Mongock how to configure writeConcern (w: 1)

[hhvitek]

Please tell me how to configure writeConcern as anything other than MAJORITY, but not completely rewrite Mongock configuration logic to use Java builder(s) manually. And also to manually create Runner and Driver Beans. Which i think works but still. It is not ideal.

We have spring boot application 2.7.18 with Mongock 4 to perform migrations. We use spring boot autoconfiguration witn annotation @EnableMongock and application.yml properties to configure mongock. We dont use transactions.

We have requirement for a single replSet clustered environment to change writeConcern for mongock. Default majority is not enough for our purposes. I found out i am simply not able to configure integer value.

From official documentation:

• anything other than majority simply fails on similar exception (neither w: 1 nor w: "1" instead of w: majority in yml works):

Caused by: com.mongodb.MongoWriteConcernException: No write concern mode named '1' found in replica set configuration

I tried this with spring boot 3 and mongock 5 and issue is still the same

I did a littbe bit dig in and i think issue might be with MongoDbConfiguration implementation and usage of new WriteConcern(String) constructor instead of new WriteConcern(int) in those cases when i want W1...

I have written simple spring boot application demonstrating the issue

https://github.com/hhvitek/mongock-writeConcern-showCase

[dieppa]

Hello @hhvitek,

I believe this is likely an easy bug to fix, and I encourage you to submit a PR. If you're unable to do so, we can take care of it, though I can't guarantee when it will be completed.

That said, I'm curious about your reasoning for using a less durable configuration than majority + journal: true. Keep in mind that lowering consistency in Mongock can cause your application to reapply the same change, which—although I don’t know the specific details of your use case—could be highly undesirable.

In the meantime, if raising a PR isn’t an option and you need an immediate solution, I recommend using the builder to explicitly enforce the desired MongoDB configuration.

[hhvitek]

Hey @dieppa,

Cluster with 4 data nodes and 1 arbiter. When 2 data nodes are intentionally taken down, I run into a major issue with majority writeConcern. Specifically, I get SocketTimeoutException, and the app simply won’t work or even start.

Reconfiguring MongoTemplate with W1 or W2 didn’t fully resolve the issue. I discovered that Mongock itself has a writeConcern configuration, likely used internally when managing changelog lock and history tables.

Since this scenario is a valid application use case, I need to ensure the app functions properly under these conditions. 🙂

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I tried builder approach and it works.

I will still give the PR a shoot

[dieppa]

Alright, let us know if you run into any issues with the builder.
When you submit a PR, I'd be happy to review it 👍🏼

[osantana85]

Hello @hhvitek , we have just released Mongock v5.5.1 including your fix. Thanks for using and collaborate with Mongock Community.