MINOR: mux-h2: report a trace event when failing to create a new stream

There are two reasons we can reject the creation of an h2 stream on the
frontend:
  - its creation would violate the MAX_CONCURRENT_STREAMS setting
  - there's no more memory available

And on the backend it's almost the same except that the setting might
have be negotiated after trying to set up the stream.

Let's add traces for such a sitaution so that it's possible to know why
the stream was rejected (currently we only know it was rejected).

It could be nice to backport this to the most recent versions.

diff --git a/src/mux_h2.c b/src/mux_h2.c
index 3d04b8e187543d450185e3c1110ba1e7f5fee291..b13ac8a97e254b835897e0ecf004cc44ab198271 100644 (file)
--- a/src/mux_h2.c
+++ b/src/mux_h2.c
@@ -1597,12 +1597,14 @@ static struct h2s *h2c_frt_stream_new(struct h2c *h2c, int id, struct buffer *in
 
        TRACE_ENTER(H2_EV_H2S_NEW, h2c->conn);
 
-       if (h2c->nb_streams >= h2_settings_max_concurrent_streams)
+       if (h2c->nb_streams >= h2_settings_max_concurrent_streams) {
+               TRACE_ERROR("HEADERS frame causing MAX_CONCURRENT_STREAMS to be exceeded", H2_EV_H2S_NEW|H2_EV_RX_FRAME|H2_EV_RX_HDR, h2c->conn);
                goto out;
+       }
 
        h2s = h2s_new(h2c, id);
        if (!h2s)
-               goto out;
+               goto out_alloc;
 
        h2s->endp = cs_endpoint_new();
        if (!h2s->endp)
@@ -1648,6 +1650,8 @@ static struct h2s *h2c_frt_stream_new(struct h2c *h2c, int id, struct buffer *in
 
  out_close:
        h2s_destroy(h2s);
+ out_alloc:
+       TRACE_ERROR("Failed to allocate a new stream", H2_EV_H2S_NEW|H2_EV_RX_FRAME|H2_EV_RX_HDR, h2c->conn);
  out:
        sess_log(sess);
        TRACE_LEAVE(H2_EV_H2S_NEW|H2_EV_H2S_ERR|H2_EV_H2S_END, h2c->conn);
@@ -1664,18 +1668,25 @@ static struct h2s *h2c_bck_stream_new(struct h2c *h2c, struct conn_stream *cs, s
 
        TRACE_ENTER(H2_EV_H2S_NEW, h2c->conn);
 
-       if (h2c->nb_streams >= h2c->streams_limit)
+       if (h2c->nb_streams >= h2c->streams_limit) {
+               TRACE_ERROR("Aborting stream since negotiated limit is too low", H2_EV_H2S_NEW, h2c->conn);
                goto out;
+       }
 
-       if (h2_streams_left(h2c) < 1)
+       if (h2_streams_left(h2c) < 1) {
+               TRACE_ERROR("Aborting stream since no more streams left", H2_EV_H2S_NEW, h2c->conn);
                goto out;
+       }
 
        /* Defer choosing the ID until we send the first message to create the stream */
        h2s = h2s_new(h2c, 0);
-       if (!h2s)
+       if (!h2s) {
+               TRACE_ERROR("Failed to allocate a new stream", H2_EV_H2S_NEW, h2c->conn);
                goto out;
+       }
 
        if (cs_attach_mux(cs, h2s, h2c->conn) < 0) {
+               TRACE_ERROR("Failed to allocate a new stream", H2_EV_H2S_NEW, h2c->conn);
                h2s_destroy(h2s);
                h2s = NULL;
                goto out;