Hello everybody!
We have a Apache httpd with mod_cache/mod_disk_cache enabled. By default the
directive CacheStaleOnError is activated. The documentation states:
| When the CacheStaleOnError directive is switched on, and when stale data is
available in the cache, the cache will respond to 5xx responses from the
backend by returning the stale data instead of the 5xx response.
That's our desired behaviour.
Additionally we want to serve a custom error page when there's no (stale) cache
data add all to serve for a specific request. So we defined an ErrorDocument
for every status of the 5xx class.
As I couldn't come up with an reliable test scenario, my question is: what will
happen when cached data for a specific request is stale and a 5xx error occures
while requesting the backend?
Our current configuration-template looks like that:
<VirtualHost *:80>
ServerName @host@
ServerAlias @hostShort@
Include conf.cache/health-check.conf
CustomLog logs/@host@/request_log \
"[%{%d/%m/%Y:%T}t.%{msec_frac}t %{%z}t]
%{X-Forwarded-For}i %{SSL_PROTOCOL}x %{SSL_CIPHER}x \"%r\" %s %b %D
\"%{User-Agent}i\" %{cache-hit}e"
#htdocs
ProxyPass /errors/ !
ProxyPass /version/ !
#BACKEND (defined in hosts.properties)
ProxyPass / http://@backend@:80/
ProxyPassReverse / http://@backend@:80/
CacheRoot /var/local/cache/@host@/
# Serve stale data on error.
CacheStaleOnError on
Include conf.cache/cache-common.conf
Include conf.cache/cache-rules.conf
Include conf.cache/ssl-cache-rules.conf
ProxyErrorOverride On
ErrorDocument 500 /errors/@host@.html
ErrorDocument 501 /errors/@host@.html
ErrorDocument 502 /errors/@host@.html
ErrorDocument 503 /errors/@host@.html
ErrorDocument 504 /errors/@host@.html
ErrorDocument 505 /errors/@host@.html
ErrorDocument 506 /errors/@host@.html
ErrorDocument 507 /errors/@host@.html
ErrorDocument 508 /errors/@host@.html
ErrorDocument 510 /errors/@host@.html
</VirtualHost>
Does httpd serve the stale data? Or does it serve the configured custom error
page? How is that prioritised?
Thanks in advance,
Alexander
--
Alexander Härtig
software engineer
dmc 030 GmbH
Kohlfurter Strasse 41/43
10999 Berlin (Germany)
Telefon: +49 30 308 3393 - 70
Telefax: +49 30 308 3393 - 93
E-Mail: alexander.haer...@dmc.de
Internet: www.dmc.de
Handelsregister: AG Berlin Charlottenburg HRB 129396 B
Geschäftsführer: Daniel Elsässer, Andreas Magg
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