diff --git a/os_collect_config/collect.py b/os_collect_config/collect.py
index f519dfb..de19a7a 100644
--- a/os_collect_config/collect.py
+++ b/os_collect_config/collect.py
@@ -170,6 +170,10 @@ def collect_all(collectors, store=False, collector_kwargs_map=None):
         except exc.SourceNotConfigured:
             logger.debug('Source [%s] Not configured.' % collector)
             continue
+        except exc.SourceAlreadyCollected:
+            logger.debug('Source [%s] Already collected and cached.'
+                         % collector)
+            continue
 
         if store:
             for output_key, output_content in content:
diff --git a/os_collect_config/ec2.py b/os_collect_config/ec2.py
index d652922..03a0ce6 100644
--- a/os_collect_config/ec2.py
+++ b/os_collect_config/ec2.py
@@ -13,9 +13,12 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import os
+
 from oslo_config import cfg
 from oslo_log import log
 
+from os_collect_config import cache
 from os_collect_config import common
 from os_collect_config import exc
 
@@ -60,5 +63,8 @@ class Collector(object):
         return content
 
     def collect(self):
+        cache_path = cache.get_path('ec2')
+        if os.path.exists(cache_path):
+            raise exc.Ec2MetadataAlreadyCollected()
         root_url = '%s/' % (CONF.ec2.metadata_url)
         return [('ec2', self._fetch_metadata(root_url, CONF.ec2.timeout))]
diff --git a/os_collect_config/exc.py b/os_collect_config/exc.py
index 73a9687..37ab039 100644
--- a/os_collect_config/exc.py
+++ b/os_collect_config/exc.py
@@ -22,10 +22,18 @@ class SourceNotConfigured(RuntimeError):
     """The requested data source is not configured."""
 
 
+class SourceAlreadyCollected(RuntimeError):
+    """The requested data source is immutable and already cached."""
+
+
 class Ec2MetadataNotAvailable(SourceNotAvailable):
     """The EC2 metadata service is not available."""
 
 
+class Ec2MetadataAlreadyCollected(SourceAlreadyCollected):
+    """The EC2 metadata has already been fetched and cached."""
+
+
 class CfnMetadataNotAvailable(SourceNotAvailable):
     """The cfn metadata service is not available."""
 
diff --git a/os_collect_config/tests/test_collect.py b/os_collect_config/tests/test_collect.py
index 5f4ef3f..05f8f32 100644
--- a/os_collect_config/tests/test_collect.py
+++ b/os_collect_config/tests/test_collect.py
@@ -447,6 +447,10 @@ class TestCollectAll(testtools.TestCase):
             cache.commit(changed)
         (changed_keys, paths2) = self._call_collect_all(store=True)
         self.assertEqual(set(), changed_keys)
+
+        # check the second collect skips ec2, it has already been cached.
+        ec2_path = os.path.join(self.cache_dir.path, 'ec2.json')
+        paths.remove(ec2_path)
         self.assertEqual(paths, paths2)
 
     def test_collect_all_no_change_softwareconfig(self):
@@ -477,6 +481,10 @@ class TestCollectAll(testtools.TestCase):
         (changed_keys, paths2) = self._call_collect_all(
             store=True, collector_kwargs_map=soft_config_map)
         self.assertEqual(set(), changed_keys)
+
+        # check the second collect skips ec2, it has already been cached.
+        ec2_path = os.path.join(self.cache_dir.path, 'ec2.json')
+        paths.remove(ec2_path)
         self.assertEqual(paths, paths2)
 
     def test_collect_all_nostore(self):
diff --git a/os_collect_config/tests/test_ec2.py b/os_collect_config/tests/test_ec2.py
index 7b27d96..e2a0e04 100644
--- a/os_collect_config/tests/test_ec2.py
+++ b/os_collect_config/tests/test_ec2.py
@@ -13,9 +13,12 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import json
+import os
 import uuid
 
 import fixtures
+from oslo_config import cfg
 import requests
 import six.moves.urllib.parse as urlparse
 import testtools
@@ -114,3 +117,15 @@ class TestEc2(testtools.TestCase):
         collect_ec2 = ec2.Collector(requests_impl=FakeFailRequests)
         self.assertRaises(exc.Ec2MetadataNotAvailable, collect_ec2.collect)
         self.assertIn('Forbidden', self.log.output)
+
+    def test_collect_ec2_collected(self):
+        collect.setup_conf()
+        cache_dir = self.useFixture(fixtures.TempDir())
+        self.addCleanup(cfg.CONF.reset)
+        cfg.CONF.set_override('cachedir', cache_dir.path)
+        ec2_path = os.path.join(cache_dir.path, 'ec2.json')
+        with open(ec2_path, 'w') as f:
+            json.dump(META_DATA, f)
+
+        collect_ec2 = ec2.Collector(requests_impl=FakeFailRequests)
+        self.assertRaises(exc.Ec2MetadataAlreadyCollected, collect_ec2.collect)