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From Benjamin>
Subject Re: Deployment on AWS
Date Sun, 04 Apr 2010 00:08:09 GMT
Right, you determine AZ by looking at the metadata.  us-east-1a is a
different AZ from us-east-1b.  You can't infer anything beyond that,
either with the AWS API or guesses about IP addressing.  My EC2 snitch
recipe builds a config file for the property snitch that treats AZs
like racks (just breaking apart the AZ name, nothing magical), and the
rest is the normal rack aware placement strategy.  I am sure folks
_could_ do interesting things on EC2 with extra code, but I don't see
extra code as required for these basic features.


On Sat, Apr 3, 2010 at 3:04 PM, Joe Stump <> wrote:
> On Apr 3, 2010, at 2:54 PM, Benjamin Black wrote:
>> I'm pretty familiar with EC2, hence the question.  I don't believe any
>> patches are required to do these things.  Regardless, as I noted in
>> that ticket, you definitely do NOT need AWS credentials to determine
>> your availability zone.  It is available through the metadata web
>> server for each instance as 'placement_availability_zone', avoiding
>> the need to speak the EC2 API or store credentials in the configs.
> Good point on the metadata web server. Though I'm unsure how Cassandra would know anything
about those AZ's without using code that's aware of such things, such as the rack-aware strategy
we made.
> Am I missing something further? I asked a friend on the EC2 networking team if you could
determine AZ by IP address and he said, "No."
> --Joe

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