Viewing Counters

Counters are a mechanism that measures (counts) different things that occur in a grid node and that may be of interest for monitoring and diagnosing the inner workings of an application. Counters are maintained for each grid node and they are not persisted, so the information is lost if a node is stopped.

Good examples of counters are Used Heap, which shows the memory consumption, and Total Requests, which shows how many requests have been handled by a thread pool in a node. However, there are many others.

One very important aspect of counters is that the counter value is sampled periodically and a history of counter values is maintained for each counter. This makes it possible to view things like memory usage over time and even get the information displayed as a graph.

To view counters

  1. Navigate to the Topology Overview Page in the Grid Management Pages.
  2. Click the name link of the node you want to monitor (remember, counters belong to nodes).
  3. Click the Advanced link.
  4. Click the Counters link.

    A list of counters will be displayed. The displayed list shows the counters with their current value. Some counters define a valid value range. If a counter is outside of the valid range, it is marked with a yellow background. A counter that is outside of its valid range is unusual and is worth investigating.

  5. Clicking on the name of a counter will display a graph with the counter values over time. At the top of the page it is possible to select units of measurement and also how often the counter history should be polled and how much of it to keep in memory. The two latter settings may also be permanently configured using the following grid properties, Counters Poll Delay and Counters Keep History.