nodejs pg-pool 似乎沒有池化

Question

我一直試圖讓 nodejs 在我的應用程序中匯集 postgresql 連接，但未成功。 這是我做的一個獨立測試：

const config = require('../config/project_config.json');
const Pool = require('pg-pool');

var pool = new Pool({
    user: config.DB_USER,
    host: config.DB_HOST,
    database: config.DB_DB,
    password: config.DB_PW,
    port: 5432,
    max: 500,
    min: 200,
    idleTimeoutMillis: 0,
    connectionTimeoutMillis: 10000
});

for (var i=0; i<100; i++){
    pool.query(
        "SELECT id, email FROM players WHERE email ~ 'ltUser'",
        [],
        (err, res) => {
            if (err !== null && err != undefined){
                console.log(`err: ${err}`);
            }
            else{
                console.log(`num rows: ${res.rows.length}`);
            }
        });
}

我得到的結果是：

num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
err: Error: Connection terminated due to connection timeout
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400
num rows: 400

如您所見，它引發了連接超時，這意味着在我創建池時它沒有創建連接。 在創建池時，我嘗試了各種參數組合，包括使用keepalive: true ，但似乎都沒有使 pg-pool 真正成為池連接。 我也嘗試過 pg 而不是 pg-pool。 但是得到了完全相同的結果，盡管我后來發現它基本上是相同的代碼。

如果我使用運行時間較長的查詢運行它，我可以連接到 psql 中的數據庫並運行

SELECT datname,usename, ssl, client_addr, count(*
FROM pg_stat_ssl
  JOIN pg_stat_activity
    ON pg_stat_ssl.pid = pg_stat_activity.pid
where usename != 'azure_superuser'
group by datname,usename, ssl, client_addr;

並觀察我的 IP 地址 go 的連接數，然后再向下。

我做錯了什么還是 pg-pool 壞了？

我在 ubuntu xenial 服務器上使用 nodejs v10.22.1。

Answer 1

事實證明，pg-pool 正在工作，只是沒有按照我在 Java 和 Erlang 等其他編程語言方面的經驗所期望的方式。 Nodejs 不會提前創建連接，而是在從池中簽出連接時。

基於此，Nodejs 中池化的主要優點是程序員不必處理打開和關閉連接，並且可以重用連接。

Answer 2

如果你想打開一定數量的后端連接，比如說 200（這個數字太大了，你可能想要大約 64）

然后你可以通過創建池來做到這一點，然后立即發出 200 個查詢，而不釋放客戶端

然后釋放所有 200 個客戶端。

從那時起，如果idleTimeoutMillis === 0 ，池將永遠保持 200 個與數據庫的打開連接，您可以將其用作初始化池

var pool = new Pool({
    user: config.DB_USER,
    host: config.DB_HOST,
    database: config.DB_DB,
    password: config.DB_PW,
    port: 5432,
    max: 200,   // set max to 200 connections to the db
    //min: 200, // min is not a configuration option
    idleTimeoutMillis: 0,
    connectionTimeoutMillis: 10000
});

// create a list to hold all the "done" functions 
//   that release clients
let releaseClientDoneList = [];

// open 200 clients, without releasing them
for (var i=0; i<200; i++){
  // callback - checkout a client
  pool.connect((err, client, done) => {
      // asyncronously store the "done" function once the client 
      //   has connected to the db
      connectedNewClient(done);
    }
  )
}

let connectedNewClient = function (doneFunction) {
  // store the "done" function in the list
  releaseClientDoneList.push(doneFunction)

  // if the list has 200 "done" functions inside, 
  //   then we know we have initialised all the clients we want
  if (releaseClientDoneList.length >= 200) {
    
    // call all the "done" functions to release all the clients
    for (let doneFunctionReleasesClient of releaseClientDoneList) {
      doneFunctionReleasesClient();
    }

    // now we know there are 200 available, 
    //   initialised db connections in the pool
    databasePoolInitialised();
  }
}

let databasePoolInitialised = function () {
  // ... rest of your application code goes here
}