Architecture: Difference between revisions
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In a standard web application architecture, the incoming user traffic is distributed through load balancers to a number of application servers that run independent instances. These application servers access a shared storage, a shared database and a shared cache. This architecture scales well up to a 6 figure number of users. The application servers are easy to scale because doubling the number of servers doubles the performance. | In a standard web application architecture, the incoming user traffic is distributed through load balancers to a number of application servers that run independent instances. These application servers access a shared storage, a shared database and a shared cache. This architecture scales well up to a 6 figure number of users. The application servers are easy to scale because doubling the number of servers doubles the performance. | ||
But scalability limitations can be found in the shared components. These are the load balancers, the database, the storage and the cache.<ref>Nextcloud introduces an architecture called �Global Scale� that is designed to scale to hundreds of millions of users. https://nextcloud.com/blog/nextcloud-announces-global-scale-architecture-as-part-of-nextcloud-12/ | But scalability limitations can be found in the shared components. These are the load balancers, the database, the storage and the cache.<ref>Nextcloud introduces an architecture called �Global Scale� that is designed to scale to hundreds of millions of users. https://nextcloud.com/blog/nextcloud-announces-global-scale-architecture-as-part-of-nextcloud-12/ | ||
</ref> | </ref> | ||
This reference architecture is also incomplete because it does not address any of the related aspects of how you must integrate this architecture into your operations. It is obviously important that you must have a means to deploy the software onto the system. It is equally important that you configure, monitor and control the infrastructure to adjust over time. Even if the infrastructure �automatically� adjusts (failover, scale-up, scale-down), you need to be able to monitor and know how these systems are performing. If the software is at all developed or deployed internally, then you must also integrate the Development, Software Quality Assurance / Testing, and Release Management disciplines. We can take this even further to address things like how does the architecture enable you to migrate to various geographic locations ([https://wikitech.wikimedia.org/wiki/Switch_Datacenter switch data center]) or fail over in catastophe. | This reference architecture is also incomplete because it does not address any of the related aspects of how you must integrate this architecture into your operations. It is obviously important that you must have a means to deploy the software onto the system. It is equally important that you configure, monitor and control the infrastructure to adjust over time. Even if the infrastructure �automatically� adjusts (failover, scale-up, scale-down), you need to be able to monitor and know how these systems are performing. If the software is at all developed or deployed internally, then you must also integrate the Development, Software Quality Assurance / Testing, and Release Management disciplines. We can take this even further to address things like how does the architecture enable you to migrate to various geographic locations ([https://wikitech.wikimedia.org/wiki/Switch_Datacenter switch data center]) or fail over in catastophe. | ||
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== Data Persistence == | == Data Persistence == | ||
old [https://github.com/wikimedia/cdb Constant Database] (CDB) wrapper around PHP's [https://secure.php.net/manual/en/book.dba.php native PHP DBA functions] (which provides a flat file store like the [https://en.wikipedia.org/wiki/Berkeley_DB Berkeley DB] style databases) is now replaced by simple PHP arrays which are file included. This allows the HHVM opcode cache to precompile and cache these data structures. In MediaWiki, it is used for the [https://www.mediawiki.org/wiki/Interwiki_cache interwiki cache], and the localization cache. This is not to say that you will want or need WMF interwiki list, but having a performant cache for the interwiki links contained in ''your'' wiki farm<ref>e.g. see https://freephile.org/w/api.php?action=query&meta=siteinfo&siprop=interwikimap</ref> is probably important. | |||
</ref> is probably important. | |||
Persistent data is stored in the following ways: | Persistent data is stored in the following ways: | ||
