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store/cache: remove iteration limit and reset on internal inconsistency #1274

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merged 1 commit into from
Jun 25, 2019
Merged

store/cache: remove iteration limit and reset on internal inconsistency #1274

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32 changes: 12 additions & 20 deletions pkg/store/cache/cache.go
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Original file line number Diff line number Diff line change
Expand Up @@ -235,8 +235,6 @@ func (c *IndexCache) set(typ string, key cacheKey, val []byte) {
// ensureFits tries to make sure that the passed slice will fit into the LRU cache.
// Returns true if it will fit.
func (c *IndexCache) ensureFits(size uint64, typ string) bool {
const saneMaxIterations = 500

if size > c.maxItemSizeBytes {
level.Debug(c.logger).Log(
"msg", "item bigger than maxItemSizeBytes. Ignoring..",
Expand All @@ -249,36 +247,30 @@ func (c *IndexCache) ensureFits(size uint64, typ string) bool {
return false
}

for i := 0; c.curSize+size > c.maxSizeBytes; i++ {
if i >= saneMaxIterations {
level.Error(c.logger).Log(
"msg", "After max sane iterations of LRU evictions, we still cannot allocate the item. Ignoring.",
"maxItemSizeBytes", c.maxItemSizeBytes,
"maxSizeBytes", c.maxSizeBytes,
"curSize", c.curSize,
"itemSize", size,
"cacheType", typ,
"iterations", i,
)
return false
}

_, _, ok := c.lru.RemoveOldest()
if !ok {
for c.curSize+size > c.maxSizeBytes {
if _, _, ok := c.lru.RemoveOldest(); !ok {
level.Error(c.logger).Log(
"msg", "LRU has nothing more to evict, but we still cannot allocate the item. Ignoring.",
"msg", "LRU has nothing more to evict, but we still cannot allocate the item. Resetting cache.",
"maxItemSizeBytes", c.maxItemSizeBytes,
"maxSizeBytes", c.maxSizeBytes,
"curSize", c.curSize,
"itemSize", size,
"cacheType", typ,
)
return false
c.reset()
}
}
return true
}

func (c *IndexCache) reset() {
c.lru.Purge()
c.current.Reset()
c.currentSize.Reset()
c.totalCurrentSize.Reset()
c.curSize = 0
}

// SetPostings sets the postings identfied by the ulid and label to the value v,
// if the postings already exists in the cache it is not mutated.
func (c *IndexCache) SetPostings(b ulid.ULID, l labels.Label, v []byte) {
Expand Down
17 changes: 9 additions & 8 deletions pkg/store/cache/cache_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -29,25 +29,26 @@ func TestIndexCache_AvoidsDeadlock(t *testing.T) {
testutil.Ok(t, err)

l, err := simplelru.NewLRU(math.MaxInt64, func(key, val interface{}) {
// Hack LRU to simulate broken accounting: evictions do not reduce current size.
size := cache.curSize
cache.onEvict(key, val)

// We hack LRU to add back entry on eviction to simulate broken evictions.
cache.lru.Add(key, val)
cache.curSize += sliceHeaderSize + uint64(len(val.([]byte))) // Slice header + bytes.
cache.curSize = size
})
testutil.Ok(t, err)
cache.lru = l

cache.SetPostings(ulid.MustNew(0, nil), labels.Label{Name: "test2", Value: "1"}, []byte{42, 33, 14, 67, 11})

testutil.Equals(t, float64(0), promtest.ToFloat64(cache.overflow.WithLabelValues(cacheTypePostings)))
testutil.Equals(t, float64(0), promtest.ToFloat64(cache.overflow.WithLabelValues(cacheTypeSeries)))
testutil.Equals(t, uint64(sliceHeaderSize+5), cache.curSize)
testutil.Equals(t, float64(cache.curSize), promtest.ToFloat64(cache.currentSize.WithLabelValues(cacheTypePostings)))
testutil.Equals(t, float64(1), promtest.ToFloat64(cache.current.WithLabelValues(cacheTypePostings)))

// This triggers deadlock logic.
cache.SetPostings(ulid.MustNew(0, nil), labels.Label{Name: "test1", Value: "1"}, []byte{42})

testutil.Equals(t, float64(1), promtest.ToFloat64(cache.overflow.WithLabelValues(cacheTypePostings)))
testutil.Equals(t, float64(0), promtest.ToFloat64(cache.overflow.WithLabelValues(cacheTypeSeries)))
testutil.Equals(t, uint64(sliceHeaderSize+1), cache.curSize)
testutil.Equals(t, float64(cache.curSize), promtest.ToFloat64(cache.currentSize.WithLabelValues(cacheTypePostings)))
testutil.Equals(t, float64(1), promtest.ToFloat64(cache.current.WithLabelValues(cacheTypePostings)))
}

func TestIndexCache_UpdateItem(t *testing.T) {
Expand Down