Forum Discussion
Ross_79174
Nimbostratus
NimbostratusHelp caching urls with unique date/time stamp
Hello irule gurus!
We have an issue on our production service where we need to cache our rss feeds to offload our backend servers. The problem is that each rss url has a unique date/time stamp attached to it....therefore it never will "hit" in the cache since no two instances are ever the same. However, we are willing to give up some security for now, to go ahead and "strip" the url so that the date/time stamp are not put into the cache, but rather just the part of the url that stays consistent.
The complete url looks something like this:
/rss/Pepcom/Pepcom+June+2008?oauth_consumer_key=ced9fcdbcae5bd941f51cf82421e6413&oauth_nonce=6191575&oauth_signature_method=HMAC-SHA1&oauth_timestamp=1236751715
However, we only need this to be able to properly serve the url:
/rss/Pepcom/Pepcom+June+2008?oauth_consumer_key=ced9fcdbcae5bd941f51cf82421e6413
We can drop everything from the first "&" on, and still serve the rss feed properly.
We would also like to keep each feed active in the cache for 10 minutes, before expiring.
Can anyone help?
Thanks,
Ross
3 Replies
Ross_79174Me again,
Here is what I have started with, but from looking at the cache hits, I know the trimright is not working correctly.
when RULE_INIT {
set ::fifteen_minutes 900
}
when HTTP_REQUEST {
if { [HTTP::uri] starts_with "/rss" } {
persist none
CACHE::enable
CACHE::uri [string trimright [HTTP::uri] &]
set cachetime $::fifteen_minutes
pool rss
} else {
pool gallery
log local0. "matches rss"
}
}
Thanks.- hoolio
Cirrostratus
Hi Ross,
TMM will crash if you force caching with CACHE::enable and the request does not contain a Host header (not required in HTTP v1.0) or a URI (required in all HTTP versions). This is described in SOL9617 (Click here). So it would be good to add a check for the Host header value and path having a length:
if { [HTTP::uri] starts_with "/rss" && [string length [HTTP::host]] && [string length [HTTP::path]] } {
To parse the portion of the URI you mention in the first post, you can use HTTP::path to get the URI minus the query string and then just the parameter value for oauth_consumer_key
So to get this:
/rss/Pepcom/Pepcom+June+2008?oauth_consumer_key=ced9fcdbcae5bd941f51cf82421e6413
You can use this:
"[HTTP::path]?oauth_consumer_key=[URI::query [HTTP::uri] oauth_consumer_key]"
Lastly, 'persist none' will disable persistence for the duration of the TCP connection. If there are multiple HTTP requests over the same TCP connection, with an RSS request followed by a non-RSS request, the non-RSS request wouldn't be persisted within the gallery pool. You would want to explicitly set persistence for both cases (persist none and persist .
Aaron - Ross_79174Hi Aaron,
Thanks for your prompt response. The string manipulations all worked and we are now happily caching RSS feeds.
I appreciate your help!
-Ross
