HTTP::Server::PSGI returns an undef writer callback when writing headers failed

[miyagawa]

HTTP::Server::PSGI passes an undef to the application when writing HTTP headers failed in the streaming mode.

214     $self->write_all($conn, join('', @lines), $self->{timeout})
215         or return;

I just can't tell if it 's a bug since this is unspecified in the PSGI specification but it's not the optimal since the caller application will eventually die out by calling undef as a sub reference.

[miyagawa]

One option is to update the code to return a null callback so the caller won't die out.

The other possibility is to update the spec to read like "the server MAY (or SHOULD) provide an undef writer callback when writing HTTP headers to the client failed earlier" or something like that - at least it will match the existing behaviors to the specification, and also a potential optimization in the caller's code, since they can know that the client already disconnected, and there's no need to continue the application process to write out the body which could be expensive, when nobody is listening.

[miyagawa]

Just for the note -

• Starman ignores the syswrite ret value from headers, continuing with writer
• Twiggy the same
• Starlet shares the same code base with HTTP::Server::PSGI, could return undef writer