org.apache.sis.util.logging

## Class PerformanceLevel

- Object
- - Level
  - - PerformanceLevel

- All Implemented Interfaces:
    Serializable

      public final class PerformanceLevel
      extends Level

  Logging levels for measurements of execution time. Different logging levels - `SLOW`, `SLOWER` and `SLOWEST` - are provided in order to log only the events taking more than some time duration. For example the console could log only the slowest events, while a file could log all events considered slow.

  Every levels defined in this class have a value between the `Level​.FINE` and `Level​.CONFIG` values. Consequently performance logging are disabled by default, and enabling them imply enabling configuration logging too. This is done that way because the configuration typically have a significant impact on performance.

  Enabling performance logging
  Performance logging can be enabled in various ways. Among others:
  - The `$JAVA_HOME/lib/logging​.properties` file can be edited in order to log messages at the `FINE` level, at least for the packages of interest.
  - The `Logger​.setLevel(Level)` can be invoked, together with `Handler​.setLevel(Level)` on all relevant logging targets (console or file, etc.).
  - The `MonolineFormatter​.install(Logger, Level)` convenience method can be invoked.
  Since:
    0.3
  See Also:
    Serialized Form

  Defined in the `sis-utility` module

- - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `static PerformanceLevel` | `PERFORMANCE` The level for logging all time measurements, regardless of their duration.
    `static PerformanceLevel` | `SLOW` The level for logging relatively slow events.
    `static PerformanceLevel` | `SLOWER` The level for logging only events slower than the ones logged at the `SLOW` level.
    `static PerformanceLevel` | `SLOWEST` The level for logging only slowest events.

    - ### Fields inherited from class Level

      `ALL, CONFIG, FINE, FINER, FINEST, INFO, OFF, SEVERE, WARNING`

  - ### Method Summary

    All Methods Static Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `static PerformanceLevel` | `forDuration(long duration, TimeUnit unit)` Returns the level to use for logging an event of the given duration.
    `long` | `getMinDuration(TimeUnit unit)` Returns the minimal duration for logging an event at this level.
    `void` | `setMinDuration(long duration, TimeUnit unit)` Sets the minimal duration for logging an event at this level.

    - ### Methods inherited from class Level

      `equals, getLocalizedName, getName, getResourceBundleName, hashCode, intValue, parse, toString`

    - ### Methods inherited from class Object

      `clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

- - ### Field Detail

    - #### PERFORMANCE

          public static final PerformanceLevel PERFORMANCE

      The level for logging all time measurements, regardless of their duration. The value of this level is 600.

    - #### SLOW

          public static final PerformanceLevel SLOW

      The level for logging relatively slow events. By default, only events having an execution time equals or greater than 0.1 second are logged at this level. However this threshold can be changed by a call to `SLOW.setMinDuration(long, TimeUnit)`.

    - #### SLOWER

          public static final PerformanceLevel SLOWER

      The level for logging only events slower than the ones logged at the `SLOW` level. By default, only events having an execution time equals or greater than 1 second are logged at this level. However this threshold can be changed by a call to `SLOWER.setMinDuration(long, TimeUnit)`.

    - #### SLOWEST

          public static final PerformanceLevel SLOWEST

      The level for logging only slowest events. By default, only events having an execution time equals or greater than 5 seconds are logged at this level. However this threshold can be changed by a call to `SLOWEST.setMinDuration(long, TimeUnit)`.

  - ### Method Detail

    - #### forDuration

          public static PerformanceLevel forDuration(long duration,
                                                     TimeUnit unit)

      Returns the level to use for logging an event of the given duration.
      Parameters:
        `duration` - the event duration.
        `unit` - the unit of the given duration value.
      Returns:
        the level to use for logging an event of the given duration.

    - #### getMinDuration

          public long getMinDuration(TimeUnit unit)

      Returns the minimal duration for logging an event at this level.
      Parameters:
        `unit` - the unit in which to express the minimal duration.
      Returns:
        the minimal duration in the given unit.

    - #### setMinDuration

          @Configuration
          public void setMinDuration(long duration,
                                                    TimeUnit unit)
                                             throws IllegalArgumentException

      Sets the minimal duration for logging an event at this level. Invoking this method may have an indirect impact of other performance levels:
      - If the given duration is longer than the duration of slower levels, then the later are also set to the given duration.
      - If the given duration is shorter than the duration of faster levels, then the later are also set to the given duration.
      Usage note: The duration of the `PERFORMANCE` level can not be modified: it is always zero. However invoking this method on the `PERFORMANCE` field will ensure that every `SLOW*` levels will have at least the given duration.
      Parameters:
        `duration` - the minimal duration.
        `unit` - the unit of the given duration value.
      Throws:
        `IllegalArgumentException` - if the given duration is negative.

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