// @flow
// Copyright (c) 2016 Uber Technologies, Inc.
//
// 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
//
// 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.
import assert from 'assert';
import * as constants from '../constants.js';
import ProbabilisticSampler from './probabilistic_sampler.js';
import GuaranteedThroughputSampler from './guaranteed_throughput_sampler.js';
type SamplersByOperation = { [key: string]: GuaranteedThroughputSampler, __proto__: null };
// PerOperationSampler keeps track of all operation names it is asked to sample
// and uses GuaranteedThroughputSampler for each operation name to ensure
// that all endpoints are represented in the sampled traces. If the number
// of distinct operation names exceeds maxOperations, all other names are
// sampled with a default probabilistic sampler.
export default class PerOperationSampler {
_maxOperations: number;
_samplersByOperation: SamplersByOperation;
_defaultSampler: ProbabilisticSampler;
_defaultLowerBound: number;
constructor(strategies: PerOperationSamplingStrategies, maxOperations: number) {
this._maxOperations = maxOperations;
this._samplersByOperation = Object.create(null);
this.update(strategies);
}
update(strategies: PerOperationSamplingStrategies): boolean {
assert(
typeof strategies.defaultLowerBoundTracesPerSecond === 'number',
'expected strategies.defaultLowerBoundTracesPerSecond to be number'
);
assert(
typeof strategies.defaultSamplingProbability === 'number',
'expected strategies.defaultSamplingProbability to be number'
);
let updated: boolean = this._defaultLowerBound !== strategies.defaultLowerBoundTracesPerSecond;
this._defaultLowerBound = strategies.defaultLowerBoundTracesPerSecond;
strategies.perOperationStrategies.forEach(strategy => {
let operation = strategy.operation;
let samplingRate = strategy.probabilisticSampling.samplingRate;
let sampler = this._samplersByOperation[operation];
if (sampler) {
if (sampler.update(this._defaultLowerBound, samplingRate)) {
updated = true;
}
} else {
sampler = new GuaranteedThroughputSampler(this._defaultLowerBound, samplingRate);
this._samplersByOperation[operation] = sampler;
updated = true;
}
});
let defaultSamplingRate = strategies.defaultSamplingProbability;
if (!this._defaultSampler || this._defaultSampler.samplingRate != defaultSamplingRate) {
this._defaultSampler = new ProbabilisticSampler(defaultSamplingRate);
updated = true;
}
return updated;
}
name(): string {
return 'PerOperationSampler';
}
toString(): string {
return `${this.name()}(maxOperations=${this._maxOperations})`;
}
isSampled(operation: string, tags: any): boolean {
let sampler: Sampler = this._samplersByOperation[operation];
if (!sampler) {
if (Object.keys(this._samplersByOperation).length >= this._maxOperations) {
return this._defaultSampler.isSampled(operation, tags);
}
sampler = new GuaranteedThroughputSampler(this._defaultLowerBound, this._defaultSampler.samplingRate);
this._samplersByOperation[operation] = sampler;
}
return sampler.isSampled(operation, tags);
}
equal(other: Sampler): boolean {
return false; // TODO equal should be removed
}
close(callback: ?Function): void {
// all nested samplers are of simple types, so we do not need to Close them
if (callback) {
callback();
}
}
}
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