Re: [PATCH] MINOR: cli: ability to set per-server maxconn

[Andrew Hayworth]

On Tue, Oct 20, 2015 at 1:56 AM, Willy Tarreau <w...@1wt.eu> wrote:
> Hi Andrew,
>
> Thanks. Normally you also need to try to dequeue pending connections
> when changing the value, because if you increase the limit, you need
> to open the door for new connections. After changing the value, you
> normally need something like this :
>
>                 if (may_dequeue_tasks(srv, srv->proxy))
>                         process_srv_queue(srv);
>
> Regards,
> Willy
>

Ah, thanks - I hadn't thought about the case where connections were
queued up. In my tests, I had a very low queue timeout. The code you
suggested seems to do the trick. Updated patch below.

-- 
- Andrew Hayworth

>From 0bad55c2cdd6d4086c11cd445de309693ec72afa Mon Sep 17 00:00:00 2001
From: Andrew Hayworth <andrew.haywo...@getbraintree.com>
Date: Tue, 27 Oct 2015 21:46:25 +0000
Subject: [PATCH] MINOR: cli: ability to set per-server maxconn

This commit adds support for setting a per-server maxconn from the stats
socket. The only really notable part of this commit is that we need to
check if maxconn == minconn before changing things, as this indicates
that we are NOT using dynamic maxconn. When we are not using dynamic
maxconn, we should update maxconn/minconn in lockstep.
---
 doc/management.txt |  5 +++++
 src/dumpstats.c    | 34 +++++++++++++++++++++++++++++++++-
 2 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/doc/management.txt b/doc/management.txt
index d67988b..a53a953 100644
--- a/doc/management.txt
+++ b/doc/management.txt
@@ -1356,6 +1356,11 @@ set maxconn frontend <frontend> <value>
   delayed until the threshold is reached. The frontend might be specified by
   either its name or its numeric ID prefixed with a sharp ('#').

+set maxconn server <backend/server> <value>
+  Dynamically change the specified server's maxconn setting. Any positive
+  value is allowed including zero, but setting values larger than the global
+  maxconn does not make much sense.
+
 set maxconn global <maxconn>
   Dynamically change the global maxconn setting within the range defined by the
   initial global maxconn setting. If it is increased and connections were
diff --git a/src/dumpstats.c b/src/dumpstats.c
index e80e45c..ef52c2b 100644
--- a/src/dumpstats.c
+++ b/src/dumpstats.c
@@ -1646,6 +1646,38 @@ static int stats_sock_parse_request(struct
stream_interface *si, char *line)

  return 1;
  }
+ else if (strcmp(args[2], "server") == 0) {
+ struct server *sv;
+ int v;
+
+ sv = expect_server_admin(s, si, args[3]);
+ if (!sv)
+ return 1;
+
+ if (!*args[4]) {
+ appctx->ctx.cli.msg = "Integer value expected.\n";
+ appctx->st0 = STAT_CLI_PRINT;
+ return 1;
+ }
+
+ v = atoi(args[4]);
+ if (v < 0) {
+ appctx->ctx.cli.msg = "Value out of range.\n";
+ appctx->st0 = STAT_CLI_PRINT;
+ return 1;
+ }
+
+ if (sv->maxconn == sv->minconn) { // static maxconn
+  sv->maxconn = sv->minconn = v;
+ } else { // dynamic maxconn
+  sv->maxconn = v;
+ }
+
+ if (may_dequeue_tasks(sv, sv->proxy))
+ process_srv_queue(sv);
+
+ return 1;
+ }
  else if (strcmp(args[2], "global") == 0) {
  int v;

@@ -1681,7 +1713,7 @@ static int stats_sock_parse_request(struct
stream_interface *si, char *line)
  return 1;
  }
  else {
- appctx->ctx.cli.msg = "'set maxconn' only supports 'frontend' and
'global'.\n";
+ appctx->ctx.cli.msg = "'set maxconn' only supports 'frontend',
'server', and 'global'.\n";
  appctx->st0 = STAT_CLI_PRINT;
  return 1;
  }
--
2.1.3

0001-MINOR-cli-ability-to-set-per-server-maxconn.patch
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