Provide a Dbus-free way for IPC using message queues.
More generally, this provides a way to develop applications as if they just wrote to/read from stdin/out. And if the app even needs to be a daemon, just pipe it to/from one of the provided scrips
make
make install
$ echo a | mqsend test
$ echo b | mqsend test
$ echo c | mqsend test
$ mqreceive test
a
b
c
$ mqbus-receive test &
$ mqbus-receive test &
$ mqbus-receive test &
$ echo event | mqbus-send test
event
event
event
mqreceive bar_to_foo | foo | mqsend foo_to_bar &
mqreceive foo_to_bar | bar | mqsend bar_to_foo
There are 4 programs this repo mqsend, mqreceive mqbus-send and mqbus-receive
The mq family supports a multi-producer-single-consumer (MPCS) model. Many clients can send messages to a single client. These scripts are just wrappers around the message queue interface.
The mqbus family supports single-producer-multi-consumer (SPMC). Many clients can receive messages from a single one. This is a bit of a hack and barely uses message queues. The sender checks a directory denoted by the message queue name, notices all named pipes in that directory and will forward all messages to all such pipes. Anytime a new receive is spawned, it will created a named pipe and place it in the directory and then send a message to the sender to check for its pipe.
| Description | mq | mqbus | Notes |
|---|---|---|---|
| May block if there's no receiver | Y | N | For mq, there is a fixed size queue of messages and it'll block if its full |
| Receiver may see old messages | Y | N | For mqbus, receivers will only see messages that occur after it was connected |
| Are all messages sent to all receivers | N | Y | If there are multiple mq-receives, messages will be split between them |
| Guaranteed message delivery | N | N | Message may be lost or sent to only some clients on crash |