Re: NETDB.. What is it?

On Tue, 18 Jul 2000, Dan Larsson wrote:

> I recently upgraded from Squid2S2 to Squid2S3. Now I get the following
> messages in my cache.log:
>
> 2000/07/18 13:01:01| NETDB state saved; 89 entries, 5 msec

The FAQ talks about this a little bit:

  7.6. Using ICMP to Measure the Network

  As of version 1.1.9, Squid is able to utilize ICMP Round-Trip-Time
  (RTT) measurements to select the optimal location to forward a cache
  miss. Previously, cache misses would be forwarded to the parent cache
  which returned the first ICP reply message. These were logged with
  FIRST_PARENT_MISS in the access.log file. Now we can select the
  parent which is closest (RTT-wise) to the origin server.

  7.6.1. Supporting ICMP in your Squid cache

  It is more important that your parent caches enable the ICMP features.
  If you are acting as a parent, then you may want to enable ICMP on
  your cache. Also, if your cache makes RTT measurements, it will fetch
  objects directly if your cache is closer than any of the parents.

  If you want your Squid cache to measure RTT's to origin servers, Squid
  must be compiled with the USE_ICMP option. This is easily
  accomplished by uncommenting "-DUSE_ICMP=1" in src/Makefile and/or
  src/Makefile.in.

  An external program called pinger is responsible for sending and
  receiving ICMP packets. It must run with root privileges. After
  Squid has been compiled, the pinger program must be installed
  separately. A special Makefile target will install pinger with
  appropriate permissions.

          % make install
          % su
          # make install-pinger

  There are three configuration file options for tuning the measurement
  database on your cache. netdb_low and netdb_high specify high and low
  water marks for keeping the database to a certain size (e.g. just
  like with the IP cache). The netdb_ttl option specifies the minimum
  rate for pinging a site. If netdb_ttl is set to 300 seconds (5 min-
  utes) then an ICMP packet will not be sent to the same site more than
  once every five minutes. Note that a site is only pinged when an HTTP
  request for the site is received.

  Another option, minimum_direct_hops can be used to try finding servers
  which are close to your cache. If the measured hop count to the
  origin server is less than or equal to minimum_direct_hops, the
  request will be forwarded directly to the origin server.
Received on Tue Jul 18 2000 - 09:48:33 MDT