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fix(sdk-trace-base): make span start times resistant to hrtime clock drift #3129

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fix(sdk-trace-base): make span start times resistant to hrtime clock drift #3129

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fix(sdk-trace-base): make span start times resistant to hrtime clock …
dyladan Jul 29, 2022
cae2b54
Changelog
dyladan Jul 29, 2022
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dyladan Jul 29, 2022
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Merge branch 'main' into time-drift
dyladan Aug 1, 2022
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Merge branch 'main' into time-drift
MSNev Aug 3, 2022
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3 changes: 3 additions & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,9 @@ All notable changes to this project will be documented in this file.

### :bug: (Bug Fix)

* fix(sdk-trace-base): make span start times resistant to hrtime clock drift
[#3129](https://github.com/open-telemetry/opentelemetry-js/issues/3129)

### :books: (Refine Doc)

### :house: (Internal)
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12 changes: 12 additions & 0 deletions packages/opentelemetry-core/src/common/time.ts
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Expand Up @@ -121,6 +121,18 @@ export function hrTimeDuration(
return [seconds, nanos];
}

/**
* Add an HrTime duration to an HrTime
*/
export function addHrTime(time: api.HrTime, duration: api.HrTime): api.HrTime {
const out: api.HrTime = [time[0] + duration[0], time[1] + duration[1]];
if (out[1] >= 1e9) {
out[1] -= 1e9;
out[0] += 1;
}
return out;
}

/**
* Convert hrTime to timestamp, for example "2019-05-14T17:00:00.000123456Z"
* @param time
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18 changes: 18 additions & 0 deletions packages/opentelemetry-core/test/common/time.test.ts
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Expand Up @@ -27,6 +27,7 @@ import {
hrTimeToMicroseconds,
hrTimeToTimeStamp,
isTimeInput,
addHrTime,
} from '../../src/common/time';

describe('time', () => {
Expand Down Expand Up @@ -151,6 +152,23 @@ describe('time', () => {
});
});

describe('#addHrTime', () => {
it('should add two HrTimes', () => {
const startTime: api.HrTime = [22, 400000000];
const endTime: api.HrTime = [32, 200000000];

const output = addHrTime(startTime, endTime);
assert.deepStrictEqual(output, [54, 600000000]);
});
it('should overflow nanoseconds', () => {
const startTime: api.HrTime = [22, 600000000];
const endTime: api.HrTime = [32, 700000000];

const output = addHrTime(startTime, endTime);
assert.deepStrictEqual(output, [55, 300000000]);
});
});

describe('#hrTimeToTimeStamp', () => {
it('should return timestamp', () => {
const time: api.HrTime = [1573513121, 123456];
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22 changes: 16 additions & 6 deletions packages/opentelemetry-sdk-trace-base/src/Span.ts
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Expand Up @@ -23,6 +23,7 @@ import {
isTimeInput,
timeInputToHrTime,
sanitizeAttributes,
addHrTime,
} from '@opentelemetry/core';
import { Resource } from '@opentelemetry/resources';
import { SemanticAttributes } from '@opentelemetry/semantic-conventions';
Expand Down Expand Up @@ -59,6 +60,7 @@ export class Span implements api.Span, ReadableSpan {
private readonly _spanProcessor: SpanProcessor;
private readonly _spanLimits: SpanLimits;
private readonly _attributeValueLengthLimit: number;
private readonly _hrStartTime: api.HrTime;

/** Constructs a new Span instance. */
constructor(
Expand All @@ -69,14 +71,15 @@ export class Span implements api.Span, ReadableSpan {
kind: api.SpanKind,
parentSpanId?: string,
links: api.Link[] = [],
startTime: api.TimeInput = hrTime()
startTime?: api.TimeInput
) {
this.name = spanName;
this._spanContext = spanContext;
this.parentSpanId = parentSpanId;
this.kind = kind;
this.links = links;
this.startTime = timeInputToHrTime(startTime);
this._hrStartTime = hrTime();
this.startTime = timeInputToHrTime(startTime ?? Date.now());
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In principle it may happen that the process gets suspended for a few 100ms between line 81 and 82 resulting in two different start times - one used as start time one used to calc duration.

Not sure if it is worth to investigate a solution to avoid this. I could imagine that we could regularly update our own performance.timeOrigin instead of relying on that on from node.js.

I'm also not sure if Date.now() is worse performance wise as it might need to access the real time clock of the system and not just an high precision counter.

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If we regularly update timeOrigin we lose the primary benefits of the hrtime anyway if it isn't monotonic

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hrtime should be monotonic. To my understanding it only drifts away.
But yes, if the correction happens between span start/end the result my be strange.

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yeah that's what i meant. if we apply a correction regularly we might apply the correction during a span and end up with a strange result like end before start which was the primary reason to use the monotonic clock in the first place.

this.resource = parentTracer.resource;
this.instrumentationLibrary = parentTracer.instrumentationLibrary;
this._spanLimits = parentTracer.getSpanLimits();
Expand All @@ -103,7 +106,7 @@ export class Span implements api.Span, ReadableSpan {

if (
Object.keys(this.attributes).length >=
this._spanLimits.attributeCountLimit! &&
this._spanLimits.attributeCountLimit! &&
!Object.prototype.hasOwnProperty.call(this.attributes, key)
) {
return this;
Expand Down Expand Up @@ -171,15 +174,22 @@ export class Span implements api.Span, ReadableSpan {
return this;
}

end(endTime: api.TimeInput = hrTime()): void {
end(endTime?: api.TimeInput): void {
if (this._isSpanEnded()) {
api.diag.error('You can only call end() on a span once.');
return;
}
this._ended = true;
this.endTime = timeInputToHrTime(endTime);

this._duration = hrTimeDuration(this.startTime, this.endTime);

if (endTime != null) {
this.endTime = timeInputToHrTime(endTime);
this._duration = hrTimeDuration(this._hrStartTime, this.endTime);
} else {
this._duration = hrTimeDuration(this._hrStartTime, hrTime());
this.endTime = addHrTime(this.startTime, this._duration);
}

if (this._duration[0] < 0) {
api.diag.warn(
'Inconsistent start and end time, startTime > endTime',
Expand Down