Re: mod_proxy in Apache 2.2 and HTTP_INTERNAL_SERVER_ERROR
-Ursprüngliche Nachricht- Von: Jiri Tulach - Position Gesendet: Freitag, 14. Dezember 2007 08:39 An: dev@httpd.apache.org Betreff: Re: mod_proxy in Apache 2.2 and HTTP_INTERNAL_SERVER_ERROR It's possible fault of mod_fastcgi which returns HTTP_INTERNAL_SERVER_ERROR in cases when server is overloaded or external fastcgi instances are unavailable. Unfortunately mod_fastcgi is not actively developed even thought lot of people use it in production sites. But I still don't understand why proxy which has an option to get proper data from another (probably) working server stops trying to failover. I think from proxy point of view it doesn't matter why server is unavailable. Or am I missing something? 1. HTTP_INTERNAL_SERVER_ERROR can be the result of an internal proxy problem. In this case it would be wrong failing over. 2. If HTTP_INTERNAL_SERVER_ERROR is returned it is possible that the backend processed at least parts of the request. And at least for non idempotent requests it would be entirely wrong to fail over. So please fix mod_fastcgi to return the correct error code. This is NO bug of the proxy. Regards Rüdiger Thanx for comments. Jiri Tulach William A. Rowe, Jr. napsal(a): Mladen Turk wrote: Jir wrote: is there any reason why HTTP_INTERNAL_SERVER_ERROR returned by proxy handler cannot failover to another worker? Because HTTP_INTERNAL_SERVER_ERROR is used to represent either misconfiguration or even worse things like memory allocation failures. In essence non recoverable error. However, I'm not saying some scheme handler doesn't have bug returning HTTP_INTERNAL_SERVER_ERROR instead something else. Considering we have... #define HTTP_BAD_GATEWAY 502 #define HTTP_SERVICE_UNAVAILABLE 503 #define HTTP_GATEWAY_TIME_OUT 504 it seems like most of the INTERNAL_SERVER_ERROR's should be considered for more explicit messages, eh?
Re: mod_proxy in Apache 2.2 and HTTP_INTERNAL_SERVER_ERROR
Jiri Tulach - Position wrote: It's possible fault of mod_fastcgi which returns HTTP_INTERNAL_SERVER_ERROR in cases when server is overloaded or external fastcgi instances are unavailable. Unfortunately mod_fastcgi is not actively developed even thought lot of people use it in production sites. But I still don't understand why proxy which has an option to get proper data from another (probably) working server stops trying to failover. I think from proxy point of view it doesn't matter why server is unavailable. Or am I missing something? The ajp proxy may have sent the request and get a partial response if you fail over after HTTP_INTERNAL_SERVER_ERROR you may duplicate a transaction. Cheers Jean-Frederic Thanx for comments. Jiri Tulach William A. Rowe, Jr. napsal(a): Mladen Turk wrote: Jir wrote: is there any reason why HTTP_INTERNAL_SERVER_ERROR returned by proxy handler cannot failover to another worker? Because HTTP_INTERNAL_SERVER_ERROR is used to represent either misconfiguration or even worse things like memory allocation failures. In essence non recoverable error. However, I'm not saying some scheme handler doesn't have bug returning HTTP_INTERNAL_SERVER_ERROR instead something else. Considering we have... #define HTTP_BAD_GATEWAY 502 #define HTTP_SERVICE_UNAVAILABLE 503 #define HTTP_GATEWAY_TIME_OUT 504 it seems like most of the INTERNAL_SERVER_ERROR's should be considered for more explicit messages, eh?
Re: mod_proxy in Apache 2.2 and HTTP_INTERNAL_SERVER_ERROR
On Fri, 14 Dec 2007 09:43:12 +0100 jean-frederic clere [EMAIL PROTECTED] wrote: But I still don't understand why proxy which has an option to get proper data from another (probably) working server stops trying to failover. I think from proxy point of view it doesn't matter why server is unavailable. Or am I missing something? The ajp proxy may have sent the request and get a partial response if you fail over after HTTP_INTERNAL_SERVER_ERROR you may duplicate a transaction. That argues that we might make want to identify idempotent requests and treat them differently. That's going to get a bit hairy: we may be using HTTP status codes in inconsistent ways here: - as errors propagated from a backend. - as errors generated in the proxy XYZ is unrecoverable. - as HTTP representations of errors from another protocol. I think the mod_proxy scheme handlers would need to decide whether a backend request can be retried, and return different statuses for when it is/isn't. That's what it does with the INTERNAL_SERVER_ERROR vs SERVICE_UNAVAILABLE distinction, albeit that's not really adequate if it's doubling up as what we return to the client. If the OP has in mind an improved scheme, perhaps he should think it through to the point where he can hack up a proposal? -- Nick Kew Application Development with Apache - the Apache Modules Book http://www.apachetutor.org/
Re: mod_proxy in Apache 2.2 and HTTP_INTERNAL_SERVER_ERROR
Hello, sorry, but I don't agree :(. 1. HTTP_INTERNAL_SERVER_ERROR can be the result of an internal proxy problem. In this case it would be wrong failing over. This means that current implementation mixes internal errors with errors on back end. I suggest to consider implementing different error status handling to distinguish what fails. 2. If HTTP_INTERNAL_SERVER_ERROR is returned it is possible that the backend processed at least parts of the request. And at least for non idempotent requests it would be entirely wrong to fail over. and jean-frederic clere wrote: The ajp proxy may have sent the request and get a partial response if you fail over after HTTP_INTERNAL_SERVER_ERROR you may duplicate a transaction. I believe most of the users want correct response from the server instead of partial. Also if server is in error state the partial response could be totally wrong or may contain inappropriate informations. /?q=inappropriatelang=en_cz If we talking about transactions how do you prevent user to don't repeat the same request if he see that his previous request failed? Ok maybe there is not user on other site but machine. So make this behavior configurable in cases where you can ensure specific environment conditions. So please fix mod_fastcgi to return the correct error code. This is NO bug of the proxy. a) I don't said there is a bug. I only asked why it is implemented in that way. b) I said mod_fastcgi is not in active development. There is almost no support for this module and I'm not a developer of this module. But this don't change the fact this is a popular module and widely used. c) You have configuration option in proxy for bad formated headers (ProxyBadHeader) so you probably assume not all back ends are correctly implemented. Why don't have another option to ensure correct responses from proxy? Sorry guys but you still didn't convinced me why proxy should care about one specific back end error - HTTP_INTERNAL_SERVER_ERROR. I rather think there is a problem with mixing internal status errors and back end errors mentioned in 1) above. But maybe I'm wrong. Regards Jiri Tulach Plüm napsal(a): -Ursprüngliche Nachricht- Von: Jiri Tulach - Position Gesendet: Freitag, 14. Dezember 2007 08:39 An: dev@httpd.apache.org Betreff: Re: mod_proxy in Apache 2.2 and HTTP_INTERNAL_SERVER_ERROR It's possible fault of mod_fastcgi which returns HTTP_INTERNAL_SERVER_ERROR in cases when server is overloaded or external fastcgi instances are unavailable. Unfortunately mod_fastcgi is not actively developed even thought lot of people use it in production sites. But I still don't understand why proxy which has an option to get proper data from another (probably) working server stops trying to failover. I think from proxy point of view it doesn't matter why server is unavailable. Or am I missing something? 1. HTTP_INTERNAL_SERVER_ERROR can be the result of an internal proxy problem. In this case it would be wrong failing over. 2. If HTTP_INTERNAL_SERVER_ERROR is returned it is possible that the backend processed at least parts of the request. And at least for non idempotent requests it would be entirely wrong to fail over. So please fix mod_fastcgi to return the correct error code. This is NO bug of the proxy. Regards Rüdiger Thanx for comments. Jiri Tulach William A. Rowe, Jr. napsal(a): Mladen Turk wrote: Jir wrote: is there any reason why HTTP_INTERNAL_SERVER_ERROR returned by proxy handler cannot failover to another worker? Because HTTP_INTERNAL_SERVER_ERROR is used to represent either misconfiguration or even worse things like memory allocation failures. In essence non recoverable error. However, I'm not saying some scheme handler doesn't have bug returning HTTP_INTERNAL_SERVER_ERROR instead something else. Considering we have... #define HTTP_BAD_GATEWAY 502 #define HTTP_SERVICE_UNAVAILABLE 503 #define HTTP_GATEWAY_TIME_OUT 504 it seems like most of the INTERNAL_SERVER_ERROR's should be considered for more explicit messages, eh?
Re: mod_proxy in Apache 2.2 and HTTP_INTERNAL_SERVER_ERROR
Mladen Turk wrote: Jir wrote: is there any reason why HTTP_INTERNAL_SERVER_ERROR returned by proxy handler cannot failover to another worker? Because HTTP_INTERNAL_SERVER_ERROR is used to represent either misconfiguration or even worse things like memory allocation failures. In essence non recoverable error. However, I'm not saying some scheme handler doesn't have bug returning HTTP_INTERNAL_SERVER_ERROR instead something else. Considering we have... #define HTTP_BAD_GATEWAY 502 #define HTTP_SERVICE_UNAVAILABLE 503 #define HTTP_GATEWAY_TIME_OUT 504 it seems like most of the INTERNAL_SERVER_ERROR's should be considered for more explicit messages, eh?
Re: mod_proxy in Apache 2.2 and HTTP_INTERNAL_SERVER_ERROR
Jir wrote: Hello, is there any reason why HTTP_INTERNAL_SERVER_ERROR returned by proxy handler cannot failover to another worker? Because HTTP_INTERNAL_SERVER_ERROR is used to represent either misconfiguration or even worse things like memory allocation failures. In essence non recoverable error. However, I'm not saying some scheme handler doesn't have bug returning HTTP_INTERNAL_SERVER_ERROR instead something else. Regards, Mladen
Re: mod_proxy in Apache 2.2 and HTTP_INTERNAL_SERVER_ERROR
It's possible fault of mod_fastcgi which returns HTTP_INTERNAL_SERVER_ERROR in cases when server is overloaded or external fastcgi instances are unavailable. Unfortunately mod_fastcgi is not actively developed even thought lot of people use it in production sites. But I still don't understand why proxy which has an option to get proper data from another (probably) working server stops trying to failover. I think from proxy point of view it doesn't matter why server is unavailable. Or am I missing something? Thanx for comments. Jiri Tulach William A. Rowe, Jr. napsal(a): Mladen Turk wrote: Jir wrote: is there any reason why HTTP_INTERNAL_SERVER_ERROR returned by proxy handler cannot failover to another worker? Because HTTP_INTERNAL_SERVER_ERROR is used to represent either misconfiguration or even worse things like memory allocation failures. In essence non recoverable error. However, I'm not saying some scheme handler doesn't have bug returning HTTP_INTERNAL_SERVER_ERROR instead something else. Considering we have... #define HTTP_BAD_GATEWAY 502 #define HTTP_SERVICE_UNAVAILABLE 503 #define HTTP_GATEWAY_TIME_OUT 504 it seems like most of the INTERNAL_SERVER_ERROR's should be considered for more explicit messages, eh?
