Use Chef search (role:cassandra) to look up seed nodes

[michaelklishin]

If search is not available, we fall back to using node's own
IP address by default.

Fixes #204.

[michaelklishin]

@vkhatri please take a look.

[sethrosenblum]

I may be mis-understanding, but won't this add a chef search to every client run, even when you're not using the default value?

Also, it's generally preferable to not have every node in your cluster be a seed, but only use a subset. That's why I use a search for a tag cassandra-seed. Maybe we could just use the first 3 nodes found when a search is performed and the ips are sorted?

[michaelklishin]

@sethrosenblum good points. Perhaps we should move this to the recipe and check if seeds has a special value (e.g. :search) then?

[michaelklishin]

One way of making search optional would be using separate recipes for that (instead of adding more conditional attributes).

[michaelklishin]

@sethrosenblum @vkhatri I've moved seed discovery into a separate recipe. Let me know what you think.

[vkhatri]

@michaelklishin sorry for the delay. this looks nice, few thoughts:

• it is better to have an attribute default['cassandra']['seed']['use_chef_search'] to allow user to enable/disable chef search
• we could add another attribute default['cassandra']['seed']['count'] = 3 to limit the number of cluster seed nodes
• we could add another attribute default['cassandra']['seed']['search_role'] = 'cassandra-seed' to limit the cluster nodes only for seed
• we could add another attribute default['cassandra']['seed']['search_query'] = 'nil' and use it as an override
• search query need to be limited further only to default['cassandra']['cluster_name']
• perhaps to add this as a helper method instead of recipe

please let me know what do you think

[michaelklishin]

@vkhatri OK, I guess this is a philosophical decision more than a technical one. I'll do what you suggest.

I'm now sure what you mean by

search query need to be limited further only to default['cassandra']['cluster_name']

Discovering cluster name is a good idea. Do you mean that we should do this regardless of the use_chef_search value?

[vkhatri]

@michaelklishin only if use_chef_search is set to true, actually i am thinking the helper method should return the final value for -seeds to be used in templates/default/cassandra.yaml.erb.

templates/default/cassandra.yaml.erb:

          - seeds: "<%= eval_seed_nodes %>"

seed helper method:

def eval_seed_nodes
  # use chef search for seed nodes
  if node['cassandra']['seed']['use_chef_search']
    if Chef::Config[:solo]
      Chef::Log.warn("Chef Solo does not support search, provide the seed nodes via node attribute node['cassandra']['seeds']")
      node['ipaddress']
    else
      if node['cassandra']['seed']['search_query']
        # user defined search query
        xs = search(:node, node['cassandra']['seed']['search_query']).map(&:ipaddress).sort.uniq
      else
        # cookbook auto search query
        search_query = "chef_environment:#{node.chef_environment} AND role:#{node['cassandra']['seed']['search_role']} AND cassandra_cluster_name:#{node['cassandra']['cluster_name']}"
        xs = search(:node, search_query).map(&:ipaddress).sort.uniq
      end

      if xs.empty?
        node['ipaddress']
      else
        xs.take(node['cassandra']['seed']['count']).join(',')
      end
    end
  else
    # user defined seed nodes
    if node['cassandra']['seeds'].is_a?(Array)
      node['cassandra']['seeds'].join(',')
    else
      node['cassandra']['seeds']
    end
  end
end

attributes:

default['cassandra']['seed']['use_chef_search'] = false
default['cassandra']['seed']['count'] = 3
default['cassandra']['seed']['search_role'] = 'cassandra-seed'
default['cassandra']['seed']['search_query'] = nil

[michaelklishin]

@vkhatri fair enough, I'll take your suggestion and run with it.

[michaelklishin]

@vkhatri @sethrosenblum ready for another round.

[michaelklishin]

I'm getting an exception that says method search is undefined in Chef::Mixin::Template::TemplateContext. So this still needs some work.

[michaelklishin]

OK, I can confirm that seed discovery using Chef search and a custom query now works well in my environment.

[vkhatri]

@michaelklishin LGTM 👍