feat(Makefile): retry discovery-url five times

Author: mboersma

Makefile

@@ -31,7 +31,19 @@ dev-cluster: discovery-url
 	deisctl install platform
 
 discovery-url:
-	sed -e "s,discovery #DISCOVERY_URL,discovery $$(curl -s -w '\n' https://discovery.etcd.io/new?size=$$DEIS_NUM_INSTANCES)," contrib/coreos/user-data.example > contrib/coreos/user-data
+	@for i in 1 2 3 4 5; do \
+		URL=`curl -s -w '\n' https://discovery.etcd.io/new?size=$$DEIS_NUM_INSTANCES`; \
+		if [ ! -z $$URL ]; then \
+			sed -e "s,discovery #DISCOVERY_URL,discovery $$URL," contrib/coreos/user-data.example > contrib/coreos/user-data; \
+			echo "Wrote $$URL to contrib/coreos/user-data"; \
+		    break; \
+		fi; \
+		if [ $$i -eq 5 ]; then \
+			echo "Failed to contact https://discovery.etcd.io after $$i tries"; \
+		else \
+			sleep 3; \
+		fi \
+	done
 
 build: check-docker
 	@$(foreach C, $(COMPONENTS), $(MAKE) -C $(C) build &&) echo done