Function execution logs are duplicated in App Service log stream

[paulbatum]

If you access the log stream for your entire function app, you will see duplicated entries for function starting/completion:

When a function executes with file logging enabled, the following entries are written to both the host log and the function log, i.e. to files in:

• D:\home\LogFiles\Application\Functions\Host\

• D:\home\LogFiles\Application\Functions\Function\function-name\

The entries look like this:

2017-04-18T22:54:20.013 Function started (Id=8c130624-cfb2-47d7-8e1f-05047a10a17d)
2017-04-18T22:54:20.013 Function completed (Success, Id=8c130624-cfb2-47d7-8e1f-05047a10a17d, Duration=0ms)

Because the same entry is written to both locations, it appears in the log stream twice.

[fmannhardt]

This is highly confusing and just cost me a few hours of searching for the reason. It should be fixed or one need to somehow be warned.

[jwisener]

This is an issue that cost a considerable amount of time. Since this issue has been open for 3 years are there any plans to address this?

[njabulomp]

I am experiencing an issue where the invocation of an http triggered function app from a logic app is happening twice, I checked the invocation logs and app insights and did indeed see two calls being made. The logic app is showing one call being made but the function app is being called twice. I am using version 2 (2.0.12961.0) of the functions sdk.

[ravick4u]

This issue was opened in 2017 and I am writing this in 2020... :) I am using Azure Function V3 and issue is still exists

[paulbatum]

I think there are two different things being discussed here. The behavior that @njabulomp mentioned is about a function actually running twice. That is not what this issue is about. This issue is about the fact that the streaming logs UX for an entire webapp/functionapp subscribes to all file log changes that happen within the D:\home\LogFiles folder. If the same log entry is written to two different files, then this consolidated view will show the entry twice.

Since this issue is filed against the functions host, the change that makes the most sense would be for the host level log not include any log entries that will appear in the per-function logs. However I am not sure whether that would break some existing workflows?

[paulbatum]

@brettsam @mathewc are there any host.json settings that would control what level of logs are written to the host log at D:\home\LogFiles\Application\Functions\Host? I am guessing no?

[mathewc]

No, the only file logging knob is "fileLoggingEnabled". The issue is that the Log Streaming view is rooted on the parent directory (getting both host/function logs), while the function Logs view is rooted on the individual function directory:

The log files/data are correct. I think we just need to change the Log Streaming view to root on the host log dir, which should include everything you'd want to see.

[paulbatum]

That might work. I'm asking someone from the portal team.

[paulbatum]

We think Mathew's suggested approach makes sense. I should have another update in a few weeks. While the work is happening in a different component, I'll leave this issue open for the time being.

[pcgeek86]

3+ years later ... any fix for this? I'm seeing this behavior as well.

#1627

[paulbatum]

@pcgeek86 Can you let us know if you're still having a problem with this? We recently deployed some of the changes that were discussed above.