Comments on: Replica Sets Part 2: What are Replica Sets?

By: ehcache.net

ehcache.net — Thu, 17 Mar 2011 15:44:26 +0000

Replica Sets Part 2: What are Replica Sets?…

you want to jump right into trying out replica sets, see Part 1: Master-Slave is so 2009. Replica sets are basically just master-slave with automatic failover. The idea is: you have a master and one or more slaves. If the master goes down, one of the s…

By: Anonymous

Anonymous — Wed, 17 Nov 2010 22:17:00 +0000

Thank you!

By: Eric Fer

Eric Fer — Wed, 17 Nov 2010 21:39:00 +0000

Congratulations for your post.
You did a great explanation. Even mongodb.org doesn’t have a text so clear and to the point.

By: Anonymous

Anonymous — Mon, 25 Oct 2010 15:49:00 +0000

The PHP driver is installed wherever your PHP code is running (your application server). If you are running your application server on a single machine that goes down, your website will go down and it won’t really matter what your database is doing. The remaining replica set members will failover and choose a new master, but no one will be connecting to it.

By: Bo

Bo — Sat, 23 Oct 2010 08:46:00 +0000

Thanks Kristina, you are being very helpful.

My last question to you is, what if the physical machine, that hosts the primary that is the mongodb and the php driver, is shut down for some reason? Then the php driver, who is as you say responsible for redirecting to a new master, not able to do so – what happens then?

By: Anonymous

Anonymous — Thu, 21 Oct 2010 15:23:00 +0000

You need each PHP install you’re using to have the latest driver installed, so you probably need to upgrade it on each app server you’re using.

The driver is responsible for redirecting to a new master. When you connect to the database using “replicaSet” => true, the driver will make a note of all of the members of the set. If the master goes down, it’ll try connecting to the others. You can print your connection (Mongo) object to see all of the members it knows about.

By: Bo

Bo — Thu, 21 Oct 2010 06:39:00 +0000

Hi Kristina

New driver installed, but I’m afraid it did not solve anything. Must be something wrong with my setup, my secondary and arbiter does not have any domain attached only the primary and there is no DNS magic between them only mongoDB that connects the 3.

Should all 3 mongoDBs have the latest PHP driver installed?

What is reponsible for redirecting to new master if server that holds the current master mongoDB is killed?

By: Anonymous

Anonymous — Tue, 19 Oct 2010 14:00:00 +0000

Yes, you can install the driver manually by downloading the source from Github, then running:

$ phpize && ./configure && sudo make install

from the command line.

By: Bo

Bo — Mon, 18 Oct 2010 21:48:00 +0000

Again thanks for answering (that quick).

I tried to do a manual installation following your advice but for some reason I cannot use PECL/phpize. I then tried to (re)install PEAR with lynx -source http://pear.php.net/go-pear | php but ran into a lot of error messages along the lines of “Warning: include_once(PEAR.php): failed to open stream: No such file or directory in – on line 682
” – is there another failproof way of installing the driver manually? Sorry for taking up your time with all these questions

By: Anonymous

Anonymous — Mon, 18 Oct 2010 15:36:00 +0000

I think there were some issues with failover in 1.0.10 of the PHP driver. I’ll be releasing 1.0.11 soon, but you could try the latest code (http://github.com/mongodb/mongo-php-driver) and see if that works better for you.

It will throw MongoConnectionExceptions until a new master is elected, but once it is the driver should failover.