TiDB Lightning Monitoring

TiDB Lightning Monitoring

tidb-lightning supports metrics collection via Prometheus. This document introduces the monitor configuration and monitoring metrics of TiDB Lightning.

Monitor configuration

If TiDB Lightning is manually installed, follow the instructions below.

The metrics of tidb-lightning can be gathered directly by Prometheus as long as it is discovered. You can set the metrics port in tidb-lightning.toml:

[lightning]
# HTTP port for debugging and Prometheus metrics pulling (0 to disable)
pprof-port = 8289
...

and in tikv-importer.toml:

# Listening address of the status server.
status-server-address = '0.0.0.0:8286'

You need to configure Prometheus to make it discover the servers. For instance, you can directly add the server address to the scrape_configs section:

...
scrape_configs:
  - job_name: 'tidb-lightning'
    static_configs:
      - targets: ['192.168.20.10:8289']
  - job_name: 'tikv-importer'
    static_configs:
      - targets: ['192.168.20.9:8286']

Grafana dashboard

Grafana is a web interface to visualize Prometheus metrics as dashboards.

Row 1: Speed

Panel	Series	Description
Import speed	write from TiDB Lightning	Speed of sending KVs from TiDB Lightning to TiKV Importer, which depends on each table’s complexity
Import speed	upload to tikv	Total upload speed from TiKV Importer to all TiKV replicas
Chunk process duration		Average time needed to completely encode one single data file

Sometimes the import speed will drop to zero allowing other parts to catch up. This is normal.

Row 2: Progress

Panel	Description
Import progress	Percentage of data files encoded so far
Checksum progress	Percentage of tables are verified to be imported successfully
Failures	Number of failed tables and their point of failure, normally empty

Row 3: Resource

Panel	Description
Memory usage	Amount of memory occupied by each service
Number of TiDB Lightning Goroutines	Number of running goroutines used by TiDB Lightning
CPU%	Number of logical CPU cores utilized by each service

Row 4: Quota

Panel	Series	Description
Idle workers	io	Number of unused `io-concurrency`, normally close to configured value (default 5), and close to 0 means the disk is too slow
Idle workers	closed-engine	Number of engines which is closed but not yet cleaned up, normally close to index + table-concurrency (default 8), and close to 0 means TiDB Lightning is faster than TiKV Importer, which will cause TiDB Lightning to stall
Idle workers	table	Number of unused `table-concurrency`, normally 0 until the end of process
Idle workers	index	Number of unused `index-concurrency`, normally 0 until the end of process
Idle workers	region	Number of unused `region-concurrency`, normally 0 until the end of process
External resources	KV Encoder	Counts active KV encoders, normally the same as `region-concurrency` until the end of process
External resources	Importer Engines	Counts opened engine files, should never exceed the `max-open-engines` setting

Row 5: Read speed

Panel	Series	Description
Chunk parser read block duration	read block	Time taken to read one block of bytes to prepare for parsing
Chunk parser read block duration	apply worker	Time elapsed to wait for an idle io-concurrency
SQL process duration	row encode	Time taken to parse and encode a single row
SQL process duration	block deliver	Time taken to send a block of KV pairs to TiKV Importer

If any of the duration is too high, it indicates that the disk used by TiDB Lightning is too slow or busy with I/O.

Row 6: Storage

Panel	Series	Description
SQL process rate	data deliver rate	Speed of delivery of data KV pairs to TiKV Importer
SQL process rate	index deliver rate	Speed of delivery of index KV pairs to TiKV Importer
SQL process rate	total deliver rate	The sum of two rates above
Total bytes	parser read size	Number of bytes being read by TiDB Lightning
Total bytes	data deliver size	Number of bytes of data KV pairs already delivered to TiKV Importer
Total bytes	index deliver size	Number of bytes of index KV pairs already delivered to TiKV Importer
Total bytes	storage_size / 3	Total size occupied by the TiKV cluster, divided by 3 (the default number of replicas)

Row 7: Import speed

Panel	Series	Description
Delivery duration	Range delivery	Time taken to upload a range of KV pairs to the TiKV cluster
Delivery duration	SST delivery	Time taken to upload an SST file to the TiKV cluster
SST process duration	Split SST	Time taken to split the stream of KV pairs into SST files
SST process duration	SST upload	Time taken to upload an SST file
SST process duration	SST ingest	Time taken to ingest an uploaded SST file
SST process duration	SST size	File size of an SST file

Monitoring metrics

This section explains the monitoring metrics of tikv-importer and tidb-lightning, if you need to monitor other metrics not covered by the default Grafana dashboard.

`tikv-importer`

Metrics provided by tikv-importer are listed under the namespace tikv_import_*.

tikv_import_rpc_duration (Histogram)

Bucketed histogram for the duration of an RPC action. Labels:
- request: what kind of RPC is executed
  - switch_mode: switched a TiKV node to import/normal mode
  - open_engine: opened an engine file
  - write_engine: received data and written into an engine
  - close_engine: closed an engine file
  - import_engine: imported an engine file into the TiKV cluster
  - cleanup_engine: deleted an engine file
  - compact_cluster: explicitly compacted the TiKV cluster
  - upload: uploaded an SST file
  - ingest: ingested an SST file
  - compact: explicitly compacted a TiKV node
- result: the execution result of the RPC
  - ok
  - error
tikv_import_write_chunk_bytes (Histogram)

Bucketed histogram for the uncompressed size of a block of KV pairs received from TiDB Lightning.
tikv_import_write_chunk_duration (Histogram)

Bucketed histogram for the time needed to receive a block of KV pairs from TiDB Lightning.
tikv_import_upload_chunk_bytes (Histogram)

Bucketed histogram for the compressed size of a chunk of SST file uploaded to TiKV.
tikv_import_upload_chunk_duration (Histogram)

Bucketed histogram for the time needed to upload a chunk of SST file to TiKV.
tikv_import_range_delivery_duration (Histogram)

Bucketed histogram for the time needed to deliver a range of KV pairs into a dispatch-job.
tikv_import_split_sst_duration (Histogram)

Bucketed histogram for the time needed to split off a range from the engine file into a single SST file.
tikv_import_sst_delivery_duration (Histogram)

Bucketed histogram for the time needed to deliver an SST file from a dispatch-job to an ImportSSTJob.
tikv_import_sst_recv_duration (Histogram)

Bucketed histogram for the time needed to receive an SST file from a dispatch-job in an ImportSSTJob.
tikv_import_sst_upload_duration (Histogram)

Bucketed histogram for the time needed to upload an SST file from an ImportSSTJob to a TiKV node.
tikv_import_sst_chunk_bytes (Histogram)

Bucketed histogram for the compressed size of the SST file uploaded to a TiKV node.
tikv_import_sst_ingest_duration (Histogram)

Bucketed histogram for the time needed to ingest an SST file into TiKV.
tikv_import_each_phase (Gauge)

Indicates the running phase. Possible values are 1, meaning running inside the phase, and 0, meaning outside the phase. Labels:
- phase: prepare/import
tikv_import_wait_store_available_count (Counter)

Counts the number of times a TiKV node is found to have insufficient space when uploading SST files. Labels:
- store_id: The TiKV store ID.

`tidb-lightning`

Metrics provided by tidb-lightning are listed under the namespace lightning_*.

lightning_importer_engine (Counter)

Counts open and closed engine files. Labels:
- type:
  - open
  - closed
lightning_idle_workers (Gauge)

Counts idle workers. Labels:
- name:
  - table: the remainder of table-concurrency, normally 0 until the end of the process
  - index: the remainder of index-concurrency, normally 0 until the end of the process
  - region: the remainder of region-concurrency, normally 0 until the end of the process
  - io: the remainder of io-concurrency, normally close to configured value (default 5), and close to 0 means the disk is too slow
  - closed-engine: number of engines which have been closed but not yet cleaned up, normally close to index + table-concurrency (default 8). A value close to 0 means TiDB Lightning is faster than TiKV Importer, which might cause TiDB Lightning to stall
lightning_kv_encoder (Counter)

Counts open and closed KV encoders. KV encoders are in-memory TiDB instances that convert SQL INSERT statements into KV pairs. The net values need to be bounded in a healthy situation. Labels:
- type:
  - open
  - closed
lightning_tables (Counter)

Counts processed tables and their statuses. Labels:
- state: the status of the table, indicating which phase should be completed
  - pending: not yet processed
  - written: all data encoded and sent
  - closed: all corresponding engine files closed
  - imported: all engine files have been imported into the target cluster
  - altered_auto_inc: AUTO_INCREMENT ID altered
  - checksum: checksum performed
  - analyzed: statistics analysis performed
  - completed: the table has been fully imported and verified
- result: the result of the current phase
  - success: the phase completed successfully
  - failure: the phase failed (did not complete)
lightning_engines (Counter)

Counts number of engine files processed and their status. Labels:
- state: the status of the engine, indicating which phase should be completed
  - pending: not yet processed
  - written: all data encoded and sent
  - closed: engine file closed
  - imported: the engine file has been imported into the target cluster
  - completed: the engine has been fully imported
- result: the result of the current phase
  - success: the phase completed successfully
  - failure: the phase failed (did not complete)
lightning_chunks (Counter)

Counts number of chunks processed and their status. Labels:
- state: a chunk’s status, indicating which phase the chunk is in
  - estimated: (not a state) this value gives total number of chunks in current task
  - pending: loaded but not yet processed
  - running: data are being encoded and sent
  - finished: the entire chunk has been processed
  - failed: errors happened during processing
lightning_import_seconds (Histogram)

Bucketed histogram for the time needed to import a table.
lightning_row_read_bytes (Histogram)

Bucketed histogram for the size of a single SQL row.
lightning_row_encode_seconds (Histogram)

Bucketed histogram for the time needed to encode a single SQL row into KV pairs.
lightning_row_kv_deliver_seconds (Histogram)

Bucketed histogram for the time needed to deliver a set of KV pairs corresponding to one single SQL row.
lightning_block_deliver_seconds (Histogram)

Bucketed histogram for the time needed to deliver a block of KV pairs to Importer.
lightning_block_deliver_bytes (Histogram)

Bucketed histogram for the uncompressed size of a block of KV pairs delivered to Importer.
lightning_chunk_parser_read_block_seconds (Histogram)

Bucketed histogram for the time needed by the data file parser to read a block.
lightning_checksum_seconds (Histogram)

Bucketed histogram for the time needed to compute the checksum of a table.
lightning_apply_worker_seconds (Histogram)

Bucketed histogram for the time needed to acquire an idle worker (see also the lightning_idle_workers gauge). Labels:
- name:
  - table
  - index
  - region
  - io
  - closed-engine