| title | summary | category |
|---|---|---|
CLUSTER_LOG |
了解 TiDB 集群日志表 `CLUSTER_LOG`。 |
reference |
集群日志表 CLUSTER_LOG 表用于查询集群当前所有 TiDB/PD/TiKV 节点日志。它通过将查询条件下推到各个节点，降低了日志查询对集群的影响。该表的查询性能优于 grep 命令。
TiDB 4.0 版本之前，要获取集群的日志，用户需要逐个登录各个节点汇总日志。TiDB 4.0 的集群日志表提供了一个全局且时间有序的日志搜索结果，为跟踪全链路事件提供了便利的手段。例如按照某一个 region id 搜索日志，可以查询该 Region 生命周期内的所有日志；类似地，通过慢日志的 txn id 搜索全链路日志，可以查询该事务在各个节点扫描的 key 数量以及流量等信息。
{{< copyable "sql" >}}
desc information_schema.cluster_log;+----------+------------------+------+------+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+------------------+------+------+---------+-------+
| TIME | varchar(32) | YES | | NULL | |
| TYPE | varchar(64) | YES | | NULL | |
| INSTANCE | varchar(64) | YES | | NULL | |
| LEVEL | varchar(8) | YES | | NULL | |
| MESSAGE | var_string(1024) | YES | | NULL | |
+----------+------------------+------+------+---------+-------+
5 rows in set (0.00 sec)
字段解释：
TIME：日志打印时间。TYPE：节点的类型，可取值为tidb，pd和tikv。INSTANCE：节点的服务地址。LEVEL：日志级别。MESSAGE：日志内容。
注意：
日志表的所有字段都会下推到对应节点执行，所以为了降低使用集群日志表的开销，需尽可能地指定更多的条件。例如
select * from cluter_log where instance='tikv-1'只会在tikv-1上执行日志搜索。
message字段支持like和regexp正则表达式，对应的 pattern 会编译为regexp。同时指定多个message条件，相当于grep命令的pipeline形式，例如：select * from cluster_log where message like 'coprocessor%' and message regexp '.*slow.*'相当于在集群所有节点执行grep 'coprocessor' xxx.log | grep -E '.*slow.*'。
查询某个 DDL 的执行过程示例如下：
{{< copyable "sql" >}}
select * from information_schema.cluster_log where message like '%ddl%' and message like '%job%58%' and type='tidb' and time > '2020-03-27 15:39:00';+-------------------------+------+------------------+-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| TIME | TYPE | INSTANCE | LEVEL | MESSAGE |
+-------------------------+------+------------------+-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| 2020/03/27 15:39:36.140 | tidb | 172.16.5.40:4008 | INFO | [ddl_worker.go:253] ["[ddl] add DDL jobs"] ["batch count"=1] [jobs="ID:58, Type:create table, State:none, SchemaState:none, SchemaID:1, TableID:57, RowCount:0, ArgLen:1, start time: 2020-03-27 15:39:36.129 +0800 CST, Err:<nil>, ErrCount:0, SnapshotVersion:0; "] |
| 2020/03/27 15:39:36.140 | tidb | 172.16.5.40:4008 | INFO | [ddl.go:457] ["[ddl] start DDL job"] [job="ID:58, Type:create table, State:none, SchemaState:none, SchemaID:1, TableID:57, RowCount:0, ArgLen:1, start time: 2020-03-27 15:39:36.129 +0800 CST, Err:<nil>, ErrCount:0, SnapshotVersion:0"] [query="create table t3 (a int, b int,c int)"] |
| 2020/03/27 15:39:36.879 | tidb | 172.16.5.40:4009 | INFO | [ddl_worker.go:554] ["[ddl] run DDL job"] [worker="worker 1, tp general"] [job="ID:58, Type:create table, State:none, SchemaState:none, SchemaID:1, TableID:57, RowCount:0, ArgLen:0, start time: 2020-03-27 15:39:36.129 +0800 CST, Err:<nil>, ErrCount:0, SnapshotVersion:0"] |
| 2020/03/27 15:39:36.936 | tidb | 172.16.5.40:4009 | INFO | [ddl_worker.go:739] ["[ddl] wait latest schema version changed"] [worker="worker 1, tp general"] [ver=35] ["take time"=52.165811ms] [job="ID:58, Type:create table, State:done, SchemaState:public, SchemaID:1, TableID:57, RowCount:0, ArgLen:1, start time: 2020-03-27 15:39:36.129 +0800 CST, Err:<nil>, ErrCount:0, SnapshotVersion:0"] |
| 2020/03/27 15:39:36.938 | tidb | 172.16.5.40:4009 | INFO | [ddl_worker.go:359] ["[ddl] finish DDL job"] [worker="worker 1, tp general"] [job="ID:58, Type:create table, State:synced, SchemaState:public, SchemaID:1, TableID:57, RowCount:0, ArgLen:0, start time: 2020-03-27 15:39:36.129 +0800 CST, Err:<nil>, ErrCount:0, SnapshotVersion:0"] |
| 2020/03/27 15:39:36.140 | tidb | 172.16.5.40:4009 | INFO | [ddl_worker.go:253] ["[ddl] add DDL jobs"] ["batch count"=1] [jobs="ID:58, Type:create table, State:none, SchemaState:none, SchemaID:1, TableID:57, RowCount:0, ArgLen:1, start time: 2020-03-27 15:39:36.129 +0800 CST, Err:<nil>, ErrCount:0, SnapshotVersion:0; "] |
| 2020/03/27 15:39:36.140 | tidb | 172.16.5.40:4009 | INFO | [ddl.go:457] ["[ddl] start DDL job"] [job="ID:58, Type:create table, State:none, SchemaState:none, SchemaID:1, TableID:57, RowCount:0, ArgLen:1, start time: 2020-03-27 15:39:36.129 +0800 CST, Err:<nil>, ErrCount:0, SnapshotVersion:0"] [query="create table t3 (a int, b int,c int)"] |
| 2020/03/27 15:39:37.141 | tidb | 172.16.5.40:4008 | INFO | [ddl.go:489] ["[ddl] DDL job is finished"] [jobID=58] |
+-------------------------+------+------------------+-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
上面查询结果表示：
- 用户将 DDL JOB ID 为
58的请求发给172.16.5.40:4008TiDB 节点。 172.16.5.40:4009TiDB 节点处理这个 DDL 请求，说明此时172.16.5.40:4009节点是 DDL owner。- DDL JOB ID 为 58 的请求处理完成。