disttask: add metrics collection for dispatcher

[JK1Zhang]

What problem does this PR solve?

Issue Number: close #47017

Problem Summary:

What is changed and how it works?

• A line chart showing the change in the number of waiting/running/cancelling/reverting tasks over time
• A line chart showing the waiting time of waiting tasks
• A line chart showing the dispatch time of dispatching tasks

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No need to test

Manual test

1. start TiDB in playground

cd tidb
make
tiup playground  --db 1 --db.binpath ./bin/tidb-server

2. test with mysql

mysql --comments --host 127.0.0.1 --port 4000 -u root

test cmd

drop database if exists test;
create database test;
use test;
set global tidb_enable_dist_task=1;
create table t(a bigint auto_random primary key) partition by hash(a) partitions 8;
insert into t values (), (), (), (), (), ();
insert into t values (), (), (), (), (), ();
insert into t values (), (), (), (), (), ();
insert into t values (), (), (), (), (), ();
create table t1(a bigint auto_random primary key);
insert into t1 values (), (), (), (), (), ();
insert into t1 values (), (), (), (), (), ();
insert into t1 values (), (), (), (), (), ();
insert into t1 values (), (), (), (), (), ();
create table t2(a bigint auto_random primary key) partition by hash(a) partitions 8;
insert into t2 values (), (), (), (), (), ();
insert into t2 values (), (), (), (), (), ();
insert into t2 values (), (), (), (), (), ();
insert into t2 values (), (), (), (), (), ();
create table t3(a bigint auto_random primary key);
insert into t3 values (), (), (), (), (), ();
insert into t3 values (), (), (), (), (), ();
insert into t3 values (), (), (), (), (), ();
insert into t3 values (), (), (), (), (), ();
split table t between (3) and (8646911284551352360) regions 50;
alter table t add index idx(a);
admin check index t idx;
split table t1 between (3) and (8646911284551352360) regions 50;
alter table t1 add index idx(a);
admin check index t1 idx;
split table t2 between (3) and (8646911284551352360) regions 50;
alter table t2 add index idx(a);
admin check index t idx;
split table t3 between (3) and (8646911284551352360) regions 50;
alter table t3 add index idx(a);
admin check index t3 idx;

3. grafana result

calculate in grafana (dispatching is happening too fast to see the data points )
panel "task dispatching time" metrics: "time() - tidb_disttask_dispatcher_start_time{status="dispatching"}/1000000"

calculate in dispatcher_manager.go
panel "task dispatching duration" metrics: tidb_disttask_dispatcher_duration{status="dispatching"}
Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None

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[okJiang]

need more enhancement

[okJiang]

How about initializing the metrics with these tasks when the DispatcherManager starts?

[okJiang]

It is precise.

[JK1Zhang]

For DistDDLTaskStarttimeGauge, I think it's not necessary to initialize here because it doesn't change.
For DistDDLTaskGauge, should I go through all the tasks in the tidb_global_task table?

[ywqzzy]

/cc @ywqzzy

[ywqzzy]

LGTM

[D3Hunter]

rest lgtm

[D3Hunter]

what does 300 means?

[JK1Zhang]

useless , deleted

[Benjamin2037]

LGTM

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Benjamin2037, okJiang

The full list of commands accepted by this bot can be found here.

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Needs approval from an approver in each of these files:

• OWNERS [okJiang]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2023-09-25 13:44:40.795615584 +0000 UTC m=+282470.513957800: ☑️ agreed by Benjamin2037.
• 2023-09-25 13:57:37.628290687 +0000 UTC m=+283247.346632904: ☑️ agreed by okJiang.