add a haproxy router for a single connection point

Author: Winslett

README.md

@@ -14,6 +14,14 @@ From there, you will see a high-availability cluster start up. Test
 different settings in the YAML files to see how behavior changes.  Kill
 some of the different components to see how the system behaves.
 
+To get a haproxy load balancing between these two hosts, run:
+
+```
+> haproxy -f haproxy.cfg
+> sh haproxy_status.sh 127.0.0.1 5432 15432
+> sh haproxy_status.sh 127.0.0.1 5433 15433
+```
+
 # Requirements on a Mac
 
 Run the following on a Mac to install requirements:

haproxy.cfg

@@ -0,0 +1,21 @@
+global
+	maxconn 100
+
+defaults
+	log	global
+	mode	tcp
+	retries 2
+	timeout client 30m
+	timeout connect 4s
+	timeout server 30m
+	timeout check 5s
+
+frontend ft_postgresql
+	bind *:5000
+	default_backend bk_db
+
+backend bk_db
+	option httpchk GET
+
+  server postgresql_127.0.0.1_5432 127.0.0.1:5432 maxconn 100 check port 15432
+  server postgresql_127.0.0.1_5433 127.0.0.1:5433 maxconn 100 check port 15433

haproxy_status.sh

@@ -0,0 +1,16 @@
+#!/bin/bash
+
+while true
+do {
+        response=$(echo "SELECT pg_is_in_recovery();" | psql -t postgres --port $2 --host $1 2> /dev/null)
+
+        if [ "${response}" == " f" ]
+        then
+                echo "HTTP/1.1 200 OK"
+                echo "X-XLOG-POSITION: $(echo "SELECT pg_current_xlog_location();" | psql -t postgres 2> /dev/null | tr -d ' ' | head -n 1)"
+        else
+                echo "HTTP/1.1 503 Service unavailable"
+                echo "X-XLOG-POSITION: $(echo "SELECT pg_last_xlog_replay_location();" | psql -t postgres 2> /dev/null | tr -d ' ' | head -n 1)"
+        fi
+
+} | nc -l $3; done