503 Server Error




In this century where the use of computer technology has become imperative in our day to day activities, users will encounter some issues such as a 503 backend fetch fail. It is normal that different computers with Windows operating systems and different brands often give different error notifications to show the same error problem.

Also, DNS_PROBE_FINISHED_NXDOMAIN error occurs when the DNS is not able to translate the website into other languages.

 

While in some cases, the user will notice the “503 error” shown on the screen, in some other cases, a word such as “503 error is used instead. According to errorcodespro.com, 503 backend fetch fail error can stand as for the status of a website. In general, it delivers this message to inform the user that the site is not working. It is a response message from the standard HyperText Transfer Protocol shown by the site. “Error 503 backend fetch failed” is a reference to the status of a web page. This error status code is five hundred, and this is equal to the internal server error. This can occur on all web browsers and all operating systems, including smartphones.

 

This issue is generally caused by web backend. However, errorcodespro.com stated that it is possible that this problem is with a user’s PC, but the probability of this is very low. Besides, it can be because the site visited was converted to maintenance mode which is displayed as “maintenance.flag” file. Hence, the user needs to remove the “maintenance.flag” to solve this problem.

There are various ways to solve this problem. One of the solutions according to James Huff is to try to manually reset the plugins which mean there are no requirements to access the dashboard.

When that issue is resolved, the next step is to reactivate each one individually until you found the cause(s).

 

However, then you can also choose to access the server via FTP or SFTP, navigate to   /wp-content/themes/   and rename the directory of the currently active theme if it’s that does not resolve the issue. This will force the default theme to activate and hopefully rule-out a theme-specific problem.

The next option is, Error 503 backend fetch failed can be solved by checking the plugin and make sure the Varnish Plugin is installed. Varnish plugins are used to increase web page speed. It is also used by some favorite web hosting companies. After Varnish Plugin is mounted on the server, the user needs to contact the network hosting the company concerned. Some of the resources state that you restart the router and modem if the Service meets DNS failure error and cannot be edited. It is also possible that the DNS server from router configuration is incorrect. So, restarting can be better option to resolve error 503.

 

Next is based on Recovery.com is by checking the plugin as the primary cause of the error 503

Is it Varnish plugin or its shortcomings. If the problem is on the site, you can check if the Varnish plugin is enabled. For those who do not know, Varnish is used to increase the speed of the website and is used by hosting companies. If plugins are allowed on the server, both hosting companies need might need a call.

The next option is to restart if the DNS failure is also on the card. This is quite is easy to solve. “Service DNS failure is not available” can signal problems with DNS instructions but you might need to restart. This correction can also help resolve errors such as “503 unhealthy backend errors” and “maximum 503 thread errors for services achieved”.

Based on github.com some of the cases can be solved by user’s probe settings with curl then replace:

.probe = {

.request =
“GET /status HTTP/1.1”
“Host: my_backend”
“Connection: close”
“User-Agent: Varnish Health Probe”;
.timeout = 5s;
.interval = 30s;
.window = 5;
.threshold = 3;
}

to the

.probe = {
.request =
“GET /status HTTP/1.1”
“Host: my_backend”
“Connection: close”
“User-Agent: Varnish Health Probe”;
.timeout = 5s;
.interval = 30s;
.window = 5;
.threshold = 3;
}

According to Mattias Geniar, the curl must be included ‘$ varnishadm -S /etc/varnish/secret -T localhost:6082 backends .list’. For the problem which is stating:-
Error 503 Backend fetch failed
Backend fetch failed
Guru Meditation:
XID: 3
Varnish cache server
It can be solved by removing

.probe = {
#.url = “/”; # short easy way (GET /)
# We prefer to only do a HEAD /
.request =
“HEAD / HTTP/1.1”
“Host: localhost”
“Connection: close”;

.interval = 5s; # check the health of each backend every 5 seconds
.timeout = 1s; # timing out after 1 second.
.window = 5; # If 3 out of the last five polls succeeded the backend is considered healthy; it will work. otherwise, it will be marked as sick
.threshold = 3;
}

Is Your Windows PC/Laptop Running Slow?

However, those probes can validate the backend, but might also not respond to those probes with a correct response. In this case, this backend can be called as “sick” and might not be able to serve traffic to it. The first try should be to run the health check from the varnish server and detect the response from it to replace the IP given below with the user’s backend server and the headers with everything from probe definition.

In this case, Mattias said the user should get an HTTP 200 OK response from it.

$ curl -i 12.23.34.45 -H "Host: yourdomain.tld" -H "Connection: close"


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