Should the emulator be using 100%+ of CPU when idle? about azure-cosmos-db-emulator-docker

[milismsft]

@tillig thanks for sharing :-)

[RichMercer]

I reported this many many months ago and they said they were aware but still no fix.

[vgofaizen]

The same issue is happening on Hyper-V with current version 2.14.5. Recreation steps: install 2.14.5, the version without official release notes. Run. View Task Manager.

[dominioncfg]

same thing happening to me using the linux version

[tillig]

I actually filed an Azure support ticket for this and got a response. Here's the relevant part of the response explaining why this is the case:

Behind all that Docker image, the ports and the Data Explorer, there's actually a Windows OS sandbox that runs more or less the same Windows 64-bit image and binaries that you will expect to run natively in on a Windows machine. Think of our container more or less like a "mini" Parallels or Virtual Box 🙂. In addition to all that, since the emulator relies on ports and HTTPS/TCP based listeners that constantly churn, looping, waiting and processing/executing requests, these also contribute to a high CPU usage. And since all these execution loops are Windows based and optimized, they are "translated"/"converted" into Unix kernel calls and that itself requires a lot more compute than when run natively.

My next question, of course, was whether there was an effort to port it to something more cross-platform so this wouldn't need to happen.

The Cosmos DB emulator has a very unique architecture, being very close to the actual implementation on the Azure. It allows the end user to configure their Cosmos clients just like when targeting the real thing; this is what makes it very appealing to our users actually. Some attempts were made to only provide a basic shim implementation of our Cosmos DB APIs, but they are lacking both the depth and the broad feature coverage.

So - they're aware of the problem, but the emulator itself isn't cross-platform and it sounds like trying to make it cross-platform is going to be a lot of work, prohibitively expensive, or both.

The suggestions as alternatives were:

• If you're on Windows, use the actual Windows/installable version of the Cosmos DB emulator, not the Docker version.
• Run a Windows VM and the Windows Cosmos DB emulator.
• Use the Cosmos DB free tier and develop against real Cosmos DB.

[RichMercer]

Interesting, thanks for sharing. It also sounds like it's extremely unlikely we'll be getting an ARM version for Apple Silicon any time soon.