Re: Load Balancer, fail tolerance and replication in PostgreSQL

["Miguel González Castaños" <mgc@tid.es>]

Sorry I pasted a message in Spanish above my message my English, sorry 
about that.

Regards,

Miguel

> Dear all,
>
>  We have a web application served by Apache with Tomcat behind for the 
> JSPs. The database backend is PostgreSQL. I have been asked to do some
> research about how to achieve fail tolerance and load balancing in our 
> application. After searching a little bit this is my first impression:
>
>  - There are integrated software for high availability using 
> PostgreSQL (i.e.: eRserver) but have commercial licences (you have to 
> pay a lot for it).
>
>  - There are some efforts for developing GPL application to achieve 
> replication, or load balancing or even clustering. My impression is 
> that they are in a earlier stage, but some of them look promising. 
> Anyway I am not very sure if any of them will suit into my setup (like 
> pgcluster or dbmirror).
>
>  What I have thought that in my setup maybe I just need to do 
> clustering  with servers with the same setup: Apache/Tomcat. Then, 
> just do some sort of replication between the PostgreSQL databases that 
> every node of the cluster should have (i dont know which is the best 
> GPL replication software). Even I thought that maybe I could use some 
> sort of dns round- robin approach for load balancing for Apache.
>
>  Anyway as you can see I´m pretty lost and I need some guidance to put 
> me in the right direction...
>
>  Sorry for my English
>
>  Many thanks in advance
>
>  Miguel
>
>
>
>
>
>
>
> Se que en Bulma sois mas forofos de MySQL que de PostgreSQL por
> vuestras experiencias con la web de bulma, pero tengo que hacer un
> estudio para usar PostgreSQL en un entorno donde se necesita balanceo de
> carga y tolerancia a fallos.
>
> Realmente lo que tenemos es una aplicacion web, con Apache y Tomcat
> como servidores de JSPs cuya base de datos es PostgreSQL, digo esto
> porque he pensado que tal vez lo de buscar un sistema de alta
> disponibilidad para PostgreSQL no sea necesario para este sistema, y
> simplemente lo que podria hacerse seria un cluster con Apache, o incluso
> utilizar un algoritmo round-robin que vaya pasando las solicitudes a los
> distintos servidores y un sistema de mirroring entre los distintos
> servidores PostgreSQL.
>
> He estado mirando en la página web de PostgreSQL y navegando un poco, y
> veo que hay alternativas que ofrecen alta disponibilidad (tolerancia a
> fallos, balanceo y replicacion), pero de pago.
>
> Como os digo se me ocurre a priori este enfoque que os digo, ya que
> realmente solo hay una base de datos que mantener sincronizada (creo que
> esto se puede hacer con dbmirror aunque no se si es solo a nivel de
> tablas o de bases de datos).
>
> Tambien he visto una herramienta llamada pgcluster. La verdad estoy un
> poco perdido, alguien me puede echar un cable?
>
> Un saludo
>
> Miguel
>
>
>
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