[PATCH] Upstream: flush low-level buffers on write retry

[Maxim Dounin]

Hello!

On Fri, Dec 01, 2017 at 04:49:29PM -0800, Piotr Sikora via nginx-devel wrote:

> # HG changeset patch
> # User Patryk Lesiewicz <patryk at google.com>
> # Date 1512172754 28800
> #      Fri Dec 01 15:59:14 2017 -0800
> # Node ID 0e2e2da798261fe5105017d9678566267b07e2b9
> # Parent  fc0d06224edac2c7cfbfd9a4def478f285d9957b
> Upstream: flush low-level buffers on write retry.
> 
> If the data to write is bigger than what the socket can send, and the
> reminder is smaller than NGX_SSL_BUFSIZE, then SSL_write() fails with
> SSL_ERROR_WANT_WRITE. The reminder of payload however is successfully
> copied to the low-level buffer and all the output chain buffers are
> flushed. This means that retry logic doesn't work because
> ngx_http_upstream_process_non_buffered_request() checks only if there's
> anything in the output chain buffers and ignores the fact that something
> may be buffered in low-level parts of the stack.
> 
> Signed-off-by: Patryk Lesiewicz <patryk at google.com>
> 
> diff -r fc0d06224eda -r 0e2e2da79826 src/http/ngx_http_upstream.c
> --- a/src/http/ngx_http_upstream.c
> +++ b/src/http/ngx_http_upstream.c
> @@ -3533,7 +3533,7 @@ ngx_http_upstream_process_non_buffered_r
>  
>          if (do_write) {
>  
> -            if (u->out_bufs || u->busy_bufs) {
> +            if (u->out_bufs || u->busy_bufs || downstream->buffered) {
>                  rc = ngx_http_output_filter(r, u->out_bufs);
>  
>                  if (rc == NGX_ERROR) {

Committed, thanks for catching this.
http://hg.nginx.org/nginx/rev/a762ddf22dbb

-- 
Maxim Dounin
http://mdounin.ru/