Introduce Exponential retry for review-apps commands

scripts/review_apps/review-apps.sh

@@ -130,7 +130,7 @@ function disable_sign_ups() {
 
   # Create the root token + Disable sign-ups
   local disable_signup_rb="token = User.find_by_username('root').personal_access_tokens.create(scopes: [:api], name: 'Token to disable sign-ups'); token.set_token('${REVIEW_APPS_ROOT_TOKEN}'); begin; token.save!; rescue(ActiveRecord::RecordNotUnique); end; Gitlab::CurrentSettings.current_application_settings.update!(signup_enabled: false)"
-  if (retry "run_task \"${disable_signup_rb}\""); then
+  if (retry_exponential "run_task \"${disable_signup_rb}\""); then
     echoinfo "Sign-ups have been disabled successfully."
   else
     echoerr "Sign-ups are still enabled!"

scripts/utils.sh

@@ -10,6 +10,28 @@ function retry() {
       return 0
     fi
   done
+
+  return 1
+}
+
+# Retry after 2s, 4s, 8s, 16s, 32, 64s, 128s
+function retry_exponential() {
+  if eval "$@"; then
+    return 0
+  fi
+
+  local sleep_time=0
+  # The last try will be after 2**7 = 128 seconds (2min8s)
+  for i in 1 2 3 4 5 6 7; do
+    sleep_time=$((2 ** i))
+
+    echo "Sleep for $sleep_time seconds..."
+    sleep $sleep_time
+    echo "[$(date '+%H:%M:%S')] Attempt #$i..."
+    if eval "$@"; then
+      return 0
+    fi
+  done
   return 1
 }