Fix: MongoDB Won't Start After Wekan Snap Update

Nov 10, 2025 by SLV Team 49 views

MongoDB Won't Start After Wekan Snap Update: A Troubleshooting Guide

Hey guys! Ever run into that super annoying issue where MongoDB just refuses to start after a Wekan snap update? You're not alone! It's a head-scratcher that can leave your server throwing 502 errors and your users staring at a blank screen. But don't panic, we're going to dive deep into this, figure out what's going on, and most importantly, how to fix it. Let's get started!

Understanding the Problem: Lock Files and MongoDB

The core issue here revolves around MongoDB's lock files. Think of these files as little notes MongoDB leaves behind, saying, "Hey, I'm running! Don't touch my data!" These lock files, specifically mongod.lock and WiredTiger.lock, are crucial for preventing data corruption when multiple instances of MongoDB try to access the same data files simultaneously.

Ideally, when MongoDB shuts down cleanly, it removes these lock files. However, sometimes things don't go as planned. Maybe the server crashed, or the shutdown process was interrupted. In these cases, the lock files can be left behind, creating a false alarm the next time MongoDB tries to start. It sees the lock files, thinks an instance is already running, and refuses to launch, leading to those dreaded 502 errors that make your Wekan board inaccessible. Understanding this mechanism is the first step to resolving the problem efficiently.

Diving Deeper into the Scenario

Let's break down the scenario step-by-step, just like the original poster described:

Clean Shutdown: MongoDB actually shut down properly. That's the good news! You can even see in the logs that it exited cleanly. This means the initial shutdown process wasn't the culprit.
Leftover Lock Files: But here's the kicker – even though it shut down cleanly, MongoDB left behind those pesky mongod.lock and WiredTiger.lock files. These files are the equivalent of leaving the keys in the ignition after you park your car, creating a potential problem for the next driver.
False Alarm: Now, when the system tries to restart MongoDB, it encounters these lock files and throws up its hands, saying, "Nope, already running!" But the truth is, MongoDB is NOT actually running. It's a classic case of mistaken identity.
Wekan Woes: As a result, Wekan can't connect to the database, and your users are greeted with 502 errors. This is where things get disruptive, as the service remains broken until someone manually steps in to fix it.

This situation highlights a critical flaw in the process: the snap service isn't effectively cleaning up these lock files or intelligently recognizing when they're remnants from a previous, terminated session. This is the root cause we need to address.

The Temporary Fix: Manual Lock File Deletion

Okay, so your Wekan is down, and you're seeing those 502 errors. What's the quickest way to get things back up and running? The temporary fix, as the original poster discovered, involves manually deleting those lock files. It's like clearing the traffic jam yourself so everyone can get moving again.

Step-by-Step Guide to Manual Deletion

Here's what you need to do:

Access Your Server: Log in to your server via SSH or however you typically access the command line.
Navigate to the Directory: Change the directory to where the lock files are located. In this case, it's /var/snap/wekan/common/.
Delete the Lock Files: Use the rm command to delete the mongod.lock and WiredTiger.lock files. The commands look like this:
```
sudo rm /var/snap/wekan/common/mongod.lock
sudo rm /var/snap/wekan/common/WiredTiger.lock
```
Important: You might need to use sudo to get the necessary permissions to delete these files. Be careful when using sudo, as it gives you elevated privileges.
Restart MongoDB: Now, restart the MongoDB service. You can usually do this with a command like:
```
sudo snap restart wekan
```
This command restarts the Wekan snap, which should also restart MongoDB.
Verify: Check if Wekan is working again. Refresh your browser, and hopefully, you'll see your Wekan board back in action.

Why This Works (and Why It's Not Ideal)

Deleting the lock files essentially tells MongoDB, "Hey, it's okay, you're not running. Go ahead and start!" This allows MongoDB to start a fresh instance and Wekan to connect to it. However, this is a temporary fix. It's like putting a band-aid on a bigger wound. It addresses the immediate symptom (MongoDB not starting) but doesn't fix the underlying problem (the snap service not cleaning up lock files).

Manually deleting files is also prone to human error. Imagine accidentally deleting the wrong file! Plus, it's not a sustainable solution. You don't want to be on call 24/7 to delete lock files every time there's a Wekan update or a server hiccup. We need a more robust, automated solution.

The Real Problem: Snap Service and Lock File Management

Let's zoom out and look at the bigger picture. The real problem isn't just that lock files are being left behind; it's that the snap service isn't handling MongoDB's shutdown and startup gracefully. The snap service, which manages the installation and updates of Wekan, should be responsible for ensuring that MongoDB starts and stops cleanly, including cleaning up those lock files.

What Should Happen?

Ideally, here's how the process should work:

MongoDB Shutdown: When MongoDB is shut down (either intentionally or due to a system event), the snap service should ensure that the lock files are removed as part of the shutdown process.
Startup Check: Before starting MongoDB, the snap service should check for the existence of lock files. If they exist, it should intelligently determine if they are remnants from a previous session (e.g., by checking the MongoDB process status) or if an actual MongoDB instance is running.
Cleanup or Start: If the lock files are orphaned, the snap service should automatically delete them before starting MongoDB. If an instance is indeed running, it should gracefully handle the situation without causing conflicts.

Why This Isn't Happening

The fact that we're seeing this issue suggests there's a bug or a missing feature in how the Wekan snap handles MongoDB's lifecycle. It's possible that:

The shutdown script isn't correctly removing the lock files.
The startup script isn't checking for orphaned lock files.
There's a race condition where the lock files are sometimes removed and sometimes not.

Whatever the reason, it's clear that the snap service needs to be smarter about managing MongoDB's lock files.

Potential Solutions and Next Steps

So, what can we do about this? Here are a few potential solutions and next steps:

1. Report the Bug

The most important thing is to report this issue to the Wekan and snapcraft communities. This helps the developers become aware of the problem and prioritize a fix. When reporting, be sure to include:

Your Wekan version
Your snap version
Your operating system
A detailed description of the problem, including the steps you took and the error messages you encountered.

2. Explore Snap Configuration Options

Snap packages often have configuration options that can be tweaked. It's worth exploring the Wekan snap documentation and configuration settings to see if there are any options related to MongoDB management or lock file handling. Maybe there's a setting you can adjust to improve the situation.

3. Create a Custom Script (Use with Caution)

For the more technically inclined, you could potentially create a custom script that runs before MongoDB starts, checks for orphaned lock files, and deletes them if necessary. This script could be integrated into the snap service or run as a separate systemd service. However, this is an advanced solution and should be approached with caution, as it could introduce new problems if not implemented correctly.

4. Consider Alternative Installation Methods

If this issue is causing significant disruption, you might consider alternative ways to install Wekan, such as using Docker or installing it directly on your operating system. These methods might give you more control over MongoDB's configuration and lifecycle.

5. Monitor and Automate (The Ideal Solution)

Ideally, this issue should be resolved within the Wekan snap itself. The long-term solution involves the snap service intelligently managing MongoDB's lock files. This might involve:

Modifying the snap's shutdown script to ensure lock files are removed.
Adding a pre-start check for orphaned lock files.
Implementing a more robust error-handling mechanism for MongoDB startup.

This is the most sustainable solution, as it automates the process and prevents the need for manual intervention.

Conclusion: Fixing MongoDB Startup Issues After Wekan Snap Updates

Dealing with MongoDB failing to start after a Wekan snap update can be frustrating, but understanding the root cause – those pesky lock files – is key to finding a solution. While manually deleting the lock files provides a quick fix, it's crucial to address the underlying problem with the snap service's handling of MongoDB's lifecycle.

By reporting the bug, exploring configuration options, and advocating for a proper fix within the Wekan snap, we can ensure a smoother experience for everyone. In the meantime, keep those temporary fixes handy, and remember, you're not alone in this! Let's work together to make Wekan and MongoDB play nicely.

Have you encountered this issue? What solutions have you tried? Share your experiences and tips in the comments below! Let's learn from each other and get those Wekan boards back online.