Hello everyone,

With a giant shout-out to Michael Merickel for all his hard work on the latest 
version of waitress.


- The send_bytes adjustment now defaults to 1 and is deprecated pending removal 
in a future release. It no longer changes how many bytes are placed into the 
socket, and instead determines how many bytes waitress should buffer before 
sending data to the client.

This change will increase interactivity for users of waitress and will increase 
how fast users will see the first byte returned from your WSGI application. 
Please report any adverse unintended side effects (I doubt there are any, but 
would love to hear them). See features below for the other change related to 


- Add a new outbuf_high_watermark adjustment which is used to apply 
backpressure on the app_iter to avoid letting it spin faster than data can be 
written to the socket. This stabilizes responses that iterate quickly with a 
lot of data. This also avoids waitress from buffering too much of app_iter and 
filling the disk.
- Stop early and close the app_iter when attempting to write to a closed socket 
due to a client disconnect. This should notify a long-lived streaming response 
when a client hangs up. Previously waitress would iterate until the app_iter 
- Adjust the flush to output SO_SNDBUF bytes instead of whatever was set in the 
send_bytes adjustment. send_bytes now only controls how much waitress will 
buffer internally before flushing to the kernel, whereas previously it used to 
also throttle how much data was sent to the kernel. This change enables a 
streaming app_iter containing small chunks to still be flushed efficiently.


- When a client closes a socket unexpectedly there was potential for memory 
leaks in which data was written to the buffers after they were closed, causing 
them to reopen.
- Fix the queue depth warnings to only show when all threads are busy. This 
avoids spurious warnings that users were seeing. Users may still wish to 
increase the thread count from the default.
- Trigger the app_iter to close as part of shutdown. This will only be 
noticeable for users of the internal server api. In more typical operations the 
server will die before benefiting from these changes.
- Fix a bug in which a streaming app_iter may never cleanup data that has 
already been sent. This would cause buffers in waitress to grow without bounds. 
These buffers now properly rotate and release their data. (see related feature 
- Fix a bug in which non-seekable subclasses of io.IOBase would trigger an 
exception when passed to the wsgi.file_wrapper callback.

To install:

pip install waitress==1.3.0b0

On pypi: https://pypi.org/project/waitress/1.3.0b0/
Issues: https://github.com/Pylons/waitress/issues

Please give this a good test run with your test/production workloads. Unless I 
hear screams, I will likely release this as soon as this coming Monday!


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