feat(health checks): implement new kubernetes 1.2 health check features

Added the following new functionalities

* HEALTHCHECK_PERIOD_SECONDS - How often (in seconds) to perform the probe
* HEALTHCHECK_SUCCESS_THRESHOLD - How many probe runs need to be done after failure to consider it a success again
* HEALTHCHECK_FAILURE_THRESHOLD - How many times a probe should fail before considered being down

These defaults are all copied from kubernetes but may have to be adjusted due to our high default timeout, or we bring the default timeout down

Closes #251

Author: helgi

rootfs/api/models/config.py

@@ -38,8 +38,19 @@ def healthcheck(self):
         timeout = int(self.values.get('HEALTHCHECK_TIMEOUT', 50))
         delay = int(self.values.get('HEALTHCHECK_INITIAL_DELAY', 50))
         port = int(self.values.get('HEALTHCHECK_PORT', 5000))
-
-        return {'path': path, 'timeout': timeout, 'delay': delay, 'port': port}
+        period_seconds = int(self.values.get('HEALTHCHECK_PERIOD_SECONDS', 10))
+        success_threshold = int(self.values.get('HEALTHCHECK_SUCCESS_THRESHOLD', 1))
+        failure_threshold = int(self.values.get('HEALTHCHECK_FAILURE_THRESHOLD', 3))
+
+        return {
+            'path': path,
+            'timeout': timeout,
+            'delay': delay,
+            'port': port,
+            'period_seconds': period_seconds,
+            'success_threshold': success_threshold,
+            'failure_threshold': failure_threshold,
+        }
 
     def set_healthchecks(self):
         """Defines default values for HTTP healthchecks"""
@@ -49,10 +60,25 @@ def set_healthchecks(self):
         # fetch set health values and any defaults
         # this approach allows new health items to be added without issues
         health = self.healthcheck()
+
+        # HTTP GET related
         self.values['HEALTHCHECK_URL'] = health['path']
+        self.values['HEALTHCHECK_PORT'] = health['port']
+
+        # Number of seconds after which the probe times out.
+        # More info: http://releases.k8s.io/HEAD/docs/user-guide/pod-states.md#container-probes
         self.values['HEALTHCHECK_TIMEOUT'] = health['timeout']
+        # Number of seconds after the container has started before liveness probes are initiated.
+        # More info: http://releases.k8s.io/HEAD/docs/user-guide/pod-states.md#container-probes
         self.values['HEALTHCHECK_INITIAL_DELAY'] = health['delay']
-        self.values['HEALTHCHECK_PORT'] = health['port']
+        # How often (in seconds) to perform the probe.
+        self.values['HEALTHCHECK_PERIOD_SECONDS'] = health['period_seconds']
+        # Minimum consecutive successes for the probe to be considered successful
+        # after having failed.
+        self.values['HEALTHCHECK_SUCCESS_THRESHOLD'] = health['success_threshold']
+        # Minimum consecutive failures for the probe to be considered failed after
+        # having succeeded.
+        self.values['HEALTHCHECK_FAILURE_THRESHOLD'] = health['failure_threshold']
 
     def save(self, **kwargs):
         """merge the old config with the new"""

rootfs/scheduler/__init__.py

@@ -986,7 +986,15 @@ def _delete_rc(self, namespace, name):
 
         return response
 
-    def _healthcheck(self, controller, routable=False, path='/', port=5000, delay=30, timeout=5):  # noqa
+    def _healthcheck(self, controller, routable=False, path='/', port=5000, delay=30, timeout=5,
+                     period_seconds=1, success_threshold=1, failure_threshold=3):  # noqa
+        """
+        Apply HTTP GET healthcehck to the application container
+
+        http://kubernetes.io/docs/user-guide/walkthrough/k8s201/#health-checking
+        http://kubernetes.io/docs/user-guide/pod-states/#container-probes
+        http://kubernetes.io/docs/user-guide/liveness/
+        """
         if not routable:
             return controller
 
@@ -1011,7 +1019,10 @@ def _healthcheck(self, controller, routable=False, path='/', port=5000, delay=30
                 # length of time to wait for a pod to initialize
                 # after pod startup, before applying health checking
                 'initialDelaySeconds': delay,
-                'timeoutSeconds': timeout
+                'timeoutSeconds': timeout,
+                'periodSeconds': period_seconds,
+                'successThreshold': success_threshold,
+                'failureThreshold': failure_threshold,
             },
             'readinessProbe': {
                 # an http probe
@@ -1022,7 +1033,10 @@ def _healthcheck(self, controller, routable=False, path='/', port=5000, delay=30
                 # length of time to wait for a pod to initialize
                 # after pod startup, before applying health checking
                 'initialDelaySeconds': delay,
-                'timeoutSeconds': timeout
+                'timeoutSeconds': timeout,
+                'periodSeconds': period_seconds,
+                'successThreshold': success_threshold,
+                'failureThreshold': failure_threshold,
             },
         }