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DNS dependancy

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Wed, 05/18/2011 - 05:48
bhughes
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Hi all,

I was reading the recommendations for membase in the cloud at http://techzone.couchbase.com/wiki/display/membase/Using+Membase+in+the+... and I have a question about that. If your hostnames are bound by their dns name instead of IP, how big of a dependancy on DNS does that create? If the DNS server is unavailable, do things immediately start failing or are the lookups cached? If it is heavily linked to DNS, how hard is the DNS server going to be hit. If it's cached, how is that cache cleared when the server address changes?

-Brent

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Wed, 05/18/2011 - 11:23
perry
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The DNS name is only used within our out-of-band clustering logic for each node to identify itself. Internally, the names are mapped to IP addresses which are then used for any communication between nodes.

I will check with our engineers on how often we refresh this info (if at all) and what the dependency on a DNS server is.

Perry

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Wed, 05/18/2011 - 11:34
alkondratenko
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We normally resolve hostnames only once on startup. And then Erlang keeps connections between nodes. Only if some connections are disconnected we'll try connecting again. In this case Erlang will use OS name resolver caching. So we don't expect any heave DNS traffic.

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