MassTransit - Stop handling erroneous messages

By default when a MassTransit consumer fails to handle a message (and throws an exception), the message is moved to an _error queue (prefixed by the receive endpoint queue name). This is OK for transient exceptions but probably not what you want when you have a bug in your system or there is another reason why none of the messages can be handled succesfully.

In that case, another feature of MassTransit becomes handy; the kill switch.

A Kill Switch is used to prevent failing consumers from moving all the messages from the input queue to the error queue. By monitoring message consumption and tracking message successes and failures, a Kill Switch stops the receive endpoint when a trip threshold has been reached.

You can configure a kill switch for a specific endpoint or for all receiver endpoints on the bus.

Here is a short example on how to configure the kill switch for all receiver endpoints:

In the above example, the kill switch will activate after 10 messages have been consumed. If the ratio of failures/attempts exceeds 15%, the kill switch with trip and stop the receive endpoint. After 1 minute, the receive endpoint will be restarted. Once restarted, if exceptions are still observed, the receive endpoint will be stopped again for 1 minute.

If you want to learn more about this feature, check out this video by Chris Patterson, the creator of Masstransit:

Podman– Command execution failed with exit code 125

After updating WSL on one of the developer machines, Podman failed to work. When we took a look through Podman Desktop, we noticed that Podman had stopped running and returned the following error message: Error: Command execution failed with exit code 125 Here are the steps we tried to fix the issue: We started by running podman info to get some extra details on what could be wrong: >podman info OS: windows/amd64 provider: wsl version: 5.3.1 Cannot connect to Podman. Please verify your connection to the Linux system using `podman system connection list`, or try `podman machine init` and `podman machine start` to manage a new Linux VM Error: unable to connect to Podman socket: failed to connect: dial tcp 127.0.0.1:2655: connectex: No connection could be made because the target machine actively refused it. That makes sense as the podman VM was not running. Let’s check the VM: >podman machine list NAME ...

Azure DevOps/ GitHub emoji

I’m really bad at remembering emoji’s. So here is cheat sheet with all emoji’s that can be used in tools that support the github emoji markdown markup: All credits go to rcaviers who created this list.

Cache stampede: when our cache turned against us

While investigating some performance issues, we ran into an ASP.NET Core API that cached a fairly expensive aggregation query for 60 seconds. Under normal load, that was fine: one request rebuilds the cache, everyone else reads from it. Under peak load, dozens of requests would arrive in that same expiry window, all see a cache miss, and all fire the same expensive query in parallel. The database didn't like that. That was the moment when our caching layer stopped helping and started hurting. A burst of requests comes in at the same time, all miss the cache, and all go hammer the database or the downstream API at once. That's a cache stampede . The cache was supposed to protect our backend, and for a few hundred milliseconds it did the opposite. Why this happens IMemoryCache.GetOrCreate (and its async sibling) looks like it protects you, but it doesn't add any locking on its own. Look at the naive version: public async Task<Report> GetReportAsync(string key) ...

The art of simplicity

Search This Blog