X-Git-Url: https://gerrit.opnfv.org/gerrit/gitweb?a=blobdiff_plain;f=src%2Fceph%2Fdoc%2Fcephfs%2Fhealth-messages.rst;fp=src%2Fceph%2Fdoc%2Fcephfs%2Fhealth-messages.rst;h=3e68e937116c8c0ec1f776d56fe88f6082afe39e;hb=812ff6ca9fcd3e629e49d4328905f33eee8ca3f5;hp=0000000000000000000000000000000000000000;hpb=15280273faafb77777eab341909a3f495cf248d9;p=stor4nfv.git diff --git a/src/ceph/doc/cephfs/health-messages.rst b/src/ceph/doc/cephfs/health-messages.rst new file mode 100644 index 0000000..3e68e93 --- /dev/null +++ b/src/ceph/doc/cephfs/health-messages.rst @@ -0,0 +1,127 @@ + +====================== +CephFS health messages +====================== + +Cluster health checks +===================== + +The Ceph monitor daemons will generate health messages in response +to certain states of the filesystem map structure (and the enclosed MDS maps). + +Message: mds rank(s) *ranks* have failed +Description: One or more MDS ranks are not currently assigned to +an MDS daemon; the cluster will not recover until a suitable replacement +daemon starts. + +Message: mds rank(s) *ranks* are damaged +Description: One or more MDS ranks has encountered severe damage to +its stored metadata, and cannot start again until it is repaired. + +Message: mds cluster is degraded +Description: One or more MDS ranks are not currently up and running, clients +may pause metadata IO until this situation is resolved. This includes +ranks being failed or damaged, and additionally includes ranks +which are running on an MDS but have not yet made it to the *active* +state (e.g. ranks currently in *replay* state). + +Message: mds *names* are laggy +Description: The named MDS daemons have failed to send beacon messages +to the monitor for at least ``mds_beacon_grace`` (default 15s), while +they are supposed to send beacon messages every ``mds_beacon_interval`` +(default 4s). The daemons may have crashed. The Ceph monitor will +automatically replace laggy daemons with standbys if any are available. + +Message: insufficient standby daemons available +Description: One or more file systems are configured to have a certain number +of standby daemons available (including daemons in standby-replay) but the +cluster does not have enough standby daemons. The standby deamons not in replay +count towards any file system (i.e. they may overlap). This warning can +configured by setting ``ceph fs set standby_count_wanted ``. Use +zero for ``count`` to disable. + + +Daemon-reported health checks +============================= + +MDS daemons can identify a variety of unwanted conditions, and +indicate these to the operator in the output of ``ceph status``. +This conditions have human readable messages, and additionally +a unique code starting MDS_HEALTH which appears in JSON output. + +Message: "Behind on trimming..." +Code: MDS_HEALTH_TRIM +Description: CephFS maintains a metadata journal that is divided into +*log segments*. The length of journal (in number of segments) is controlled +by the setting ``mds_log_max_segments``, and when the number of segments +exceeds that setting the MDS starts writing back metadata so that it +can remove (trim) the oldest segments. If this writeback is happening +too slowly, or a software bug is preventing trimming, then this health +message may appear. The threshold for this message to appear is for the +number of segments to be double ``mds_log_max_segments``. + +Message: "Client *name* failing to respond to capability release" +Code: MDS_HEALTH_CLIENT_LATE_RELEASE, MDS_HEALTH_CLIENT_LATE_RELEASE_MANY +Description: CephFS clients are issued *capabilities* by the MDS, which +are like locks. Sometimes, for example when another client needs access, +the MDS will request clients release their capabilities. If the client +is unresponsive or buggy, it might fail to do so promptly or fail to do +so at all. This message appears if a client has taken longer than +``mds_revoke_cap_timeout`` (default 60s) to comply. + +Message: "Client *name* failing to respond to cache pressure" +Code: MDS_HEALTH_CLIENT_RECALL, MDS_HEALTH_CLIENT_RECALL_MANY +Description: Clients maintain a metadata cache. Items (such as inodes) in the +client cache are also pinned in the MDS cache, so when the MDS needs to shrink +its cache (to stay within ``mds_cache_size`` or ``mds_cache_memory_limit``), it +sends messages to clients to shrink their caches too. If the client is +unresponsive or buggy, this can prevent the MDS from properly staying within +its cache limits and it may eventually run out of memory and crash. This +message appears if a client has taken more than ``mds_recall_state_timeout`` +(default 60s) to comply. + +Message: "Client *name* failing to advance its oldest client/flush tid" +Code: MDS_HEALTH_CLIENT_OLDEST_TID, MDS_HEALTH_CLIENT_OLDEST_TID_MANY +Description: The CephFS client-MDS protocol uses a field called the +*oldest tid* to inform the MDS of which client requests are fully +complete and may therefore be forgotten about by the MDS. If a buggy +client is failing to advance this field, then the MDS may be prevented +from properly cleaning up resources used by client requests. This message +appears if a client appears to have more than ``max_completed_requests`` +(default 100000) requests that are complete on the MDS side but haven't +yet been accounted for in the client's *oldest tid* value. + +Message: "Metadata damage detected" +Code: MDS_HEALTH_DAMAGE, +Description: Corrupt or missing metadata was encountered when reading +from the metadata pool. This message indicates that the damage was +sufficiently isolated for the MDS to continue operating, although +client accesses to the damaged subtree will return IO errors. Use +the ``damage ls`` admin socket command to get more detail on the damage. +This message appears as soon as any damage is encountered. + +Message: "MDS in read-only mode" +Code: MDS_HEALTH_READ_ONLY, +Description: The MDS has gone into readonly mode and will return EROFS +error codes to client operations that attempt to modify any metadata. The +MDS will go into readonly mode if it encounters a write error while +writing to the metadata pool, or if forced to by an administrator using +the *force_readonly* admin socket command. + +Message: *N* slow requests are blocked" +Code: MDS_HEALTH_SLOW_REQUEST, +Description: One or more client requests have not been completed promptly, +indicating that the MDS is either running very slowly, or that the RADOS +cluster is not acknowledging journal writes promptly, or that there is a bug. +Use the ``ops`` admin socket command to list outstanding metadata operations. +This message appears if any client requests have taken longer than +``mds_op_complaint_time`` (default 30s). + +Message: "Too many inodes in cache" +Code: MDS_HEALTH_CACHE_OVERSIZED +Description: The MDS is not succeeding in trimming its cache to comply with the +limit set by the administrator. If the MDS cache becomes too large, the daemon +may exhaust available memory and crash. By default, this message appears if +the actual cache size (in inodes or memory) is at least 50% greater than +``mds_cache_size`` (default 100000) or ``mds_cache_memory_limit`` (default +1GB). Modify ``mds_health_cache_threshold`` to set the warning ratio.