Core: added a warning about reusing connections.
Previously, reusing connections happened silently and was only
visible in monitoring systems. This was shown to be not very user-friendly,
and administrators often didn't realize there were too few connections
available to withstand the load, and configured timeouts (keepalive_timeout
and http2_idle_timeout) were effectively reduced to keep things running.
To provide at least some information about this, a warning is now logged
(at most once per second, to avoid flooding the logs).
diff --git a/src/core/ngx_connection.c b/src/core/ngx_connection.c
index 88fefce..91e1b3b 100644
--- a/src/core/ngx_connection.c
+++ b/src/core/ngx_connection.c
@@ -1298,6 +1298,19 @@
ngx_queue_t *q;
ngx_connection_t *c;
+ if (cycle->reusable_connections_n == 0) {
+ return;
+ }
+
+ if (cycle->connections_reuse_time != ngx_time()) {
+ cycle->connections_reuse_time = ngx_time();
+
+ ngx_log_error(NGX_LOG_WARN, cycle->log, 0,
+ "%ui worker_connections are not enough, "
+ "reusing connections",
+ cycle->connection_n);
+ }
+
n = ngx_max(ngx_min(32, cycle->reusable_connections_n / 8), 1);
for (i = 0; i < n; i++) {
diff --git a/src/core/ngx_cycle.h b/src/core/ngx_cycle.h
index 54fa2e6..0f7d9bc 100644
--- a/src/core/ngx_cycle.h
+++ b/src/core/ngx_cycle.h
@@ -55,6 +55,7 @@
ngx_queue_t reusable_connections_queue;
ngx_uint_t reusable_connections_n;
+ time_t connections_reuse_time;
ngx_array_t listening;
ngx_array_t paths;