In RHQ we support some kinds of metrics:
- Dynamic: metric values are 'randomly' going up and down. An example could be the free main memory of a computer
- Trendsup: a metric whose values are monotonically increasing. This could e.g. be the number of transactions committed or request served
- Trendsdown: the counterpart of trendsup where values are monotonically decreasing.
Usually the absolute number of commits or requests does not really tell much. More interesting is the dirst deviation by time: how many requests are coming in per minute. Here you can directly see if you have a request storm coming in or if it is quiet.
Now lets have a look at an excerpt from a screen shot of the metrics table in RHQ:
The counter for "requests served" will be reset to zero when the web-app is started again e.g. by fully restarting the web-container (or app server) .