How Bobcares prevents configuration errorsДЄs a quick aside, hereвЂ™s how we prevent server errors related to config issues.Д¬onfiguration errors are generally caused by stale server settings thatвЂ™s not adjusted for new traffic or site upgrades. We are online 24/7 and can attend your ticket within a few mins. If you need help fixing a similar error, click here to talk to our Nginx admins. If you are not familiar with PHP or web server settings, it is best to ask a server administrator. WARNING: server reached max_children setting (30), consider raising itД®RROR: unable to read what child say: Bad file descriptor (9) this error here says the PHP application reached the maximum limit of processes (defined by pm.max_children setting) allowed. You really need to scan the error log and pay attention to what the error says.ДЇor eg. There is no easy way to find out a configuration error. Capacity limits (like no: of connections per IP) set too restrictively causing legit visits to fail.Incorrect memory or file limits set for PHP applications.Apache firewall settings (mod_security) syntax error causing Apache to crash.DB login details set incorrectly after a recent migration, restore or upgrade.DNS resolver misconfigured in Nginx causing domain lookups to fail.Some configuration issues that weвЂ™ve seen are: If even one of these services have a wrong config entry, that service will fail to respond, and Nginx will show вЂњ502 bad gatewayвЂќ error. This includes DNS resolution, Apache processes, PHP services, DB server, etc. Your Nginx server and the backend services relies on many sub-systems to work properly. We are online 24/7 and can help you in a few minutes. If your server is currently under high load, and you need urgent help, click here to contact our Emergency Server Support techs. The we find out which service is abusing that resource, and from that point, find out which user in that service owns the abusive script or software.Д¬lick here to know more about high load troubleshooting. To troubleshoot a high load issue, first we figure out which resource is being abused (I/O, Memory, CPU or Net). Application bugs that cause memory leaks or resource hogging.Brute force attacks thatвЂ™s designed to exploit web apps.Comment spamming or other vulnerability exploits.Sudden spike in website traffic (can be seasonal or marketing / promotional).WeвЂ™ve seen these reasons for load spikes: Load spikes cause services to not respond. The second most common reason for вЂњ502 bad gatewayвЂќ in Nginx is high load average in backend servers. Click here if you need help resolving your server error. If the service restart didnвЂ™t work, you may need to get someone to take a closer look at the server health. Warning : Do not use these commands if you are not sure how it works. * Restarting PHP FastCGI Process Manager php-fpm If you suspect a backend service is unresponsive or failed, you can try killing all unresponsive processes and restarting the service.ДЇor instance, hereвЂ™s one way we kill defunct PHP-FPM processes and restart services. The reasons for service failure can range from traffic spikes and resource limits to disk errors and DDoS attacks. Some services that weвЂ™ve seen to fail are: So, if any of these services crash or freeze, Nginx wonвЂ™t get any data from them, resulting in вЂњ502 Bad gatewayвЂќ error. Nginx depends on backend services like PHP-FPM, database services and cache servers to run web applications.

WeвЂ™ve listed the top 5 reasons for 502 Bad Gateway error, and how we fix them. You know something is messed up, because it says вЂњ failedвЂќ and вЂњ refusedвЂњ.Д«ut WHAT? You hardly have time to get a PhD in computer science. So, many web masters roll up their sleeves and look at the error log:Д¤ 08:34:43 949#949: * 7 connect() failed (111: Connection refused) while connecting to upstream, client:, server:, request: 'GET /myurl-this/ HTTP/1.0', subrequest: '/redis-fetch', upstream: 'redis://127.0.0.1:6379', host: '', referrer: '' 3 word error message вЂ“ because Nginx doesnвЂ™t love you.

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