```go
type interInst struct {
x int
}
type inter interface {
}
var sink []inter
func BenchmarkX(b *testing.B) {
sink = make([]inter, b.N)
for i := 0; i < b.N; i++ {
sink[i] = &interInst{}
}
clear(sink)
sink = sink[:0]
runtime.GC()
var ms runtime.MemStats
runtime.ReadMemStats(&ms)
b.Log(b.N, ms.Frees) // Frees is the cumulative count of heap objects freed.
}
```
```
clear:
ioz_test.go:35: 1 589
ioz_test.go:35: 100 711
ioz_test.go:35: 10000 10729
ioz_test.go:35: 1000000 1010750 <-- 1m+ freed
ioz_test.go:35: 16076874 17087643
ioz_test.go:35: 19514749 36602412
```
```
no clear:
ioz_test.go:35: 1 585
ioz_test.go:35: 100 606
ioz_test.go:35: 10000 725
ioz_test.go:35: 1000000 10745 <-- some "overhead" objects freed, not the slice.
ioz_test.go:35: 16391445 1010765
ioz_test.go:35: 21765238 17402230
```
This is documented at https://go.dev/wiki/SliceTricks:
> NOTE If the type of the element is a pointer or a struct with pointer
fields, which need to be garbage collected, the above implementations of
Cut and Delete have a potential memory leak problem: some elements with
values are still referenced by slice a’s underlying array, just not
“visible” in the slice. Because the “deleted” value is referenced in the
underlying array, the deleted value is still “reachable” during GC, even
though the value cannot be referenced by your code. If the underlying
array is long-lived, this represents a leak.
Followed by examples of how zeroing out the slice elements solves
the problem. This PR does the same.
Ensure the `Record` and `Provider` continue to be non-comparable.
Restrict `BatchProcessor` and `SimpleProcessor` to be non-comparable.
There is no obvious reason an end-user will need to compare these types,
and we want to keep the possibility of changing the internals without
changing this behavior.
if comparability is required by end-users in the future we can add
`Equal(other T)` methods in the future.
Applying attribute limits in `Record` uses value receiver.
But it should add count of dropped attrs.
In this PR I add using of pointer receiver.
Also it's slightly faster with pointer receiver:
```
goos: darwin
goarch: arm64
pkg: go.opentelemetry.io/otel/sdk/log
│ old.txt │ new.txt │
│ sec/op │ sec/op vs base │
SetAddAttributes-10 175.7n ± 3% 159.8n ± 4% -9.08% (p=0.000 n=10)
│ old.txt │ new.txt │
│ B/op │ B/op vs base │
SetAddAttributes-10 48.00 ± 0% 48.00 ± 0% ~ (p=1.000 n=10) ¹
¹ all samples are equal
│ old.txt │ new.txt │
│ allocs/op │ allocs/op vs base │
SetAddAttributes-10 1.000 ± 0% 1.000 ± 0% ~ (p=1.000 n=10) ¹
¹ all samples are equal
```
Fix#5317
According to the
[specification](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/logs/sdk.md#logrecord-limits),
there should be a message printed in the SDK's log to indicate to the
user that an attribute was discarded due to such a limit. To prevent
excessive logging, the message must be printed at most once per
`LogRecord` (i.e., not per discarded attribute).
This change centralizes the `Record` dropped field writes and calls a
global logging function. This will at most log once per any `Record`
dropping attributes, meeting the specification requirement.
This does not log once per `Record` when an attribute is dropped. To do
that we would need to maintain state within the `Record` (i.e.
`sync.Mutex` or `sync.Once`). These types cannot be copied, meaning the
`Record` would take on this "no copy" requirement. This seems too
restrictive and with the permissive specification allowing a single log
line, that is the solution added.
---------
Co-authored-by: Robert Pająk <pellared@hotmail.com>
* Replace Record lim methods with DroppedAttributes
* Add changelog entry
* Add TestRecordDroppedAttributes
* Add TestRecordCompactAttr
* Add an indexPool
* Fix gramatical error
* Apply feedback
Reduce indentation level.
* Apply feedback
Comment compactAttr and deduplicate.
* Deduplicate all attributes when added
* Comment why head is not used
* Clarify comments
* Move TestAllocationLimits to new file
Do not run this test when the race detector is on.
* Comment follow-up task
