[chef] Re: Configure server to integer mapping

[Tensibai < >]

I do something near to get a minute of execution for different servers, for your case you may use:

 

  oldrand=srand "server_name".sum # set the random number generator to a known value (sum of the hostname)

  id=rand(254) # Get a random (but still the same for this server) number

  srand oldrand # reset the random number generator to its previous seed

 

this would give the same origin to random and ends up with the same number at end.

With that you'll have a fixed id for a server name.

 

!WARNING! you may have a collision if two server use the same letters in name:

irb(main):023:0> "abc".sum
=> 294
irb(main):024:0> "bac".sum
=> 294
irb(main):025:0> "cba".sum
=> 294

 

Here we're naming servers like srv0001 and increasing and I'm using the numeric part for srand instead of sum,

this gives something like oldrand = srand "server_name"[/([0-9]+),1].to_i 

For now I didn't hit the wall with collision in the same cluster.

 

Le 2014-10-30 03:50, a écrit :

Hi everyone,

For a few services like zookeeper or kafka, they require a server to integer
mapping like this,

server a - 1
server b - 2
...

This is particularly difficult to do in Chef (outside of manually configuring
this) using things like search. Some methods I have tried or seen,

 1. Search for nodes and sort nodes by name. Use the index of each server as
their id. This can cause servers to use the same id for a moment if
provisioning servers concurrently. This can also cause problems if a new node
doesn't get appended to the end causing a number of servers to change their
ids.

 2. Convert ipaddress or some other attribute into an integer. Unfortunately
this produces an integer too large as services like zookeeper only allow ids
between 0-255.

 3. Set this id on the node during provisioning and track the current id
somewhere. Then you can use search to just get the mapping.

Does anyone have other suggestions? It seems like 3 is the best option though
not terrible easy to do. It could be easier than I think if I use something
like chef-metal and define each machine with an id.

Bryan