Re: need help about cache HIT/MISS

mån 2003-02-24 klockan 18.35 skrev atit_ldce:
> when squid forward http request to the peer cache which address is used as outoging address.
>
> does it one defined in tcp_outgoing_address..

Yes, as selected by the call to getOutgoingAddr() from fwdConnectStart()
in forward.cc

> i also need explanation about fields within structure _peer and
> ps_state

Which specific fields do you need to have explained?

Most of the fields of the peer type is explained by the cache_peer
directive and it's documentation in squid.conf.

the ps_state is used while selecting which peers to use, and contain
references to the information used while selecting suitable peers for a
given reqest.

> working of peerSelectFoo(ps_state) is not clear.
> specially logic related to const DIRECT_XXX

The different "direct" states are:

  DIRECT_UNKNOWN -> sufficient data is not yet available (starts here).
  DIRECT_NO -> MUST not be sent directly (never_direct true)
  DIRECT_YES -> MUST be sent directly (always_direct true)
  DIRECT_MAYBE -> May be sent via a peer or directly (normal case)

When peer selection starts "direct" starts out as DIRECT_UNKNOWN. When
always_direct and never_direct have been evaluated sufficient
information is available and the true value of "direct" is evaluated.

The first "if (direct == DIRECT_UNKNOWN)" deals with the case that
never_direct and/or always_direct have not yet been evaluated and the
"directness" of the request is not yet known. In such case the acl code
is called for evaluating always_direct and/or never_direct and when
completed peerSelectFoo() is called again.

While the request is waiting for always_direct/never_direct/ICP lookups
to complete, the ps_state keeps track of the needed state information
for peer selection.

> what is HTCP?

An alternative to ICP. Ignore this for now unless you are specifically
interested in HTCP. Some documentation on what HTCP is and it's packet
format can be found in the doc/ directory of Squid.

> what is the outgoing address used for dsn lookup?

udp_outgoing_address.

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