如何在Postgresql的pg_stat_activity中找到ClientRead wait_event的原因?

3

我有一个接收大量数据的端点。它将数据插入名为ingress的表中。我还编写了几个解析器,循环遍历ingress表中的消息并将其解析到其他各种表中。

我们的Postgres集群最近一直存在着性能问题,我无法找到原因。所以我首先开始查看pg_stat_activity表,以查看哪些查询需要花费很长时间。在那里,我找到了这个:

postgres=> select pid, query_start, age(clock_timestamp(), query_start) as age, state, wait_event_type, wait_event, LEFT(query, 40) 
from pg_stat_activity where state like '%idle%' and datname = 'mydatabase' 
order by query_start asc limit 5;

 pid  |          query_start          |       age       | state | wait_event_type | wait_event |                   left                   
------+-------------------------------+-----------------+-------+-----------------+------------+------------------------------------------
 9429 | 2021-08-04 12:20:55.790618+02 | 00:05:29.874102 | idle  | Client          | ClientRead | INSERT INTO "ingress_message" ("created_
 9551 | 2021-08-04 12:21:42.384146+02 | 00:04:43.280586 | idle  | Client          | ClientRead | INSERT INTO "ingress_message" ("created_
 9776 | 2021-08-04 12:23:37.849208+02 | 00:02:47.815526 | idle  | Client          | ClientRead | select 1
 9922 | 2021-08-04 12:25:02.207894+02 | 00:01:23.456841 | idle  | Client          | ClientRead | INSERT INTO "ingress_message" ("created_
 9891 | 2021-08-04 12:25:02.378745+02 | 00:01:23.285992 | idle  | Client          | ClientRead | INSERT INTO "ingress_message" ("created_
(5 rows)

您可以看到,最长运行的查询已经运行了5分钟以上(!!),并且由“ClientRead”引起。这对我来说似乎很奇怪。为什么读取会阻止写入?或者这是否意味着某个进程正在锁定整个表格进行读取?

我检查了pg_locks表,它向我展示了下面的结果。我一直在研究pg_locks,但我无法真正理解这些信息告诉我的内容。

我主要想知道的是:我能否找出哪个查询导致了ClientRead锁定,从而导致插入操作如此缓慢?

postgres=> select * from pg_locks;

   locktype    | database | relation | page | tuple | virtualxid | transactionid | classid | objid | objsubid | virtualtransaction |  pid  |       mode       | granted | fas
tpath 
---------------+----------+----------+------+-------+------------+---------------+---------+-------+----------+--------------------+-------+------------------+---------+----
------
 relation      |    82586 |    11645 |      |       |            |               |         |       |          | 93/129             |  3764 | AccessShareLock  | t       | t
 virtualxid    |          |          |      |       | 93/129     |               |         |       |          | 93/129             |  3764 | ExclusiveLock    | t       | t
 relation      |    82586 | 22442205 |      |       |            |               |         |       |          | 42/6323            |  3141 | RowExclusiveLock | t       | t
 relation      |    82586 |  9898413 |      |       |            |               |         |       |          | 42/6323            |  3141 | RowExclusiveLock | t       | t
 relation      |    82586 |  9898449 |      |       |            |               |         |       |          | 42/6323            |  3141 | RowExclusiveLock | t       | t
 relation      |    82586 | 12134578 |      |       |            |               |         |       |          | 42/6323            |  3141 | AccessShareLock  | t       | t
 relation      |    82586 | 12134578 |      |       |            |               |         |       |          | 42/6323            |  3141 | RowExclusiveLock | t       | t
 relation      |    82586 | 12103296 |      |       |            |               |         |       |          | 42/6323            |  3141 | AccessShareLock  | t       | t
 relation      |    82586 | 12103296 |      |       |            |               |         |       |          | 42/6323            |  3141 | RowExclusiveLock | t       | t
 relation      |    82586 | 12103295 |      |       |            |               |         |       |          | 42/6323            |  3141 | AccessShareLock  | t       | t
 relation      |    82586 | 12103295 |      |       |            |               |         |       |          | 42/6323            |  3141 | RowExclusiveLock | t       | t
 relation      |    82586 | 12102372 |      |       |            |               |         |       |          | 42/6323            |  3141 | AccessShareLock  | t       | t
 relation      |    82586 | 12102372 |      |       |            |               |         |       |          | 42/6323            |  3141 | RowExclusiveLock | t       | t
 relation      |    82586 | 12102338 |      |       |            |               |         |       |          | 42/6323            |  3141 | AccessShareLock  | t       | t
 relation      |    82586 | 12102338 |      |       |            |               |         |       |          | 42/6323            |  3141 | RowExclusiveLock | t       | t
 relation      |    82586 | 12102331 |      |       |            |               |         |       |          | 42/6323            |  3141 | AccessShareLock  | t       | t
 relation      |    82586 | 12102331 |      |       |            |               |         |       |          | 42/6323            |  3141 | RowShareLock     | t       | t
 relation      |    82586 | 12102331 |      |       |            |               |         |       |          | 42/6323            |  3141 | RowExclusiveLock | t       | t
 virtualxid    |          |          |      |       | 42/6323    |               |         |       |          | 42/6323            |  3141 | ExclusiveLock    | t       | t
 relation      |    19825 | 12429831 |      |       |            |               |         |       |          | 31/7218            |  3128 | AccessShareLock  | t       | t
 relation      |    19825 | 12429819 |      |       |            |               |         |       |          | 31/7218            |  3128 | AccessShareLock  | t       | t
 relation      |    19825 | 12429818 |      |       |            |               |         |       |          | 31/7218            |  3128 | AccessShareLock  | t       | t
 relation      |    19825 | 12429770 |      |       |            |               |         |       |          | 31/7218            |  3128 | AccessShareLock  | t       | t
 relation      |    19825 | 12429751 |      |       |            |               |         |       |          | 31/7218            |  3128 | AccessShareLock  | t       | t
 relation      |    19825 | 12429744 |      |       |            |               |         |       |          | 31/7218            |  3128 | AccessShareLock  | t       | t
 virtualxid    |          |          |      |       | 31/7218    |               |         |       |          | 31/7218            |  3128 | ExclusiveLock    | t       | t
 relation      |    19825 | 12429831 |      |       |            |               |         |       |          | 30/6218            |  3127 | AccessShareLock  | t       | t
 relation      |    19825 | 12429819 |      |       |            |               |         |       |          | 30/6218            |  3127 | AccessShareLock  | t       | t
 relation      |    19825 | 12429818 |      |       |            |               |         |       |          | 30/6218            |  3127 | AccessShareLock  | t       | t
 relation      |    19825 | 12429770 |      |       |            |               |         |       |          | 30/6218            |  3127 | AccessShareLock  | t       | t
 relation      |    19825 | 12429751 |      |       |            |               |         |       |          | 30/6218            |  3127 | AccessShareLock  | t       | t
 relation      |    19825 | 12429744 |      |       |            |               |         |       |          | 30/6218            |  3127 | AccessShareLock  | t       | t
 virtualxid    |          |          |      |       | 30/6218    |               |         |       |          | 30/6218            |  3127 | ExclusiveLock    | t       | t
 relation      |    19825 | 12429831 |      |       |            |               |         |       |          | 29/5284            |  3126 | AccessShareLock  | t       | t
 relation      |    19825 | 12429819 |      |       |            |               |         |       |          | 29/5284            |  3126 | AccessShareLock  | t       | t
 relation      |    19825 | 12429818 |      |       |            |               |         |       |          | 29/5284            |  3126 | AccessShareLock  | t       | t
 relation      |    19825 | 12429770 |      |       |            |               |         |       |          | 29/5284            |  3126 | AccessShareLock  | t       | t
 relation      |    19825 | 12429751 |      |       |            |               |         |       |          | 29/5284            |  3126 | AccessShareLock  | t       | t
 relation      |    19825 | 12429744 |      |       |            |               |         |       |          | 29/5284            |  3126 | AccessShareLock  | t       | t
 virtualxid    |          |          |      |       | 29/5284    |               |         |       |          | 29/5284            |  3126 | ExclusiveLock    | t       | t
 relation      |    19825 | 12429831 |      |       |            |               |         |       |          | 28/5964            |  3123 | AccessShareLock  | t       | t
 relation      |    19825 | 12429819 |      |       |            |               |         |       |          | 28/5964            |  3123 | AccessShareLock  | t       | t
 relation      |    19825 | 12429818 |      |       |            |               |         |       |          | 28/5964            |  3123 | AccessShareLock  | t       | t
 relation      |    19825 | 12429770 |      |       |            |               |         |       |          | 28/5964            |  3123 | AccessShareLock  | t       | t
 relation      |    19825 | 12429751 |      |       |            |               |         |       |          | 28/5964            |  3123 | AccessShareLock  | t       | t
 relation      |    19825 | 12429744 |      |       |            |               |         |       |          | 28/5964            |  3123 | AccessShareLock  | t       | t
 virtualxid    |          |          |      |       | 28/5964    |               |         |       |          | 28/5964            |  3123 | ExclusiveLock    | t       | t
 relation      |    29251 |    31001 |      |       |            |               |         |       |          | 71/415             | 10820 | AccessShareLock  | t       | t
 relation      |    29251 |    30988 |      |       |            |               |         |       |          | 71/415             | 10820 | AccessShareLock  | t       | t
 relation      |    29251 |    30981 |      |       |            |               |         |       |          | 71/415             | 10820 | AccessShareLock  | t       | t
 virtualxid    |          |          |      |       | 71/415     |               |         |       |          | 71/415             | 10820 | ExclusiveLock    | t       | t
 relation      |    29251 |    30981 |      |       |            |               |         |       |          | 72/645             | 10821 | AccessShareLock  | t       | t
 virtualxid    |          |          |      |       | 72/645     |               |         |       |          | 72/645             | 10821 | ExclusiveLock    | t       | t
 transactionid |          |          |      |       |            |    1762434479 |         |       |          | 42/6323            |  3141 | ExclusiveLock    | t       | f
(54 rows)

3个回答

2
我认为您没有锁定或服务器端的问题。根据文档

ClientRead:等待从客户端读取数据。

看起来,服务器正在等待客户端提供INSERT查询的数据。也许是网络问题?

1
对我来说,这行代码似乎意味着另一个客户端已经获得了写锁,并且此查询正在等待其他客户端。此外,所有的数据已经在机器上;它就在查询中(我只在第一个查询的结果中显示了前40个字符)。所以这似乎不是情况。 - kramer65
@kramer65,你可以打开log_lock_waits,这样你就可以确定问题是否来自锁。 - Steeeve

1

这些是空闲连接。 插入操作已完成。 您看到的时间是连接空闲的时间。 如果状态为“active”,则表示查询正在运行,如果存在等待事件,则在这种情况下您正在等待。(如果没有等待事件并且您处于活动状态,则可以在CPU上运行)

Kyle


0
在浏览器中使用的可能原因之一是客户端读取(ClientRead)持久化上下文内存已满,垃圾回收器开始处理自身,因此无法从数据库中获取结果。尝试刷新。请查看这篇文章:点击此处阅读文章

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