Add support for subscriptions

README.md

@@ -5,8 +5,9 @@ This filter extension provides the Sensu Core built-in filter `check_dependencie
 This filter matches events when an event already exists, enabling the user to
 reduce notification noise and only be notified for the “root cause” of a given
 failure. Check dependencies can be defined in the check definition, using
-dependencies, an array of checks (e.g. `check_app`) or Sensu client/check pairs
-(e.g. `db-01/check_mysql`).
+dependencies, an array of checks (e.g. `check_app`), Sensu client/check pairs
+(e.g. `db-01/check_mysql`), or a subscription/check pair
+(e.g. `subscription:mysql/check_mysql`).
 
 [![Build Status](https://travis-ci.org/sensu-extensions/sensu-extensions-check-dependencies.svg?branch=master)](https://travis-ci.org/sensu-extensions/sensu-extensions-check-dependencies)
 
@@ -73,6 +74,26 @@ Specify a dependency on the `mysql` check:
 }
 ```
 
+... or specify a dependency on any `mysql` check in the `mysql_nodes`
+subscription:
+
+``` javascript
+{
+  "checks": {
+    "web_application_api": {
+      "command": "check-http.rb -u https://localhost:8080/api/v1/health",
+      "subscribers": [
+        "web_application"
+      ],
+      "interval": 20,
+      "dependencies": [
+        "subscription:mysql_nodes/mysql"
+      ]
+    }
+  }
+}
+```
+
 Apply the `check_dependencies` filter to one or more handlers:
 
 ``` javascript

lib/sensu/extensions/check-dependencies.rb

@@ -36,27 +36,47 @@ def sensu_api_get_request(path)
       # @param client_name [String]
       # @param check_name [String]
       # @return [Boolean]
-      def event_exists?(client_name, check_name)
+      def client_event_exists?(client_name, check_name)
         path = "/events/#{client_name}/#{check_name}"
         response = sensu_api_get_request(path)
         response.code.to_i == 200
       end
 
+      # Check to see if an event exists for a subscription/check pair. This
+      # method is looking for a HTTP response code of `200`.
+      #
+      # @param subscription_name [String]
+      # @param check_name [String]
+      # @return [Boolean]
+      def subscription_event_exists?(subscription_name, check_name)
+        path = "/events"
+        response = sensu_api_get_request(path)
+        events = JSON.load(response.body)
+        !events.select { |event| event[:client][:subscriptions].include?(subscription_name) && event[:check][:name] == check_name}.empty?
+      end
+
       # Determine if an event exists for any of the check
       # dependencies declared in the event data, specified in array,
       # check `dependencies`. A check dependency can be a check
-      # executed by the same Sensu client (eg. `check_app`), or a
-      # client/check pair (eg.`i-424242/check_mysql`).
+      # executed by the same Sensu client (eg. `check_app`), a
+      # client/check pair (eg.`i-424242/check_mysql`), or a
+      # subscription/check pair (eg. `subscription:mysql/check_mysql`).
       #
       # @param event [Hash]
       # @return [Boolean]
       def dependency_events_exist?(event)
         if event[:check][:dependencies].is_a?(Array)
           event[:check][:dependencies].any? do |dependency|
             begin
-              check_name, client_name = dependency.split("/").reverse
-              client_name ||= event[:client][:name]
-              event_exists?(client_name, check_name)
+              check_name, entity = dependency.split("/").reverse
+              if entity =~ /^subscription:.*$/
+                subscription_name = entity.split(":")[1]
+                subscription_event_exists?(subscription_name, check_name)
+              else
+                client_name = entity
+                client_name ||= event[:client][:name]
+                client_event_exists?(client_name, check_name)
+              end
             rescue => error
               @logger.error("failed to query api for a check dependency event", :error => error)
               false

spec/check_dependencies_spec.rb

@@ -61,4 +61,25 @@
       end
     end
   end
+
+  it "can determine if an event exists for a check dependency subscription/check pair" do
+    async_wrapper do
+      event = event_template
+      event2 = event_template
+      event[:check][:dependencies] = ["subscription:foo/bar"]
+      stub_request(:get, "127.0.0.1:4567/events").
+        to_return(:status => 200, :body => JSON.dump([event2]))
+      @extension.safe_run(event) do |output, status|
+        expect(status).to eq(1)
+        event2[:client][:subscriptions] = ["foo"]
+        event2[:check][:name] = "bar"
+        stub_request(:get, "127.0.0.1:4567/events").
+          to_return(:status => 200, :body => JSON.dump([event2]))
+        @extension.safe_run(event) do |output, status|
+          expect(status).to eq(0)
+          async_done
+        end
+      end
+    end
+  end
 end