From 72fea25d271b53601cbded03087adddc76950cdd Mon Sep 17 00:00:00 2001
From: Joao Morais <jcmoraisjr@gmail.com>
Date: Sun, 17 Dec 2017 16:34:15 -0200
Subject: [PATCH] New reload strategy - reusesocket

---
 README.md                                |  1 +
 pkg/controller/controller.go             |  4 ++--
 rootfs/etc/haproxy/template/haproxy.tmpl |  2 +-
 rootfs/haproxy-reload.sh                 | 14 ++++++++++++++
 rootfs/start.sh                          |  2 +-
 5 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/README.md b/README.md
index df01970eb..f512b3a1d 100644
--- a/README.md
+++ b/README.md
@@ -487,6 +487,7 @@ The `--reload-strategy` command-line argument is used to select which reload str
 HAProxy should use. The following options are available:
 
 * `native`: Uses native HAProxy reload option `-sf`. This is the default option.
+* `reusesocket`: (starting on v0.6) Uses HAProxy `-x` command-line option to pass the listening sockets between old and new HAProxy process, allowing hitless reloads.
 * `multibinder`: Uses GitHub's [multibinder](https://github.com/github/multibinder). This [link](https://githubengineering.com/glb-part-2-haproxy-zero-downtime-zero-delay-reloads-with-multibinder/)
 describes how it works.
 
diff --git a/pkg/controller/controller.go b/pkg/controller/controller.go
index 14035d530..9de6ccb83 100644
--- a/pkg/controller/controller.go
+++ b/pkg/controller/controller.go
@@ -102,7 +102,7 @@ func (haproxy *HAProxyController) UpdateIngressStatus(*extensions.Ingress) []api
 // command line arguments
 func (haproxy *HAProxyController) ConfigureFlags(flags *pflag.FlagSet) {
 	haproxy.reloadStrategy = flags.String("reload-strategy", "native",
-		`Name of the reload strategy. Options are: native (default) or multibinder`)
+		`Name of the reload strategy. Options are: native (default), reusesocket or multibinder`)
 	ingressClass := flags.Lookup("ingress-class")
 	if ingressClass != nil {
 		ingressClass.Value.Set("haproxy")
@@ -112,7 +112,7 @@ func (haproxy *HAProxyController) ConfigureFlags(flags *pflag.FlagSet) {
 
 // OverrideFlags allows controller to override command line parameter flags
 func (haproxy *HAProxyController) OverrideFlags(flags *pflag.FlagSet) {
-	if *haproxy.reloadStrategy == "native" {
+	if *haproxy.reloadStrategy == "native" || *haproxy.reloadStrategy == "reusesocket" {
 		haproxy.configFile = "/etc/haproxy/haproxy.cfg"
 		haproxy.template = newTemplate("haproxy.tmpl", "/etc/haproxy/template/haproxy.tmpl")
 	} else if *haproxy.reloadStrategy == "multibinder" {
diff --git a/rootfs/etc/haproxy/template/haproxy.tmpl b/rootfs/etc/haproxy/template/haproxy.tmpl
index abee2de26..7b6824851 100644
--- a/rootfs/etc/haproxy/template/haproxy.tmpl
+++ b/rootfs/etc/haproxy/template/haproxy.tmpl
@@ -2,7 +2,7 @@
 {{- $cfg := .Cfg -}}
 global
     daemon
-    stats socket {{ $cfg.StatsSocket }} level admin
+    stats socket {{ $cfg.StatsSocket }} level admin expose-fd listeners
 {{- if $cfg.LoadServerState }}
     server-state-file state-global
     server-state-base /var/lib/haproxy/
diff --git a/rootfs/haproxy-reload.sh b/rootfs/haproxy-reload.sh
index e2a389b72..f15e2730a 100755
--- a/rootfs/haproxy-reload.sh
+++ b/rootfs/haproxy-reload.sh
@@ -20,6 +20,9 @@
 #  native <.cfg>
 #    Uses native HAProxy soft restart. Running it for the first time starts
 #    HAProxy, each subsequent invocation will perform a soft-reload.
+#  reusesocket <.cfg>
+#    Pass the listening sockets to the new HAProxy process instead of
+#    rebinding them, allowing hitless reloads.
 #  multibinder <.cfg.erb>
 #    Used on multibinder deployment. Send USR2 to the
 #    multibinder-haproxy-wrapper process.
@@ -30,6 +33,7 @@
 #  -D run as daemon
 #  -sf soft reload, wait for pids to finish handling requests
 #      send pids a resume signal if reload of new config fails
+#  -x get the listening sockets from the old HAProxy process
 
 set -e
 
@@ -47,6 +51,16 @@ case "$1" in
         HAPROXY_PID=/var/run/haproxy.pid
         haproxy -f "$CONFIG" -p "$HAPROXY_PID" -D -sf $(cat "$HAPROXY_PID" 2>/dev/null || :)
         ;;
+    reusesocket)
+        CONFIG="$2"
+        HAPROXY_PID=/var/run/haproxy.pid
+        OLD_PID=$(cat "$HAPROXY_PID" 2>/dev/null || :)
+        if [ -S "$HAPROXY_SOCKET" ]; then
+            haproxy -f "$CONFIG" -p "$HAPROXY_PID" -sf $OLD_PID -x "$HAPROXY_SOCKET"
+        else
+            haproxy -f "$CONFIG" -p "$HAPROXY_PID" -sf $OLD_PID
+        fi
+        ;;
     multibinder)
         HAPROXY=/usr/local/sbin/haproxy
         CONFIG="$2"
diff --git a/rootfs/start.sh b/rootfs/start.sh
index 33bad0cb0..a8431ab57 100755
--- a/rootfs/start.sh
+++ b/rootfs/start.sh
@@ -26,7 +26,7 @@ init() {
     )
     reloadStrategy="${reloadStrategy:-native}"
     case "$reloadStrategy" in
-        native)
+        native|reusesocket)
             ;;
         multibinder)
             HAPROXY=/usr/local/sbin/haproxy