Module jdk.jfr

Package jdk.jfr

Annotation Interface Period

@Retention(RUNTIME)
@Inherited
@Target(TYPE)
public @interface Period

Event annotation, specifies the default setting value for a periodic event.

The following example shows how the Period annotation can be used to emit events at different intervals.

@Period("1 s")
@Name("Counter")
class CountEvent extends Event {
    int count;
}
@Period("3 s")
@Name("Fizz")
class FizzEvent extends Event {
}
@Period("5 s")
@Name("Buzz")
class BuzzEvent extends Event {
}

var counter = new AtomicInteger();
FlightRecorder.addPeriodicEvent(CountEvent.class, () -> {
    CountEvent event = new CountEvent();
    event.count = counter.incrementAndGet();
    event.commit();
});
FlightRecorder.addPeriodicEvent(FizzEvent.class, () -> {
    new FizzEvent().commit();
});
FlightRecorder.addPeriodicEvent(BuzzEvent.class, () -> {
    new BuzzEvent().commit();
});

var sb = new StringBuilder();
var last = new AtomicInteger();
var current = new AtomicInteger();
try (var r = new RecordingStream()) {
    r.onEvent("Counter", e -> current.set(e.getValue("count")));
    r.onEvent("Fizz", e -> sb.append("Fizz"));
    r.onEvent("Buzz", e -> sb.append("Buzz"));
    r.onFlush(() -> {
        if (current.get() != last.get()) {
            System.out.println(sb.isEmpty() ? current : sb);
            last.set(current.get());
            sb.setLength(0);
        }
    });
    r.start();
}

Since:

9

Optional Element Summary

Optional Elements

Modifier and Type	Optional Element	Description
String	value	Returns the default setting value for a periodic setting.

Field Summary

Fields

Modifier and Type	Field	Description
static final String	NAME	Settings name "period" for configuring periodic events

Field Details

NAME

static final String NAME

Settings name "period" for configuring periodic events

See Also:

• Constant Field Values

Element Details

value

String value

Returns the default setting value for a periodic setting.

String representation of a positive Long value followed by an empty space and one of the following units:

"ns" (nanoseconds)
"us" (microseconds)
"ms" (milliseconds)
"s" (seconds)
"m" (minutes)
"h" (hours)
"d" (days)

Example values: "0 ns", "10 ms", and "1 s".

A period may also be "everyChunk" to specify that it occurs at least once for every recording file. The number of events that are emitted depends on how many times the file rotations occur when data is recorded.

Returns:

the default setting value, not null

Default:

"everyChunk"