Add exponential backoff

entry.sh

@@ -1,4 +1,5 @@
 #!/bin/sh
+unset RETRY_INTERVAL
 while true; do
     RUN_TIME="$(date '+%s')"
     # shellcheck disable=SC2086
@@ -8,10 +9,17 @@ while true; do
     MOD_TIME="$(date -r "/data/$XMLTV_FILENAME" '+%s')"
     if test "$MOD_TIME" -gt "$RUN_TIME"; then
         echo "Will run again in $SLEEPTIME seconds."
+        unset RETRY_INTERVAL
         sleep "$SLEEPTIME"
+    elif [ -z "$RETRY_INTERVAL" ]; then
+        echo 'This run did not complete successfully, trying again...'
+        RETRY_INTERVAL='30'
     else
-        echo 'This run did not complete successfully.'
-        echo 'Pausing for 30 seconds and trying again...'
-        sleep 30
+        echo "This run did not complete successfully, trying again in $RETRY_INTERVAL seconds..."
+        sleep "$RETRY_INTERVAL"
+        RETRY_INTERVAL="$(( RETRY_INTERVAL * 2 ))"
+        if test "$RETRY_INTERVAL" -gt "$SLEEPTIME"; then
+            RETRY_INTERVAL='30'
+        fi
     fi
 done