Merge pull request ceph#58647 from rishabh-d-dave/mgr-vol-mod-disable

mgr: allow disabling always-on modules

Author: hkadam134

PendingReleaseNotes

@@ -25,6 +25,9 @@
    - osd_op_num_shards_hdd = 1 (was 5)
    - osd_op_num_threads_per_shard_hdd = 5 (was 1)
   For more details see https://tracker.ceph.com/issues/66289.
+* MGR: MGR's always-on modulues/plugins can now be force-disabled. This can be
+  necessary in cases where MGR(s) needs to be prevented from being flooded by
+  the module commands when coresponding Ceph service is down/degraded.
 
 * CephFS: Modifying the FS setting variable "max_mds" when a cluster is
   unhealthy now requires users to pass the confirmation flag

doc/cephfs/fs-volumes.rst

@@ -1419,5 +1419,28 @@ set with this id was present in the database
 
   $ ceph fs quiesce fs1 sub1 sub2 sub3 --set-id="external-id" --if-version=0
 
+
+.. _disabling-volumes-plugin:
+
+Disabling Volumes Plugin
+------------------------
+By default the volumes plugin is enabled and set to ``always on``. However, in
+certain cases it might be appropriate to disable it. For example, when a CephFS
+is in a degraded state, the volumes plugin commands may accumulate in MGR
+instead of getting served. Which eventually causes policy throttles to kick in
+and the MGR becomes unresponsive.
+
+In this event, volumes plugin can be disabled even though it is an
+``always on`` module in MGR. To do so, run ``ceph mgr module disable volumes
+--yes-i-really-mean-it``. Do note that this command will disable operations
+and remove commands of volumes plugin since it will disable all CephFS
+services on the Ceph cluster accessed through this plugin.
+
+Before resorting to a measure as drastic as this, it is a good idea to try less
+drastic measures and then assess if the file system experience has improved due
+to it. One example of such less drastic measure is to disable asynchronous
+threads launched by volumes plugins for cloning and purging trash.
+
+
 .. _manila: https://github.com/openstack/manila
 .. _CSI: https://github.com/ceph/ceph-csi

doc/cephfs/troubleshooting.rst

@@ -412,6 +412,11 @@ its associated key. A less drastic but half-fix is to change the osd cap for
 your user to just ``caps osd = "allow rw"``  and delete ``tag cephfs
 data=....``
 
+Disabling Volumes Plugin
+========================
+In certain scenarios, volumes plugin might be needed to disabled to prevent compromise
+for rest of the Ceph cluster. For details see: :ref:`disabling-volumes-plugin`
+
 Reporting Issues
 ================
 

qa/cephfs/overrides/ignorelist_health.yaml

@@ -24,3 +24,4 @@ overrides:
       - BLUESTORE_SLOW_OP_ALERT
       - slow operation indications in BlueStore
       - experiencing slow operations in BlueStore
+      - MGR_MODULE_ERROR

qa/tasks/cephfs/test_admin.py

@@ -2740,3 +2740,184 @@ def test_when_healthy_with_confirm(self):
         '''
         self.fs.set_max_mds(2, confirm=True)
         self.assertEqual(self.fs.get_var('max_mds'), 2)
+
+
+class TestToggleVolumes(CephFSTestCase):
+    '''
+    Contains code for enabling/disabling mgr/volumes plugin.
+    '''
+
+    VOL_MOD_NAME = 'volumes'
+    CONFIRM = '--yes-i-really-mean-it'
+
+    def tearDown(self):
+        '''
+        Ensure that the volumes plugin is enabled after the test has finished
+        running since not doing so might affect tearDown() of CephFSTestCase or
+        other superclasses.
+        '''
+        json_output = self.get_ceph_cmd_stdout('mgr module ls --format json')
+        json_output = json.loads(json_output)
+
+        if 'volumes' in json_output['force_disabled_modules']:
+            self.run_ceph_cmd(f'mgr module enable {self.VOL_MOD_NAME}')
+
+        super(TestToggleVolumes, self).tearDown()
+
+    def test_force_disable_with_confirmation(self):
+        '''
+        Test that running "ceph mgr module force disable volumes
+        --yes-i-really-mean-it" successfully disables volumes plugin.
+
+        Also test "ceph mgr module ls" output after this.
+        '''
+        self.run_ceph_cmd(f'mgr module force disable {self.VOL_MOD_NAME} '
+                          f'{self.CONFIRM}')
+
+        json_output = self.get_ceph_cmd_stdout('mgr module ls --format json')
+        json_output = json.loads(json_output)
+
+        self.assertIn(self.VOL_MOD_NAME, json_output['always_on_modules'])
+        self.assertIn(self.VOL_MOD_NAME, json_output['force_disabled_modules'])
+
+        self.assertNotIn(self.VOL_MOD_NAME, json_output['enabled_modules'])
+        self.assertNotIn(self.VOL_MOD_NAME, json_output['disabled_modules'])
+
+    def test_force_disable_fails_without_confirmation(self):
+        '''
+        Test that running "ceph mgr module force disable volumes" fails with
+        EPERM when confirmation flag is not passed along.
+
+        Also test that output of this command suggests user to pass
+        --yes-i-really-mean-it.
+        '''
+        proc = self.run_ceph_cmd(
+            f'mgr module force disable {self.VOL_MOD_NAME}',
+            stderr=StringIO(), check_status=False)
+
+        self.assertEqual(proc.returncode, errno.EPERM)
+
+        proc_stderr = proc.stderr.getvalue()
+        self.assertIn('EPERM', proc_stderr)
+        # ensure that the confirmation flag was recommended
+        self.assertIn(self.CONFIRM, proc_stderr)
+
+    def test_force_disable_idempotency(self):
+        '''
+        Test that running "ceph mgr module force disable volumes" passes when
+        volumes plugin was already force disabled.
+        '''
+        self.run_ceph_cmd(f'mgr module force disable {self.VOL_MOD_NAME} '
+                          f'{self.CONFIRM}')
+        sleep(5)
+
+        json_output = self.get_ceph_cmd_stdout('mgr module ls --format '
+                                              'json-pretty')
+        json_output = json.loads(json_output)
+
+        self.assertIn(self.VOL_MOD_NAME, json_output['always_on_modules'])
+        self.assertIn(self.VOL_MOD_NAME, json_output['force_disabled_modules'])
+
+        self.assertNotIn(self.VOL_MOD_NAME, json_output['enabled_modules'])
+        self.assertNotIn(self.VOL_MOD_NAME, json_output['disabled_modules'])
+
+        # XXX: this this test, running this command 2nd time should pass.
+        self.run_ceph_cmd(f'mgr module force disable {self.VOL_MOD_NAME}')
+
+    def test_force_disable_nonexistent_mod(self):
+        '''
+        Test that passing non-existent name to "ceph mgr module force disable"
+        command leads to an error.
+        '''
+        proc = self.run_ceph_cmd(
+            f'mgr module force disable abcd {self.CONFIRM}',
+            check_status=False, stderr=StringIO())
+        self.assertEqual(proc.returncode, errno.EINVAL)
+        self.assertIn('EINVAL', proc.stderr.getvalue())
+
+    def test_force_disable_non_alwayson_mod(self):
+        '''
+        Test that passing non-existent name to "ceph mgr module force disable"
+        command leads to an error.
+        '''
+        json_output = self.get_ceph_cmd_stdout(
+            'mgr module ls --format json-pretty', check_status=False,
+            stderr=StringIO())
+        output_dict = json.loads(json_output)
+        some_non_alwayson_mod = output_dict['enabled_modules'][0]
+
+        proc = self.run_ceph_cmd(
+            f'mgr module force disable {some_non_alwayson_mod} {self.CONFIRM}',
+            check_status=False, stderr=StringIO())
+        self.assertEqual(proc.returncode, errno.EINVAL)
+        self.assertIn('EINVAL', proc.stderr.getvalue())
+
+    def test_enabled_by_default(self):
+        '''
+        Test that volumes plugin is enabled by default and is also reported as
+        "always on".
+        '''
+        json_output = self.get_ceph_cmd_stdout('mgr module ls --format json')
+        json_output = json.loads(json_output)
+
+        self.assertIn(self.VOL_MOD_NAME, json_output['always_on_modules'])
+
+        self.assertNotIn(self.VOL_MOD_NAME, json_output['enabled_modules'])
+        self.assertNotIn(self.VOL_MOD_NAME, json_output['disabled_modules'])
+        self.assertNotIn(self.VOL_MOD_NAME, json_output['force_disabled_modules'])
+
+    def test_disable_fails(self):
+        '''
+        Test that running "ceph mgr module disable volumes" fails with EPERM.
+
+        This is expected since volumes is an always-on module and therefore
+        it can only be disabled using command "ceph mgr module force disable
+        volumes".
+        '''
+        proc = self.run_ceph_cmd(f'mgr module disable {self.VOL_MOD_NAME}',
+                                 stderr=StringIO(), check_status=False)
+        self.assertEqual(proc.returncode, errno.EPERM)
+
+        proc_stderr = proc.stderr.getvalue()
+        self.assertIn('EPERM', proc_stderr)
+
+    def test_enable_idempotency(self):
+        '''
+        Test that enabling volumes plugin when it is already enabled doesn't
+        exit with non-zero return value.
+
+        Also test that it reports plugin as already enabled.
+        '''
+        proc = self.run_ceph_cmd(f'mgr module enable {self.VOL_MOD_NAME}',
+                                 stderr=StringIO())
+        self.assertEqual(proc.returncode, 0)
+
+        proc_stderr = proc.stderr.getvalue()
+        self.assertIn('already enabled', proc_stderr)
+        self.assertIn('always-on', proc_stderr)
+
+    def test_enable_post_disabling(self):
+        '''
+        Test that enabling volumes plugin after (force-)disabling it works
+        successfully.
+
+        Alo test "ceph mgr module ls" output for volumes plugin afterwards.
+        '''
+        self.run_ceph_cmd(f'mgr module force disable {self.VOL_MOD_NAME} '
+                          f'{self.CONFIRM}')
+        # give bit of time for plugin to be disabled.
+        sleep(5)
+
+        self.run_ceph_cmd(f'mgr module enable {self.VOL_MOD_NAME}')
+        # give bit of time for plugin to be functional again
+        sleep(5)
+        json_output = self.get_ceph_cmd_stdout('mgr module ls --format json')
+        json_output = json.loads(json_output)
+        self.assertIn(self.VOL_MOD_NAME, json_output['always_on_modules'])
+        self.assertNotIn(self.VOL_MOD_NAME, json_output['enabled_modules'])
+        self.assertNotIn(self.VOL_MOD_NAME, json_output['disabled_modules'])
+        self.assertNotIn(self.VOL_MOD_NAME, json_output['force_disabled_modules'])
+
+        # plugin is reported properly by "ceph mgr module ls" command, check if
+        # it is also working fine.
+        self.run_ceph_cmd('fs volume ls')

src/mgr/PyModuleRegistry.cc

@@ -151,7 +151,8 @@ bool PyModuleRegistry::handle_mgr_map(const MgrMap &mgr_map_)
     return false;
   } else {
     bool modules_changed = mgr_map_.modules != mgr_map.modules ||
-      mgr_map_.always_on_modules != mgr_map.always_on_modules;
+      mgr_map_.always_on_modules != mgr_map.always_on_modules ||
+      mgr_map_.force_disabled_modules != mgr_map.force_disabled_modules;
     mgr_map = mgr_map_;
 
     if (standby_modules != nullptr) {
@@ -240,10 +241,20 @@ void PyModuleRegistry::active_start(
     // Anything we're skipping because of !can_run will be flagged
     // to the user separately via get_health_checks
     if (!(i.second->is_enabled() && i.second->is_loaded())) {
+      dout(8) << __func__ << " Not starting module '" << i.first << "', it is "
+	      << "not enabled and loaded"  << dendl;
       continue;
     }
 
-    dout(4) << "Starting " << i.first << dendl;
+    // These are always-on modules but user force-disabled them.
+    if (mgr_map.force_disabled_modules.find(i.first) !=
+	mgr_map.force_disabled_modules.end()) {
+      dout(8) << __func__ << " Not starting module '" << i.first << "', it is "
+	      << "force-disabled" << dendl;
+      continue;
+    }
+
+    dout(4) << "Starting module '" << i.first << "'" << dendl;
     active_modules->start_one(i.second);
   }
 }

src/mon/MgrMap.h

@@ -297,6 +297,9 @@ class MgrMap
   // active version.
   std::map<uint32_t, std::set<std::string>> always_on_modules;
 
+  // Modules which are always-on but have been force-disabled by user.
+  std::set<std::string> force_disabled_modules;
+
   // Modules which are reported to exist
   std::vector<ModuleInfo> available_modules;
 
@@ -448,7 +451,7 @@ class MgrMap
       ENCODE_FINISH(bl);
       return;
     }
-    ENCODE_START(13, 6, bl);
+    ENCODE_START(14, 6, bl);
     encode(epoch, bl);
     encode(active_addrs, bl, features);
     encode(active_gid, bl);
@@ -473,13 +476,14 @@ class MgrMap
     encode(clients_addrs, bl, features);
     encode(clients_names, bl, features);
     encode(flags, bl);
+    encode(force_disabled_modules, bl);
     ENCODE_FINISH(bl);
     return;
   }
 
   void decode(ceph::buffer::list::const_iterator& p)
   {
-    DECODE_START(13, p);
+    DECODE_START(14, p);
     decode(epoch, p);
     decode(active_addrs, p);
     decode(active_gid, p);
@@ -549,6 +553,11 @@ class MgrMap
     if (struct_v >= 13) {
       decode(flags, p);
     }
+
+    if (struct_v >= 14) {
+      decode(force_disabled_modules, p);
+    }
+
     DECODE_FINISH(p);
   }
 
@@ -603,6 +612,13 @@ class MgrMap
       f->close_section();
     }
     f->close_section(); // always_on_modules
+
+    f->open_object_section("force_disabled_modules");
+    for (auto& m : force_disabled_modules) {
+        f->dump_string("module", m);
+      }
+    f->close_section();
+
     f->dump_int("last_failure_osd_epoch", last_failure_osd_epoch);
     f->open_array_section("active_clients");
     for (const auto& i : clients) {