nats-io / gnatsd / 3315

91%

master: 91%

Pull #965

travis-ci

Gateways: Fix race for request reply

This addresses the following race:
- client connection creates a subscription on a reply subject
- client connection sends a request
- server sends the subscription to inbound gateway
- server sends the message to outbound gateway (those may be
  to different servers)
- receiving server sends to sub interested in request subject
- app sends reply
- its server then check for interest on the reply's subject

In interestOnly mode, there is a possibility that this server
has not received the interest on the reply subject yet and would
then drop the reply.

This PR detects above scenario and will prefix the reply subject
to identify the origin cluster if it is detected that the last
subscription from the sending connection was created less than
a second ago.
Once the destination has this prefix, the destination cluster
will always send back that message to origin cluster even if
there is no registered interest.

Signed-off-by: Ivan Kozlovic <ivan@synadia.com>

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