The client (issue 0003e, part 1) accepts a LIST of NATS seeds and a LIST
of control-plane URLs so a node loss is transparent.
pkg/client:
- Options.NatsServers: extra NATS seeds beyond the primary. The client
connects to the joined seed list with MaxReconnects(-1) +
RetryOnFailedConnect, so nats.go fails over to a surviving node when the
one a client is attached to dies and rejoins a node that comes back.
- Options.CtrlURLs: extra control-plane endpoints. doJSON/putBlob/getBlob
now try each endpoint in order, falling over on a transport error to the
next (an HTTP response from any node is authoritative — every node
serves the same state under the KV store). newSignedRequest becomes
newSignedRequestTo(base, ...); each failover attempt mints a fresh nonce
(the signature covers method+path+ts+nonce+body, not the host), so a
retried request is never seen as a replay.
- ConnectedServer()/IsConnected(): observability for which node the data
plane is attached to, for ops and failover tests.
- New/Connect/NewWithOptions keep their signatures (a single URL = a
one-element list), so worker/chat/mobile/playground are unchanged.
Test (DoD edge — the issue's "kill node A" case):
- TestClientFailoverAcrossNodes: A seeds two clustered nodes, subscribes,
receives a cross-node message; the node A is attached to is KILLED; A
reconnects to the survivor and still receives messages — session intact.
agent