On 12/08/2010 08:45 PM, Leif Hedstrom wrote:
On 12/08/2010 08:36 PM, Victor Lucero wrote:
Hi.
Im writing a plugin to implement Load balancing. im facing some
problem doing it with a remap plugin because its looks like when i
alter new_host its also alter the "host" header in the http petition
(and i dont want that)
I need a way to alter the conection to Original Server and change the
ip(so i can select between the servers in the pool). but there is no
hook in this step.
You have two options:
Well, there's a third option, I meant to say there are "two options" if
you want to do this as a remap plugin (which makes a fair amount of
sense, since you might want to easily configure this plugin per remap rule).
The third option is to use "trunk", which has a few changes to the hooks
and APIs. In particular, there are two useful hooks (one is merely
renamed, but still):
TS_HTTP_PRE_REMAP_HOOK
TS_HTTP_POST_REMAP_HOOK
In addition, there's a new, very useful API (when running as a reverse
proxy only):
tsapi TSReturnCode TSSkipRemappingSet(TSHttpTxn txnp, int flag);
All three of my "suggestions" probably suffers from the fact that
changing the destination "url" also affects the cache key (if the
content is cacheable). In most cases, that would be undesirable, so you
should also look into using this API to control the cache key:
tsapi TSReturnCode TSCacheUrlSet(TSHttpTxn txnp, const char *url,
int length);
As a side note, for real load balancing, we need a way to intercept all
DNS / hostDB lookups in a plugin. So, you'd do something like
map http://www.example.com/ http://real.example.com/
and when real.example.com is looked up in our hostDB / DNS (on every
request), you would intercept it with a plugin (new hook required,
there's no way to do this now afaik) that allows you to return an IP
based on your own code. It's unclear to me right now how such a hook
would interact with hostDB, and the existing code we have for marking
IPs as down etc. (i.e. it's important for the core to communicate
connect failures to a plugin in a new hook like this). It's something we
should noodle about (I'll file a bug later), it'd be great to get core
changes in before v3.0.
Cheers,
-- leif
