2 Troubleshooting logging and debugging #
Typically, when you add debugging to your Ceph configuration, you do so at
runtime. You can also add Ceph debug logging to your Ceph configuration
file if you are encountering issues when starting your cluster. You may view
Ceph log files under /var/log/ceph (the default
location).
When debug output slows down your system, the latency can hide race conditions.
Logging is resource intensive. If you are encountering a problem in a specific area of your cluster, enable logging for that area of the cluster. For example, if your OSDs are running fine, but your metadata servers are not, you should start by enabling debug logging for the specific metadata server instance(s) giving you trouble. Enable logging for each subsystem as needed.
Verbose logging can generate over 1GB of data per hour. If your OS disk reaches its capacity, the node will stop working.
If you enable or increase the rate of Ceph logging, ensure that you have sufficient disk space on your OS disk. See Sezione 2.3, «Accelerating log rotation» for details on rotating log files. When your system is running well, remove unnecessary debugging settings to ensure your cluster runs optimally. Logging debug output messages is relatively slow, and a waste of resources when operating your cluster. See Sezione 2.5, «Enable system, log, and debug settings» for details on available settings.
2.1 Accessing configuration settings at runtime #
If you would like to see the configuration settings at runtime, you must log in to a host with a running daemon and execute the following:
cephuser@adm > ceph daemon {daemon-name} config show | lessFor example:
cephuser@adm > ceph daemon osd.0 config show | less
To activate Ceph’s debugging output (i.e., dout()) at
runtime, use the ceph tell command to inject arguments
into the runtime configuration:
cephuser@adm > ceph tell {daemon-type}.{daemon id or *} config set {name} {value}
Replace {daemon-type} with one of osd, mon or mds. You may
apply the runtime setting to all daemons of a particular type with
*, or specify a specific daemon’s ID. For example, to
increase debug logging for a ceph-osd daemon named osd.0,
execute the following:
cephuser@adm > ceph tell osd.0 config set debug_osd 0/5
The ceph tell command goes through the monitors. If you
cannot bind to the monitor, you can make the change by logging into the
daemon host using ceph daemon. For example:
cephuser@adm > sudo ceph daemon osd.0 config set debug_osd 0/5See Sezione 2.5, «Enable system, log, and debug settings» for details on available settings.
2.2 Activating Ceph debugging at boot time #
To activate Ceph’s debugging output (i.e., dout()) at
boot time, you must add settings to your Ceph configuration file. Subsystems
common to each daemon may be set under [global] in your
configuration file. Subsystems for particular daemons are set under the
daemon section in your configuration file (e.g., [mon],
[osd], [mds]). For example:
[global]
debug ms = 1/5
[mon]
debug mon = 20
debug paxos = 1/5
debug auth = 2
[osd]
debug osd = 1/5
debug filestore = 1/5
debug journal = 1
debug monc = 5/20
[mds]
debug mds = 1
debug mds balancer = 1See Sezione 2.5, «Enable system, log, and debug settings» for details.
2.3 Accelerating log rotation #
If your OS disk is relatively full, you can accelerate log rotation by
modifying the Ceph log rotation file at
etc/logrotate.d/ceph. Add a size setting after the
rotation frequency to accelerate log rotation (via cronjob) if your logs
exceed the size setting. For example, the default setting looks like this:
rotate 7 weekly compress sharedscripts
Modify it by adding a size setting:
rotate 7 weekly size 500M compress sharedscripts
Then, start the crontab editor for your user space:
crontab -e
Finally, add an entry to check the etc/logrotate.d/ceph
file:
30 * * * * /usr/sbin/logrotate /etc/logrotate.d/ceph >/dev/null 2><&1
The preceding example checks the etc/logrotate.d/ceph
file every 30 minutes.
2.4 Monitoring memory utilization #
To monitor the memory utilization of the Ceph processes, pay attention to
the top command's VIRT or the output of ps -u
ceph -l in the VSZ column. While some
fluctuation of memory utilization over time is normal, it should not
constantly increase and this will help you pinpoint the problematic process
if facing low- or out-of-memory concerns.
2.5 Enable system, log, and debug settings #
In most cases, you will enable debug logging output via subsystems.
2.5.1 Enabling Ceph subsystems #
Each subsystem has a logging level for its output logs, and for its logs in-memory. You may set different values for each of these subsystems by setting a log file level and a memory level for debug logging. Ceph’s logging levels operate on a scale of 1 to 20, where 1 is terse and 20 is verbose 1. In general, the logs in-memory are not sent to the output log unless:
a fatal signal is raised or
an
assertin source code is triggered orupon request.
A debug logging setting can take a single value for the log level and the memory level, which sets them both as the same value. For example, if you specify debug ms = 5, Ceph will treat it as a log level and a memory level of 5. You may also specify them separately. The first setting is the log level, and the second setting is the memory level. You must separate them with a forward slash (/). For example, if you want to set the ms subsystem’s debug logging level to 1 and its memory level to 5, you would specify it as debug ms = 1/5. For example:
debug {subsystem} = {log-level}/{memory-level}
#for example
debug mds balancer = 1/20The following table provides a list of Ceph subsystems and their default log and memory levels. Once you complete your logging efforts, restore the subsystems to their default level or to a level suitable for normal operations.
| Subsystem | Log Level | Memory Level |
|---|---|---|
default
| 0 | 5 |
lockdep
| 0 | 1 |
context
| 0 | 1 |
crush
| 1 | 1 |
mds
| 1 | 5 |
mds balancer
| 1 | 5 |
mds locker
| 1 | 5 |
mds log
| 1 | 5 |
mds log expire
| 1 | 5 |
mds migrator
| 1 | 5 |
buffer
| 0 | 1 |
timer
| 0 | 1 |
filer
| 0 | 1 |
striper
| 0 | 1 |
objector
| 0 | 1 |
rados
| 0 | 5 |
rbd
| 0 | 5 |
rbd mirror
| 0 | 5 |
rbd replay
| 0 | 5 |
journaler
| 0 | 5 |
objectcacher
| 0 | 5 |
client
| 0 | 5 |
osd
| 1 | 5 |
optracker
| 0 | 5 |
optracker
| 0 | 5 |
objclass
| 0 | 5 |
filestore
| 1 | 3 |
journal
| 1 | 3 |
ms
| 0 | 5 |
mon
| 1 | 5 |
monc
| 0 | 10 |
paxos
| 1 | 5 |
tp
| 0 | 5 |
auth
| 1 | 5 |
crypto
| 1 | 5 |
finisher
| 1 | 1 |
reserver
| 1 | 1 |
heartbeatmap
| 1 | 5 |
perfcounter
| 1 | 5 |
rgw
| 1 | 5 |
rgw sync
| 1 | 5 |
civetweb
| 1 | 10 |
javaclient
| 1 | 5 |
asok
| 1 | 5 |
throttle
| 1 | 1 |
refs
| 0 | 0 |
compressor
| 1 | 5 |
bluestore
| 1 | 5 |
bluefs
| 1 | 5 |
bdev
| 1 | 3 |
kstore
| 1 | 5 |
rocksdb
| 4 | 5 |
leveldb
| 4 | 5 |
memdb
| 4 | 5 |
fuse
| 1 | 5 |
mgr
| 1 | 5 |
mgrc
| 1 | 5 |
dpdk
| 1 | 5 |
eventtrace
| 1 | 5 |
2.5.2 Logging settings #
Logging and debugging settings are not required in a Ceph configuration file, but you may override default settings as needed. Ceph supports the following settings:
log fileDescription: The location of the logging file for your cluster.
Type: String
Required: No
Default:
/var/log/ceph/$cluster-$name.loglog max newDescription: The maximum number of new log files.
Type: Integer
Required: No
Default: 1000
log max recentDescription: The maximum number of recent events to include in a log file.
Type: Integer
Required: No
Default: 10000
log to stderrDescription: Determines if logging messages should appear in
stderr.Type: Boolean
Required: No
Default:
trueerr to stderrDescription: Determines if error messages should appear in
stderr.Type: Boolean
Required: No
Default:
truelog to syslogDescription: Determines if logging messages should appear in
syslog.Type: Boolean
Required: No
Default:
falseerr to syslogDescription: Determines if error messages should appear in
syslog.Type: Boolean
Required: No
Default:
falselog flush on exitDescription: Determines if Ceph should flush the log files after exit.
Type: Boolean
Required: No
Default:
trueclog to monitorsDescription: Determines if
clogmessages should be sent to monitors.Type: Boolean
Required: No
Default:
trueclog to syslogDescription: Determines if
clogmessages should be sent to syslog.Type: Boolean
Required: No
Default:
falsemon cluster log to syslogDescription: Determines if the cluster log messages should be output to the syslog.
Type: Boolean
Required: No
Default:
falsemon cluster log fileDescription: The locations of the cluster’s log files. There are two channels in Ceph:
clusterandaudit. This option represents a mapping from channels to log files, where the log entries of that channel are sent to. The default entry is a fallback mapping for channels not explicitly specified. So, the following default setting will send cluster log to$cluster.log, and send audit log to$cluster.audit.log, where$clusterwill be replaced with the actual cluster name.Type: String
Required: No
Default:
default=/var/log/ceph/$cluster.$channel.log,cluster=/var/log/ceph/$cluster.log
2.5.3 OSD #
osd debug drop ping probabilityDescription: ?
Type: Double
Required: No
Default: 0
osd debug drop ping durationDescription:
Type: Integer
Required: No
Default: 0
osd debug drop pg create probabilityDescription:
Type: Integer
Required: No
Default: 0
osd debug drop pg create durationDescription: ?
Type: Double
Required: No
Default: 1
osd min pg log entriesDescription: The minimum number of log entries for placement groups.
Type: 32-bit Unsigned Integer
Required: No
Default: 250
osd op log thresholdDescription: How many op log messages to show up in one pass.
Type: Integer
Required: No
Default: 5
2.5.4 Filestore #
filestore debug omap checkDescription: Debugging check on synchronization. This is an expensive operation.
Type: Boolean
Required: No
Default:
false
2.5.5 MDS #
mds debug scatterstatDescription: Ceph will assert that various recursive stat invariants are true (for developers only).
Type: Boolean
Required: No
Default:
falsemds debug fragDescription: Ceph will verify directory fragmentation invariants when convenient (developers only).
Type: Boolean
Required: No
Default:
falsemds debug auth pinsDescription: The debug auth pin invariants (for developers only).
Type: Boolean
Required: No
Default:
falsemds debug subtreesDescription: The debug subtree invariants (for developers only).
Type: Boolean
Required: No
Default:
false
2.5.6 RADOS gateway (RGW) #
rgw log nonexistent bucketDescription: Should we log a non-existent buckets?
Type: Boolean
Required: No
Default:
falsergw log object nameDescription: Should an object’s name be logged. // man date to see codes (a subset are supported)
Type: String
Required: No
Default:
%Y-%m-%d-%H-%i-%nrgw log object name utcDescription: Object log name contains UTC?
Type: Boolean
Required: No
Default:
falsergw enable ops logDescription: Enables logging of every RGW operation.
Type: Boolean
Required: No
Default:
truergw enable usage logDescription: Enable logging of RGW’s bandwidth usage.
Type: Boolean
Required: No
Default:
falsergw usage log flush thresholdDescription: Threshold to flush pending log data.
Type: Integer
Required: No
Default: 1024
rgw usage log tick intervalDescription: Flush pending log data every s seconds.
Type: Integer
Required: No
Default: 30
rgw intent log object nameDescription:
Type: String
Required: No
Default:
%Y-%m-%d-%i-%nrgw intent log object name utcDescription: Include a UTC timestamp in the intent log object name.
Type: Boolean
Required: No
Default:
false
2.6 Logging kernel RBD and CephFS clients #
The RBD and CephFS kernel clients provide means to enable runtime logging that allow low-level debugging. However, the performance penalty may be high, which is why dynamic debugging is turned off by default. Also, analysing these logs requires comparing them with the kernel source code.
For example, to see the debug messages related with CephFS snapshot handling, you could try the following:
root # echo "file fs/ceph/snap.c +pf" > /sys/kernel/debug/dynamic_debug/control
The kernel logs would now include any debug messages in file
fs/ceph/snap.c. In order to disable dynamic debugging:
root # echo "file fs/ceph/snap.c -p" > /sys/kernel/debug/dynamic_debug/control2.7 Per-service and per-daemon events #
In order to simplify debugging failed daemon deployments, cephadm stores events on a per-service and per-daemon basis. To view the list of events for a specific service, run the following example command:
cephuser@adm > ceph orch ls --service_name=alertmanager --format yaml
service_type: alertmanager
service_name: alertmanager
placement:
hosts:
- unknown_host
[...]
events:
- 2021-02-01T08:58:02.741162 service:alertmanager [INFO] "service was created"
- 2021-02-01T12:09:25.264584 service:alertmanager [ERROR] "Failed to apply: \
Cannot place <AlertManagerSpec for service_name=alertmanager> on \
unknown_host: Unknown hosts"'As opposed to a specific service, to view the list of events for a specific daemon, for example, run the following command:
cephuser@adm > ceph orch ceph --service-type mds \
--daemon-id=hostname.ppdhsz --format yaml
daemon_type: mds
daemon_id: cephfs.hostname.ppdhsz
hostname: hostname
[...]
events:
- 2021-02-01T08:59:43.845866 daemon:mds.cephfs.hostname.ppdhsz [INFO] \
"Reconfigured mds.cephfs.hostname.ppdhsz on host 'hostname'"