Hi Tait,
On Wed, Dec 05, 2012 at 04:48:57PM -0500, Tait Clarridge wrote:
> Hey List,
>
> Considering there is no option yet for maxconnrate for servers (I heard
> this is on the roadmap), I wrote an ACL to check a backend server
> session rate which we use to send to an "overflow" backend to prevent
> latency responses to our clients (very sensitive latency requirements).
>
> Unfortunately since it on a server by server basis, I have to set quite
> a few of them in our environment.
>
> I'm not much of a programmer, so if this is completely wrong let me know
> however I can confirm this works as expected and does limit it properly
> when called.
>
> src/backend.c
>
> @@ -1612,6 +1587,20 @@
> return 1;
> }
>
> +static int
> +acl_fetch_srv_sess_rate(struct proxy *px, struct session *l4, void *l7,
> unsigned int opt,
> + const struct arg *args, struct sample *smp)
> +{
> + smp->flags = SMP_F_VOL_TEST;
> + smp->type = SMP_T_UINT;
> + smp->data.uint = read_freq_ctr(&args->data.srv->sess_per_sec);
> + return 1;
> +}
> +
> /* Note: must not be declared <const> as its list will be overwritten.
> * Please take care of keeping this list alphabetically sorted.
> */
> @@ -1620,11 +1609,11 @@
> { "be_conn", acl_parse_int, acl_fetch_be_conn,
> acl_match_int, ACL_USE_NOTHING, ARG1(1,BE) },
> { "be_id", acl_parse_int, acl_fetch_be_id,
> acl_match_int, ACL_USE_NOTHING, 0 },
> { "be_sess_rate", acl_parse_int, acl_fetch_be_sess_rate,
> acl_match_int, ACL_USE_NOTHING, ARG1(1,BE) },
> { "connslots", acl_parse_int, acl_fetch_connslots,
> acl_match_int, ACL_USE_NOTHING, ARG1(1,BE) },
> { "nbsrv", acl_parse_int, acl_fetch_nbsrv,
> acl_match_int, ACL_USE_NOTHING, ARG1(1,BE) },
> { "queue", acl_parse_int, acl_fetch_queue_size,
> acl_match_int, ACL_USE_NOTHING, ARG1(1,BE) },
> { "srv_conn", acl_parse_int, acl_fetch_srv_conn,
> acl_match_int, ACL_USE_NOTHING, ARG1(1,SRV) },
> + { "srv_sess_rate", acl_parse_int, acl_fetch_srv_sess_rate,
> acl_match_int, ACL_USE_NOTHING, ARG1(1,SRV) },
> { "srv_id", acl_parse_int, acl_fetch_srv_id,
> acl_match_int, ACL_USE_RTR_INTERNAL, 0 },
> { "srv_is_up", acl_parse_nothing, acl_fetch_srv_is_up,
> acl_match_nothing, ACL_USE_NOTHING, ARG1(1,SRV) },
> { NULL, NULL, NULL, NULL },
>
> Let me know your thoughts.
Your patch looks totally right to me. I'm not sure it will be of much
use in other environments than yours, but it doesn't cost anything to
merge it (at least it will save you from maintaining the patch). Please
could you send a short doc update with it, and I'll happily apply it.
Also, you said you have to use a number of these rules. Wouldn't it be
easier in your situation to rely on an average rate per server ? You
have the backend's session rate, you have the number of active servers,
so with a divide, you have the average per-server rate. Look at the
avg_queue ACL to see how that can be done. I'm sure it will be even
more useful for you !
Regards,
Willy
