Seeking an understanding about migrating Application Insights to Log Analytics Workspace

[jknureva]

Concerning the following:
https://docs.microsoft.com/en-us/azure/azure-monitor/app/convert-classic-resource

I'm looking to understand more about the impacts of migrating existing Application Insights based logs to an Azure Monitor "Log Analytics Workspace" resource.  At my company we already have quite a few dashboards, queries, and alerts built against the existing App Insights solution.  I fear that the migration of logs will break all of these.  For example, "customEvents" will become "AppEvents" and that will may break many things according to this:

https://docs.microsoft.com/en-us/azure/azure-monitor/app/apm-tables

Am I understanding correctly?  Can anyone advise an upgrade path that won't break things?

When you try to migrate an App Insights resource you get a message that says "Telemetry stored in both locations will be merged when making queries.".  Can anyone clarify this?  Does that mean we can continue using the old saved queries and dashboards within App Insights and they will continue to function after the migration (but reading the new Workspace)?

Is it possible to start feeding logs to the Workspace in parallel while still feeding them into the old App Insights solution?  This would allow us to gradually convert our queries and dashboards to the new Workspace without instantly breaking them all in an instant, and then perform the full migration only when done the updates.

Is there a way to identify all saved log queries and log usages in Azure?  We have many teams and resources in use and may have unknown log usages we don't want to miss.

Thank you,

Jonathan

[#2]

An update. I ran a number of experiments to test the migration procedure from the classic App-Insights to the new Log Analytics Workspace way of doing things. Within a Sandbox environment I created the classic App-Insights resource, fed logs into it, performed the migration, and then fed more logs. Repeatedly, after the migration was performed there were a considerable number of logs missing from the new Workspace. Feeding brand new logs into the system, the new log entries would all appear in the classic environment but only 25% of the logs would show in the new Workspace. I ran this test multiple times to confirm the results (completely setting up a new environment every time).

We then created a brand new Azure subscription specifically to test this. Within this brand new subscription we encountered exactly the same problem again - after the migration was performed 75% of all new logs did NOT appear in the new Log Analytics Workspace, while still showing up in the classic environment. There was no clear pattern which log entries were missing (such as only info logs were missing while errors were present). It was a blanket loss of 75% of all log data. I created a support ticket with Microsoft to get help as I had run out of options. Despite the SLA saying they'd respond within 4 hours it's been nearly a week now with no response from Microsoft.

However, I discovered something else. After a few days the new Log Analytics Workspace environment appears to begin working correctly. I'm now able to feed new logs in and can see those new log entries appear in the new Workspace 100% matching the classic environment. Could it be that this problem only exists for new log entries? How long does it take before it "warms up" and functions properly after a migration is performed? I hate not being able to explain the missing log entries even if it eventually functions.

Jonathan

[#3]

@jknureva Did you manage to find out if classic appinsights based dashboard, alerts, log query alerts etc were working after the migration?

[#4]

@Hari Praghash Kalyanasundaram Subramaniam 

Yes, the classic content continues to work after the migration.  I think this functionality will eventually be removed, but for now you can migrate to the new Log Analytics Workspace and continue to use the old interfaces, log queries, dashboards, and so on.