Adapt dashboard to show idle and used runners

lib/runner/strategy/docker_container_pool.rb

@@ -166,7 +166,7 @@ class Runner::Strategy::DockerContainerPool < Runner::Strategy
     url = "#{config[:url]}/docker_container_pool/quantities"
     response = Faraday.get(url)
     pool_size = JSON.parse(response.body)
-    pool_size.transform_keys(&:to_i)
+    pool_size.deep_symbolize_keys
   rescue Faraday::Error => e
     raise Runner::Error::FaradayError.new("Request to DockerContainerPool failed: #{e.inspect}")
   rescue JSON::ParserError => e

lib/runner/strategy/poseidon.rb

@@ -176,7 +176,23 @@ class Runner::Strategy::Poseidon < Runner::Strategy
   end
 
   def self.pool_size
-    {}
+    url = "#{config[:url]}/statistics/execution-environments"
+    Rails.logger.debug { "#{Time.zone.now.getutc.inspect}: Getting statistics from #{url}" }
+    response = http_connection.get url
+    case response.status
+      when 200
+        response_body = parse response
+        response_body
+      else
+        handle_error response
+    end
+  rescue Faraday::Error => e
+    raise Runner::Error::FaradayError.new("Request to Poseidon failed: #{e.inspect}")
+  rescue JSON::ParserError => e
+    # Poseidon should not send invalid json
+    raise Runner::Error::UnexpectedResponse.new("Error parsing response from Poseidon: #{e.message}")
+  ensure
+    Rails.logger.debug { "#{Time.zone.now.getutc.inspect}: Finished getting statistics" }
   end
 
   def self.websocket_header