fcgi remote backends intelligent availability check
say, i have configured three fcgi-handlers for one URI in lighttpd.
if lighttpd, sees that fcgi backend is unavailable (say, connection refused), it marks it offline (fcgi server disabled). if in case all of them are disabled, it would be neccessary that the fcgi servers are instantly checked for availability again, without the existing timeout. since the servers might have returned. real case: i restarted fcgi backend daemons one by one. and i had to restart lighttpd to make it again serve fcgi requests.
my idea would be that the timeout for checking fcgi backend is lowered for fcgi server, if all of them are unavailable for same URI, and perhaps exponentally increased if the check of all fcgi servers fails (again). and of course initial first check must be done instantly (ie without timeout). and perhaps if the fcgi server becames available, the disabled-timeout is set back to default normal value.
[core] server.error-handler new directive for error pages (fixes #2702)
server.error-handler preserves HTTP status error code when error page
is static, and allows dynamic handlers to change HTTP status code
when error page is provided by dynamic handler. server.error-handler
intercepts all HTTP status codes >= 400 except when the content is
generated by a dynamic handler (cgi, ssi, fastcgi, scgi, proxy, lua).
The request method is unconditionally changed to GET for the request
to service the error handler, and the original request method is
later restored (for logging purposes). request body from the
original request, if present, is discarded.
server.error-handler is somewhat similar to server.error-handler-404,
but server.error-handler-404 is now deprecated, intercepts only 404
and 403 HTTP status codes, and returns 200 OK for static error pages,
a source of confusion for some admins. On the other hand, the new
server.error-handler, when set, will intercept all HTTP status error
codes >= 400. server.error-handler takes precedence over
server.error-handler-404 when both are set.
NOTE: a major difference between server.error-handler and the
now-deprecated server.error-handler-404 is that the values of the
non-standard CGI environment variables REQUEST_URI and REDIRECT_URI
have been swapped. Since REDIRECT_STATUS is the original HTTP
status code, REDIRECT_URI is now the original request, and REQUEST_URI
is the current request (e.g. the URI/URL to the error handler).
The prior behavior -- which reversed REQUEST_URI and REDIRECT_URI values
from those described above -- is preserved for server.error-handler-404.
Additionally, REDIRECT_STATUS is now available to mod_magnet, which
continues to have access to request.uri and request.orig_uri.
github: closes #36
Updated by Anonymous almost 14 years ago
until this above is not implemented, what about improving retry_timeout checks.
when one of the fcgi servers is out (connection refused). then webserver cycles such log entries every $FCGI_RETRY_TIMEOUT seconds:
2005-12-05 20:27:28: (mod_fastcgi.c.2493) fcgi-server re-enabled: 192.168.5.85 3001 2005-12-05 20:27:29: (mod_fastcgi.c.2665) establishing connection failed: Connection refused 2005-12-05 20:27:29: (mod_fastcgi.c.2804) fcgi-server disabled: 192.168.5.85 3001i propose to check the fcgi-server:
- in tcp level (establish tcp connection).
- fcgi protocol level.
and if those succeed, mark fcgi-server online, and send next request there.
i'm not sure, but i think it's possible to do fcgi service check without actually doing FCGI_BEGIN_REQUEST. because sending actual request to fcgi-server to test if it's alive is not very safe operation.
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