The application writes the errors with following codes when something fails when trying to fetch the given URL.
1X - Bad Input
E10 - Invalid URL
The given URL is invalid. For example:http://example.com:bad-port/
2X - DNS errors
E20 - Invalid Domain
The URL has non existant domain.
E21 - DNS Timeout
The hostname couldn't be resolved within :ref:`config_dns_timeout` seconds.
3X - Connection Errors
E30 - Connection Refused
Connection refused by the server.
E31 - Connect Timeout
Connection couldn't be established within :ref:`config_connect_timeout` seconds.
E32 - Initial Data Timeout
Initial data (HTTP headers) couldn't be obtained within :ref:`config_initial_data_timeout` seconds.
E33 - Read Timeout
When reading data from the remote server, no data was received for :ref:`config_read_timeout` seconds.
E34 - Connection Dropped
The remote server dropped the connection before all the data was received.
E39 - Unexpected Connection Error
Unexpected connection error when receiving data from the remote server.
4X - Resource Limits
E40 - Response Too Big
The response length is bigger than :ref:`config_max_response_size` bytes.
E41 - Request Took Too Long
The request was not completed within :ref:`config_max_request_time` seconds.
In all these cases, the application responds back with status
with a record contain status
302 Bad Gateway.