cache_test.go

Documentation: github.com/go-kit/kit/sd/internal/instance

     1  package instance
     2  
     3  import (
     4  	"context"
     5  	"fmt"
     6  	"io"
     7  	"reflect"
     8  	"testing"
     9  	"time"
    10  
    11  	"github.com/go-kit/kit/endpoint"
    12  	"github.com/go-kit/kit/sd"
    13  	"github.com/go-kit/log"
    14  )
    15  
    16  var _ sd.Instancer = (*Cache)(nil) // API check
    17  
    18  // The test verifies the following:
    19  //   registering causes initial notification of the current state
    20  //   instances are sorted
    21  //   different update causes new notification
    22  //   identical notifications cause no updates
    23  //   no updates after de-registering
    24  func TestCache(t *testing.T) {
    25  	e1 := sd.Event{Instances: []string{"y", "x"}} // not sorted
    26  	e2 := sd.Event{Instances: []string{"c", "a", "b"}}
    27  
    28  	cache := NewCache()
    29  	if want, have := 0, len(cache.State().Instances); want != have {
    30  		t.Fatalf("want %v instances, have %v", want, have)
    31  	}
    32  
    33  	cache.Update(e1) // sets initial state
    34  	if want, have := 2, len(cache.State().Instances); want != have {
    35  		t.Fatalf("want %v instances, have %v", want, have)
    36  	}
    37  
    38  	r1 := make(chan sd.Event)
    39  	go cache.Register(r1)
    40  	expectUpdate(t, r1, []string{"x", "y"})
    41  
    42  	go cache.Update(e2) // different set
    43  	expectUpdate(t, r1, []string{"a", "b", "c"})
    44  
    45  	cache.Deregister(r1)
    46  	close(r1)
    47  }
    48  
    49  func expectUpdate(t *testing.T, r chan sd.Event, expect []string) {
    50  	select {
    51  	case e := <-r:
    52  		if want, have := expect, e.Instances; !reflect.DeepEqual(want, have) {
    53  			t.Fatalf("want: %v, have: %v", want, have)
    54  		}
    55  	case <-time.After(time.Second):
    56  		t.Fatalf("did not receive expected update %v", expect)
    57  	}
    58  }
    59  
    60  func TestRegistry(t *testing.T) {
    61  	reg := make(registry)
    62  	c1 := make(chan sd.Event, 1)
    63  	c2 := make(chan sd.Event, 1)
    64  	reg.register(c1)
    65  	reg.register(c2)
    66  
    67  	// validate that both channels receive the update
    68  	reg.broadcast(sd.Event{Instances: []string{"x", "y"}})
    69  	if want, have := []string{"x", "y"}, (<-c1).Instances; !reflect.DeepEqual(want, have) {
    70  		t.Fatalf("want: %v, have: %v", want, have)
    71  	}
    72  	if want, have := []string{"x", "y"}, (<-c2).Instances; !reflect.DeepEqual(want, have) {
    73  		t.Fatalf("want: %v, have: %v", want, have)
    74  	}
    75  
    76  	reg.deregister(c1)
    77  	reg.deregister(c2)
    78  	close(c1)
    79  	close(c2)
    80  	// if deregister didn't work, broadcast would panic on closed channels
    81  	reg.broadcast(sd.Event{Instances: []string{"x", "y"}})
    82  }
    83  
    84  // This test is meant to be run with the race detector enabled: -race.
    85  // It ensures that every registered observer receives a copy
    86  // of sd.Event.Instances because observers can directly modify the field.
    87  // For example, endpointCache calls sort.Strings() on sd.Event.Instances.
    88  func TestDataRace(t *testing.T) {
    89  	instances := make([]string, 0)
    90  	// the number of iterations here maters because we need sort.Strings to
    91  	// perform a Swap in doPivot -> medianOfThree to cause a data race.
    92  	for i := 1; i < 1000; i++ {
    93  		instances = append(instances, fmt.Sprintf("%v", i))
    94  	}
    95  	e1 := sd.Event{Instances: instances}
    96  	cache := NewCache()
    97  	cache.Update(e1)
    98  	nullEndpoint := func(_ context.Context, _ interface{}) (interface{}, error) {
    99  		return nil, nil
   100  	}
   101  	nullFactory := func(instance string) (endpoint.Endpoint, io.Closer, error) {
   102  		return nullEndpoint, nil, nil
   103  	}
   104  	logger := log.Logger(log.LoggerFunc(func(keyvals ...interface{}) error {
   105  		return nil
   106  	}))
   107  
   108  	sd.NewEndpointer(cache, nullFactory, logger)
   109  	sd.NewEndpointer(cache, nullFactory, logger)
   110  }
   111
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