TiKV Control User Guide

TiKV Control (tikv-ctl) is a command line tool of TiKV, used to manage the cluster.

When you compile TiKV, the tikv-ctl command is also compiled at the same time. If the cluster is deployed using Ansible, the tikv-ctl binary file exists in the corresponding tidb-ansible/resources/bin directory. If the cluster is deployed using the binary, the tikv-ctl file is in the bin directory together with other files such as tidb-server, pd-server, tikv-server, etc.

General options

tikv-ctl provides two operation modes:

• Remote mode: use the --host option to accept the service address of TiKV as the argument

  For this mode, if SSL is enabled in TiKV, tikv-ctl also needs to specify the related certificate file. For example:

  $ tikv-ctl --ca-path ca.pem --cert-path client.pem --key-path client-key.pem --host 127.0.0.1:20160 <subcommands>

  However, sometimes tikv-ctl communicates with PD instead of TiKV. In this case, you need to use the --pd option instead of --host. Here is an example:

  $ tikv-ctl --pd 127.0.0.1:2379 compact-cluster
  store:"127.0.0.1:20160" compact db:KV cf:default range:([], []) success!

• Local mode: use the --db option to specify the local TiKV data directory path

Unless otherwise noted, all commands supports both the remote mode and the local mode.

Additionally, tikv-ctl has two simple commands --to-hex and --to-escaped, which are used to make simple changes to the form of the key.

Generally, use the escaped form of the key. For example:

$ tikv-ctl --to-escaped 0xaaff
\252\377
$ tikv-ctl --to-hex "\252\377"
AAFF

Note:

When you specify the escaped form of the key in a command line, it is required to enclose it in double quotes. Otherwise, bash eats the backslash and a wrong result is returned.

Subcommands, some options and flags

This section describes the subcommands that tikv-ctl supports in detail. Some subcommands support a lot of options. For all details, run tikv-ctl --help <subcommand>.

View information of the Raft state machine

Use the raft subcommand to view the status of the Raft state machine at a specific moment. The status information includes two parts: three structs (RegionLocalState, RaftLocalState, and RegionApplyState) and the corresponding Entries of a certain piece of log.

Use the region and log subcommands to obtain the above information respectively. The two subcommands both support the remote mode and the local mode at the same time. Their usage and output are as follows:

$ tikv-ctl --host 127.0.0.1:20160 raft region -r 2
region id: 2
region state key: \001\003\000\000\000\000\000\000\000\002\001
region state: Some(region {id: 2 region_epoch {conf_ver: 3 version: 1} peers {id: 3 store_id: 1} peers {id: 5 store_id: 4} peers {id: 7 store_id: 6}})
raft state key: \001\002\000\000\000\000\000\000\000\002\002
raft state: Some(hard_state {term: 307 vote: 5 commit: 314617} last_index: 314617)
apply state key: \001\002\000\000\000\000\000\000\000\002\003
apply state: Some(applied_index: 314617 truncated_state {index: 313474 term: 151})

View the Region size

Use the size command to view the Region size:

$ tikv-ctl --db /path/to/tikv/db size -r 2
region id: 2
cf default region size: 799.703 MB
cf write region size: 41.250 MB
cf lock region size: 27616

Scan to view MVCC of a specific range

The --from and --to options of the scan command accept two escaped forms of raw key, and use the --show-cf flag to specify the column families that you need to view.

$ tikv-ctl --db /path/to/tikv/db scan --from 'zm' --limit 2 --show-cf lock,default,write
key: zmBootstr\377a\377pKey\000\000\377\000\000\373\000\000\000\000\000\377\000\000s\000\000\000\000\000\372
         write cf value: start_ts: 399650102814441473 commit_ts: 399650102814441475 short_value: "20"
key: zmDB:29\000\000\377\000\374\000\000\000\000\000\000\377\000H\000\000\000\000\000\000\371
         write cf value: start_ts: 399650105239273474 commit_ts: 399650105239273475 short_value: "\000\000\000\000\000\000\000\002"
         write cf value: start_ts: 399650105199951882 commit_ts: 399650105213059076 short_value: "\000\000\000\000\000\000\000\001"

View MVCC of a given key

Similar to the scan command, the mvcc command can be used to view MVCC of a given key.

$ tikv-ctl --db /path/to/tikv/db mvcc -k "zmDB:29\000\000\377\000\374\000\000\000\000\000\000\377\000H\000\000\000\000\000\000\371" --show-cf=lock,write,default
key: zmDB:29\000\000\377\000\374\000\000\000\000\000\000\377\000H\000\000\000\000\000\000\371
         write cf value: start_ts: 399650105239273474 commit_ts: 399650105239273475 short_value: "\000\000\000\000\000\000\000\002"
         write cf value: start_ts: 399650105199951882 commit_ts: 399650105213059076 short_value: "\000\000\000\000\000\000\000\001"

In this command, the key is also the escaped form of raw key.

Print a specific key value

To print the value of a key, use the print command.

Print some properties about Region

In order to record Region state details, TiKV writes some statistics into the SST files of Regions. To view these properties, run tikv-ctl with the region-properties sub-command:

$ tikv-ctl --host localhost:20160 region-properties -r 2
num_files: 0
num_entries: 0
num_deletes: 0
mvcc.min_ts: 18446744073709551615
mvcc.max_ts: 0
mvcc.num_rows: 0
mvcc.num_puts: 0
mvcc.num_versions: 0
mvcc.max_row_versions: 0
middle_key_by_approximate_size:

The properties can be used to check whether the Region is healthy or not. If not, you can use them to fix the Region. For example, splitting the Region manually by middle_key_approximate_size.

Compact data of each TiKV manually

Use the compact command to manually compact data of each TiKV. If you specify the --from and --to options, then their flags are also in the form of escaped raw key. You can use the --host option to specify the TiKV that you need to compact. The -d option is used to specify the RocksDB that will be compacted. The optional values are kv and raft. Also, the --threads option allows you to specify the concurrency that you compact and its default value is 8. Generally, a higher concurrency comes with a faster compact speed, which might yet affect the service. You need to choose an appropriate concurrency based on the scenario.

$ tikv-ctl --host 127.0.0.1:20160 compact -d kv
success!

Compact data of the whole TiKV cluster manually

Use the compact-cluster command to manually compact data of the whole TiKV cluster. The flags of this command have the same meanings and usage as those of the compact command.

Set a Region to tombstone

The tombstone command is usually used in circumstances where the sync-log is not enabled, and some data written in the Raft state machine is lost caused by power down.

In a TiKV instance, you can use this command to set the status of some Regions to Tombstone. Then when you restart the instance, those Regions are skipped. Those Regions need to have enough healthy replicas in other TiKV instances to be able to continue writing and reading through the Raft mechanism.

pd-ctl>> operator add remove-peer <region_id> <peer_id>
$ tikv-ctl --db /path/to/tikv/db tombstone -p 127.0.0.1:2379 -r 2
success!

Note:

• This command only supports the local mode.
• The argument of the -p option specifies the PD endpoints without the http prefix. Specifying the PD endpoints is to query whether PD can securely switch to Tombstone. Therefore, before setting a PD instance to Tombstone, you need to take off the corresponding Peer of this Region on the machine in pd-ctl.

Send a consistency-check request to TiKV

Use the consistency-check command to execute a consistency check among replicas in the corresponding Raft of a specific Region. If the check fails, TiKV itself panics. If the TiKV instance specified by --host is not the Region leader, an error is reported.

$ tikv-ctl --host 127.0.0.1:20160 consistency-check -r 2
success!
$ tikv-ctl --host 127.0.0.1:21061 consistency-check -r 2
DebugClient::check_region_consistency: RpcFailure(RpcStatus { status: Unknown, details: Some("StringError(\"Leader is on store 1\")") })

Note:

• This command only supports the remote mode.
• Even if this command returns success!, you need to check whether TiKV panics. This is because this command is only a proposal that requests a consistency check for the leader, and you cannot know from the client whether the whole check process is successful or not.

Dump snapshot meta

This sub-command is used to parse a snapshot meta file at given path and print the result.

Print the Regions where the Raft state machine corrupts

To avoid checking the Regions while TiKV is started, you can use the tombstone command to set the Regions where the Raft state machine reports an error to Tombstone. Before running this command, use the bad-regions command to find out the Regions with errors, so as to combine multiple tools for automated processing.

$ tikv-ctl --db /path/to/tikv/db bad-regions
all regions are healthy

If the command is successfully executed, it prints the above information. If the command fails, it prints the list of bad Regions. Currently, the errors that can be detected include the mismatches between last index, commit index and apply index, and the loss of Raft log. Other conditions like the damage of snapshot files still need further support.

View Region properties

• To view in local the properties of Region 2 on the TiKV instance that is deployed in /path/to/tikv:

  $ tikv-ctl --db /path/to/tikv/data/db region-properties -r 2

• To view online the properties of Region 2 on the TiKV instance that is running on 127.0.0.1:20160:

  $ tikv-ctl --host 127.0.0.1:20160 region-properties -r 2

Modify the RocksDB configuration of TiKV dynamically

You can use the modify-tikv-config command to dynamically modify the configuration arguments. Currently, it only supports dynamically modifying RocksDB related arguments.

• -m is used to specify the target RocksDB. You can set it to kvdb or raftdb.
• -n is used to specify the configuration name. You can refer to the arguments of [rocksdb] and [raftdb] (corresponding to kvdb and raftdb) in the TiKV configuration template. You can use default|write|lock + . + argument name to specify the configuration of different CFs. For kvdb, you can set it to default, write, or lock; for raftdb, you can only set it to default.

• -v is used to specify the configuration value.

  $ tikv-ctl modify-tikv-config -m kvdb -n max_background_jobs -v 8
  success！
  $ tikv-ctl modify-tikv-config -m kvdb -n write.block-cache-size -v 256MB
  success!
  $ tikv-ctl modify-tikv-config -m raftdb -n default.disable_auto_compactions -v true
  success!

Force Region to recover the service from failure of multiple replicas

Use the unsafe-recover remove-fail-stores command to remove the failed machines from the peer list of the specified Regions. This command has only one mode “local”. Before running this command, you need to stop the target TiKV process to release the file lock.

The -s option accepts multiple store_id separated by comma and uses the -r flag to specify involved Regions. To recover the service from the failure of multiple replicas for all the Regions in one store, specify --all-regions.

$ tikv-ctl --db /path/to/tikv/db unsafe-recover remove-fail-stores -s 3 -r 1001,1002
success!

$ tikv-ctl --db /path/to/tikv/db unsafe-recover remove-fail-stores -s 4,5 --all-regions

Then after you restart TiKV, these Regions can continue to provide services using the other healthy replicas. This command is usually used in circumstances where multiple TiKV stores are damaged or deleted.

Note:

• This command only supports the local mode. It prints success! when successfully run.
• Generally, you need to run this command for all stores where the peers of the specified Regions are located.
• If you specify --all-regions, run this command for all the other healthy stores in the cluster.

Recover from MVCC data corruption

Use the recover-mvcc command in circumstances where TiKV cannot run normally caused by MVCC data corruption. It cross-checks 3 CFs (“default”, “write”, “lock”) to recover from various kinds of inconsistency.

Use the -r option to specify involved Regions by region_id. Use the -p option to specify PD endpoints.

$ tikv-ctl --db /path/to/tikv/db recover-mvcc -r 1001,1002 -p 127.0.0.1:2379
success!

Note:

• This command only supports the local mode. It prints success! when successfully run.
• The argument of the -p option specifies the PD endpoints without the http prefix. Specifying the PD endpoints is to query whether the specified region_id is validated or not.
• You need to run this command for all stores where specified Regions’ peers locate.