From e240d88d4497afd2493358e938f74486750bc776 Mon Sep 17 00:00:00 2001 From: Maxim Dounin Date: Mon, 10 Aug 2020 18:52:59 +0300 Subject: 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). --- src/core/ngx_connection.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'src/core/ngx_connection.c') diff --git a/src/core/ngx_connection.c b/src/core/ngx_connection.c index 88fefcea2..91e1b3b2e 100644 --- a/src/core/ngx_connection.c +++ b/src/core/ngx_connection.c @@ -1298,6 +1298,19 @@ ngx_drain_connections(ngx_cycle_t *cycle) 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++) { -- cgit From 348bc94086d94f27dbda5904174cd379bce7f931 Mon Sep 17 00:00:00 2001 From: Maxim Dounin Date: Mon, 10 Aug 2020 18:53:07 +0300 Subject: Core: reusing connections in advance. Reworked connections reuse, so closing connections is attempted in advance, as long as number of free connections is less than 1/16 of worker connections configured. This ensures that new connections can be handled even if closing a reusable connection requires some time, for example, for a lingering close (ticket #2017). The 1/16 ratio is selected to be smaller than 1/8 used for disabling accept when working with accept mutex, so nginx will try to balance new connections to different workers first, and will start reusing connections only if this won't help. --- src/core/ngx_connection.c | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-) (limited to 'src/core/ngx_connection.c') diff --git a/src/core/ngx_connection.c b/src/core/ngx_connection.c index 91e1b3b2e..c082d0dac 100644 --- a/src/core/ngx_connection.c +++ b/src/core/ngx_connection.c @@ -1107,12 +1107,9 @@ ngx_get_connection(ngx_socket_t s, ngx_log_t *log) return NULL; } - c = ngx_cycle->free_connections; + ngx_drain_connections((ngx_cycle_t *) ngx_cycle); - if (c == NULL) { - ngx_drain_connections((ngx_cycle_t *) ngx_cycle); - c = ngx_cycle->free_connections; - } + c = ngx_cycle->free_connections; if (c == NULL) { ngx_log_error(NGX_LOG_ALERT, log, 0, @@ -1298,7 +1295,9 @@ ngx_drain_connections(ngx_cycle_t *cycle) ngx_queue_t *q; ngx_connection_t *c; - if (cycle->reusable_connections_n == 0) { + if (cycle->free_connection_n > cycle->connection_n / 16 + || cycle->reusable_connections_n == 0) + { return; } -- cgit