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https://issues.apache.org/jira/browse/GEODE-1494?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Anthony Baker closed GEODE-1494.
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> Allow users to provide callbacks to sample statistics
> -----------------------------------------------------
>
> Key: GEODE-1494
> URL: https://issues.apache.org/jira/browse/GEODE-1494
> Project: Geode
> Issue Type: Improvement
> Reporter: Dan Smith
> Assignee: Dan Smith
> Fix For: 1.0.0-incubating.M3
>
>
> The Statistics interface has methods to increment, set, and get the value of
> various statistics. The statistics are sampled at the sample-rate by the stat
> sampling thread.
> We should add a way to provide a callback that computes the value of the
> statistic. The callback can be called by the stat sampling thread to compute
> the value at the sample time.
> This is useful because some statistics are hard to update correctly using
> using increment operations. For example, tracking the total number of entries
> in a parallel async event queue is tricky, because buckets may move on and
> off of a node while concurrent operations are also adding entries. But
> measuring the current size of the queue is easy by just calling size on the
> underlying regions.
> Here are the proposed new methods on the statistics interface:
> {code}
> /**
> * Provide a callback to compute the value of this statistic
> * every sample interval and use that as the value of the stat.
> * <p>
> * The callback should return quickly because it is invoked on a shared
> thread.
> * It should not do any expensive computations, network calls, or access
> any resources
> * under locks that may be locked by long running processes.
> * <p>
> * This callback will only be invoked if the distributed system property
> * statistic-sampling-enabled is set to true, and it will be invoked at
> intervals
> * determined by the statistic-sampling-rate.
> * <p>
> * Get methods are not guaranteed to recompute a new value, they may return
> * the last sampled value
> * @param id a statistic id obtained with {@link #nameToId}
> * or {@link StatisticsType#nameToId}.
> * @param supplier a callback that will return the value of the stat. This
> * replaces any previously registered supplier. If the passed in suppplier
> is null, it
> * will remove any existing supplier
> * @return the previously registered supplier, or null if there was no
> previously registered supplier
> * @throws ArrayIndexOutOfBoundsException If the id is invalid.
> * @throws IllegalArgumentException if the type of this
> * stat is not int
> */
> public IntSupplier setIntSupplier(int id, IntSupplier supplier);
> public LongSupplier setLongSupplier(int id, LongSupplier supplier);
> public DoubleSupplier setDoubleSupplier(int id, DoubleSupplier supplier);
> public IntSupplier setIntSupplier(String name, IntSupplier supplier);
> public LongSupplier setLongSupplier(String name, LongSupplier supplier);
> public DoubleSupplier setDoubleSupplier(String name, DoubleSupplier
> supplier);
> public IntSupplier setIntSupplier(StatisticDescriptor descriptor,
> IntSupplier supplier);
> public LongSupplier setLongSupplier(StatisticDescriptor descriptor,
> LongSupplier supplier);
> public DoubleSupplier setDoubleSupplier(StatisticDescriptor descriptor,
> DoubleSupplier supplier);
> {code}
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