From: "Iñaki Baz Castillo" <ibc@...>
Date: 2011-06-22T23:19:54+09:00
Subject: Re: How to order a hash based on its keys?

2011/6/22 Robert Klemme <shortcutter@googlemail.com>:
> Hm...  Now I am not sure any more whether you need a associative
> container at all.  Now we have three steps.  From what I understand
> you do:
>
> 1. items are collected
> 2. items are ordered by priority (what you call second container above)
> 3. items are ordered by some randomization algorithm
>
> I'm obviously missing other access operations out here.  So far I
> don't see any need for a Hash or similar structure.  What else is it
> that you need to do with these items?  What properties do they have?


Step 1)

I get data (DNS SRV records), which is an array with entries like this:

  #<EventMachine::Udns::RR_SRV:0x00000001ea4970 @domain="domain.org",
@priority=1, @weight=50, @port=5062>

Each entry is a SRV record. It has a priority (lowest value is the
best) and weight (higher value means more probability to choose it).

The client getting such array of SRV records wants to connect to a
server based on SRV priorities/weight, which works as follows:
- SRV records with best priority must be used first.
- If there are various SRV records with same priority, then the
probability of choosing each one depends on its weight value (random
with weight).
- If the chosen SRV record fails to connect (i.e. server down) next
one (based on same priority/weight rules) must be tryed.


-- 
Iñaki Baz Castillo
<ibc@aliax.net>