Question

Web SIte ACross Multiple Servers WIth Authentication

Asked by: Fatlog

hi,

this is probably more of a discussion thing.
i have an application which is located on multiple servers. a complete version of the application is located on ecah server and runs away doing its thing. runs fine. no issues there. i have a website that gathers data from each server and displays it on one page. this is important. all the data has to be displayed in one loctaion. webiste is built in PHP and MySQL. Server is linux and webserver is apache there are two issues that i want to get opinions on...

1. i currently use CURL to request data from each server(data is returned as xml) and then combine this data together to form the page for the user. is this the best way to share data between the servers? or would it be better/more advisable to just connect directly to each servers version of MySQL and query it for the data directly instead of requesting and generating XML. this is more a design consideration than functionality. if you were building an application across multiple servers what approach would you take? the servers are all located within the same providers data centre and have private net.

2. my second issue is authentication. i currently employ a simple cookie system for authenticating users. i want to move to using digest authentication across all my sub-domains so a user can move from one server to the next without being asked for username/password again. this works fine in practice(got around the MS IE problems with GET variables as well). only problem is none of my current CURL requests between servers work when i use digest. if i were to stick with the CURL setup is there anyway to allow page requests that originate from the server/domain to be bypass the authentication check?

any and all commenst are welcome.

thanks

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Asked On
2006-09-22 at 03:15:43ID21998997
Topic

Apache Web Server

Participating Experts
2
Points
100
Comments
5

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Answers

 

by: periwinklePosted on 2006-09-22 at 14:56:11ID: 17581050

Might it make more sense to password protect using MySQL database table?  Then you could just access the appropriate server, and keep records of who is logged in, and the time they last accessed the site (so that you could tell if the login had expired)?

 

by: shatteredstonePosted on 2006-09-23 at 09:01:04ID: 17583904

For issue #1 :
This really depends on your application. If all the intermediary is doing is repackaging a mySQL response (i.e. no processing to speak of), going directly to an SQL connection will be speedier with less overhead (XML processing, by and large, is slow). If you envision that the data source may, at some point, be externalized, going with Web-Services like you do might be preferrable, since you'll be able to more easily write wrappers.
If "all" that the backend server is doing is holding data, then running just mySQL and giving it as many resources as possible with as few context switches as possible is, IMHO, a better use of resources than running a complete Web server stack on the same machine, as well.

#2 :
This depends again on how you currently implement authentication :-) Sure it's possible to stip digest authentication based on source addresses. (On Apache, the Satisfy directive (http://httpd.apache.org/docs/2.2/mod/core.html#satisfy) would be what you are looking for).
I'm wondering though ... since you use CURL to query data from backend-servers -- are those backend-server enduser-visible ? If so, why ?

 

by: FatlogPosted on 2006-09-24 at 10:25:55ID: 17587613

hi,

thanks for the replies. in response to periwinkle. the reason i am going down the  HTTP Digest route is that i have a number of files that i cannot add any user validation code to for various reasons. i need to be able to secure the entire directory.

shatterdstone.
#1. yeah thats what i was thinking. i can't forsee the data sources being externalized. so i probably would be better having direct mysql connections for gathering the data.

#2. yeas the back-end servers are end-user visible. never really thought of not having them end  user visible. thinking of it now they probably should be. only reason i can think of for having them end user visible is redundancy. if one server goes down i can move the reporting element to one of the orther servers. but in reality this is highly unlikely as they are well managed and constantly monitored by the providers.

so i take it you're recommendation would be to change from using CURL requests to conections to MySQL? this should also remedy my authentication question.

any other comments or issues that spring to mind?

 

by: shatteredstonePosted on 2006-09-24 at 23:38:41ID: 17590070

In this case yes, direct connections to the DB should yield a nice performance boost and eliminate one link that could break.

As for having the back-ends user-visible : you could still achieve essentially the same flexibility by using RFC1918-addresses (i.e. 10.x.x.x or 192.168.x.x or similar) for communication between your servers within your vlan/switch-segment, but still assign a public IP address/DNS name to each of them. You could then configure them as a hot-spare and still switch in times of need. Backend services would not be exposed on the public IP addresses, just the private ones. (This will not be the most secure setup, since that would imply that the backend-servers have no connections to the internet at large at all and communicate over a switch that is not connected to a router; depending on the sensitivity on your data, that may be the way to go, but that's another question entirely ;)

Other issues depend on your application. If the volume gets too high to be handled by a single database instance or a single webserver generating reports, either can be scaled up fairly painlessly (the database by making it a cluster -- although the MySQL clustering solutions are not yet very mature -- disk-based clustering has only been available since very recently (5.1), memory-based clustering since 5.0; If you intend to update the database a lot, this would still be the only way to keep the data consistent between database servers. If, however, your queries are mostly reads in nature and do not have to be 100% time-consistent (within bounds), you could use database replication, which mySQL has supported since 3.x versions; in that case you'd have a master database that is being replicated to multiple slaves; write queries would only be sent to the master, while read-queries would be load-balanced between the slaves (and potentially the master as well. The webserver-side of things can be scaled up by various means of load-balancing (from the simple DNS round robin, to the more complex dedicated hardware balancing solutions, to anycast-systems spanning the globe).
In any case it would be a good idea to plan for this eventuality by designing your application with future scalability in mind :-)

20120131-EE-VQP-002

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