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problem: no thread-safe alternative for ZMQ_PAIR

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Solution: create ZMQ_CHANNEL, the thread safe alternative
This commit is contained in:
Doron Somech
2020-05-09 07:44:32 +03:00
parent 28cb820f4f
commit 3da84c6d06
14 changed files with 392 additions and 14 deletions
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2
doc/zmq_bind.txt
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@@ -30,7 +30,7 @@ The 'endpoint' is a string consisting of a 'transport'`://` followed by an
'vmci':: virtual machine communications interface (VMCI), see linkzmq:zmq_vmci[7]
'udp':: unreliable unicast and multicast using UDP, see linkzmq:zmq_udp[7]
Every 0MQ socket type except 'ZMQ_PAIR' supports one-to-many and many-to-one
Every 0MQ socket type except 'ZMQ_PAIR' and 'ZMQ_CHANNEL' supports one-to-many and many-to-one
semantics. The precise semantics depend on the socket type and are defined in
linkzmq:zmq_socket[3].

4
doc/zmq_connect.txt
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@@ -30,7 +30,7 @@ The 'endpoint' is a string consisting of a 'transport'`://` followed by an
'vmci':: virtual machine communications interface (VMCI), see linkzmq:zmq_vmci[7]
'udp':: unreliable unicast and multicast using UDP, see linkzmq:zmq_udp[7]
Every 0MQ socket type except 'ZMQ_PAIR' supports one-to-many and many-to-one
Every 0MQ socket type except 'ZMQ_PAIR' and 'ZMQ_CHANNEL' supports one-to-many and many-to-one
semantics. The precise semantics depend on the socket type and are defined in
linkzmq:zmq_socket[3].
@@ -39,7 +39,7 @@ immediately but as needed by 0MQ. Thus a successful call to _zmq_connect()_
does not mean that the connection was or could actually be established.
Because of this, for most transports and socket types the order in which
a 'server' socket is bound and a 'client' socket is connected to it does not
matter. The _ZMQ_PAIR_ sockets are an exception, as they do not automatically
matter. The _ZMQ_PAIR_ and _ZMQ_CHANNEL_ sockets are an exception, as they do not automatically
reconnect to endpoints.
NOTE: following a _zmq_connect()_, for socket types except for ZMQ_ROUTER,

44
doc/zmq_socket.txt
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@@ -41,7 +41,7 @@ the event that a peer is unavailable to receive them.
Conventional sockets allow only strict one-to-one (two peers), many-to-one
(many clients, one server), or in some cases one-to-many (multicast)
relationships. With the exception of 'ZMQ_PAIR', 0MQ sockets may be connected
relationships. With the exception of 'ZMQ_PAIR' and 'ZMQ_CHANNEL', 0MQ sockets may be connected
*to multiple endpoints* using _zmq_connect()_, while simultaneously accepting
incoming connections *from multiple endpoints* bound to the socket using
_zmq_bind()_, thus allowing many-to-many relationships.
@@ -60,6 +60,7 @@ Following are the thread safe sockets:
* ZMQ_SCATTER
* ZMQ_GATHER
* ZMQ_PEER
* ZMQ_CHANNEL
.Socket types
The following sections present the socket types defined by 0MQ, grouped by the
@@ -476,6 +477,47 @@ Outgoing routing strategy:: See text
Incoming routing strategy:: Fair-queued
Action in mute state:: Return EAGAIN
Channel pattern
~~~~~~~~~~~~~~~~~~~~~~
The channel pattern is the thread-safe version of the exclusive pair pattern.
The channel pattern is used to connect a peer to precisely one other
peer. This pattern is used for inter-thread communication across the inproc
transport.
NOTE: Channel is still in draft phase.
ZMQ_CHANNEL
^^^^^^^^
A socket of type 'ZMQ_CHANNEL' can only be connected to a single peer at any one
time. No message routing or filtering is performed on messages sent over a
'ZMQ_CHANNEL' socket.
When a 'ZMQ_CHANNEL' socket enters the 'mute' state due to having reached the
high water mark for the connected peer, or, for connection-oriented transports,
if the ZMQ_IMMEDIATE option is set and there is no connected peer, then
any linkzmq:zmq_send[3] operations on the socket shall block until the peer
becomes available for sending; messages are not discarded.
While 'ZMQ_CHANNEL' sockets can be used over transports other than linkzmq:zmq_inproc[7],
their inability to auto-reconnect coupled with the fact new incoming connections will
be terminated while any previous connections (including ones in a closing state)
exist makes them unsuitable for TCP in most cases.
NOTE: 'ZMQ_CHANNEL' sockets are designed for inter-thread communication across
the linkzmq:zmq_inproc[7] transport and do not implement functionality such
as auto-reconnection.
NOTE: 'ZMQ_CHANNEL' sockets are threadsafe. They do not accept ZMQ_RCVMORE on receives.
This limits them to single part data.
[horizontal]
.Summary of ZMQ_CHANNEL characteristics
Compatible peer sockets:: 'ZMQ_CHANNEL'
Direction:: Bidirectional
Send/receive pattern:: Unrestricted
Incoming routing strategy:: N/A
Outgoing routing strategy:: N/A
Action in mute state:: Block
Native Pattern
~~~~~~~~~~~~~~