Update alertmanager image to v0.20.0

Update alertmanager image from v0.11.0 to v0.20.0

Change-Id: I0ba14d1001a53964ebc28bc9ea9be999402d54fb

prometheus-alertmanager/templates/bin/_alertmanager.sh.tpl

@@ -19,9 +19,9 @@ COMMAND="${@:-start}"
 
 function start () {
   exec /bin/alertmanager \
-    -config.file=/etc/alertmanager/config.yml \
+    --config.file=/etc/alertmanager/config.yml \
-    -storage.path={{ .Values.conf.command_flags.storage.path }} \
+    --storage.path={{ .Values.conf.command_flags.storage.path }} \
-    -mesh.listen-address={{ .Values.conf.command_flags.mesh.listen_address }} \
+    --cluster.listen-address={{ .Values.conf.command_flags.cluster.listen_address }} \
     $(generate_peers)
 }
 
@@ -29,7 +29,7 @@ function generate_peers () {
   final_pod_suffix=$(( {{ .Values.pod.replicas.alertmanager }}-1 ))
   for pod_suffix in `seq 0 "$final_pod_suffix"`
   do
-    echo -mesh.peer={{ .Release.Name }}-$pod_suffix.$DISCOVERY_SVC:$MESH_PORT
+    echo --cluster.peer={{ .Release.Name }}-$pod_suffix.$DISCOVERY_SVC:$MESH_PORT
   done
 }
 

prometheus-alertmanager/values.yaml

@@ -18,7 +18,7 @@
 ---
 images:
   tags:
-    alertmanager: docker.io/prom/alertmanager:v0.11.0
+    alertmanager: docker.io/prom/alertmanager:v0.20.0
     dep_check: quay.io/airshipit/kubernetes-entrypoint:v1.0.0
     image_repo_sync: docker.io/docker:17.07.0
   pull_policy: IfNotPresent
@@ -196,7 +196,7 @@ conf:
   command_flags:
     storage:
       path: /var/lib/alertmanager/data
-    mesh:
+    cluster:
       listen_address: "0.0.0.0:6783"
   alertmanager:
     global: