DistributedSession always loads session in CommitAsync even when session is not modified

[MichalSznajder]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

As part of f99b482 code is DistributedSession.CommitsAsync was modified to check IsAvailable.

aspnetcore/src/Middleware/Session/src/DistributedSession.cs

Line 263 in 4aa4ec3

public async Task CommitAsync(CancellationToken cancellationToken = default)

IsAvailable always loads session from backing store and loads it in synchronous way.

aspnetcore/src/Middleware/Session/src/DistributedSession.cs

Line 96 in 4aa4ec3

public bool IsAvailable

On the other hand SessionMiddleware always calls DistributedSession.CommitAsync to save session. This means that in 6.0 session is always loaded even if application code did not touch it at all. In case of using Redis as backing store this incurs two Redis calls on each RazorPage rendered.

aspnetcore/src/Middleware/Session/src/SessionMiddleware.cs

Line 119 in 4aa4ec3

await feature.Session.CommitAsync();

In the past (5.0) when session was not touched DistributedSession._isModified prevented session data from being loaded when session was not modified.

aspnetcore/src/Middleware/Session/src/DistributedSession.cs

Line 274 in 4aa4ec3

if (_isModified)

@pranavkm Could you tell why IsAvailable was moved?

Expected Behavior

Don't loading session data from backing store when session data is not modified by app code.

.NET Version

6.0.300

Thanks for contacting us.

We're moving this issue to the .NET 7 Planning milestone for future evaluation / consideration. We would like to keep this around to collect more feedback, which can help us with prioritizing this work. We will re-evaluate this issue, during our next planning meeting(s).
If we later determine, that the issue has no community involvement, or it's very rare and low-impact issue, we will close it - so that the team can focus on more important and high impact issues.
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[adityamandaleeka]

Reopening for 6.0 servicing consideration. The performance impact of this is meaningfully affecting people (e.g. #43059 (comment))