BUG/MAJOR: fix freezes during compression

Recent commit d7ad9f5 ("MAJOR: channel: add a new flag CF_WAKE_WRITE to
notify the task of writes") introduced this new CF_WAKE_WRITE flag that
an analyser which requires some free space to write must set if it wants
to be notified.

Unfortunately, some places were missing. More specifically, the
compression engine can rarely be stuck by a lack of output space,
especially when dealing with non-compressible data. It then has to
stop until some pending data are flushed and for this it must set
the CF_WAKE_WRITE flag. But these cases were missed by the commit
above.

Fortunately, this change was introduced very recently and never
released, so the impact was limited.

Huge thanks to Sander Klein who first reported this issue and who kindly
and patiently provided lots of traces and test data that made it possible
to reproduce, analyze, then fix this issue.

diff --git a/src/proto_http.c b/src/proto_http.c
index cd8ceae7303fafe9f68782ca91d5f1e35ea38aab..bc5b0149aada530eda619aca99832c8aa8f1d4d4 100644 (file)
--- a/src/proto_http.c
+++ b/src/proto_http.c
@@ -4864,8 +4864,10 @@ int http_request_forward_body(struct session *s, struct channel *req, int an_bit
 
                if (msg->msg_state == HTTP_MSG_DATA) {
                        /* must still forward */
-                       if (req->to_forward)
+                       if (req->to_forward) {
+                               req->flags |= CF_WAKE_WRITE;
                                goto missing_data;
+                       }
 
                        /* nothing left to forward */
                        if (msg->flags & HTTP_MSGF_TE_CHNK)
@@ -5986,8 +5988,10 @@ int http_response_forward_body(struct session *s, struct channel *res, int an_bi
 
        if (s->comp_algo != NULL) {
                ret = http_compression_buffer_init(s, res->buf, tmpbuf); /* init a buffer with headers */
-               if (ret < 0)
+               if (ret < 0) {
+                       res->flags |= CF_WAKE_WRITE;
                        goto missing_data; /* not enough spaces in buffers */
+               }
                compressing = 1;
        }
 
@@ -6012,8 +6016,10 @@ int http_response_forward_body(struct session *s, struct channel *res, int an_bi
                                        goto aborted_xfer;
                        }
 
-                       if (res->to_forward || msg->chunk_len)
+                       if (res->to_forward || msg->chunk_len) {
+                               res->flags |= CF_WAKE_WRITE;
                                goto missing_data;
+                       }
 
                        /* nothing left to forward */
                        if (msg->flags & HTTP_MSGF_TE_CHNK) {