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      /** Registers generic custom metric. */

<T extends Metric> T metric(T metric);

/**
 * Custom metric manager. Allows to add own metrics in registers with names starting with "custom.".
 */
public interface IgniteMetrics {
    /**
     * Registers metric in register 'custom.' + {@code registryName}. Adds new register if absent.
     *
     * @return New {@code metric} if absent. Previous metric if exists with the same name.
     */
    <T extends Metric> T metric(String registryName, T metric);

    /** Removes custommetric metricfrom namedregister '"custom."' + {@code nameregistryName}'. */
    void removeMetric(String registryName, String namemetricName);

    /** @return custom Metric registry named '"custom." + {@code nameregistryName}'. */
    ReadOnlyMetricRegistry registry(String registryName);

    /** @return Removes registry named '"custom." + {@code registryName}'. */
    ReadOnlyMetricRegistry removeRegistry(String registryName);name);
   


    // Simple type metrics.

    /**
     * Registers {@link LongMetric} in register 'custom.' + {@code registryName}. Adds register if absent.
     *
     * @return New or previous long value setter.
     */
    LongConsumer longMetric(String registryName, String namemetricName, @Nullable String description);

    /**
     * Registers a {@link DoubleMetric} in register 'custom.' + {@code registryName}. Adds register if absent.
     *
     * @return New or previous double value setter.
     */
    DoubleConsumer doubleMetric(String registryName, String namemetricName, @Nullable String description);

    /**
     * Registers a {@link BooleanMetric} in register 'custom.' + {@code registryName}. Adds register if absent.
     *
     * @return New or previous boolean value setter.
     */
    Consumer<Boolean> booleanMetric(String registryName, String namemetricName, @Nullable String description);

    /**
     * Registers a {@link ObjectMetric} in register 'custom.' + {@code registryName}. Adds register if absent.
     *
     * @return New or previous object setter.
     */
    <T> Consumer<T> objectMetric(String registryName, String namemetricName, Class<T> valueType, @Nullable String description);


    // Might be useful the gauges:

   void doubleMetric(String name, DoubleSupplier /**
     * Registers a {@link LongMetric} metric in register 'custom.' + {@code registryName} with long value supplier {@code valueSupplier}. 
     * Adds register if absent.
     *
     * @return {@code True} if metric was added. {@code False} if another meric already exists under the same name.  
     */
    boolean longMetric(String registryName, String metricName, LongSupplier valueSupplier, @Nullable String description);

    /**
     * Registers a {@link DoubleMetric} metric in register 'custom.' + {@code registryName} with double value supplier {@code valueSupplier}. 
     * Adds register if absent.
     *
     * @return {@code True} if metric was added. {@code False} if another meric already exists under the same name.  
     */
   void boolean booleanMetricdoubleMetric(String registryName, String namemetricName, BooleanSupplierDoubleSupplier valueSupplier, @Nullable String description);

    /**
     * Registers a {@link BooleanMetric} metric in register 'custom.' + {@code registryName} with boolean value supplier {@code valueSupplier}. 
     * Adds register if absent.
     *
     * @return {@code True} if metric was added. {@code False} if another meric already exists under the same name.  
     */
   <T> voidboolean objectMetricbooleanMetric(String nameregistryName, Class<T>String valueTypemetricName, Supplier<T>BooleanSupplier valueSupplier, @Nullable String description);

    /**
     * Registers a {@link ObjectMetric} metric in register 'custom.' + {@code registryName} with object value supplier {@code valueSupplier}. 
     * Adds register if absent.
     *
     * @return {@code True} if metric was added. {@code False} if another meric already exists under the same name.  
     */
    <T> voidboolean longMetricobjectMetric(String registryName, String name metricName, Class<T> valueType, LongSupplierSupplier<T> valueSupplier, @Nullable String description);
}

Risks and Assumptions

    Custom metrics can affect the performance.

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