Defined API for initialization of cgroups

azurelinuxagent/common/cgroupapi.py

@@ -0,0 +1,137 @@
+# Copyright 2018 Microsoft Corporation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+# Requires Python 2.6+ and Openssl 1.0+
+
+import errno
+import os
+
+from azurelinuxagent.common import logger
+from azurelinuxagent.common.exception import CGroupsException
+from azurelinuxagent.common.future import ustr
+from azurelinuxagent.common.osutil import get_osutil
+from azurelinuxagent.common.utils import fileutil
+
+CGROUPS_FILE_SYSTEM_ROOT = '/sys/fs/cgroup'
+CGROUP_CONTROLLERS = ["cpu", "memory"]
+VM_AGENT_CGROUP_NAME = "walinuxagent.service"
+EXTENSIONS_ROOT_CGROUP_NAME = "walinuxagent.extensions"
+
+class CGroupsApi(object):
+    """
+    Interface for the cgroups API
+    """
+    def create_agent_cgroups(self):
+        raise NotImplementedError()
+
+    def create_extension_cgroups_root(self):
+        raise NotImplementedError()
+
+
+class FileSystemCgroupsApi(CGroupsApi):
+    """
+    Cgroups interface using the cgroups file system directly
+    """
+    _osutil = get_osutil()
+
+    @staticmethod
+    def _try_mkdir(path):
+        """
+        Try to create a directory, recursively. If it already exists as such, do nothing. Raise the appropriate
+        exception should an error occur.
+
+        :param path: str
+        """
+        if not os.path.isdir(path):
+            try:
+                os.makedirs(path, 0o755)
+            except OSError as e:
+                if e.errno == errno.EEXIST:
+                    if not os.path.isdir(path):
+                        raise CGroupsException("Create directory for cgroup {0}: normal file already exists with that name".format(path))
+                    else:
+                        pass # There was a race to create the directory, but it's there now, and that's fine
+                elif e.errno == errno.EACCES:
+                    # This is unexpected, as the agent runs as root
+                    raise CGroupsException("Create directory for cgroup {0}: permission denied".format(path))
+                else:
+                    raise
+
+    @staticmethod
+    def _foreach_controller(operation, message):
+        """
+        Executes the given operation on all controllers that need to be tracked; outputs 'message' if the controller is not mounted.
+        """
+        mounted_controllers = os.listdir(CGROUPS_FILE_SYSTEM_ROOT)
+
+        for controller in CGROUP_CONTROLLERS:
+            if controller not in mounted_controllers:
+                logger.warn('Controller "{0}" is not mounted. {1}'.format(controller, message))
+            else:
+                operation(controller)
+
+    def create_agent_cgroups(self):
+        cgroup_paths = []
+
+        pid = int(os.getpid())
+
+        def __impl(controller):
+            try:
+                path = os.path.join(CGROUPS_FILE_SYSTEM_ROOT, controller, VM_AGENT_CGROUP_NAME)
+
+                if not os.path.isdir(path):
+                    FileSystemCgroupsApi._try_mkdir(path)
+                    logger.info("Created cgroup {0}".format(path))
+
+                tasks_file = os.path.join(path, 'cgroup.procs')
+                fileutil.append_file(tasks_file, "{0}\n".format(pid))
+
+                logger.info("Added Agent (PID {0}) to cgroup {1}".format(pid, path))
+
+                cgroup_paths.append(path)
+
+            except Exception as e:
+                logger.warn('Cannot create "{0}" cgroup for the agent. Error: {1}'.format(controller, ustr(e)))
+
+        FileSystemCgroupsApi._foreach_controller(__impl, 'Will not create a cgroup for the VM Agent')
+
+        if len(cgroup_paths) == 0:
+            raise CGroupsException("Failed to create any cgroup for the VM Agent")
+
+        return cgroup_paths
+
+    def create_extension_cgroups_root(self):
+        def __impl(controller):
+            path = os.path.join(CGROUPS_FILE_SYSTEM_ROOT, controller, EXTENSIONS_ROOT_CGROUP_NAME)
+
+            if not os.path.isdir(path):
+                FileSystemCgroupsApi._try_mkdir(path)
+                logger.info("Created {0}".format(path))
+
+        FileSystemCgroupsApi._foreach_controller(__impl, 'Will not create a root cgroup for extensions')
+
+
+class SystemdCgroupsApi(CGroupsApi):
+    """
+    Cgroups interface via systemd
+    """
+    def create_agent_cgroups(self):
+        pass
+
+    def create_extension_cgroups_root(self):
+        pass
+
+
+
+