NodeJS - MongoDB 触发器 [英] NodeJS - MongoDB triggers

问题描述

我正在尝试使用 DerbyJS、Racer 和 MongoDB 开发日志查看器.日志会由不同的源不断插入到 MongoDB 数据库中，我的日志查看器应该能够自动更新用户界面上的日志表.

I'm trying to develop a Log Viewer using DerbyJS, Racer and MongoDB. The logs will be inserted into the MongoDB database by a different source continuously, and my Log Viewer should be able to update the Logs Table on the user interface automatically.

我想知道是否有一种本地方式来监听 MongoDB 事件，例如:

I was wondering if there is a native way of listening to MongoDB events, like:

 - On update
 - On delete

这些类似于 Oracle DB 触发器.

These would be similar to, for example, Oracle DB triggers.

推荐答案

您可以使用特殊集合监听 mongodb 中的 insert、update 等事件以及其他数据事件名为oplog.您只需要使用 mongod --master 或 mongod --replicaSet 在您的数据库实例上启用复制.

You can listen to events like insert, update, and other data events in mongodb using special collection named oplog. You just need to enable replication on your db instance either using mongod --master or mongod --replicaSet.

Oplog 实际上是一个被 mongodb 内部用来实现复制的有上限的集合.如果您使用主/从复制，您将找到名为 oplog.$main 的集合，如果您使用副本集，它将被命名为 oplog.rs.

Oplog is actually a capped collection which is used by mongodb internally to implement replication. If you are using master/slave replication you will find the collection by the name of oplog.$main, if you are using replica sets it will be named oplog.rs.

您可以在 oplog 上使用可尾光标，应该可以.

You can use a tailable cursor on oplog, that should work.

Oplog 实际上就是日志本身.因此，您可能不需要为了记录目的而单独存储它们.但是它的大小是固定的.这意味着当其完整的旧数据被删除时.

Oplog, in effect, is logs itself. So you might not need to store them separately for logging purpose. However its size is fixed. Meaning when its full, older data gets deleted.

这是 mongoskin wiki 页面

skin = require "mongoskin"
db = skin.db "localhost:27017/local"

#//Cursor on oplog (a capped collection) which maintains a history for replication
#//oplog can be used only when replication is enabled
#//Use oplog.rs instead of oplog.$main if you are using replica set

oplog = db.collection "oplog.$main"
cursor = oplog.find({'ns': "icanvc.projects"},{tailable: yes, awaitData: yes})

#//Using cursor.nextObject will be slow
cursor.each (err, log)->
    console.error err if err
    console.log log if not err

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