With the 19.14 series this hangs:

curl 'http://localhost:8123/?query=SELECT%201&cancel_http_readonly_queries_on_client_close=1'

When the cancel_http_readonly_queries_on_client_close setting is omitted or set to 0, it works.

With the 19.13 series and earlier the above request successfully returns results as expected. (We did not check if it correctly cancelled the requests but assume so.)

The cancel_http_readonly_queries_on_client_close feature is documented as: "Cancel HTTP readonly queries when a client closes the connection without waiting for response."

I haven't investigated why test 00834_cancel_http_readonly_queries_on_client_close.sh passes but it looks like that test may be flawed or have missing coverage.