NAME¶
ctdb-tunables - CTDB tunable configuration variables
DESCRIPTION¶
CTDB's behaviour can be configured by setting run-time tunable variables. This
lists and describes all tunables. See the
ctdb(1)listvars,
setvar and
getvar commands for more details.
MaxRedirectCount¶
Default: 3
If we are not the DMASTER and need to fetch a record across the network we first
send the request to the LMASTER after which the record is passed onto the
current DMASTER. If the DMASTER changes before the request has reached that
node, the request will be passed onto the "next" DMASTER. For very
hot records that migrate rapidly across the cluster this can cause a request
to "chase" the record for many hops before it catches up with the
record. this is how many hops we allow trying to chase the DMASTER before we
switch back to the LMASTER again to ask for new directions.
When chasing a record, this is how many hops we will chase the record for before
going back to the LMASTER to ask for new guidance.
SeqnumInterval¶
Default: 1000
Some databases have seqnum tracking enabled, so that samba will be able to
detect asynchronously when there has been updates to the database. Everytime a
database is updated its sequence number is increased.
This tunable is used to specify in 'ms' how frequently ctdb will send out
updates to remote nodes to inform them that the sequence number is increased.
ControlTimeout¶
Default: 60
This is the default setting for timeout for when sending a control message to
either the local or a remote ctdb daemon.
TraverseTimeout¶
Default: 20
This setting controls how long we allow a traverse process to run. After this
timeout triggers, the main ctdb daemon will abort the traverse if it has not
yet finished.
KeepaliveInterval¶
Default: 5
How often in seconds should the nodes send keepalives to eachother.
KeepaliveLimit¶
Default: 5
After how many keepalive intervals without any traffic should a node wait until
marking the peer as DISCONNECTED.
If a node has hung, it can thus take KeepaliveInterval*(KeepaliveLimit+1)
seconds before we determine that the node is DISCONNECTED and that we require
a recovery. This limitshould not be set too high since we want a hung node to
be detectec, and expunged from the cluster well before common CIFS timeouts
(45-90 seconds) kick in.
RecoverTimeout¶
Default: 20
This is the default setting for timeouts for controls when sent from the
recovery daemon. We allow longer control timeouts from the recovery daemon
than from normal use since the recovery dameon often use controls that can
take a lot longer than normal controls.
RecoverInterval¶
Default: 1
How frequently in seconds should the recovery daemon perform the consistency
checks that determine if we need to perform a recovery or not.
ElectionTimeout¶
Default: 3
When electing a new recovery master, this is how many seconds we allow the
election to take before we either deem the election finished or we fail the
election and start a new one.
TakeoverTimeout¶
Default: 9
This is how many seconds we allow controls to take for IP failover events.
MonitorInterval¶
Default: 15
How often should ctdb run the event scripts to check for a nodes health.
TickleUpdateInterval¶
Default: 20
How often will ctdb record and store the "tickle" information used to
kickstart stalled tcp connections after a recovery.
EventScriptTimeout¶
Default: 20
How long should ctdb let an event script run before aborting it and marking the
node unhealthy.
EventScriptTimeoutCount¶
Default: 1
How many events in a row needs to timeout before we flag the node UNHEALTHY.
This setting is useful if your scripts can not be written so that they do not
hang for benign reasons.
EventScriptUnhealthyOnTimeout¶
Default: 0
This setting can be be used to make ctdb never become UNHEALTHY if your
eventscripts keep hanging/timing out.
RecoveryGracePeriod¶
Default: 120
During recoveries, if a node has not caused recovery failures during the last
grace period, any records of transgressions that the node has caused recovery
failures will be forgiven. This resets the ban-counter back to zero for that
node.
RecoveryBanPeriod¶
Default: 300
If a node becomes banned causing repetitive recovery failures. The node will
eventually become banned from the cluster. This controls how long the culprit
node will be banned from the cluster before it is allowed to try to join the
cluster again. Don't set to small. A node gets banned for a reason and it is
usually due to real problems with the node.
DatabaseHashSize¶
Default: 100001
Size of the hash chains for the local store of the tdbs that ctdb manages.
DatabaseMaxDead¶
Default: 5
How many dead records per hashchain in the TDB database do we allow before the
freelist needs to be processed.
RerecoveryTimeout¶
Default: 10
Once a recovery has completed, no additional recoveries are permitted until this
timeout has expired.
EnableBans¶
Default: 1
When set to 0, this disables BANNING completely in the cluster and thus nodes
can not get banned, even it they break. Don't set to 0 unless you know what
you are doing. You should set this to the same value on all nodes to avoid
unexpected behaviour.
DeterministicIPs¶
Default: 0
When enabled, this tunable makes ctdb try to keep public IP addresses locked to
specific nodes as far as possible. This makes it easier for debugging since
you can know that as long as all nodes are healthy public IP X will always be
hosted by node Y.
The cost of using deterministic IP address assignment is that it disables part
of the logic where ctdb tries to reduce the number of public IP assignment
changes in the cluster. This tunable may increase the number of IP
failover/failbacks that are performed on the cluster by a small margin.
LCP2PublicIPs¶
Default: 1
When enabled this switches ctdb to use the LCP2 ip allocation algorithm.
ReclockPingPeriod¶
Default: x
Obsolete
NoIPFailback¶
Default: 0
When set to 1, ctdb will not perform failback of IP addresses when a node
becomes healthy. Ctdb WILL perform failover of public IP addresses when a node
becomes UNHEALTHY, but when the node becomes HEALTHY again, ctdb will not fail
the addresses back.
Use with caution! Normally when a node becomes available to the cluster ctdb
will try to reassign public IP addresses onto the new node as a way to
distribute the workload evenly across the clusternode. Ctdb tries to make sure
that all running nodes have approximately the same number of public addresses
it hosts.
When you enable this tunable, CTDB will no longer attempt to rebalance the
cluster by failing IP addresses back to the new nodes. An unbalanced cluster
will therefore remain unbalanced until there is manual intervention from the
administrator. When this parameter is set, you can manually fail public IP
addresses over to the new node(s) using the 'ctdb moveip' command.
DisableIPFailover¶
Default: 0
When enabled, ctdb will not perform failover or failback. Even if a node fails
while holding public IPs, ctdb will not recover the IPs or assign them to
another node.
When you enable this tunable, CTDB will no longer attempt to recover the cluster
by failing IP addresses over to other nodes. This leads to a service outage
until the administrator has manually performed failover to replacement nodes
using the 'ctdb moveip' command.
NoIPTakeover¶
Default: 0
When set to 1, ctdb will not allow IP addresses to be failed over onto this
node. Any IP addresses that the node currently hosts will remain on the node
but no new IP addresses can be failed over to the node.
NoIPHostOnAllDisabled¶
Default: 0
If no nodes are healthy then by default ctdb will happily host public IPs on
disabled (unhealthy or administratively disabled) nodes. This can cause
problems, for example if the underlying cluster filesystem is not mounted.
When set to 1 on a node and that node is disabled it, any IPs hosted by this
node will be released and the node will not takeover any IPs until it is no
longer disabled.
DBRecordCountWarn¶
Default: 100000
When set to non-zero, ctdb will log a warning when we try to recover a database
with more than this many records. This will produce a warning if a database
grows uncontrollably with orphaned records.
DBRecordSizeWarn¶
Default: 10000000
When set to non-zero, ctdb will log a warning when we try to recover a database
where a single record is bigger than this. This will produce a warning if a
database record grows uncontrollably with orphaned sub-records.
DBSizeWarn¶
Default: 1000000000
When set to non-zero, ctdb will log a warning when we try to recover a database
bigger than this. This will produce a warning if a database grows
uncontrollably.
VerboseMemoryNames¶
Default: 0
This feature consumes additional memory. when used the talloc library will
create more verbose names for all talloc allocated objects.
RecdPingTimeout¶
Default: 60
If the main dameon has not heard a "ping" from the recovery dameon for
this many seconds, the main dameon will log a message that the recovery daemon
is potentially hung.
RecdFailCount¶
Default: 10
If the recovery daemon has failed to ping the main dameon for this many
consecutive intervals, the main daemon will consider the recovery daemon as
hung and will try to restart it to recover.
LogLatencyMs¶
Default: 0
When set to non-zero, this will make the main daemon log any operation that took
longer than this value, in 'ms', to complete. These include "how long
time a lockwait child process needed", "how long time to write to a
persistent database" but also "how long did it take to get a
response to a CALL from a remote node".
RecLockLatencyMs¶
Default: 1000
When using a reclock file for split brain prevention, if set to non-zero this
tunable will make the recovery dameon log a message if the fcntl() call to
lock/testlock the recovery file takes longer than this number of ms.
RecoveryDropAllIPs¶
Default: 120
If we have been stuck in recovery, or stopped, or banned, mode for this many
seconds we will force drop all held public addresses.
VerifyRecoveryLock¶
Default: 1
Should we take a fcntl() lock on the reclock file to verify that we are the sole
recovery master node on the cluster or not.
VacuumInterval¶
Default: 10
Periodic interval in seconds when vacuuming is triggered for volatile databases.
VacuumMaxRunTime¶
Default: 120
The maximum time in seconds for which the vacuuming process is allowed to run.
If vacuuming process takes longer than this value, then the vacuuming process
is terminated.
RepackLimit¶
Default: 10000
During vacuuming, if the number of freelist records are more than
RepackLimit, then databases are repacked to get rid of the freelist
records to avoid fragmentation.
Databases are repacked only if both
RepackLimit and
VacuumLimit
are exceeded.
VacuumLimit¶
Default: 5000
During vacuuming, if the number of deleted records are more than
VacuumLimit, then databases are repacked to avoid fragmentation.
Databases are repacked only if both
RepackLimit and
VacuumLimit
are exceeded.
VacuumFastPathCount¶
Default: 60
When a record is deleted, it is marked for deletion during vacuuming. Vacuuming
process usually processes this list to purge the records from the database. If
the number of records marked for deletion are more than VacuumFastPathCount,
then vacuuming process will scan the complete database for empty records
instead of using the list of records marked for deletion.
DeferredAttachTO¶
Default: 120
When databases are frozen we do not allow clients to attach to the databases.
Instead of returning an error immediately to the application the attach
request from the client is deferred until the database becomes available again
at which stage we respond to the client.
This timeout controls how long we will defer the request from the client before
timing it out and returning an error to the client.
HopcountMakeSticky¶
Default: 50
If the database is set to 'STICKY' mode, using the 'ctdb setdbsticky' command,
any record that is seen as very hot and migrating so fast that hopcount
surpasses 50 is set to become a STICKY record for StickyDuration seconds. This
means that after each migration the record will be kept on the node and
prevented from being migrated off the node.
This setting allows one to try to identify such records and stop them from
migrating across the cluster so fast. This will improve performance for
certain workloads, such as locking.tdb if many clients are opening/closing the
same file concurrently.
StickyDuration¶
Default: 600
Once a record has been found to be fetch-lock hot and has been flagged to become
STICKY, this is for how long, in seconds, the record will be flagged as a
STICKY record.
StickyPindown¶
Default: 200
Once a STICKY record has been migrated onto a node, it will be pinned down on
that node for this number of ms. Any request from other nodes to migrate the
record off the node will be deferred until the pindown timer expires.
StatHistoryInterval¶
Default: 1
Granularity of the statistics collected in the statistics history.
AllowClientDBAttach¶
Default: 1
When set to 0, clients are not allowed to attach to any databases. This can be
used to temporarily block any new processes from attaching to and accessing
the databases.
RecoverPDBBySeqNum¶
Default: 1
When set to zero, database recovery for persistent databases is record-by-record
and recovery process simply collects the most recent version of every
individual record.
When set to non-zero, persistent databases will instead be recovered as a whole
db and not by individual records. The node that contains the highest value
stored in the record "__db_sequence_number__" is selected and the
copy of that nodes database is used as the recovered database.
By default, recovery of persistent databses is done using __db_sequence_number__
record.
FetchCollapse¶
Default: 1
When many clients across many nodes try to access the same record at the same
time this can lead to a fetch storm where the record becomes very active and
bounces between nodes very fast. This leads to high CPU utilization of the
ctdbd daemon, trying to bounce that record around very fast, and poor
performance.
This parameter is used to activate a fetch-collapse. A fetch-collapse is when we
track which records we have requests in flight so that we only keep one
request in flight from a certain node, even if multiple smbd processes are
attemtping to fetch the record at the same time. This can improve performance
and reduce CPU utilization for certain workloads.
This timeout controls if we should collapse multiple fetch operations of the
same record into a single request and defer all duplicates or not.
Samba3AvoidDeadlocks¶
Default: 0
Enable code that prevents deadlocks with Samba (only for Samba 3.x).
This should be set to 1 when using Samba version 3.x to enable special code in
CTDB to avoid deadlock with Samba version 3.x. This code is not required for
Samba version 4.x and must not be enabled for Samba 4.x.
SEE ALSO¶
ctdb(1),
ctdbd(1),
ctdbd.conf(5),
ctdb(7),
http://ctdb.samba.org/
AUTHOR¶
This documentation was written by Ronnie Sahlberg, Amitay Isaacs, Martin
Schwenke
COPYRIGHT¶
Copyright © 2007 Andrew Tridgell, Ronnie Sahlberg
This program is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation; either version 3 of the License, or (at your option) any later
version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with
this program; if not, see
http://www.gnu.org/licenses.