Unable to access the 4000 port of tidb_server

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This topic has been translated from a Chinese forum by GPT and might contain errors.

Original topic: tidb_server的4000端口无法访问

| username: 等一分钟

[TiDB Usage Environment] Production Environment
[TiDB Version] 6.5.1
[Reproduction Path] Unable to access TiDB’s 4000 port using MySQL client

| username: 等一分钟 | Original post link

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| username: 等一分钟 | Original post link

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| username: 等一分钟 | Original post link

The monitoring looks normal, but there are a lot of connections. The port can be reached via telnet, but it cannot be connected using the client.

| username: 等一分钟 | Original post link

[2023/08/29 14:59:11.967 +08:00] [WARN] [region_request.go:1498] [“tikv reports ServerIsBusy retry later”] [reason=“scheduler is busy”] [ctx=“region ID: 1844813, meta: id:1844813 start_key:"t\200\000\000\000\000\t.A_i\200\000\000\000\000\000\000\001\001b0db888d\377-5071-48\377c0-b2f5-\377af3137a9\3776dfc\000\000\000\000\373" end_key:"t\200\000\000\000\000\t.A_i\200\000\000\000\000\000\000\001\001b3e0c6ad\377-56e3-4a\37717-93c3-\3777166207f\3776ffb\000\000\000\000\373" region_epoch:<conf_ver:14 version:253815 > peers:<id:1844814 store_id:336113 > peers:<id:1844815 store_id:411332 > peers:<id:1844816 store_id:486560 > , peer: id:1844814 store_id:336113 , addr: 192.168.3.62:20160, idx: 0, reqStoreType: TiKvOnly, runStoreType: tikv”]

| username: 等一分钟 | Original post link

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| username: 等一分钟 | Original post link

Is this state normal?

| username: 像风一样的男子 | Original post link

The number of connections keeps rising. Are there a lot of slow queries causing it to hang?

| username: Fly-bird | Original post link

Can it be connected using Navicat?

| username: 等一分钟 | Original post link

Unable to connect. It was found that the available disk space of TiKV is around 30GB. Is it possible that the disk space is insufficient?

| username: 裤衩儿飞上天 | Original post link

Check the monitoring: tikv-details → scheduler → scheduler writing bytes

| username: tidb菜鸟一只 | Original post link

It looks like it can’t be submitted.

| username: wzf0072 | Original post link

A large number of “long transactions” is abnormal.

| username: wzf0072 | Original post link

The default GC is 10 minutes. The transaction has been running for over 20 minutes. Check the TiKV and TiDB logs.

| username: 等一分钟 | Original post link

Restored, it was just a lack of disk space.

| username: ShawnYan | Original post link

How much space was allocated to the data disk?

| username: tidb菜鸟一只 | Original post link

Did you change reserve-space to 0?

| username: 等一分钟 | Original post link

Directly expanded the disk by 200G.

| username: TiDBer_oHSwKxOH | Original post link

It seems to be stuck. Expanding the capacity should solve the problem.