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

Maxim Dounin mdounin at mdounin.ru
Tue Dec 5 15:14:12 UTC 2017

details:   http://hg.nginx.org/nginx/rev/a762ddf22dbb
changeset: 7166:a762ddf22dbb
user:      Patryk Lesiewicz <patryk at google.com>
date:      Fri Dec 01 15:59:14 2017 -0800
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>


 src/http/ngx_http_upstream.c |  2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diffs (12 lines):

diff --git a/src/http/ngx_http_upstream.c b/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) {

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