@opentelemetry/core
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OpenTelemetry Core provides constants and utilities shared by all OpenTelemetry SDK packages.
61 lines • 2.74 kB
JavaScript
;
/*
* Copyright The OpenTelemetry Authors
*
* Licensed 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
*
* https://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.
*/
Object.defineProperty(exports, "__esModule", { value: true });
exports.AnchoredClock = void 0;
/**
* A utility for returning wall times anchored to a given point in time. Wall time measurements will
* not be taken from the system, but instead are computed by adding a monotonic clock time
* to the anchor point.
*
* This is needed because the system time can change and result in unexpected situations like
* spans ending before they are started. Creating an anchored clock for each local root span
* ensures that span timings and durations are accurate while preventing span times from drifting
* too far from the system clock.
*
* Only creating an anchored clock once per local trace ensures span times are correct relative
* to each other. For example, a child span will never have a start time before its parent even
* if the system clock is corrected during the local trace.
*
* Heavily inspired by the OTel Java anchored clock
* https://github.com/open-telemetry/opentelemetry-java/blob/main/sdk/trace/src/main/java/io/opentelemetry/sdk/trace/AnchoredClock.java
*/
class AnchoredClock {
_monotonicClock;
_epochMillis;
_performanceMillis;
/**
* Create a new AnchoredClock anchored to the current time returned by systemClock.
*
* @param systemClock should be a clock that returns the number of milliseconds since January 1 1970 such as Date
* @param monotonicClock should be a clock that counts milliseconds monotonically such as window.performance or perf_hooks.performance
*/
constructor(systemClock, monotonicClock) {
this._monotonicClock = monotonicClock;
this._epochMillis = systemClock.now();
this._performanceMillis = monotonicClock.now();
}
/**
* Returns the current time by adding the number of milliseconds since the
* AnchoredClock was created to the creation epoch time
*/
now() {
const delta = this._monotonicClock.now() - this._performanceMillis;
return this._epochMillis + delta;
}
}
exports.AnchoredClock = AnchoredClock;
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