I wrote a quick library (lives in elasticsearch/libraries) to wrap search for discovering nodes in our applications and haproxy cookbooks that rely on it.
module ElasticSearch
class Discovery
attr_accessor :additional_conditions, :dc, :datacenter_restriction, :logger
attr_reader :environment
def initialize(recipe_context, opts = {})
We need to access chef search methods and the easiest way to get them is through
passing self from the chef recipe referencing this class
@recipe_context = recipe_context
@environment = opts.fetch(:environment)
@dc = opts.fetch(:dc, 'default-datacenter-name')
@conditions are non-overridable attributes used in the search like environment
and es-cluster role
@conditions = opts.fetch(:conditions, {
chef_environment: self.environment,
role: opts.fetch(:backend_role, 'elasticsearch-cluster'),
elasticsearch_cluster_name: opts.fetch(:cluster_name)
})
@additional_conditions = opts.fetch(:additional_conditions, Hash.new)
@logger = opts.fetch(:logger, Chef::Log)
@logger.info "Initialized discovery in #{self.environment}/#{self.dc} for #{@conditions[:role]}"
end
def conditions
merged_conditions = @conditions.merge(self.additional_conditions)
@logger.info "Search conditions are #{merged_conditions.flatten}"
merged_conditions
end
def query
@conditions.inject() do |query,condition|
query << "(#{condition.first}:#{condition.last})"
end.join(' AND ')
end
def search(opts = {})
sorted = opts.fetch(:sorted, false)
@logger.info "Searching with #{self.query}"
@results = @recipe_context.search(:node, self.query)
(sorted) ? sorted_results : @results
end
def restrict_to_datacenter!
@logger.info "Restricting search to #{@dc}"
@conditions[:dc] = @dc
end
def restricted_to_datacenter?
@conditions[:dc] == @dc
end
def sorted_results
return unless @results
@results.sort { |node1, node2| node1[:fqdn] <=> node2[:fqdn] }
end
def to_a
@results.collect { |node| { :ip => node[:ipaddress], :fqdn => node[:fqdn], :datacenter => node[:dc] } }
end
end
end
It's used like the following:
es_discovery = ElasticSearch::Discovery.new(self,
environment: node.chef_environment,
backend_role: node[:haproxy][:edge_backend_role],
cluster_name: node[:elasticsearch][:cluster_name]
)
es_discovery.restrict_to_datacenter! if node[:haproxy][:edge_datacenter_restriction]
es_discovery.additional_conditions = node[:haproxy][:additional_conditions] if node[:haproxy][:additional_conditions].is_a?(Hash)
results = es_discovery.search(sorted: true)
This way it'll find all the nodes in a specific cluster but I can also add extra conditions for restricting the search if needed on a per-node/role basis. It needs some work and should probably be generalized for discovering other services besides ES but it could be a start for you.
Dan
On Tuesday, December 18, 2012 at 2:59 PM, Kevin Nuckolls wrote:
We had a long discussion today about a pain point we've had with Chef thus far. We'd like to rely on the search functionality that chef provides so things will automatically wire up with each other in a given environment. But during cookbook development we'd like to have more flexibility with the search functionality.
We decided that we'd like to have a bit more control over the search functionality and be able to provide overrides while we're working on something. Has anyone already written a library for doing something like that?
Thanks,
-Kevin