【TiDB 4.0 PCTA 学习笔记】- 3.7.2 The lifecycle of a SQL and relevant metrics（TiDB 的 SQL 的生命周期和关键监控指标）@2班+胡宏强

[林夕一指]

课程名称：课程版本（101/201/301）+ 3.7.2 The lifecycle of a SQL and relevant metrics（TiDB 的 SQL 的生命周期和关键监控指标）

学习时长：10

课程内容：

一、 sql 在 tidb 的流程

• 在执行前

  • Get Token
    • Token limits the concurrency of SQLS
    • Relates to config ‘token-timit’
    • Grafana: Get Token Duration
  • Get TSO
    • Get timestamp from PD asynchronously
    • Dashboard (SQL Statements & Slow Queries)
    • Grafana: PD TSO Wait Duration (relate to load on TiDB itself)
    • Grafana: PD TSO RPC Duration (latency between TiDB and PD & load on PD)

• Parse and Compile

  • Parse
    • Dashboard (sQL Statements & Slow Queries)
    • Grafana: Parse Duration
  • compile
    • Preprocess(validator & type infer)+ Optimize
    • Dashboard (SQL Statements & Slow Queries)
    • Grafana: Compile Duration
  • Prepared Statements
    • Saves cost of parsing and preprocessing
    • Grafana: Prepare Statement Count
  • Prepared Plan Cache
    • Saves cost of optimizing
    • Grafana: Plan Cache Hits

• 执行

  • Execution Duration
  • Expensive Executors OPS
    • HashAgg / Sort / lndexLookUp …
    • Relates to system variables `tidb_{operator}_concurrency
  • KV Request
    • KV Request Duration 99
    • TiClient Region Error OPS
    • Lock Resolve OPS

• DistSQL : tidb 向tikv 发送请求接收数据的接口

  • DistSQL Duration
    • Requests are sent concurrently
    • Relates to system variable 'tidb_distsql_scan_concurrency
  • Scan Keys
    • Dashboard (SQL Statements & Slow Queries)
    • Grafana: Scan Keys
  • Coprocessor & Get & Batch Get
    • KV Request OPS

• 事务

  • KV Transaction Duration
  • Local Latch
    • waits for memory lock in TiDB before prewriting
    • Suitable for high conflicting scenarios and disabled by default
    • Dashboard (SQL Statements & Slow Queries)
    • Grafana: Local Latch Wait Time
  • Transaction Retry
    • Some errors are retriable, e.g. write conflicts
    • Dashboard (SQL Statements & Slow Queries)。
    • Grafana: Transaction Retry Num
      二、 Tikv组件内的流程
      
      

• KV 请求

  • gRPC Message Duration (indicates all time cost in TiKV)
    • kv_get / kv_batch_get / coprocessor
    • KV Duration in TiDB ~= gRPC Message Duration + network RTT

• 事务

  • Prewrite & Commit
    • Dashboard (SQL Statements & Slow Queries)
  • Resolve Lock
    • Dashboard (SQL Statements & Slow Queries)
    • Lock Resolve OPS

• Raft Store : Raft store uses Raft to keep replicas consistent.

  • Raft propose
    • Propose wait duration
    • Apply wait duration
  • Raft lO
    • Append log duration
    • Apply log duration
    • Commit log duration

• Coprocessor

  • Coprocessor Execution Time
    • Dashboard (SQL Statements & Slow Queries)
    • Request Duration
  • coprocessor Wait Time
    • Dashboard (SQL Statements & Slow Queries)
    • Wait Duration
    • Can be optimized through coprocessor cache

• RocksDB : Each TikV instance has 2 RocksDB instances: Raft and KV.

  • Read
    • Get / Seek duration
    • Memtable hit
    • Block cache hit
    • SST read duration
  • Write
    • Write duration
  • Compaction
    • Compaction operations
    • Compaction duration

三、

学习过程中遇到的问题或延伸思考：

• 问题 1：
• 问题 2：
• 延伸思考 1：
• 延伸思考 2：

学习过程中参考的其他资料

• 文档名称
• 文档名称
• 文档名称

[TiDB_学习助手]

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