Subscribe every WebSocket client to a unique topic, by default under
zeek/cluster/websocket/client/<identifier>/
Add tests that verify that WebSocket clients receive messages on these topics
even if they didn't explicitly pass them in their handshake message.
This is somewhere between feature and bug fix. It aids the ZeroMQ backend
implementation: A WebSocket client that doesn't provide any subscriptions
and immediately starts publishing would discard events until receiving
other nodes subscriptions from the central XPUB/XSUB proxy. ZeroMQ does sender
side topic filtering. When using subscriptions, the client waits until
its own subscriptions are returned from the central XPUB/XSUB proxy,
thereby also learning about other node's subscriptions.
Also, make the no-subscriptions.zeek test use 32 clients sequentially to
trigger potential issues more quickly.
Due to prefix matching, worker-1's node_topic() also matched worker-10,
worker-11, etc. Suffix the node topic with a `.`. The original implementation
came from NATS, where subjects are separated by `.`.
Adapt nodeid_topic() for consistency.
It is not safe to use the same socket from different threads, but the
current code used the xsub socket directly from the main thread (to setup
subscriptions) and from the internal thread for polling and reading.
Leverage the PAIR socket already in use for forwarding publish operations
to the internal thread also for subscribe and unsubscribe.
The failure mode is/was a bit annoying. Essentially, closing of the
context would hang indefinitely in zmq_ctx_term().
This is a cluster backend implementation using a central XPUB/XSUB proxy
that by default runs on the manager node. Logging is implemented leveraging
PUSH/PULL sockets between logger and other nodes, rather than going
through XPUB/XSUB.
The test-all-policy-cluster baseline changed: Previously, Broker::peer()
would be called from setup-connections.zeek, causing the IO loop to be
alive. With the ZeroMQ backend, the IO loop is only alive when
Cluster::init() is called, but that doesn't happen anymore.
