Re: need help about ICP

mån 2003-02-24 klockan 16.10 skrev atit_ldce:
> which function will handle ICP_HIT message?
>
> means which function actually sends HTTP request to the peer which has replied with ICP_HIT.

These two functions are separate.

First ICP is used to determine which peers are alive and if any of these
have the object.

Then peer selection selects the most suitable of the peers found.

> icpHandleIcpV2 will filter ICP message types?

Yes, and record the status of the reply.

> can u explain from this how flow works until http request to peer is send?

Then a ICP HIT reply is received this for the neighbor by calling
neighborsUdpAck. If this finds a request waiting for this ICP message
then a callback is made into the module who initiated the ICP pinging
(the ICP pingning was initiated by calling neighborsUdpPing)

neighborsUdpPing is called from peer_select.cc, which is the module
which is responsible for selecting which peer to use for the request
based on the information available (including results of ICP pings). The
function in neighborsUdpPing which acts on ICP messages is
peerHandlePingReply.

> i also want explaination about following function
> enter_suid()
> leave_suid()

These two is used when Squid needs to perform privileged operations
which may require root access.

> icpCheckUdpHit

This function checks is a existing store entry is valid for responding
with a ICP HIT or not..

> icpSetCacheKey

This calculates the ICP message key for a new ICP query. The ICP message
key is used to tell replies to different requests for the same URL apart
from each other.

> and about following structure(s)
>
> struct _peer

This struct defines a cache_peer. Mostly related to the cache_peer
directive in squid.conf.

> struct _acl_access

This struct defines a access list such as http_access. Each entry is one
access rule from squid.conf.

> struct statCounter.icp

This struct keeps the ICP related statistics counters shown in cachemgr
and the SNMP interfaces..

-- 
Henrik Nordstrom <hno@squid-cache.org>
MARA Systems AB, Sweden