sample_test.go

// Copyright 2022 The OpenZipkin 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
//
//     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 zipkin_test

import (
	"fmt"
	"math/rand"
	"testing"
	"time"

	zipkin "github.com/openzipkin/zipkin-go"
)

func TestBoundarySampler(t *testing.T) {
	type triple struct {
		id       uint64
		salt     int64
		rate     float64
		hasError bool
	}
	for input, sampled := range map[triple]bool{
		{123, 456, 1.0, false}:               true,
		{123, 456, 999, true}:                true,
		{123, 456, 0.0, false}:               false,
		{123, 456, -42, true}:                false,
		{0xffffffffffffffff, 0, 0.01, false}: false,
		{0xa000000000000000, 0, 0.01, false}: false,
		{0x028f5c28f5c28f5f, 0, 0.01, false}: true,
		{0x028f5c28f5c28f60, 0, 0.01, false}: false,
		{1, 0xfffffffffffffff, 0.01, false}:  false,
		{999, 0, 0.99, false}:                true,
	} {
		sampler, err := zipkin.NewBoundarySampler(input.rate, input.salt)
		if want, have := input.hasError, (err != nil); want != have {
			t.Fatalf("%#+v: want error %t, have error %t", input, want, have)
		}
		if input.hasError {
			want := fmt.Errorf("rate should be 0.0 or between 0.0001 and 1: was %f", input.rate)
			if have := err; have == nil || want.Error() != have.Error() {
				t.Fatalf("%#+v: want error %+v, have error %+v", input, want, have)
			}
			continue
		}
		if want, have := sampled, sampler(input.id); want != have {
			t.Errorf("%#+v: want %v, have %v", input, want, have)
		}

	}
}

func TestBoundarySamplerProducesSamplingDecisionsTrueToTheRate(t *testing.T) {
	rand.Uint64()
	c := 0
	sampler, _ := zipkin.NewBoundarySampler(0.01, 0)
	n := 10000
	for i := 0; i < n; i++ {
		id := rand.Uint64()
		if sampler(id) {
			c++
		}
	}
	if !(c > 50 && c < 150) {
		t.Error("should sample at 1%, should be in vicinity of 100")
	}
}

func TestCountingSampler(t *testing.T) {
	{
		_, have := zipkin.NewCountingSampler(0.009)
		want := fmt.Errorf("rate should be 0.0 or between 0.01 and 1: was %f", 0.009)
		if have == nil || want.Error() != have.Error() {
			t.Errorf("rate 0.009, want error %+v, got %+v", want, have)
		}
	}
	{
		_, have := zipkin.NewCountingSampler(1.001)
		want := fmt.Errorf("rate should be 0.0 or between 0.01 and 1: was %f", 1.001)
		if have == nil || want.Error() != have.Error() {
			t.Errorf("rate 1.001, want error %+v, got %+v", want, have)
		}
	}
	for n := 0; n <= 100; n++ {
		var (
			rate       = float64(n) / 100
			sampler, _ = zipkin.NewCountingSampler(rate)
			found      = 0
		)
		for i := 0; i < 1000; i++ {
			if sampler(1) {
				found++
			}
		}
		if found != n*10 {
			t.Errorf("rate %f, want %d, have %d", rate, n, found)
		}
	}
}

func TestModuleSampler(t *testing.T) {
	rand.Seed(time.Now().Unix())

	for mod := uint64(1); mod <= 100; mod++ {
		var (
			sampler = zipkin.NewModuloSampler(mod)
			want    = uint64(rand.Intn(1000))
			max     = mod * want
			found   = uint64(0)
		)

		for i := uint64(0); i < max; i++ {
			if sampler(i) {
				found++
			}
		}

		if want, have := max/mod, found; want != have {
			t.Errorf("expected %d samples, got %d", want, have)
		}
	}

}