🔗 Feature: SRV based origin server location
- Goal: Make use of DNS SRV records to locate the origin server for a given website.
- 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
- Version:
- Proof of Concept: FrancescoChemolli
- Developer:
- More:
🔗 Proof Of Concept Code
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.
Categories: WantedFeature
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