Does Azure Application Insights have a max log length?

Question

I have an Azure Function (Python) tied to an App Insights instance. The Function downloads large blobs from Azure Storage for processing. The BlobClient makes numerous calls to the blob container as part of loading into memory.

A file of ~2GB results in an App Insights log that is truncated (the last message in the log should be ### File Successfully Processed ###):

The Kusto query is:

union traces
| union exceptions
| where timestamp > ago(30d)
| where operation_Id == 'bigGUID'
| where customDimensions['InvocationId'] == 'bigGUID2'
| order by timestamp asc
| project timestamp, message = iff(message != '', message, iff(innermostMessage != '', innermostMessage, customDimensions.['prop__{OriginalFormat}'])), logLevel = customDimensions.['LogLevel']

Is there a limit to App Insights log length for a single event?

Answer 1

Yes, there's a max length. Please find the answer here:

Azure Application Insight. Custom attribute length restriction

The message has the highest allowed limit of 32768. For items in the property collection ,value has max limit of 8192.
Reference: https://github.com/microsoft/ApplicationInsights-Home/blob/master/EndpointSpecs/Schemas/Bond/MessageData.bond