Common 503 errors – debugging fastly help guides gas vs diesel prices


Increasing your backend timeout settings. After benchmarking some of the slower paths in your application, you should have an idea of your ideal backend response time. Adjust the backend timeout values on the Edit a host page in the Advanced options area. Also, if there is an external interface in front of the origin (such as a load balancer or firewall), review the timeouts for these interfaces. Error 503 connection timed out

This error occurs if the request times out while waiting for Fastly to establish a TCP connection to your origin or waiting for your origin to respond to the request. Similar to backend read errors, connection timeouts can be caused by transient network issues, long trips to origin, and origin latency. Two common ways to alleviate these timeout errors include:

This error generally occurs because of a network issue between the client and Fastly. It can also occur when a user abandons the loading of a page (e.g., a page is loading too slowly and the user clicks stop in the browser). It is similar to the backend read error but occurs when reading information from a client. If you get this error, contact Fastly support for help identifying the network issue. Origin configuration errors

This error occurs when Fastly attempts to make a connection to your origin over a specific port and the server refuses the connection. It typically appears when the wrong port is specified for the host in the Fastly web interface. To resolve this error, you may need to adjust your port number to ensure you’re using the port needed to connect to your origin. If adjusting your port number doesn’t work, you may also need review your origin configurations to ensure you’re allowing connections from Fastly specific IPs. Error 503 illegal vary header from backend

This error occurs when a backend returns a malformed vary header with its response. A well-formed vary header tells Fastly to serve a different version of an object based on the value of the request header included within it. Error 503 network unreachable

This error appears when Fastly can’t find a route to the given IP range. This generally occurs because of misconfigured or non-operational routers. To resolve this error, check your routers to ensure they are operational or configured correctly. Origin health errors

This error appears when custom health checks report a backend as down. It typically occurs when a Fastly edge server receives a client request and must make a request to your origin, but because the backend is considered unhealthy, Fastly doesn’t try to send the request at all. This error may mistakenly appear instead of the backend.max_conn reached error the first time Fastly encounters the maximum number of connections to your backend. Some of the reasons this error may occur are:

This error occurs when you configure Fastly to serve stale objects in the event of a backend failure but the stale object has expired and your backend is still failing for some reason (thus, no stale object is available). To resolve this error, you will need either to fix your origin or check your network. Connection limit errors

This error occurs when Varnish makes a request to a backend in your Fastly service that has reached its defined maximum number of connections. By default, Fastly limits you to 200 origin connections from a single edge node to protect the origins from overload. For the majority of sites, this should be enough. If you get this error message with less than 10,000 non-hit requests per second, make sure your origin is responding normally (e.g., there are no origin slow downs). If you just increase the number of maximum connections, you may be exacerbating the problem. If you have determined that your origin is not the issue, increase the maximum connections limit to your origin or reach out to Fastly support for further help with this issue. This error may also appear as "Error 503 maximum threads for service reached." Error 503 maximum threads for service reached

This error occurs when a Director used for balancing requests among a group of backends (only available via the Fastly API) can’t cache the specified content because there are no healthy backends available in its group. Error 503 all backends failed or unhealthy

This error occurs when a Director used for balancing requests among a group of backends (only available via the Fastly API) fails because all the backends are unhealthy or multiple backends from which the Director tried to fetch information failed with the same error. Error 503 quorum weight not reached

To resolve any of these errors, you should either check for and resolve any issues with your origin or make sure the quorum setting is correct. Also, make sure you are setting the quorum setting correctly. For example, in a five backend director, 85% of the quorum will mark the director unhealthy if a single backend is unhealthy. TLS errors

This error occurs when a certificate in the certificate chain is missing or invalid. To better determine which of these issues is the cause of the error, we suggest running an SSL test on your origin to highlight any issues with the certificate installed there. There are two common ways you can resolve this error:

This error occurs when the certificate hostname specified in your service’s origin TLS settings does not match either the Common Name (CN) or available Subject Alternate Names (SANs). To resolve this error, enter a certificate hostname value that matches the CN or SAN entries on your origin’s certificate. Error 503:14077410:SSL routines:SSL23_GET_SERVER_HELLO:sslv3 alert

This error occurs when Server Name Indication (SNI) is required in the TLS handshake to origin, but the SNI hostname field is either blank or incorrect. To correct this error, enter a hostname value in the SNI hostname field. Often this will match the value specified in the certificate hostname field. Error 503 certificate has expired