High CPU Usage (100%) in Specific Scenarios

[niceskylei]

Description:

I'm experiencing an issue with the h2 crate where the CPU usage reaches 100% under specific conditions. This issue is consistently reproducible and significantly affects the performance of my application.

Steps to Reproduce:

• Set up a tonic RPC server using the h2 crate.
• Establish a connection from a remote client.
• Disconnect the remote client unexpectedly (e.g., by closing the client application or terminating the network connection).
• Observe the CPU usage on the server.

Expected Behavior:

The CPU usage should remain within normal operating limits and not spike to 100% when the remote client disconnects.

Actual Behavior:

When the remote client disconnects, the CPU usage spikes to 100% and remains there, causing severe performance degradation.

Environment:

• h2 version: 0.3.26
• tonic version: 0.8.2
• Rust version: rustc 1.80.0-nightly (6e1d94708 2024-05-10)
• Operating System: iOS 17.5

Additional Context:

use instruments analyse cpu usage

Log Files/Output:

using trace log level, repeatedly print below log:
queued_data_frame=false

How fix it:

I have applied a preliminary fix which seems to mitigate the issue, as the high CPU usage has not reoccurred during my initial tests. However, this fix has not been fully validated, and I am unsure if there are any other side effects or impacts.

[seanmonstar]

Hm, good point, it seems that if a call to write() returns 0, that implies the socket has been closed. A similar looking patch in a pull request would be welcome. The part to discuss is how to signal to the user that not all bytes were written. Perhaps returning a WriteZero io error?