Feature: DNS-based origin server location
Goal: Make use of informations available in DNS to locate the origin server for a given website. The needed information can be found in SRV records, where available.
Status: In progress; a working redirector-based proof-of-concept is available. It can be improved upon, with the aim of mimicking Squid's internal processes.
ETA: unknown
ETA: A few days for the POC. Work needed to get into Squid body is unknown.
Version: 3.x
Priority: 3
Proof of Concept: FrancescoChemolli
Developer:
More:
Proof Of Concept Code
- [get | view] (2007-12-28 02:13:09, 7.3 KB) [[attachment:srv-redir-0.4.pl]]
- [get | view] (2007-12-22 20:45:41, 2.9 KB) [[attachment:srv-redir.pl]]
Configuration snippet:
url_rewrite_program /path/to/srv-redir.pl url_rewrite_children 5 url_rewrite_concurrency 0 url_rewrite_host_header off
Some tuneables are in the redirector script itself.
Details
DNS SRV records, defined in RFC 2782 can help attain some level of high availability and load balancing in a very straightforward manner. Their query structure includes a naming convention to locate a certain well-known network service, and their reply structure includes two different fields to indicate the level of priority a certain pointer of a set has.
For example a query: _http._tcp.www.kinkie.it. SRV Might return results similar to those:
priority |
weight |
target |
10 |
10 |
srv1.kinkie.it. |
10 |
10 |
srv2.kinkie.it. |
20 |
5 |
backupsrv.kinkie.it. |
Quoting from the RFC:
A client MUST attempt to contact the target host with the lowest-numbered priority it can reach; target hosts with the same priority SHOULD be tried in an order defined by the weight field. The range is 0-65535. This is a 16 bit unsigned integer in network byte order. [...] The weight field specifies a relative weight for entries with the same priority. Larger weights SHOULD be given a proportionately higher probability of being selected.
The (expired) Internet Draft draft-andrews-http-srv tries to address some inconsistencies of the general addressing scheme.
Status
The redirector is RFC-compliant at version 0.4. Andrews' draft is the next target for integration.