Please check the following to avoid HTTP Error: 503.
1.) Please check if there is enough free disk space available for SearchBlox to operate.
2.) Delete the ../elasticsearch/data folder before starting elasticsearch.
3.) Delete the ../webapps/searchblox/tempdocs folder before starting SearchBlox.
After you access the SearchBlox console, please re-index the collections as the search index will be reset.
To learn more about monitoring SearchBlox read: Monitoring SearchBlox