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| -rw-r--r-- | README | 72 |
1 files changed, 72 insertions, 0 deletions
@@ -0,0 +1,72 @@ +sbus is simple message bus based on unix domain, sequenced-packet sockets. + +Features: + Support for multi-user buses. + No support state-keeping in clients. + Supports all send(2)/recv(2) flags. + Support for routing keys with wildcards. + +Non-features: + No IP or cluster support, should be implemented as a separate service. + No support for overly larged messages, should be implemented at application level. + No persistence support, should be implemented as a separate service. + No support for automatic unsubscriptions. + No support for reply-to keys, should be implemented at application level. + No support for shared queues, should be implemented as a separate service. + +Routing keys: + Routing keys are used to filter received messages. A routing key + may contain any byte, whoever there are two bytes with special + meaning: '*' and '.'. '*' should not be used in routin keys, but + only in routing key patterns, it matches until the next '.' or + end if there are not more '.'s. Additionally if a routing key + pattern ends with '.' that '.' will match to a '.' and any + subsequent byte. For example 'a.*.c.' will match 'a.b.c.' and + 'a.b.c.d.e' but not 'a.b.c' or 'a.c.d'. And empty routiung key + pattern shall match everything. + +Protocol: + Communication is done over unix domain, sequenced-packet sockets. + Each packet is interpreted as a complete message. A packet cannot + contain multiple message, and a message cannot be split over + multiple packets. There are 3 types of messages: + + Subscribe: + Send a routing key pattern to the server for the client. + The server shall send all messages with matching routing + keys to this client. The server shall store the key even + if there is already an identical routing key pattern + registered for the client. + + Messages of this type shall match the regular expression + + ^SUB \([^\x00]*\)\(\x00.*\)\?$ + + where \1 is the routing key pattern, \2 is ignored. + + Unsubscribe: + Tell the server to remove a routing key pattern for the + client. The server may choose to disconnect the client + if it sends a routing key pattern that is not registered + for the client. + + Messages of this type shall match the regular expression + + ^UNSUB \([^\x00]*\)\(\x00.*\)\?$ + + where \1 is the routing key pattern, \2 is ignored. + + Publish: + Publish a message on the bus. The server shall send a + copy of packet to all clients with a matching routing + key pattern, including the client that sent the packet + if and only if that client has a matching routing key + pattern. The server may not send a copy of the packet + to any clients without a matching routing key pattern. + + Messages of this type shall match the regular expression + + ^MSG \([^\x00]*\)\x00\(.*\)$ + + where \1 is the routing key for the message and \2 + is the message payload. |