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06c94de584
This introduces two config parameters:
mds_cache_memory_limit: Sets the soft maximum of the cache to the given
byte count. (Like mds_cache_size, this doesn't actually limit the maximum
size of the cache. It just dictates the steady-state size.)
mds_cache_reservation: This replaces mds_health_cache_threshold everywhere
except the Beacon heartbeat sent to the mons. The idea here is to specify a
reservation of memory (5% by default) for operations and the MDS tries to
always maintain that reservation. So, the MDS will recall caps from clients
when it begins dipping into its reservation of memory.
mds_cache_size still limits the cache by Inode count but is now by-default 0
(i.e. unlimited). The new preferred way of specifying cache limits is by memory
size. The default is 1GB.
Fixes: http://tracker.ceph.com/issues/20594
Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1464976
Signed-off-by: Patrick Donnelly <pdonnell@redhat.com>
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.. _cephfs-health-messages:
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======================
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CephFS health messages
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======================
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Cluster health checks
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=====================
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The Ceph monitor daemons will generate health messages in response
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to certain states of the filesystem map structure (and the enclosed MDS maps).
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Message: mds rank(s) *ranks* have failed
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Description: One or more MDS ranks are not currently assigned to
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an MDS daemon; the cluster will not recover until a suitable replacement
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daemon starts.
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Message: mds rank(s) *ranks* are damaged
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Description: One or more MDS ranks has encountered severe damage to
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its stored metadata, and cannot start again until it is repaired.
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Message: mds cluster is degraded
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Description: One or more MDS ranks are not currently up and running, clients
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may pause metadata IO until this situation is resolved. This includes
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ranks being failed or damaged, and additionally includes ranks
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which are running on an MDS but have not yet made it to the *active*
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state (e.g. ranks currently in *replay* state).
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Message: mds *names* are laggy
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Description: The named MDS daemons have failed to send beacon messages
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to the monitor for at least ``mds_beacon_grace`` (default 15s), while
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they are supposed to send beacon messages every ``mds_beacon_interval``
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(default 4s). The daemons may have crashed. The Ceph monitor will
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automatically replace laggy daemons with standbys if any are available.
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Message: insufficient standby daemons available
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Description: One or more file systems are configured to have a certain number
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of standby daemons available (including daemons in standby-replay) but the
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cluster does not have enough standby daemons. The standby deamons not in replay
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count towards any file system (i.e. they may overlap). This warning can
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configured by setting ``ceph fs set <fs> standby_count_wanted <count>``. Use
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zero for ``count`` to disable.
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Daemon-reported health checks
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=============================
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MDS daemons can identify a variety of unwanted conditions, and
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indicate these to the operator in the output of ``ceph status``.
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This conditions have human readable messages, and additionally
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a unique code starting MDS_HEALTH which appears in JSON output.
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Message: "Behind on trimming..."
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Code: MDS_HEALTH_TRIM
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Description: CephFS maintains a metadata journal that is divided into
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*log segments*. The length of journal (in number of segments) is controlled
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by the setting ``mds_log_max_segments``, and when the number of segments
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exceeds that setting the MDS starts writing back metadata so that it
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can remove (trim) the oldest segments. If this writeback is happening
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too slowly, or a software bug is preventing trimming, then this health
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message may appear. The threshold for this message to appear is for the
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number of segments to be double ``mds_log_max_segments``.
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Message: "Client *name* failing to respond to capability release"
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Code: MDS_HEALTH_CLIENT_LATE_RELEASE, MDS_HEALTH_CLIENT_LATE_RELEASE_MANY
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Description: CephFS clients are issued *capabilities* by the MDS, which
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are like locks. Sometimes, for example when another client needs access,
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the MDS will request clients release their capabilities. If the client
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is unresponsive or buggy, it might fail to do so promptly or fail to do
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so at all. This message appears if a client has taken longer than
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``mds_revoke_cap_timeout`` (default 60s) to comply.
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Message: "Client *name* failing to respond to cache pressure"
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Code: MDS_HEALTH_CLIENT_RECALL, MDS_HEALTH_CLIENT_RECALL_MANY
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Description: Clients maintain a metadata cache. Items (such as inodes) in the
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client cache are also pinned in the MDS cache, so when the MDS needs to shrink
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its cache (to stay within ``mds_cache_size`` or ``mds_cache_memory_limit``), it
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sends messages to clients to shrink their caches too. If the client is
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unresponsive or buggy, this can prevent the MDS from properly staying within
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its cache limits and it may eventually run out of memory and crash. This
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message appears if a client has taken more than ``mds_recall_state_timeout``
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(default 60s) to comply.
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Message: "Client *name* failing to advance its oldest client/flush tid"
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Code: MDS_HEALTH_CLIENT_OLDEST_TID, MDS_HEALTH_CLIENT_OLDEST_TID_MANY
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Description: The CephFS client-MDS protocol uses a field called the
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*oldest tid* to inform the MDS of which client requests are fully
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complete and may therefore be forgotten about by the MDS. If a buggy
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client is failing to advance this field, then the MDS may be prevented
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from properly cleaning up resources used by client requests. This message
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appears if a client appears to have more than ``max_completed_requests``
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(default 100000) requests that are complete on the MDS side but haven't
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yet been accounted for in the client's *oldest tid* value.
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Message: "Metadata damage detected"
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Code: MDS_HEALTH_DAMAGE,
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Description: Corrupt or missing metadata was encountered when reading
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from the metadata pool. This message indicates that the damage was
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sufficiently isolated for the MDS to continue operating, although
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client accesses to the damaged subtree will return IO errors. Use
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the ``damage ls`` admin socket command to get more detail on the damage.
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This message appears as soon as any damage is encountered.
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Message: "MDS in read-only mode"
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Code: MDS_HEALTH_READ_ONLY,
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Description: The MDS has gone into readonly mode and will return EROFS
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error codes to client operations that attempt to modify any metadata. The
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MDS will go into readonly mode if it encounters a write error while
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writing to the metadata pool, or if forced to by an administrator using
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the *force_readonly* admin socket command.
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Message: *N* slow requests are blocked"
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Code: MDS_HEALTH_SLOW_REQUEST,
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Description: One or more client requests have not been completed promptly,
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indicating that the MDS is either running very slowly, or that the RADOS
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cluster is not acknowledging journal writes promptly, or that there is a bug.
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Use the ``ops`` admin socket command to list outstanding metadata operations.
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This message appears if any client requests have taken longer than
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``mds_op_complaint_time`` (default 30s).
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Message: "Too many inodes in cache"
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Code: MDS_HEALTH_CACHE_OVERSIZED
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Description: The MDS is not succeeding in trimming its cache to comply with the
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limit set by the administrator. If the MDS cache becomes too large, the daemon
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may exhaust available memory and crash. By default, this message appears if
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the actual cache size (in inodes or memory) is at least 50% greater than
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``mds_cache_size`` (default 100000) or ``mds_cache_memory_limit`` (default
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1GB). Modify ``mds_health_cache_threshold`` to set the warning ratio.
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