仅在事务完成后触发 post_save 信号 [英] Trigering post_save signal only after transaction has completed

问题描述

我已经编写了一些 API，它们各自的功能在事务块中执行.我在一个/几个模型/s的实例/s上调用save()方法(经过一些修改)，并在Elasticsearch中连续索引实例/s的一些JSON相关信息.我希望数据库回滚，即使出于某种原因，其中一个实例的 save() 或索引到 Elasticsearch 失败.

I have written some APIs, for which the respective functions executive inside a transaction block. I am calling the save() method (after some modifications) on instance/s of a/several Model/s, and also consecutively indexing some JSON related information of the instance/s in Elasticsearch. I want the database to rollback even if for some reason the save() for one of the instances or indexing to the Elasticsearch fails.

现在，问题出现了，即使在事务块内部，post_save() 信号也会被调用，这是一个问题，因为一些通知正在从这些信号中触发.

Now, the problem is arising that even inside the transaction block, the post_save() signals gets called, and that is an issue because some notifications are being triggered from those signals.

有没有办法在交易成功完成后触发 post_save() 信号?

Is there a way to trigger post_save() signals only after the transactions have completed successful?

推荐答案

并非如此.这些信号与 db 事务的成功或失败无关，而是与 save 方法本身有关 - 在调用之前你有 pre_save 信号被触发，在调用之后你有 post_save 信号被触发.

Not really. The signals have nothing to do with the db transaction success or failure, but with the save method itself - before the call you have the pre_save signal fired and after the call you have the post_save signal fired.

这里有两种方法:

• 您将检查 post_save 方法中的实例并决定模型是否成功保存；最简单的方法:在 save 方法中，在事务成功执行后，用一个标志注释你的实例，比如 instance.saved_successfully = True，你将在 post_save 处理程序中测试.
• 您将放弃 post_save 信号并为自己创建一个自定义信号，您将在交易成功运行后触发该信号.

• you are going to inspect the instance in the post_save method and decide that the model was saved successfully or not; simplest way to do that: in the save method, after the transaction executed successfully, annotate your instance with a flag, say instance.saved_successfully = True, which you will test in the post_save handler.
• you are going to ditch the post_save signal and create a custom signal for yourself, which you will trigger after the transaction ran successfully.

有意义吗?

附言

如果您确实需要绑定到事务提交信号，请查看此包:https://django-transaction-hooks.readthedocs.org/en/latest/;看起来该功能已集成在 Django 1.9a 中.

If you strictly need to bind to the transaction commit signal, have a look over this package: https://django-transaction-hooks.readthedocs.org/en/latest/; it looks like the functionality is integrated in Django 1.9a.

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