...

    IgniteMetrics metrics();

}

3.  Interfaces for existing metrics

...

Instead of #4, we could create interfaces for the existing metrics implementations.

...

3.3 Updatable metric interfaces list

To the package "org.apache.ignite.metric" we add:

• BooleanValueMetric
• IntValueMetric
• LongValueMetric
• LongSumMetric (a long adder)
• DoubleValueMetric
• AnyValueMetric<T> (an object metric)

...

    /**
    * Adds a long value custom metric.
    *
    * @return New or previously registered long value metric. {@code Null} if previous metric is not a {@link LongConsumer}.
    */
    @Nullable LongConsumer longMetric(String registryName, String metricName, @Nullable String description);

    /**
    * Adds a double value custom metric.
    *
    * @return New or previously registered long value metric. {@code Null} if previous metric is not a {@link DoubleConsumer}.
    */
    @Nullable DoubleConsumer doubleMetric(String registryName, String metricName, @Nullable String description);

    /**
    * Adds a int value custom metric.
    *
    * @return New or previously registered long value metric. {@code Null} if previous metric is not an {@link IntConsumer}.
    */
    @Nullable IntConsumer booleanMetric(String registryName, String metricName, @Nullable String description);

    /**
    * Adds a long value custom metric.
    *
    * @return {@code True} if {@code supplier} has been registered as a new int metric. {@code False}, if a previous
    * value supplier already exists.
    */
    boolean longMetric(String registryName, String metricName, LongSupplier supplier, @Nullable String description);

    /**
    * Adds a double value custom metric.
    *
    * @return {@code True} if {@code supplier} has been registered as a new int metric. {@code False}, if a previous
    * value supplier already exists.
    */
    boolean doubleMetric(String registryName, String metricName, DoubleSupplier supplier, @Nullable String description);

    /**
    * Adds a int value custom metric.
    *
    * @return {@code True} if {@code supplier} has been registered as a new int metric. {@code False}, if a previous
    * value supplier already exists.
    */
    boolean intMetric(String registryName, String metricName, BooleanSupplier supplier, @Nullable String description);

    /** Removes certain custom metric. */
    void removeCustomMetric(String registryName, String metricName);

    /** Removes entire custom metric registry. */
    void removeCustomRegistry(String registryName);

    /** Provides custom or internal read-only metric registry. */
    @Nullable ReadOnlyMetricRegistry findRegistry(String registryName);
}

Code example

Custom metric within a service

...

/** */
public static final class TestCustomMetricsService implements TestService {
    /** */
    @IgniteInstanceResource
    private Ignite ignite;

    /** */
    @ServiceContextResource
    private ServiceContext ctx;

    /** */
    private AtomicReference<UUID> remoteId;

    /** */
    private final AtomicInteger metricValue = new AtomicInteger();

    /** {@inheritDoc} */
    @Override public void init() throws Exception {
        remoteId = new AtomicReference<>();
          

...