Apply capacity algorithm changes

* This also adds fields to the instance view for tracking cpu and
  memory usage as well as information on what the capacity ranges are
* Also adds a flag for enabling/disabling instances which removes them
  from all queues and has them stop processing new work
* The capacity is now based almost exclusively on some value relative
  to forks
* capacity_adjustment allows you to commit an instance to a certain
  amount of forks, cpu focused or memory focused
* Each job run adds a single fork overhead (that's the reasoning
  behind the +1)

awx/main/models/ha.py

@@ -1,6 +1,8 @@
 # Copyright (c) 2015 Ansible, Inc.
 # All Rights Reserved.
 
+from decimal import Decimal
+
 from django.db import models, connection
 from django.db.models.signals import post_save, post_delete
 from django.dispatch import receiver
@@ -10,6 +12,7 @@ from django.utils.timezone import now, timedelta
 
 from solo.models import SingletonModel
 
+from awx import __version__ as awx_application_version
 from awx.api.versioning import reverse
 from awx.main.managers import InstanceManager, InstanceGroupManager
 from awx.main.fields import JSONField
@@ -17,6 +20,7 @@ from awx.main.models.inventory import InventoryUpdate
 from awx.main.models.jobs import Job
 from awx.main.models.projects import ProjectUpdate
 from awx.main.models.unified_jobs import UnifiedJob
+from awx.main.utils import get_cpu_capacity, get_mem_capacity, get_system_task_capacity
 
 __all__ = ('Instance', 'InstanceGroup', 'JobOrigin', 'TowerScheduleState',)
 
@@ -39,6 +43,30 @@ class Instance(models.Model):
         default=100,
         editable=False,
     )
+    capacity_adjustment = models.DecimalField(
+        default=Decimal(1.0),
+        max_digits=3,
+        decimal_places=2,
+    )
+    enabled = models.BooleanField(
+        default=True
+    )
+    cpu = models.IntegerField(
+        default=0,
+        editable=False,
+    )
+    memory = models.BigIntegerField(
+        default=0,
+        editable=False,
+    )
+    cpu_capacity = models.IntegerField(
+        default=0,
+        editable=False,
+    )
+    mem_capacity = models.IntegerField(
+        default=0,
+        editable=False,
+    )
 
     class Meta:
         app_label = 'main'
@@ -68,6 +96,20 @@ class Instance(models.Model):
         return Instance.objects.filter(rampart_groups__controller__instances=self).exists()
 
 
+    def refresh_capacity(self):
+        cpu = get_cpu_capacity()
+        mem = get_mem_capacity()
+        self.capacity = get_system_task_capacity(self.capacity_adjustment)
+        self.cpu = cpu[0]
+        self.memory = mem[0]
+        self.cpu_capacity = cpu[1]
+        self.mem_capacity = mem[1]
+        self.version = awx_application_version
+        self.save(update_fields=['capacity', 'version', 'modified', 'cpu',
+                                 'memory', 'cpu_capacity', 'mem_capacity'])
+
+    
+
 class InstanceGroup(models.Model):
     """A model representing a Queue/Group of AWX Instances."""
     objects = InstanceGroupManager()