Fwd: busywaiting without blocking event loop OR timers
fin at xbhd.org
Mon Aug 29 13:35:15 UTC 2011
[this is a crosspost from nginx-devel, which seems awful quiet these days …]
i'm working on a module that uses ngx_event_connect to connect to a
3rdparty service and parses its request.
the answer depends on the request hostname, so now i'm implementing a
cache in shared memory to cache the responses on a hostname basis.
i'm protecting access to every cache entry using a ngx_atomic_t.
now i'd like to prevent multiple concurrent connections from requests
to the same hostname to the 3rd party service.
i see two ways to solve that:
* busy-wait on ngx_atomic_t as long as a request to the service is open
* create an event and wait for it
now, how can i busy-wait on a ngx_atomic_t without blocking the
handling of other requests in the same process?
(these requests can last up to 10 seconds in worst-case)
-> can i yield to the event loop while busy-waiting?
can i create events independent of I/O, like timer events?
thanks in advance
our howto on doing what we're doing in our module:
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