com.google.common.flogger.backend.system

Class Clock

java.lang.Object

com.google.common.flogger.backend.system.Clock

Direct Known Subclasses:

SystemClock

public abstract class Clock
extends java.lang.Object

A clock to return walltime timestamps for log statements. This is implemented as an abstract class (rather than an interface) to reduce to risk of breaking existing implementations if the API changes.

Essential Implementation Restrictions

Any implementation of this API MUST follow the rules listed below to avoid any risk of re-entrant code calling during logger initialization. Failure to do so risks creating complex, hard to debug, issues with Flogger configuration.

1. Implementations MUST NOT attempt any logging in static methods or constructors.
2. Implementations MUST NOT statically depend on any unknown code.
3. Implementations MUST NOT depend on any unknown code in constructors.

Note that logging and calling arbitrary unknown code (which might log) are permitted inside the instance methods of this API, since they are not called during platform initialization. The easiest way to achieve this is to simply avoid having any non-trivial static fields or any instance fields at all in the implementation.

While this sounds onerous it's not difficult to achieve because this API is a singleton, and can delay any actual work until its methods are called. For example if any additional state is required in the implementation, it can be held via a "lazy holder" to defer initialization.

Constructor Summary

Constructors

Constructor and Description
Clock()

Method Summary

Modifier and Type	Method and Description
abstract long	getCurrentTimeNanos() Returns the current time from the epoch (00:00 1st Jan, 1970) with nanosecond granularity, though not necessarily nanosecond precision.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Clock

public Clock()

Method Detail

getCurrentTimeNanos

public abstract long getCurrentTimeNanos()

Returns the current time from the epoch (00:00 1st Jan, 1970) with nanosecond granularity, though not necessarily nanosecond precision. This clock measures UTC and is not required to handle leap seconds.