demo: Add formatting and mounting to etcd image

Signed-off-by: Rolf Neugebauer <rolf.neugebauer@docker.com>

projects/demo/etcd/Dockerfile

@@ -1,6 +1,10 @@
 # A dockerfile to build an etcd container image from the upstream one
 # with a script as entry point
 FROM quay.io/coreos/etcd:v3.1.5
+
+# sfdisk and jq re required to mount the disk
+RUN apk add --no-cache sfdisk jq
+
 COPY ./etcd.sh /
 
 ENTRYPOINT ["/etcd.sh"]

projects/demo/etcd/etcd.sh

@@ -4,6 +4,39 @@
 set -x
 set -v
 
+MOUNTPOINT=/var/etcd
+
+mount_drive()
+{
+	mkdir -p "$MOUNTPOINT"
+
+	# TODO fix for multiple disks, cdroms etc
+	DEVS="$(find /dev -maxdepth 1 -type b ! -name 'loop*' ! -name 'nbd*' | grep -v '[0-9]$' | sed 's@.*/dev/@@' | sort)"
+
+	for DEV in $DEVS
+	do
+		DRIVE="/dev/${DEV}"
+
+		# see if it has a partition table
+		if sfdisk -d "${DRIVE}" >/dev/null 2>/dev/null
+		then
+			# 83 is Linux partition identifier
+			DATA=$(sfdisk -J "$DRIVE" | jq -e -r '.partitiontable.partitions | map(select(.type=="83")) | .[0].node')
+			if [ $? -eq 0 ]
+			then
+				mount "$DATA" "$MOUNTPOINT" && return
+			fi
+		fi
+	done
+
+	echo "WARNING: Failed to mount a persistent volume (is there one?)"
+
+	# not sure if we want to fatally bail here, in some debug situations it is ok
+	# exit 1
+}
+
+mount_drive
+
 # Wait till we have an IP address
 IP=""
 while [ -z "$IP" ]; do
@@ -17,13 +50,20 @@ PREFIX=$(echo ${IP} | cut -d . -f 1,2,3)
 NAME=infra${NUM}
 
 # This should come from Metadata
-INIT_CLUSTER=infra200=http://${PREFIX}.200:2380,infra201=http://${PREFIX}.201:2380,infra202=http://${PREFIX}.202:2380,infra203=http://${PREFIX}.203:2380,infra204=http://${PREFIX}.204:2380
+INIT_CLUSTER="infra200=http://${PREFIX}.200:2380,infra201=http://${PREFIX}.201:2380,infra202=http://${PREFIX}.202:2380,infra203=http://${PREFIX}.203:2380,infra204=http://${PREFIX}.204:2380"
 
-# Try to start in *new* cluster mode
+# We currently have no easy way to determine if we join a cluster for
+# the first time or if we got restarted and need to join an existing
+# cluster. So we first try joining a *new* cluster. This fails if we
+# had already joined it previously. As a fallback we then try to join
+# an existing cluster.
+
+# Try to join an new cluster
 /usr/local/bin/etcd \
     --name ${NAME} \
     --debug \
     --log-package-levels etcdmain=DEBUG,etcdserver=DEBUG \
+    --data-dir $MOUNTPOINT \
     --initial-advertise-peer-urls http://${IP}:2380 \
     --listen-peer-urls http://${IP}:2380 \
     --listen-client-urls http://${IP}:2379,http://127.0.0.1:2379 \
@@ -34,11 +74,12 @@ INIT_CLUSTER=infra200=http://${PREFIX}.200:2380,infra201=http://${PREFIX}.201:23
 
 [ $? -eq 0 ] && exit 0
 
-# Joining the new cluster failed. Let's try joining an *existing* cluster
+# Try to join an existing cluster
 /usr/local/bin/etcd \
     --name ${NAME} \
     --debug \
     --log-package-levels etcdmain=DEBUG,etcdserver=DEBUG \
+    --data-dir $MOUNTPOINT \
     --initial-advertise-peer-urls http://${IP}:2380 \
     --listen-peer-urls http://${IP}:2380 \
     --listen-client-urls http://${IP}:2379,http://127.0.0.1:2379 \