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package limithandler
import (
"context"
"strconv"
"sync"
"testing"
"time"
"github.com/stretchr/testify/assert"
"github.com/stretchr/testify/require"
"gitlab.com/gitlab-org/gitaly/v14/internal/testhelper"
)
type counter struct {
sync.Mutex
max int
current int
queued int
dequeued int
enter int
exit int
}
func (c *counter) up() {
c.Lock()
defer c.Unlock()
c.current = c.current + 1
if c.current > c.max {
c.max = c.current
}
}
func (c *counter) down() {
c.Lock()
defer c.Unlock()
c.current = c.current - 1
}
func (c *counter) currentVal() int {
c.Lock()
defer c.Unlock()
return c.current
}
func (c *counter) Queued(ctx context.Context) {
c.Lock()
defer c.Unlock()
c.queued++
}
func (c *counter) Dequeued(ctx context.Context) {
c.Lock()
defer c.Unlock()
c.dequeued++
}
func (c *counter) Enter(ctx context.Context, acquireTime time.Duration) {
c.Lock()
defer c.Unlock()
c.enter++
}
func (c *counter) Exit(ctx context.Context) {
c.Lock()
defer c.Unlock()
c.exit++
}
func TestLimiter(t *testing.T) {
t.Parallel()
tests := []struct {
name string
concurrency int
maxConcurrency int
iterations int
buckets int
wantMonitorCalls bool
}{
{
name: "single",
concurrency: 1,
maxConcurrency: 1,
iterations: 1,
buckets: 1,
wantMonitorCalls: true,
},
{
name: "two-at-a-time",
concurrency: 100,
maxConcurrency: 2,
iterations: 10,
buckets: 1,
wantMonitorCalls: true,
},
{
name: "two-by-two",
concurrency: 100,
maxConcurrency: 2,
iterations: 4,
buckets: 2,
wantMonitorCalls: true,
},
{
name: "no-limit",
concurrency: 10,
maxConcurrency: 0,
iterations: 200,
buckets: 1,
wantMonitorCalls: false,
},
{
name: "wide-spread",
concurrency: 1000,
maxConcurrency: 2,
// We use a long delay here to prevent flakiness in CI. If the delay is
// too short, the first goroutines to enter the critical section will be
// gone before we hit the intended maximum concurrency.
iterations: 40,
buckets: 50,
wantMonitorCalls: true,
},
}
for _, tt := range tests {
tt := tt
t.Run(tt.name, func(t *testing.T) {
t.Parallel()
ctx, cancel := testhelper.Context()
defer cancel()
expectedGaugeMax := tt.maxConcurrency * tt.buckets
if tt.maxConcurrency <= 0 {
expectedGaugeMax = tt.concurrency
}
gauge := &counter{}
limiter := NewLimiter(tt.maxConcurrency, gauge)
wg := sync.WaitGroup{}
wg.Add(tt.concurrency)
full := sync.NewCond(&sync.Mutex{})
// primePump waits for the gauge to reach the minimum
// expected max concurrency so that the limiter is
// "warmed" up before proceeding with the test
primePump := func() {
full.L.Lock()
defer full.L.Unlock()
gauge.up()
if gauge.max >= expectedGaugeMax {
full.Broadcast()
return
}
full.Wait() // wait until full is broadcast
}
// We know of an edge case that can lead to the rate limiter
// occasionally letting one or two extra goroutines run
// concurrently.
for c := 0; c < tt.concurrency; c++ {
go func(counter int) {
for i := 0; i < tt.iterations; i++ {
lockKey := strconv.Itoa((i ^ counter) % tt.buckets)
_, err := limiter.Limit(ctx, lockKey, func() (interface{}, error) {
primePump()
current := gauge.currentVal()
require.True(t, current <= expectedGaugeMax, "Expected the number of concurrent operations (%v) to not exceed the maximum concurrency (%v)", current, expectedGaugeMax)
require.True(t, limiter.countSemaphores() <= tt.buckets, "Expected the number of semaphores (%v) to be lte number of buckets (%v)", limiter.countSemaphores(), tt.buckets)
gauge.down()
return nil, nil
})
require.NoError(t, err)
}
wg.Done()
}(c)
}
wg.Wait()
assert.Equal(t, expectedGaugeMax, gauge.max, "Expected maximum concurrency")
assert.Equal(t, 0, gauge.current)
assert.Equal(t, 0, limiter.countSemaphores())
var wantMonitorCallCount int
if tt.wantMonitorCalls {
wantMonitorCallCount = tt.concurrency * tt.iterations
} else {
wantMonitorCallCount = 0
}
assert.Equal(t, wantMonitorCallCount, gauge.enter)
assert.Equal(t, wantMonitorCallCount, gauge.exit)
assert.Equal(t, wantMonitorCallCount, gauge.queued)
assert.Equal(t, wantMonitorCallCount, gauge.dequeued)
})
}
}
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