Commit fa68da5d authored by Giacomo Strangolino's avatar Giacomo Strangolino
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Update README.md

parent 041a1912
......@@ -44,7 +44,7 @@ replies synchronously or not.
In this situation, *ca-proxy* receives a *subscribe* request from a client and forwards it to the *ca-server async*
for *monitoring* and *publishing* results over *nchan* channels.
Similarly, when a client unsubscribes from a channel or a set of sources, the request is handed to *caserver async*
through *ca-proxy*. The *caserver* will stop monitoring the source(s). A behaving client shall send a *global unsubscribe*
through *ca-proxy*. The *caserver* will stop monitoring the source(s). A well behaved client shall send a *global unsubscribe*
request on shutdown.
*ca-proxy* periodically monitors *heartbeats* from clients in order to detect vanished ones. In that case, the disappeared
......@@ -53,10 +53,11 @@ client's sources are *globally unsubscribed* by the *ca-proxy*.
#### <a name="subunsub2casup"></a> ca-proxy subscribe and unsubscribe requests forwarding to ca-supervisor
**Subscription and unsubscription operations shall be notified with a message to the ca-supervisor** so that
the *activities* table is updated by the latter. This message shall be sent *only after an OK reply is received by
the caserver async*. If the communication with *caserver* fails, the behaviour of the *ca-proxy* depends on the request:
the *activities* table is updated by the latter. If the communication with *caserver* fails, the behaviour
of the *ca-proxy* depends on the request:
- *subscribe*: an error condition shall be reported back (to NGINX!!) so that NGINX retries with another *upstream server*.
- *subscribe*: an error condition shall be reported back (to NGINX!!) with a proper HTTP header so that
NGINX retries with another *upstream server*.
Database is left untouched by the proxy instance failing to *subscribe* to its correspondent *caserver* party.
If another upstream server is available, it will take care of the new request.
......
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