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[aggregator] Fix panic on shutdown in ForwardedWriter #2987

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merged 1 commit into from
Dec 7, 2020
Merged

[aggregator] Fix panic on shutdown in ForwardedWriter #2987

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16 changes: 9 additions & 7 deletions src/aggregator/aggregator/forwarded_writer.go
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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,7 @@ import (
xerrors "github.com/m3db/m3/src/x/errors"

"github.com/uber-go/tally"
"go.uber.org/atomic"
)

const (
Expand Down Expand Up @@ -141,7 +142,7 @@ type forwardedWriter struct {
shard uint32
client client.AdminClient

closed bool
closed atomic.Bool
aggregations map[idKey]*forwardedAggregation // Aggregations for each forward metric id
metrics forwardedWriterMetrics
aggregationMetrics *forwardedAggregationMetrics
Expand All @@ -168,7 +169,7 @@ func (w *forwardedWriter) Register(
metricID id.RawID,
aggKey aggregationKey,
) (writeForwardedMetricFn, onForwardedAggregationDoneFn, error) {
if w.closed {
if w.closed.Load() {
w.metrics.registerWriterClosed.Inc(1)
return nil, nil, errForwardedWriterClosed
}
Expand All @@ -188,7 +189,7 @@ func (w *forwardedWriter) Unregister(
metricID id.RawID,
aggKey aggregationKey,
) error {
if w.closed {
if w.closed.Load() {
w.metrics.unregisterWriterClosed.Inc(1)
return errForwardedWriterClosed
}
Expand Down Expand Up @@ -219,6 +220,10 @@ func (w *forwardedWriter) Prepare() {
}

func (w *forwardedWriter) Flush() error {
if w.closed.Load() {
return errForwardedWriterClosed
}

if err := w.client.Flush(); err != nil {
w.metrics.flushErrorsClient.Inc(1)
return err
Expand All @@ -230,12 +235,9 @@ func (w *forwardedWriter) Flush() error {
// NB: Do not close the client here as it is shared by all the forward
// writers. The aggregator is responsible for closing the client.
func (w *forwardedWriter) Close() error {
if w.closed {
if w.closed.Swap(true) {
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Swap returns previous value. If Close() is called more than once, this would cause 2nd and subsequent calls return error which it probably shouldn't because this function doesn't do anything besides setting the w.closed.

Should we use w.closed.Store(true) instead?

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it might still be useful for tests, though - and is a pervasive pattern around here.

return errForwardedWriterClosed
}
w.closed = true
w.client = nil
w.aggregations = nil
return nil
}

Expand Down
47 changes: 40 additions & 7 deletions src/aggregator/aggregator/forwarded_writer_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -21,7 +21,9 @@
package aggregator

import (
"sync"
"testing"
"time"

"github.com/m3db/m3/src/aggregator/client"
"github.com/m3db/m3/src/metrics/aggregation"
Expand All @@ -32,6 +34,7 @@ import (
"github.com/m3db/m3/src/metrics/policy"

"github.com/golang/mock/gomock"
"github.com/stretchr/testify/assert"
"github.com/stretchr/testify/require"
"github.com/uber-go/tally"
)
Expand All @@ -54,11 +57,43 @@ func TestForwardedWriterRegisterWriterClosed(t *testing.T) {
mt = metric.CounterType
mid = id.RawID("foo")
aggKey = testForwardedWriterAggregationKey
closed = make(chan struct{})
wg sync.WaitGroup
)
w.Close()

_, _, err := w.Register(mt, mid, aggKey)
require.Equal(t, errForwardedWriterClosed, err)
c.EXPECT().Flush().AnyTimes()

wg.Add(1)
go func() {
defer wg.Done()

for {
var err error

assert.NotPanics(t, func() {
if err = w.Flush(); err != nil {
require.Equal(t, errForwardedWriterClosed, err)
}
})

if err != nil {
break
}
time.Sleep(1 * time.Microsecond)
}

assert.NotPanics(t, func() {
_, _, err := w.Register(mt, mid, aggKey)
require.Equal(t, errForwardedWriterClosed, err)

err = w.Flush()
require.Equal(t, errForwardedWriterClosed, err)
})
}()

require.NoError(t, w.Close())
close(closed)
wg.Wait()
}

func TestForwardedWriterRegisterNewAggregation(t *testing.T) {
Expand Down Expand Up @@ -390,12 +425,10 @@ func TestForwardedWriterCloseWriterClosed(t *testing.T) {
w = newForwardedWriter(0, c, tally.NoopScope)
)

// Close the writer and validate that the fields are nil'ed out.
// Close the writer
require.NoError(t, w.Close())
fw := w.(*forwardedWriter)
require.True(t, fw.closed)
require.Nil(t, fw.client)
require.Nil(t, fw.aggregations)
require.True(t, fw.closed.Load())

// Closing the writer a second time results in an error.
require.Equal(t, errForwardedWriterClosed, w.Close())
Expand Down