Upstream service php-fpm is up and running but reports {"errors": {"status_code": 502,"status": "php-fpm server is down"}}

[Kaushal Shriyan]

Hi Maxim,

I have a follow up question regarding the settings below in nginx.conf
where the php-fpm upstream server is processing all php files for Drupal
CMS.

fastcgi_intercept_errors off
proxy_intercept_errors off

User -> Nginx -> php-fpm -> MySQL DB.

For example if the php-fpm upstream server is down then nginx should render
502 bad gateway
                     if MySQL DB service is down then nginx should render
500 ISE.

Is there a way to render any of the messages or any custom messages to the
User from the php-fpm upstream server that should be passed to a client
without being intercepted by the Nginx web server. Any examples? I have
attached the file for your reference. Please guide me. Thanks in advance.

Best Regards,

Kaushal

On Fri, Dec 16, 2022 at 7:22 AM Kaushal Shriyan <kaushalshriyan at gmail.com>
wrote:

>
>
> On Fri, Dec 16, 2022 at 1:38 AM Maxim Dounin <mdounin at mdounin.ru> wrote:
>
>> Hello!
>>
>> On Thu, Dec 15, 2022 at 09:53:11PM +0530, Kaushal Shriyan wrote:
>>
>> >
>> > I am running the nginx version: nginx/1.22 as a reverse proxy server on
>> > CentOS Linux release 7.9.2009 (Core). When I hit
>> http://mydomain.com/apis I
>> > see the below message on the browser even if the upstream server php-fpm
>> > server is up and running.
>> >
>> > *{"errors": {"status_code": 502,"status": "php-fpm server is down"}}*
>> >
>> > I have set the below in the nginx.conf file and attached the file for
>> your
>> > reference.
>> >
>> > if ($upstream_http_content_type = "") {
>> >                      add_header 'Content-Type' 'application/json'
>> always;
>> >                      add_header 'Content-Type-3'
>> > $upstream_http_content_type$isdatatypejson"OK" always;
>> >                       return 502 '{"errors": {"status_code":
>> 502,"status":
>> > "php-fpm server is down"}}';
>> >                   }
>>
>> The "if" directive makes it possible to conditionally select
>> configuration to handle a request, and therefore can only use
>> information available before the request is handled.  In your
>> case, before the request is sent to the upstream server.  See
>> http://nginx.org/en/docs/http/ngx_http_rewrite_module.html for
>> more details.
>>
>> As such, $upstream_http_content_type will be always empty, since
>> there are no upstream response yet, and therefore the
>> configuration will always return 502.  This matches your
>> observations.
>>
>> An obvious fix would be to remove the configuration chunk in
>> question.
>>
>> Instead, you probably need something like:
>>
>>     error_page 502 /502.json;
>>
>>     location = /502.json {
>>         return 200 '{"errors": {"status_code": 502, "status": "php-fpm
>> server is down"}}';
>>     }
>>
>>
> Thanks Maxim for the suggestion. I will try it out and keep you posted
> with the testing as it progresses. I am obliged to this mailing list.
> Thanks in advance.
>
> Best Regards,
>
> Kaushal
>
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