1 files changed, 133 insertions, 0 deletions
diff --git a/gemfeed/examples/conf/frontends/scripts/dns-failover.ksh b/gemfeed/examples/conf/frontends/scripts/dns-failover.ksh
new file mode 100644
index 00000000..dfc24ee3
--- /dev/null
+++ b/gemfeed/examples/conf/frontends/scripts/dns-failover.ksh
@@ -0,0 +1,133 @@
+#!/bin/ksh
+
+ZONES_DIR=/var/nsd/zones/master/
+DEFAULT_MASTER=fishfinger.buetow.org
+DEFAULT_STANDBY=blowfish.buetow.org
+
+determine_master_and_standby () {
+    local master=$DEFAULT_MASTER
+    local standby=$DEFAULT_STANDBY
+
+    # Weekly auto-failover for Let's Encrypt automation
+    local -i -r week_of_the_year=$(date +%U)
+    if [ $(( week_of_the_year % 2 )) -ne 0 ]; then
+        local tmp=$master
+        master=$standby
+        standby=$tmp
+    fi
+
+    local -i health_ok=1
+    if ! ftp -4 -o - https://$master/index.txt | grep -q "Welcome to $master"; then
+        echo "https://$master/index.txt IPv4 health check failed"
+        health_ok=0
+    elif ! ftp -6 -o - https://$master/index.txt | grep -q "Welcome to $master"; then
+        echo "https://$master/index.txt IPv6 health check failed"
+        health_ok=0
+    fi
+
+    if [ $health_ok -eq 0 ]; then
+        local tmp=$master
+        master=$standby
+        standby=$tmp
+    fi
+
+    echo "Master is $master, standby is $standby"
+
+    host $master | awk '/has address/ { print $(NF) }' >/var/nsd/run/master_a
+    host $master | awk '/has IPv6 address/ { print $(NF) }' >/var/nsd/run/master_aaaa
+    host $standby | awk '/has address/ { print $(NF) }' >/var/nsd/run/standby_a
+    host $standby | awk '/has IPv6 address/ { print $(NF) }' >/var/nsd/run/standby_aaaa
+}
+
+transform () {
+    sed -E '
+        /IN A .*; Enable failover/ {
+            /^standby/! {
+                s/^(.*) 300 IN A (.*) ; (.*)/\1 300 IN A '$(cat /var/nsd/run/master_a)' ; \3/;
+            }
+            /^standby/ {
+                s/^(.*) 300 IN A (.*) ; (.*)/\1 300 IN A '$(cat /var/nsd/run/standby_a)' ; \3/;
+            }
+        }
+        /IN AAAA .*; Enable failover/ {
+            /^standby/! {
+                s/^(.*) 300 IN AAAA (.*) ; (.*)/\1 300 IN AAAA '$(cat /var/nsd/run/master_aaaa)' ; \3/;
+            }
+            /^standby/ {
+                s/^(.*) 300 IN AAAA (.*) ; (.*)/\1 300 IN AAAA '$(cat /var/nsd/run/standby_aaaa)' ; \3/;
+            }
+        }
+        / ; serial/ {
+            s/^( +) ([0-9]+) .*; (.*)/\1 '$(date +%s)' ; \3/;
+        }
+    '
+}
+
+zone_is_ok () {
+    local -r zone=$1
+    local -r domain=${zone%.zone}
+    dig $domain @localhost | grep -q "$domain.*IN.*NS"
+}
+
+failover_zone () {
+    local -r zone_file=$1
+    local -r zone=$(basename $zone_file)
+
+    # Race condition (e.g. script execution abored in the middle previous run)
+    if [ -f $zone_file.bak ]; then
+        mv $zone_file.bak $zone_file
+    fi
+
+    cat $zone_file | transform > $zone_file.new.tmp 
+
+    grep -v ' ; serial' $zone_file.new.tmp > $zone_file.new.noserial.tmp
+    grep -v ' ; serial' $zone_file > $zone_file.old.noserial.tmp
+
+    echo "Has zone $zone_file changed?"
+    if diff -u $zone_file.old.noserial.tmp $zone_file.new.noserial.tmp; then
+        echo "The zone $zone_file hasn't changed"
+        rm $zone_file.*.tmp
+        return 0
+    fi
+
+    cp $zone_file $zone_file.bak
+    mv $zone_file.new.tmp $zone_file
+    rm $zone_file.*.tmp
+    echo "Reloading nsd"
+    nsd-control reload
+
+    if ! zone_is_ok $zone; then
+        echo "Rolling back $zone_file changes"
+        cp $zone_file $zone_file.invalid
+        mv $zone_file.bak $zone_file
+        echo "Reloading nsd"
+        nsd-control reload
+        zone_is_ok $zone
+        return 3
+    fi
+
+    for cleanup in invalid bak; do
+        if [ -f $zone_file.$cleanup ]; then
+            rm $zone_file.$cleanup
+        fi
+    done
+
+    echo "Failover of zone $zone to $MASTER completed"
+    return 1
+}
+
+main () {
+    determine_master_and_standby
+
+    local -i ec=0
+    for zone_file in $ZONES_DIR/*.zone; do
+        if ! failover_zone $zone_file; then
+            ec=1
+        fi
+    done
+
+    # ec other than 0: CRON will send out an E-Mail.
+    exit $ec
+}
+
+main