com.datastax.oss.driver.internal.core.time.Clock Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.datastax.oss.driver.internal.core.time;
import com.datastax.oss.driver.internal.core.os.Native;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* A small abstraction around system clock that aims to provide microsecond precision with the best
* accuracy possible.
*/
public interface Clock {
Logger LOG = LoggerFactory.getLogger(Clock.class);
/**
* Returns the best implementation for the current platform.
*
* Usage with non-blocking threads: beware that this method may block the calling thread on its
* very first invocation, because native libraries used by the driver will be loaded at that
* moment. If that is a problem, consider invoking this method once from a thread that is allowed
* to block. Subsequent invocations are guaranteed not to block.
*/
static Clock getInstance(boolean forceJavaClock) {
if (forceJavaClock) {
LOG.info("Using Java system clock because this was explicitly required in the configuration");
return new JavaClock();
} else if (!Native.isCurrentTimeMicrosAvailable()) {
LOG.info(
"Could not access native clock (see debug logs for details), "
+ "falling back to Java system clock");
return new JavaClock();
} else {
LOG.info("Using native clock for microsecond precision");
return new NativeClock();
}
}
/**
* Returns the difference, measured in microseconds, between the current time and and the
* Epoch (that is, midnight, January 1, 1970 UTC).
*/
long currentTimeMicros();
}