

__getitem__(self, key)¶

Returns subhandler or terminal function decorated by method().

Raises KeyError:
	if key is not found.

See also

start_server() coroutine.

class aiozmq.rpc.AttrHandler¶

Subclass of AbstractHandler. Does lookup for subhandlers and rpc methods by getattr().

There is an example of trivial handler:

class ServerHandler(aiozmq.rpc.AttrHandler):
    @aiozmq.rpc.method
    def remote_func(self, a:int, b:int) -> int:
        return a + b

class aiozmq.rpc.Service¶

RPC service base class.

Instances of Service (or descendants) are returned by coroutines that creates clients or servers (connect_rpc(), serve_rpc() and others).

Implements asyncio.AbstractServer.

transport¶

The readonly property that returns service’s transport.

You can use the transport to dynamically bind/unbind, connect/disconnect etc.

Raises aiozmq.rpc.ServiceClosedError:
	if the service has been closed.

close()¶

Stop serving.

This leaves existing connections open.

wait_closed()¶

Coroutine to wait until service is closed.

See also

Signature validation

class aiozmq.rpc.RPCClient¶

Class that returned by connect_rpc() call. Inherited from Service.

For RPC calls use rpc property.

call¶

The readonly property that returns ephemeral object used to making RPC call.

Construction like:

ret = yield from client.call.ns.method(1, 2, 3)

makes a remote call with arguments(1, 2, 3) and returns answer from this call.

You can also pass named parameters:

ret = yield from client.call.ns.method(1, b=2, c=3)

If the call raises exception that exception propagates to client side.

Say, if remote raises ValueError client catches ValueError instance with args sent by remote:

try:
    yield from client.call.raise_value_error()
except ValueError as exc:
    process_error(exc)

with_timeout(timeout)¶

Override default timeout for client. Can be used in two forms:

yield from client.with_timeout(1.5).call.func()

and:

with client.with_timeout(1.5) as new_client:
    yield from new_client.call.func1()
    yield from new_client.call.func2()

Parameters:	timeout (float) – a timeout for RPC calls. If timeout is not None and remote call takes longer than timeout seconds then asyncio.TimeoutError will be raised at client side. If the server will return an answer after timeout has been raised that answer is ignored. See also connect_rpc() coroutine.

See also

Exception translation at client side and Signature validation

class aiozmq.rpc.PipelineClient¶

Class that returned by connect_pipeline() call. Inherited from Service.

notify¶

The readonly property that returns ephemeral object used to making notification call.

Construction like:

ret = yield from client.notify.ns.method(1, 2, 3)

makes a remote call with arguments(1, 2, 3) and returns None.

You cannot get any answer from the server.

class aiozmq.rpc.PubSubClient¶

Class that returned by connect_pubsub() call. Inherited from Service.

For pubsub calls use publish() method.

publish(topic)¶

The call that returns ephemeral object used to making publisher call.

Construction like:

ret = yield from client.publish('topic').ns.method(1, b=2)

makes a remote call with arguments (1, b=2) and topic name b'topic' and returns None.

You cannot get any answer from the server.

See also

Signature validation

Logger¶

aiozmq.rpc.logger¶

An instance of logging.Logger with name aiozmq.rpc.

The library sends log messages (Logging exceptions from remote calls at server side for example) to this logger. You can configure your own handlers to fiter, save or what-you-wish the log events from the library.

Simple DEALER-ROUTER pair implemented on Core level¶

import asyncio
import aiozmq
import zmq


class ZmqDealerProtocol(aiozmq.ZmqProtocol):

    transport = None

    def __init__(self, queue, on_close):
        self.queue = queue
        self.on_close = on_close

    def connection_made(self, transport):
        self.transport = transport

    def msg_received(self, msg):
        self.queue.put_nowait(msg)

    def connection_lost(self, exc):
        self.on_close.set_result(exc)


class ZmqRouterProtocol(aiozmq.ZmqProtocol):

    transport = None

    def __init__(self, on_close):
        self.on_close = on_close

    def connection_made(self, transport):
        self.transport = transport

    def msg_received(self, msg):
        self.transport.write(msg)

    def connection_lost(self, exc):
        self.on_close.set_result(exc)


@asyncio.coroutine
def go():
    router_closed = asyncio.Future()
    dealer_closed = asyncio.Future()
    router, _ = yield from aiozmq.create_zmq_connection(
        lambda: ZmqRouterProtocol(router_closed),
        zmq.ROUTER,
        bind='tcp://127.0.0.1:*')

    addr = next(iter(router.bindings()))
    queue = asyncio.Queue()
    dealer, _ = yield from aiozmq.create_zmq_connection(
        lambda: ZmqDealerProtocol(queue, dealer_closed),
        zmq.DEALER,
        connect=addr)

    for i in range(10):
        msg = (b'data', b'ask', str(i).encode('utf-8'))
        dealer.write(msg)
        answer = yield from queue.get()
        print(answer)
    dealer.close()
    yield from dealer_closed
    router.close()
    yield from router_closed


def main():
    asyncio.get_event_loop().run_until_complete(go())
    print("DONE")


if __name__ == '__main__':
    main()

Remote Procedure Call¶

import asyncio
import aiozmq.rpc


class ServerHandler(aiozmq.rpc.AttrHandler):

    @aiozmq.rpc.method
    def remote_func(self, a: int, b: int) -> int:
        return a + b


@asyncio.coroutine
def go():
    server = yield from aiozmq.rpc.serve_rpc(
        ServerHandler(), bind='tcp://*:*')
    server_addr = next(iter(server.transport.bindings()))

    client = yield from aiozmq.rpc.connect_rpc(
        connect=server_addr)

    ret = yield from client.call.remote_func(1, 2)
    assert 3 == ret

    server.close()
    client.close()


def main():
    asyncio.get_event_loop().run_until_complete(go())
    print("DONE")


if __name__ == '__main__':
    main()

Pipeline aka Notifier¶

import asyncio
import aiozmq.rpc


class Handler(aiozmq.rpc.AttrHandler):

    @aiozmq.rpc.method
    def handle_some_event(self, a: int, b: int):
        pass


@asyncio.coroutine
def go():
    listener = yield from aiozmq.rpc.serve_pipeline(
        Handler(), bind='tcp://*:*')
    listener_addr = next(iter(listener.transport.bindings()))

    notifier = yield from aiozmq.rpc.connect_pipeline(
        connect=listener_addr)

    yield from notifier.notify.handle_some_event(1, 2)

    listener.close()
    notifier.close()


def main():
    asyncio.get_event_loop().run_until_complete(go())
    print("DONE")


if __name__ == '__main__':
    main()

Publish-Subscribe¶

import asyncio
import aiozmq.rpc


class Handler(aiozmq.rpc.AttrHandler):

    @aiozmq.rpc.method
    def remote_func(self, a: int, b: int):
        pass


@asyncio.coroutine
def go():
    subscriber = yield from aiozmq.rpc.serve_pubsub(
        Handler(), subscribe='topic', bind='tcp://*:*')
    subscriber_addr = next(iter(subscriber.transport.bindings()))

    publisher = yield from aiozmq.rpc.connect_pubsub(
        connect=subscriber_addr)

    yield from publisher.publish('topic').remote_func(1, 2)

    subscriber.close()
    publisher.close()


def main():
    asyncio.get_event_loop().run_until_complete(go())
    print("DONE")


if __name__ == '__main__':
    main()

Translation RPC exceptions back to client¶

import asyncio
import aiozmq.rpc


class CustomError(Exception):

    def __init__(self, val):
        self.val = val
        super().__init__(val)


exc_name = CustomError.__module__+'.'+CustomError.__name__
error_table = {exc_name: CustomError}


class ServerHandler(aiozmq.rpc.AttrHandler):
    @aiozmq.rpc.method
    def remote(self, val):
        raise CustomError(val)


@asyncio.coroutine
def go():
    server = yield from aiozmq.rpc.serve_rpc(
        ServerHandler(), bind='tcp://*:*')
    server_addr = next(iter(server.transport.bindings()))

    client = yield from aiozmq.rpc.connect_rpc(
        connect=server_addr,
        error_table=error_table)

    try:
        yield from client.call.remote('value')
    except CustomError as exc:
        exc.val == 'value'

    server.close()
    client.close()


def main():
    asyncio.get_event_loop().run_until_complete(go())
    print("DONE")


if __name__ == '__main__':
    main()

Translation instances of custom classes via RPC¶

import asyncio
import aiozmq.rpc
import msgpack


class Point:

    def __init__(self, x, y):
        self.x = x
        self.y = y

    def __eq__(self, other):
        if isinstance(other, Point):
            return (self.x, self.y) == (other.x, other.y)
        return NotImplemented


translation_table = {
    0: (Point,
        lambda value: msgpack.packb((value.x, value.y)),
        lambda binary: Point(*msgpack.unpackb(binary))),
}


class ServerHandler(aiozmq.rpc.AttrHandler):
    @aiozmq.rpc.method
    def remote(self, val):
        return val


@asyncio.coroutine
def go():
    server = yield from aiozmq.rpc.serve_rpc(
        ServerHandler(), bind='tcp://*:*',
        translation_table=translation_table)
    server_addr = next(iter(server.transport.bindings()))

    client = yield from aiozmq.rpc.connect_rpc(
        connect=server_addr,
        translation_table=translation_table)

    ret = yield from client.call.remote(Point(1, 2))
    assert ret == Point(1, 2)

    server.close()
    client.close()


def main():
    asyncio.get_event_loop().run_until_complete(go())
    print("DONE")


if __name__ == '__main__':
    main()

Validation of RPC methods¶

import asyncio
import aiozmq.rpc


class ServerHandler(aiozmq.rpc.AttrHandler):

    @aiozmq.rpc.method
    def remote_func(self, a: int, b: int) -> int:
        return a + b


@asyncio.coroutine
def go():
    server = yield from aiozmq.rpc.serve_rpc(
        ServerHandler(), bind='tcp://*:*')
    server_addr = next(iter(server.transport.bindings()))

    client = yield from aiozmq.rpc.connect_rpc(
        connect=server_addr)

    try:
        yield from client.call.unknown_function()
    except aiozmq.rpc.NotFoundError as exc:
        print("client.rpc.unknown_function(): {}".format(exc))

    try:
        yield from client.call.remote_func(bad_arg=1)
    except aiozmq.rpc.ParametersError as exc:
        print("client.rpc.remote_func(bad_arg=1): {}".format(exc))

    try:
        yield from client.call.remote_func(1)
    except aiozmq.rpc.ParametersError as exc:
        print("client.rpc.remote_func(1): {}".format(exc))

    try:
        yield from client.call.remote_func('a', 'b')
    except aiozmq.rpc.ParametersError as exc:
        print("client.rpc.remote_func('a', 'b'): {}".format(exc))

    server.close()
    client.close()


def main():
    asyncio.get_event_loop().run_until_complete(go())
    print("DONE")


if __name__ == '__main__':
    main()

RPC lookup in nested namespaces¶

import asyncio
import aiozmq.rpc


class Handler(aiozmq.rpc.AttrHandler):

    def __init__(self, ident):
        self.ident = ident
        self.subhandler = SubHandler(self.ident, 'subident')

    @aiozmq.rpc.method
    def a(self):
        return (self.ident, 'a')


class SubHandler(aiozmq.rpc.AttrHandler):

    def __init__(self, ident, subident):
        self.ident = ident
        self.subident = subident

    @aiozmq.rpc.method
    def b(self):
        return (self.ident, self.subident, 'b')


@asyncio.coroutine
def go():
    server = yield from aiozmq.rpc.serve_rpc(
        Handler('ident'), bind='tcp://*:*')
    server_addr = next(iter(server.transport.bindings()))

    client = yield from aiozmq.rpc.connect_rpc(
        connect=server_addr)

    ret = yield from client.call.a()
    assert ('ident', 'a') == ret

    ret = yield from client.call.subhandler.b()
    assert ('ident', 'subident', 'b') == ret

    server.close()
    client.close()


def main():
    asyncio.get_event_loop().run_until_complete(go())
    print("DONE")


if __name__ == '__main__':
    main()

Use dict as RPC lookup table¶

import asyncio
import aiozmq.rpc


@aiozmq.rpc.method
def a():
    return 'a'


@aiozmq.rpc.method
def b():
    return 'b'


handlers_dict = {'a': a,
                 'subnamespace': {'b': b}}


@asyncio.coroutine
def go():
    server = yield from aiozmq.rpc.serve_rpc(
        handlers_dict, bind='tcp://*:*')
    server_addr = next(iter(server.transport.bindings()))

    client = yield from aiozmq.rpc.connect_rpc(
        connect=server_addr)

    ret = yield from client.call.a()
    assert 'a' == ret

    ret = yield from client.call.subnamespace.b()
    assert 'b' == ret

    server.close()
    client.close()


def main():
    asyncio.get_event_loop().run_until_complete(go())
    print("DONE")


if __name__ == '__main__':
    main()

Use dynamic RPC lookup¶

import asyncio
import aiozmq.rpc


class DynamicHandler(aiozmq.rpc.AttrHandler):

    def __init__(self, namespace=()):
        self.namespace = namespace

    def __getitem__(self, key):
        try:
            return getattr(self, key)
        except AttributeError:
            return DynamicHandler(self.namespace + (key,))

    @aiozmq.rpc.method
    def func(self):
        return (self.namespace, 'val')


@asyncio.coroutine
def go():
    server = yield from aiozmq.rpc.serve_rpc(
        DynamicHandler(), bind='tcp://*:*')
    server_addr = next(iter(server.transport.bindings()))

    client = yield from aiozmq.rpc.connect_rpc(
        connect=server_addr)

    ret = yield from client.call.func()
    assert ((), 'val') == ret, ret

    ret = yield from client.call.a.func()
    assert (('a',), 'val') == ret, ret

    ret = yield from client.call.a.b.func()
    assert (('a', 'b'), 'val') == ret, ret

    server.close()
    client.close()


def main():
    asyncio.get_event_loop().run_until_complete(go())
    print("DONE")


if __name__ == '__main__':
    main()