getNumPoolThreads(), which calls getPoolSize() is missing from Pollerd's MBean.
In addition, numPoolThreads, maxPoolThreads and peakPoolThreads are all missing from Pollerd's section in jmx-datacollection-config.xml.
This makes it impossible to graph how many available threads there are for Pollerd without manually keeping the graph updated with the configured amount of threads. Due to this, there is no ThreadPool graph for Pollerd as of the current version.
In addition, the existing ThreadPool graph for Collectd seems to graph two (nearly?) identical values as far as I can tell, due to getPoolSize() (numPoolThreads) and getMaximumPoolSize() (maxPoolThreads) being the same with the current fixed pool implementation.
The ThreadPool graph would be a lot more useful if it instead included the amount of currently active threads.
By including the amount of active threads, there would presumably be no need for a separate graph for this.
Updated sample graph, based on the most recent commit: