A PubSub & Request/Response WebSocket Server, in Go.
MiddleMan distributes messages between connected services and clients. It allows stateless and stateful services from diverse platforms to be quickly integrated into a running cluster of services.
This is the middleman protocol.
- When a client connects to middleman, the the first message is the API key.
A servce API key enables all messages, a client API key only enables messages that a service has explicitly enabled.
Eg:
MyServerKey
The middleman will then respond with:
MM OK
if the key was accepted. If the key is not accepted, the connection is closed.
- Each message then follows this structure:
COMMAND TARGET
Header:Value
Body
.
Note that the message body is terminated with a single dot and newline, just like SMTP.
- Commands are:
PUB: Publish a message with a name (target). Message is received by all subscribers.
SUB: Request that all published messages of (target) are delivered.
REQ: Request something from a service. Must have ReqID header. This is delivered to only one service, even if multiple services have subscribed to the target.
RES: Respond to a request. Must have a ReqID header.
EPUB: Allow clients to publish to this target.
EREQ: Allow clients to request from this target.
ESUB: Allow clients to subscribe to this target.
A PUB command distributes to all services and clients. A REQ command is effectively load balanced between any waiting services.
+------------------+
| | +--------------+
+-------------+ +-----+-------+ +-------------+----+ Service #1 |
| Client #1 +------+ Client Key | | Server Key | +--------------+
+-------------+ | | | |
| | | |
++-+----------+ +----------+-++
| | | | | | +--------------+
| | | | | +-----+ Service #2 |
+-------------+ | | | MiddleMan | | +--------------+
| Client #2 +-------+ | | | |
+-------------+ | | | |
| +------------------+ |
| | +--------------+
| +-------+ Service #N |
| +--------------+
+-------------+ |
| Client #N +---------+
+-------------+
PUB #Name EPUB #Name
#Body
ESUB #Name
SUB #Name
EREQ #Name
REQ #Name
#Body
RES #Name
#Body