tower fact cache implementation

* Tower now injects facts into jobs via memcached for use by Ansible
playbooks. On the Ansible side, this is accomplished by the existing
mechanism, an Ansible Fact Cache Plugin + memcached. On the Tower side,
memcached is leveraged heavily.

awx/main/tests/unit/models/test_jobs.py

@@ -0,0 +1,115 @@
+import pytest
+
+from awx.main.models import (
+    Job,
+    Inventory,
+    Host,
+)
+
+
+class CacheMock(object):
+    def __init__(self):
+        self.d = dict()
+
+    def get(self, key):
+        if key not in self.d:
+            return None
+        return self.d[key]
+
+    def set(self, key, val):
+        self.d[key] = val
+
+    def delete(self, key):
+        del self.d[key]
+
+
+@pytest.fixture
+def hosts():
+    return [
+        Host(name='host1', ansible_facts={"a": 1, "b": 2}),
+        Host(name='host2', ansible_facts={"a": 1, "b": 2}),
+        Host(name='host3', ansible_facts={"a": 1, "b": 2}),
+    ]
+
+
+@pytest.fixture
+def hosts2():
+    return [
+        Host(name='host2', ansible_facts="foobar"),
+    ]
+
+
+@pytest.fixture
+def inventory():
+    return Inventory(id=5)
+
+
+@pytest.fixture
+def mock_cache(mocker):
+    cache = CacheMock()
+    mocker.patch.object(cache, 'set', wraps=cache.set)
+    mocker.patch.object(cache, 'get', wraps=cache.get)
+    mocker.patch.object(cache, 'delete', wraps=cache.delete)
+    return cache
+
+
+@pytest.fixture
+def job(mocker, hosts, inventory, mock_cache):
+    j = Job(inventory=inventory, id=2)
+    j._get_inventory_hosts = mocker.Mock(return_value=hosts)
+    j._get_memcache_connection = mocker.Mock(return_value=mock_cache)
+    return j
+
+
+@pytest.fixture
+def job2(mocker, hosts2, inventory, mock_cache):
+    j = Job(inventory=inventory, id=3)
+    j._get_inventory_hosts = mocker.Mock(return_value=hosts2)
+    j._get_memcache_connection = mocker.Mock(return_value=mock_cache)
+    return j
+
+
+def test_start_job_fact_cache(hosts, job, inventory, mocker):
+
+    job.start_job_fact_cache()
+
+    job._get_memcache_connection().set.assert_any_call('{}'.format(5), [h.name for h in hosts])
+    for host in hosts:  
+        job._get_memcache_connection().set.assert_any_call('{}-{}'.format(5, host.name), host.ansible_facts)
+        job._get_memcache_connection().set.assert_any_call('{}-{}-modified'.format(5, host.name), False)
+
+
+def test_start_job_fact_cache_existing_host(hosts, hosts2, job, job2, inventory, mocker):
+
+    job.start_job_fact_cache()
+
+    for host in hosts:  
+        job._get_memcache_connection().set.assert_any_call('{}-{}'.format(5, host.name), host.ansible_facts)
+        job._get_memcache_connection().set.assert_any_call('{}-{}-modified'.format(5, host.name), False)
+
+    job._get_memcache_connection().set.reset_mock()
+
+    job2.start_job_fact_cache()
+
+    # Ensure hosts2 ansible_facts didn't overwrite hosts ansible_facts
+    ansible_facts_cached = job._get_memcache_connection().get('{}-{}'.format(5, hosts2[0].name))
+    assert ansible_facts_cached == hosts[1].ansible_facts
+
+
+def test_finish_job_fact_cache(job, hosts, inventory, mocker):
+
+    job.start_job_fact_cache()
+
+    host = hosts[1]
+    host_key = job.memcached_fact_host_key(host.name)
+    modified_key = job.memcached_fact_modified_key(host.name)
+    host.save = mocker.Mock()
+
+    job._get_memcache_connection().set(host_key, 'blah')
+    job._get_memcache_connection().set(modified_key, True)
+    
+    job.finish_job_fact_cache()
+
+    assert host.ansible_facts == 'blah'
+    host.save.assert_called_once_with()
+