在node.js中关闭Postgres（pg）客户端连接 [英] Closing postgres (pg) client connection in node.js

问题描述

我有一个要在节点中按计划运行的脚本。该脚本没有终止并退出。我怀疑这是因为我的数据库客户端仍处于打开状态。

I have a script that I want to run on a scheduled basis in node. The script is not terminating and exiting. I suspect that this is because my database client is still open.

var client = new pg.Client(conString);
client.connect();

function registerBundle (innerHash, outterHash) {
    // some stuff here
}

var query = client.query("SELECT id, chain FROM mytable where \
    state_ready = true and transaction_id='' ");

query.on('row', function(row) {
    var chain = row['chain'];
    var pg_record = row['id'];
    console.log(pg_record);
    var innerHash = "something";
    var outerHash = "something else";
    var registrar = registerBundle(innerHash, outerHash);

    var update = client.query('UPDATE mytable SET transaction_id = $1::text \
    where id=$2::int', [transactionHash, pg_record]);
    console.log(chain);
});

如果我添加以下内容，则客户端连接会在更新有时间触发之前关闭。

if I include the following, the client connection closes before the updates have a time to fire.

query.on('end', function() {
    client.end();
});

我无法使用setTimeout或任何其他此类机制，因为我不知道等待多长时间registerBundle函数完成。我也认为query.on（'end'会在更新完成时触发。不确定如何测试。

I cannot use setTimeout or any other such mechanism because I don't know how long to wait for the registerBundle function to complete. Also I think query.on('end' will fire when the update is completed. Not sure how to test this.

我的问题是，我需要按顺序触发

My question, I need things to fire in order.

• 查询数据库


• 处理每一行（query.on


• 使用registerBundle返回的值更新每一行


• 在处理完所有行后关闭数据库客户端/连接。


• 终止脚本并退出node

• Query DB
• Process each row (query.on
• Update each row with value returned from registerBundle
• Close db client/connection when all rows have been processed.
• Terminate script and exit node

似乎从python / php世界中非常简单，但是在我的JavaScript世界中却分崩离析。

Seems pretty straightforward from a python/php world but falls apart in my javascript world.

推荐答案

基于承诺的界面，例如 pg-promise 是必经之路：

A promise-based interface like pg-promise is the way to go:

var bluebird = require('bluebird');
var pgp = require('pg-promise')({
    promiseLib: bluebird
});
var db = pgp(/*connection details*/);

db.tx(t => {
    // BEGIN executed
    return t.map('SELECT id, chain FROM mytable where state_ready = $1 and transaction_id = $2', [true, 123], a => {
        var chain = data.chain;
        var pg_record = data.id;
        return t.none('UPDATE mytable SET transaction_id = $1::text where id=$2::int', [transactionHash, pg_record]);
    }).then(t.batch); // settling all internal queries
})
    .then(data => {
        // success, COMMIT executed
    })
    .catch(error => {
        // error, ROLLBACK executed
    })
    .finally(pgp.end); // shuts down the connection pool

上面的示例完全符合您的要求，并且使用了交易。但实际上，出于性能原因，您将想要在一个查询中完成所有操作；）

The example above does exactly what you asked for, plus it uses a transaction. But in reality you're gonna want to do it all in one query, for performance reasons ;)

请参见更多示例。

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