Tungsten Monitor is focused on a single problem: providing continuous notifications of the state of resources in a cluster. Each monitor executes a simple process loop to check the resource and broadcast the resulting status. The status information answers the following questions:
- What type of resource is this?
- What is its name?
- Is the resource up or down?
- If a replica database, what is the latency compared to a master?
First, there's no centralized agent framework. You just start a monitor on a replicator, database, etc., and it starts to generate notifications. The off-the-shelf configuration monitors Tungsten Replicator--to get started you unpack code, copy one file, and start. That's it. The monitor figures out everything else automatically.
Second, Tungsten Monitor broadcasts notifications using group communications, which is a protocol for reliable, broadcast messaging between a set of processes known as a "group." Manager processes can tell that a new resource is available because its monitor joins the group and starts to broadcast notifications that the resource is up. If the new resource is a database, this is enough for a smart proxying service to start sending traffic to it automatically without any further management intervention.
Third, you can add new resource checks and notification methods yourself. With just 13 Java classes to start, you obviously won't be getting a lot off the shelf. :) We will add MySQL, PostgreSQL, and Oracle monitors shortly but any competent Java programmer could do the same in an hour or two without waiting for us.
In the meantime, you can download Tungsten Monitor source and binary builds from SourceForge.net. Also, here's a wiki article that describes basic installation and configuration. Take it for a spin, especially if you are using Tungsten Replicator already.
Interested? I hope so. Tungsten Monitor integrates with another of our March projects to route SQL connections automatically to available databases in a master/slave or master/master cluster. Stay tuned for more on that next week. Things are just starting to get interesting around here.
p.s., I did a bit of coding on the monitor but it really belongs to Gillles Rayrat, a colleague of mine in Grenoble. Nice job, Gilles!