Question

现在我正在阅读关于http://docs.sequelizejs.com/manual/installation/getting-started.html

的文章

并且无法理解下面写的这句话。

如果您要从多个流程连接到数据库，那么您必须这样做每个进程创建一个实例，但每个实例都应该有一个 最大连接池大小＆＃34; 最大连接池大小除以实例数＆＃34;。所以，如果你想要一个最大连接池大小为90，并且您有3个工作进程，每个进程都有实例的最大连接池大小应为30。

pool: {
  max: 5,
  min: 0,
  idle: 10000
}

连接池的大小是多少？这意味着什么？

我现在正在理解像这样的连接池。如果＆＃34; max＆＃34;是5，3个用户想要到达DB， 3个连接分配给个人用户。

如果6个用户想要获取数据库， 5个连接都分配给个人用户，由于只有5个连接，第6个用户必须等待。

所以我无法理解

每个实例的最大连接池大小＆＃34; 最大连接池大小除以实例数＆＃34;。

有人可以解释一下吗？

Answer 1

这是一个非常广泛的问题，但这里有非常广泛的概述

每当我们连接到数据库服务器时，它实际上都会分配一个新进程来完成该请求。正如您所料，这很昂贵。因此，池允许我们在db服务器中保持活动的进程数。 max表示无论您的应用（节点）获得多少请求，它都不会使用数据库服务器打开新进程。

如果6个用户想要获取数据库，则5个连接都被分配给个人用户，因为只有5个连接，第6个用户必须等待。

在上述情况下，只有5个并行请求可以与db服务器（不是应用服务器）一起运行

这是good link to read

Answer 2

下面是一个示例，演示了from rest_framework.decorators import action @actions(detail=True) def comments(self, request, pk): # things to do here和pool.max选项的作用。

环境：

pool.idle
"sequelize": "^5.21.3"：node
v12.16.1：PostgreSQL

客户代码：

9.6：

db.ts

const sequelize = new Sequelize({ dialect: 'postgres', host: envVars.POSTGRES_HOST, username: envVars.POSTGRES_USER, password: envVars.POSTGRES_PASSWORD, database: envVars.POSTGRES_DB, port: Number.parseInt(envVars.POSTGRES_PORT, 10), define: { freezeTableName: true, timestamps: false, }, pool: { max: 5, min: 0, idle: 10 * 1000, }, }); export { sequelize };：

pool_test.ts

通过docker容器运行PostgreSQL服务器：

import { sequelize } from '../../db';

for (let i = 0; i < 100; i++) {
  sequelize.query('select pg_sleep(1);');
}

运行测试代码：

CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS              PORTS                    NAMES
3c9c0fd1bf53        postgres:9.6        "docker-entrypoint.s…"   5 months ago        Up 27 hours         0.0.0.0:5430->5432/tcp   node-sequelize-examples_pg_1

调试日志：

DEBUG=sequelize* npx ts-node ./pool_test.ts

输入docker容器，检查连接过程：

  sequelize:pool pool created with max/min: 5/0, no replication +0ms
  sequelize:connection:pg connection acquired +0ms
  sequelize:connection:pg connection acquired +38ms
  sequelize:connection:pg connection acquired +3ms
  sequelize:connection:pg connection acquired +0ms
  sequelize:connection:pg connection acquired +1ms
  sequelize:connection:pg connection acquired +1ms
  sequelize:pool connection acquired +97ms
  sequelize:sql:pg Executing (default): select pg_sleep(1); +0ms
Executing (default): select pg_sleep(1);
  sequelize:pool connection acquired +2ms
  sequelize:pool connection acquired +0ms
  sequelize:pool connection acquired +0ms
  sequelize:pool connection acquired +0ms
  sequelize:sql:pg Executing (default): select pg_sleep(1); +2ms
Executing (default): select pg_sleep(1);
  sequelize:sql:pg Executing (default): select pg_sleep(1); +2ms
Executing (default): select pg_sleep(1);
  sequelize:sql:pg Executing (default): select pg_sleep(1); +0ms
Executing (default): select pg_sleep(1);
  sequelize:sql:pg Executing (default): select pg_sleep(1); +0ms
Executing (default): select pg_sleep(1);
  sequelize:sql:pg Executed (default): select pg_sleep(1); +1s
  sequelize:pool connection released +1s
  sequelize:pool connection acquired +1ms
  sequelize:sql:pg Executed (default): select pg_sleep(1); +2ms
  sequelize:sql:pg Executed (default): select pg_sleep(1); +0ms
  sequelize:sql:pg Executed (default): select pg_sleep(1); +0ms
  sequelize:sql:pg Executed (default): select pg_sleep(1); +0ms
  sequelize:sql:pg Executing (default): select pg_sleep(1); +1ms
Executing (default): select pg_sleep(1);
  sequelize:pool connection released +1ms
  sequelize:pool connection released +0ms
  sequelize:pool connection released +0ms
  sequelize:pool connection released +0ms
  sequelize:pool connection acquired +1ms
  sequelize:pool connection acquired +0ms
  sequelize:pool connection acquired +0ms
  sequelize:pool connection acquired +0ms

如您所见，有 5（pool.max）个连接过程。

连接完成IDLE 10（pool.idle）秒后。连接过程将被破坏。

root@3c9c0fd1bf53:/# date '+%A %W %Y %X' && ps aux | grep "postgres: testuser"
Thursday 31 2020 09:51:34 AM
postgres 13615  0.0  0.7 289496 16064 ?        Ss   08:29   0:00 postgres: testuser node-sequelize-examples [local] idle
postgres 14335  0.0  0.5 288384 11248 ?        Ss   09:51   0:00 postgres: testuser node-sequelize-examples 172.18.0.1(45704) SELECT
postgres 14336  0.0  0.5 288384 11248 ?        Ss   09:51   0:00 postgres: testuser node-sequelize-examples 172.18.0.1(45706) SELECT
postgres 14337  0.0  0.5 288384 11252 ?        Ss   09:51   0:00 postgres: testuser node-sequelize-examples 172.18.0.1(45708) SELECT
postgres 14338  0.0  0.5 288384 11248 ?        Ss   09:51   0:00 postgres: testuser node-sequelize-examples 172.18.0.1(45710) SELECT
postgres 14339  0.0  0.5 288384 11248 ?        Ss   09:51   0:00 postgres: testuser node-sequelize-examples 172.18.0.1(45712) SELECT
postgres 86437  0.0  0.6 288804 13704 ?        Ss   00:57   0:00 postgres: testuser node-sequelize-examples [local] idle

客户端调试日志：

root@3c9c0fd1bf53:/# date '+%A %W %Y %X' && ps aux | grep "postgres: testuser"
Thursday 31 2020 09:53:48 AM
postgres 13615  0.0  0.7 289496 16064 ?        Ss   08:29   0:00 postgres: testuser node-sequelize-examples [local] idle
postgres 14352  0.0  0.5 288384 11248 ?        Ss   09:53   0:00 postgres: testuser node-sequelize-examples 172.18.0.1(45716) idle
postgres 14353  0.0  0.5 288384 11252 ?        Ss   09:53   0:00 postgres: testuser node-sequelize-examples 172.18.0.1(45718) idle
postgres 14354  0.0  0.5 288384 11248 ?        Ss   09:53   0:00 postgres: testuser node-sequelize-examples 172.18.0.1(45720) SELECT
postgres 14355  0.0  0.5 288384 11248 ?        Ss   09:53   0:00 postgres: testuser node-sequelize-examples 172.18.0.1(45722) idle
postgres 14356  0.0  0.5 288384 11248 ?        Ss   09:53   0:00 postgres: testuser node-sequelize-examples 172.18.0.1(45724) SELECT
root     14440  0.0  0.0  12784   972 pts/3    S+   09:53   0:00 grep postgres: testuser
postgres 86437  0.0  0.6 288804 13704 ?        Ss   00:57   0:00 postgres: testuser node-sequelize-examples [local] idle
root@3c9c0fd1bf53:/# date '+%A %W %Y %X' && ps aux | grep "postgres: testuser"
Thursday 31 2020 09:53:49 AM
postgres 13615  0.0  0.7 289496 16064 ?        Ss   08:29   0:00 postgres: testuser node-sequelize-examples [local] idle
postgres 14352  0.0  0.5 288384 11248 ?        Ss   09:53   0:00 postgres: testuser node-sequelize-examples 172.18.0.1(45716) idle
postgres 14353  0.0  0.5 288384 11252 ?        Ss   09:53   0:00 postgres: testuser node-sequelize-examples 172.18.0.1(45718) idle
postgres 14354  0.0  0.5 288384 11248 ?        Ss   09:53   0:00 postgres: testuser node-sequelize-examples 172.18.0.1(45720) idle
postgres 14355  0.0  0.5 288384 11248 ?        Ss   09:53   0:00 postgres: testuser node-sequelize-examples 172.18.0.1(45722) idle
postgres 14356  0.0  0.5 288384 11248 ?        Ss   09:53   0:00 postgres: testuser node-sequelize-examples 172.18.0.1(45724) idle
postgres 86437  0.0  0.6 288804 13704 ?        Ss   00:57   0:00 postgres: testuser node-sequelize-examples [local] idle
root@3c9c0fd1bf53:/# date '+%A %W %Y %X' && ps aux | grep "postgres: testuser"
Thursday 31 2020 09:53:55 AM
postgres 13615  0.0  0.7 289496 16064 ?        Ss   08:29   0:00 postgres: testuser node-sequelize-examples [local] idle
postgres 14352  0.0  0.5 288384 11248 ?        Ss   09:53   0:00 postgres: testuser node-sequelize-examples 172.18.0.1(45716) idle
postgres 14353  0.0  0.5 288384 11252 ?        Ss   09:53   0:00 postgres: testuser node-sequelize-examples 172.18.0.1(45718) idle
postgres 14354  0.0  0.5 288384 11248 ?        Ss   09:53   0:00 postgres: testuser node-sequelize-examples 172.18.0.1(45720) idle
postgres 14355  0.0  0.5 288384 11248 ?        Ss   09:53   0:00 postgres: testuser node-sequelize-examples 172.18.0.1(45722) idle
postgres 14356  0.0  0.5 288384 11248 ?        Ss   09:53   0:00 postgres: testuser node-sequelize-examples 172.18.0.1(45724) idle
root     14446  0.0  0.0  12784   932 pts/3    S+   09:53   0:00 grep postgres: testuser
postgres 86437  0.0  0.6 288804 13704 ?        Ss   00:57   0:00 postgres: testuser node-sequelize-examples [local] idle
root@3c9c0fd1bf53:/# date '+%A %W %Y %X' && ps aux | grep "postgres: testuser"
Thursday 31 2020 09:53:58 AM
postgres 13615  0.0  0.7 289496 16064 ?        Ss   08:29   0:00 postgres: testuser node-sequelize-examples [local] idle
root     14449  0.0  0.0  12784   940 pts/3    S+   09:53   0:00 grep postgres: testuser
postgres 86437  0.0  0.6 288804 13704 ?        Ss   00:57   0:00 postgres: testuser node-sequelize-examples [local] idle

如果将... sequelize:pool connection released +25ms sequelize:pool connection destroy +10s sequelize:pool connection destroy +0ms sequelize:pool connection destroy +0ms sequelize:pool connection destroy +0ms sequelize:pool connection destroy +1ms更改为pool.max，请检查连接过程的数量：

sequelize - 连接池大小

2 个答案: