wait_until_active script for update checking

docker/wait_until_active.sh

@@ -0,0 +1,19 @@
+#!/bin/bash
+
+URL="http://localhost:2342"
+TIMEOUT=5
+INTERVAL=1
+ELAPSED=0
+
+while true; do
+    if curl --output /dev/null --silent --head --fail "$URL"; then
+        exit 0
+    fi
+
+    if [[ $ELAPSED -ge $TIMEOUT ]]; then
+        exit 1
+    fi
+
+    sleep $INTERVAL
+    ELAPSED=$((ELAPSED + INTERVAL))
+done