* filer: keep the existing peer subscription on a repeated add
A cluster node add for a peer that is already followed restarted the
subscription, dropping the metadata events between the two runs.
* master: tell a connecting client the current cluster membership
Cluster node updates are only broadcast to the clients connected at that
moment. A filer that lost its master stream while a peer came back never
learned about the peer, and stopped replicating its metadata for good.
* test: a filer joining the master learns about the filers already there
* test: a filer resubscribes to a peer that registered while it was disconnected
Runs the reported sequence against real processes: filer2 leaves, filer1
is paused and its master stream is broken, filer2 registers again, and
filer1 has to replicate from it after reconnecting.
Chris LuandGitHub
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