Serverless deployment code location errors: DagsterUserCodeUnreachableError: Could not reach user code server. gRPC Error code: UNAVAILABLE

[garethbrickman]

Symptoms

Specifically for Dagster+ Serverless deployments, attempting to add a new code location, or redeploy an existing code location, results in errors like:

• dagster.­_core.errors.DagsterUserCodeUnreachableError: Could not reach user code server. gRPC Error code: UNAVAILABLE

Possible causes

• Typically these errors are caused due to user code taking too long to load, or a call within the user code hanging such as to an external API.
• In some other instances, the cause is Serverless compute and memory resource limits being exceeded.

[garethbrickman]

Solutions

• Confirm long code load time and timeout by running Dagster locally
• If your project is using dbt assets, something to check is if your code is generating a dbt manifest at run time, rather than at the recommended build time. See more in: Loading dbt models from a dbt project
• Sometimes the root cause is sensor evaluations constantly timing out. See more in: [Guide] Managing sensor timeouts #20021
• More generally, we have a guide showing how to profile your code using py-spy. Another utility that is useful is memray