[nginx] Upstream keepalive: keepalive_requests directive.

[Robert Paprocki]

Quite the patch. I recall this behavior being discussed a number of times
in the past.

Question: why the default of 100? This feels like a significantly breaking
change wrt. the previous behavior. Are there any plans for advanced
communication regarding this change, outside of a nominal changelog entry
(e.g., "introduced 'keepalive_requests' directive")?

On Fri, Aug 10, 2018 at 1:02 PM, Maxim Dounin <mdounin at mdounin.ru> wrote:

> details:   http://hg.nginx.org/nginx/rev/70c6b08973a0
> branches:
> changeset: 7340:70c6b08973a0
> user:      Maxim Dounin <mdounin at mdounin.ru>
> date:      Fri Aug 10 21:54:46 2018 +0300
> description:
> Upstream keepalive: keepalive_requests directive.
>
> The directive configures maximum number of requests allowed on
> a connection kept in the cache.  Once a connection reaches the number
> of requests configured, it is no longer saved to the cache.
> The default is 100.
>
> Much like keepalive_requests for client connections, this is mostly
> a safeguard to make sure connections are closed periodically and the
> memory allocated from the connection pool is freed.
>
> diffstat:
>
>  src/http/modules/ngx_http_upstream_keepalive_module.c |  14
> ++++++++++++++
>  src/http/ngx_http_upstream.c                          |   2 ++
>  2 files changed, 16 insertions(+), 0 deletions(-)
>
> diffs (64 lines):
>
> diff --git a/src/http/modules/ngx_http_upstream_keepalive_module.c
> b/src/http/modules/ngx_http_upstream_keepalive_module.c
> --- a/src/http/modules/ngx_http_upstream_keepalive_module.c
> +++ b/src/http/modules/ngx_http_upstream_keepalive_module.c
> @@ -12,6 +12,7 @@
>
>  typedef struct {
>      ngx_uint_t                         max_cached;
> +    ngx_uint_t                         requests;
>      ngx_msec_t                         timeout;
>
>      ngx_queue_t                        cache;
> @@ -92,6 +93,13 @@ static ngx_command_t  ngx_http_upstream_
>        offsetof(ngx_http_upstream_keepalive_srv_conf_t, timeout),
>        NULL },
>
> +    { ngx_string("keepalive_requests"),
> +      NGX_HTTP_UPS_CONF|NGX_CONF_TAKE1,
> +      ngx_conf_set_num_slot,
> +      NGX_HTTP_SRV_CONF_OFFSET,
> +      offsetof(ngx_http_upstream_keepalive_srv_conf_t, requests),
> +      NULL },
> +
>        ngx_null_command
>  };
>
> @@ -142,6 +150,7 @@ ngx_http_upstream_init_keepalive(ngx_con
>                                            ngx_http_upstream_keepalive_
> module);
>
>      ngx_conf_init_msec_value(kcf->timeout, 60000);
> +    ngx_conf_init_uint_value(kcf->requests, 100);
>
>      if (kcf->original_init_upstream(cf, us) != NGX_OK) {
>          return NGX_ERROR;
> @@ -312,6 +321,10 @@ ngx_http_upstream_free_keepalive_peer(ng
>          goto invalid;
>      }
>
> +    if (c->requests >= kp->conf->requests) {
> +        goto invalid;
> +    }
> +
>      if (!u->keepalive) {
>          goto invalid;
>      }
> @@ -500,6 +513,7 @@ ngx_http_upstream_keepalive_create_conf(
>       */
>
>      conf->timeout = NGX_CONF_UNSET_MSEC;
> +    conf->requests = NGX_CONF_UNSET_UINT;
>
>      return conf;
>  }
> 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
> @@ -1546,6 +1546,8 @@ ngx_http_upstream_connect(ngx_http_reque
>
>      c = u->peer.connection;
>
> +    c->requests++;
> +
>      c->data = r;
>
>      c->write->handler = ngx_http_upstream_handler;
> _______________________________________________
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>
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