MINOR: connection: Add way to disable active connection closing during soft-stop

If the "close-spread-time" option is set to "infinite", active
connection closing during a soft-stop can be disabled. The 'connection:
close' header or the GOAWAY frame will not be added anymore to the
server's response and active connections will only be closed once the
clients disconnect. Idle connections will not be closed all at once when
the soft-stop starts anymore, and each idle connection will follow its
own timeout based on the multiple timeouts set in the configuration (as
is the case during regular execution).

This feature request was described in GitHub issue #1614.
This patch should be backported to 2.5. It depends on 'MEDIUM: global:
Add a "close-spread-time" option to spread soft-stop on time window'.

doc/configuration.txt

@@ -1165,16 +1165,22 @@ close-spread-time <time>
   close" line to the HTTP response, or by sending a GOAWAY frame in case of
   HTTP2. When this option is set, connection closing will be spread over this
   set <time>.
+  If the close-spread-time is set to "infinite", active connection closing
+  during a soft-stop will be disabled. The "Connection: close" header will not
+  be added to HTTP responses (or GOAWAY for HTTP2) anymore and idle connections
+  will only be closed once their timeout is reached (based on the various
+  timeouts set in the configuration).
 
   Arguments :
     <time>  is a time window (by default in milliseconds) during which
-            connection closing will be spread during a soft-stop operation.
+            connection closing will be spread during a soft-stop operation, or
+            "infinite" if active connection closing should be disabled.
 
   It is recommended to set this setting to a value lower than the one used in
   the "hard-stop-after" option if this one is used, so that all connections
   have a chance to gracefully close before the process stops.
 
-  See also: grace, hard-stop-after
+  See also: grace, hard-stop-after, idle-close-on-response
 
 cpu-map [auto:]<process-set>[/<thread-set>] <cpu-set>...
   On some operating systems, it is possible to bind a process or a thread to a

include/haproxy/global-t.h

@@ -74,6 +74,7 @@
 #define GTUNE_SCHED_LOW_LATENCY  (1<<19)
 #define GTUNE_IDLE_POOL_SHARED   (1<<20)
 #define GTUNE_DISABLE_H2_WEBSOCKET (1<<21)
+#define GTUNE_DISABLE_ACTIVE_CLOSE (1<<22)
 
 /* SSL server verify mode */
 enum {

src/mux_h1.c

@@ -1198,7 +1198,9 @@ static void h1_set_cli_conn_mode(struct h1s *h1s, struct h1m *h1m)
 	}
 
 	/* If KAL, check if the frontend is stopping. If yes, switch in CLO mode
-	 * unless a 'close-spread-time' option is set.
+	 * unless a 'close-spread-time' option is set (either to define a
+	 * soft-close window or to disable active closing (close-spread-time
+	 * option set to 0).
 	 */
 	if (h1s->flags & H1S_F_WANT_KAL && (fe->flags & (PR_FL_DISABLED|PR_FL_STOPPED))) {
 		int want_clo = 1;
@@ -1215,6 +1217,8 @@ static void h1_set_cli_conn_mode(struct h1s *h1s, struct h1m *h1m)
 				want_clo = (remaining_window <= statistical_prng_range(global.close_spread_time));
 			}
 		}
+		else if (global.tune.options & GTUNE_DISABLE_ACTIVE_CLOSE)
+			want_clo = 0;
 
 		if (want_clo) {
 			h1s->flags = (h1s->flags & ~H1S_F_WANT_MSK) | H1S_F_WANT_CLO;
@@ -3088,6 +3092,8 @@ static int h1_process(struct h1c * h1c)
 						send_close = (remaining_window <= statistical_prng_range(global.close_spread_time));
 					}
 				}
+				else if (global.tune.options & GTUNE_DISABLE_ACTIVE_CLOSE)
+					send_close = 0; /* let the client close his connection himself */
 				if (send_close)
 					goto release;
 			}

src/mux_h2.c

@@ -4059,6 +4059,8 @@ static int h2_process(struct h2c *h2c)
 				send_goaway = (remaining_window <= statistical_prng_range(global.close_spread_time));
 			}
 		}
+		else if (global.tune.options & GTUNE_DISABLE_ACTIVE_CLOSE)
+			send_goaway = 0; /* let the client close his connection himself */
 		/* frontend is stopping, reload likely in progress, let's try
 		 * to announce a graceful shutdown if not yet done. We don't
 		 * care if it fails, it will be tried again later.

src/proxy.c

@@ -2087,6 +2087,16 @@ static int proxy_parse_close_spread_time(char **args, int section_type, struct p
 		memprintf(err, "'%s' expects <time> as argument.\n", args[0]);
 		return -1;
 	}
+
+	/* If close-spread-time is set to "infinite", disable the active connection
+	 * closing during soft-stop.
+	 */
+	if (strcmp(args[1], "infinite") == 0) {
+		global.tune.options |= GTUNE_DISABLE_ACTIVE_CLOSE;
+		global.close_spread_time = TICK_ETERNITY;
+		return 0;
+	}
+
 	res = parse_time_err(args[1], &global.close_spread_time, TIME_UNIT_MS);
 	if (res == PARSE_TIME_OVER) {
 		memprintf(err, "timer overflow in argument '%s' to '%s' (maximum value is 2147483647 ms or ~24.8 days)",
@@ -2102,6 +2112,8 @@ static int proxy_parse_close_spread_time(char **args, int section_type, struct p
 		memprintf(err, "unexpected character '%c' in argument to <%s>.\n", *res, args[0]);
 		return -1;
 	}
+	global.tune.options &= ~GTUNE_DISABLE_ACTIVE_CLOSE;
+
 	return 0;
 }