Add support for the development attributes advisory parameter - #8135

…elemetry#8135)

From [the
spec](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/api.md#instrument-advisory-parameter-attributes):

> ##### Instrument advisory parameter: `Attributes`

> **Status**: [Development](../document-status.md)

> Applies to all instrument types.

> `Attributes` (a list of [attribute
keys](../common/README.md#attribute)) is
the recommended set of attribute keys to be used for the resulting
metrics.

We already have `WithAttributes` options, so i've opted to name this
`WithDefaultAttributes` to avoid naming collisions. We could also
consider `WithAttributeKeys`, or `WithDefaultAttributeKeys`

Follows the pattern for experimental options introduced in
open-telemetry#8111

---------

Co-authored-by: Robert Pająk <pellared@hotmail.com>

### Added

- Add `ByteSlice` and `ByteSliceValue` functions for new `BYTESLICE`
attribute type in `go.opentelemetry.io/otel/attribute`. (#7948)
- Apply attribute value limit to the `KindBytes` attribute type in
`go.opentelemetry.io/otel/sdk/log`. (#7990)
- Apply attribute value limit to the `BYTESLICE` attribute type in
`go.opentelemetry.io/otel/sdk/trace`. (#7990)
- Support `BYTESLICE` attributes in `go.opentelemetry.io/otel/trace`.
(#8153)
- Support `BYTESLICE` attributes in
`go.opentelemetry.io/otel/exporters/otlp/otlptrace`. (#8153)
- Support `BYTESLICE` attributes in
`go.opentelemetry.io/otel/exporters/otlp/otlplog`. (#8153)
- Support `BYTESLICE` attributes in
`go.opentelemetry.io/otel/exporters/otlp/otlpmetric`. (#8153)
- Support `BYTESLICE` attributes in
`go.opentelemetry.io/otel/exporters/zipkin`. (#8153)
- Add `String` method for `Value` type in
`go.opentelemetry.io/otel/attribute`. (#8142)
- Add `Slice` and `SliceValue` functions for new `SLICE` attribute type
in `go.opentelemetry.io/otel/attribute`. (#8166)
- Support `SLICE` attributes in
`go.opentelemetry.io/otel/exporters/otlp/otlptrace`. (#8216)
- Support `SLICE` attributes in
`go.opentelemetry.io/otel/exporters/otlp/otlplog`. (#8216)
- Support `SLICE` attributes in
`go.opentelemetry.io/otel/exporters/otlp/otlpmetric`. (#8216)
- Support `SLICE` attributes in
`go.opentelemetry.io/otel/exporters/zipkin`. (#8216)
- Apply `AttributeValueLengthLimit` to `attribute.SLICE` type attribute
values in `go.opentelemetry.io/otel/sdk/trace`, recursively truncating
contained string values. (#8217)
- Add `Error` field on `Record` type in
`go.opentelemetry.io/otel/log/logtest`. (#8148)
- Add `WithMaxRequestSize` option in
`go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc`.
(#8157)
- Add `WithMaxRequestSize` option in
`go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp`.
(#8157)
- Add `WithMaxRequestSize` option in
`go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc`.
(#8157)
- Add `WithMaxRequestSize` option in
`go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp`.
(#8157)
- Add `WithMaxRequestSize` option in
`go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploggrpc`. (#8157)
- Add `WithMaxRequestSize` option in
`go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploghttp`. (#8157)
- Add `Settable` to `go.opentelemetry.io/otel/metric/x` to allow reusing
attribute options. (#8178)
- Add experimental support for splitting metric data across multiple
batches in `go.opentelemetry.io/otel/sdk/metric`.
Set `OTEL_GO_X_METRIC_EXPORT_BATCH_SIZE=<max_size>` to enable for all
periodic readers.
See `go.opentelemetry.io/otel/sdk/metric/internal/x` for feature
documentation. (#8071)
- Add experimental self-observability metrics in
`go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc`.
  Enable with `OTEL_GO_X_SELF_OBSERVABILITY=true` environment variable.
See
`go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc/internal/x`
for feature documentation. (#8192)
- Add experimental self-observability metrics in
`go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp`.
  Enable with `OTEL_GO_X_SELF_OBSERVABILITY=true` environment variable.
See
`go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp/internal/x`
for feature documentation. (#8194)
- Add experimental self-observability metrics in
`go.opentelemetry.io/otel/exporters/stdout/stdoutlog`.
  Enable with `OTEL_GO_X_SELF_OBSERVABILITY=true` environment variable.
See `go.opentelemetry.io/otel/stdout/stdoutlog/internal/x` for feature
documentation. (#8263)
- Add `WithDefaultAttributes` to `go.opentelemetry.io/otel/metric/x` to
support setting default attributes on instruments. (#8135)
- Add `go.opentelemetry.io/otel/semconv/v1.41.0` package.
The package contains semantic conventions from the `v1.41.0` version of
the OpenTelemetry Semantic Conventions.
See the [migration documentation](./semconv/v1.41.0/MIGRATION.md) for
information on how to upgrade from
`go.opentelemetry.io/otel/semconv/v1.40.0`. (#8324)
- Add Observable variants of instruments to
`go.opentelemetry.io/otel/semconv/v1.41.0` package. (#8350)
- Generate explicit histogram bucket boundaries from weaver
configuration for HTTP and RPC duration instruments in
`go.opentelemetry.io/otel/semconv/v1.41.0`. (#8002)

### Changed

- ⚠️ **Breaking Change:** `go.opentelemetry.io/otel/sdk/metric` now
applies a default cardinality limit of 2000 to comply with the Metrics
SDK specification recommendation.
New attribute sets are dropped when the cardinality limit is reached.
The measurement of these sets are aggregated into a special attribute
set containing `attribute.Bool("otel.metric.overflow", true)`.
  This can break users who relied on the previous unlimited default.
Set `WithCardinalityLimit(0)` or the deprecated
`OTEL_GO_X_CARDINALITY_LIMIT=0` environment variable to preserve
unlimited cardinality.
Note that support for `OTEL_GO_X_CARDINALITY_LIMIT` may be removed in a
future release. (#8247)
- `ErrorType` in `go.opentelemetry.io/otel/semconv` now unwraps errors
created with `fmt.Errorf` when deriving the `error.type` attribute.
(#8133)
- `go.opentelemetry.io/otel/sdk/log` now unwraps error chains created
with `fmt.Errorf` when deriving the `error.type` attribute from errors
on log records. (#8133)
- `Set.MarshalLog` method in `go.opentelemetry.io/otel/attribute` now
uses `Value.String` formatting following the [OpenTelemetry AnyValue
representation for non-OTLP
protocols](https://opentelemetry.io/docs/specs/otel/common/#anyvalue).
(#8169)
- Optimize `go.opentelemetry.io/otel/sdk/metric` to return a drop
reservoir and short-circuit `Offer` calls to the exemplar reservoir when
`exemplar.AlwaysOffFilter` is configured. (#8211) (#8267)
- Optimize `go.opentelemetry.io/otel/sdk/metric` to return a drop
reservoir for asynchronous instruments when `exemplar.TraceBasedFilter`
is configured. (#8286)

### Deprecated

- Deprecate `Value.Emit` method in `go.opentelemetry.io/otel/attribute`.
  Use `Value.String` instead. (#8176)

### Fixed

- Limit OTLP request size to 64 MiB by default in
`go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc`.
The limit applies before compression, oversized requests are treated as
non-retryable errors, and the limit can be configured with the new
`WithMaxRequestSize` option. (#8157, #8365)
- Limit OTLP request size to 64 MiB by default in
`go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp`.
The limit applies before compression, oversized requests are treated as
non-retryable errors, and the limit can be configured with the new
`WithMaxRequestSize` option. (#8157, #8365)
- Limit OTLP request size to 64 MiB by default in
`go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc`.
The limit applies before compression, oversized requests are treated as
non-retryable errors, and the limit can be configured with the new
`WithMaxRequestSize` option. (#8157, #8365)
- Limit OTLP request size to 64 MiB by default in
`go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp`.
The limit applies before compression, oversized requests are treated as
non-retryable errors, and the limit can be configured with the new
`WithMaxRequestSize` option. (#8157, #8365)
- Limit OTLP request size to 64 MiB by default in
`go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploggrpc`.
The limit applies before compression, oversized requests are treated as
non-retryable errors, and the limit can be configured with the new
`WithMaxRequestSize` option. (#8157, #8365)
- Limit OTLP request size to 64 MiB by default in
`go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploghttp`.
The limit applies before compression, oversized requests are treated as
non-retryable errors, and the limit can be configured with the new
`WithMaxRequestSize` option. (#8157, #8365)
- Fix gzipped request body replay on redirect in
`go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp`.
(#8135)
- Fix gzipped request body replay on redirect in
`go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploghttp`. (#8152)
- `go.opentelemetry.io/otel/exporters/prometheus` now uses
`Value.String` formatting for label values following the [OpenTelemetry
AnyValue representation for non-OTLP
protocols](https://opentelemetry.io/docs/specs/otel/common/#anyvalue).
(#8170)
- Propagate errors from the exporter when calling `Shutdown` on
`BatchSpanProcessor` in `go.opentelemetry.io/otel/sdk/trace`. (#8197)
- Fix stale status code reporting on self-observability metrics in
`go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp` and
`go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploghttp`. (#8226)
- Fix a concurrent `Collect` data race and potential panic in
`go.opentelemetry.io/otel/exporters/prometheus` when
`WithResourceAsConstantLabels` option is used. (#8227)
- Fix race condition in `FixedSizeReservoir` in
`go.opentelemetry.io/otel/sdk/metric/exemplar` by reverting #7447.
(#8249)
- Fix `FixedSizeReservoir` in
`go.opentelemetry.io/otel/sdk/metric/exemplar` to safely handle zero
size.
A capacity check in the constructor initializes the reservoir safely and
skips initialization for zero-cap; early returns in `Offer()` and
`Collect()` ensure no-op behavior. (#8295)
- Fix counting of spans and logs in self-observability metrics in
`go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc`,
`go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp`,
`go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploggrpc`, and
`go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploghttp`. (#8254)
- Drop conflicting scope attributes named `name`, `version`, or
`schema_url` from metric labels in
`go.opentelemetry.io/otel/exporters/prometheus`, preserving the
dedicated `otel_scope_name`, `otel_scope_version`, and
`otel_scope_schema_url` labels. (#8264)
- Close schema files opened by `ParseFile` in
`go.opentelemetry.io/otel/schema/v1.0` and
`go.opentelemetry.io/otel/schema/v1.1`.
([GHSA-995v-fvrw-c78m](GHSA-995v-fvrw-c78m))
- Enforce the 8192-byte baggage size limit during extraction/parsing,
changing behavior when the limit is exceeded in
`go.opentelemetry.io/otel/baggage` and
`go.opentelemetry.io/otel/propagation`. (#8222)
- Fix `go.opentelemetry.io/otel/semconv/v1.41.0` to include `Attr*`
helper methods for required attributes on observable instruments.
(#8361)
- Limit baggage extraction error reporting in
`go.opentelemetry.io/otel/propagation` to prevent malformed or oversized
baggage headers from flooding logs.
([GHSA-5wrp-cwcj-q835](GHSA-5wrp-cwcj-q835))

…meter (open-telemetry#5392)

Part of
open-telemetry#3785

## Changes

Clarifies in `specification/metrics/sdk.md` that `Exemplar`s retain
measurement attributes filtered out by the `Attributes` instrument
advisory parameter (in addition to those filtered out by aggregation or
View configuration), and updates the privacy/documentation note under
View `attribute_keys` accordingly.

### Motivation

Even within the `Stable` `## Exemplar` section,
`specification/metrics/sdk.md` already defines an Exemplar's attributes
as:
> *"The set of [Attributes](../common/README.md#attribute) associated
with the `Measurement` not already included in a metric data point."*
>
> *"Joining together attributes on an `Exemplar` with those available on
its associated metric data point should result in the full set of
attributes from the original sample measurement."*

And under `Stream configuration` -> `attribute_keys`, `sdk.md` already
specifies that the `Attributes` advisory parameter serves as the
fallback for the stream's `attribute_keys` when no View specifies
`attribute_keys`. However, because `View` configuration was originally
the only way to filter attributes from a metric stream prior to open-telemetry#3546,
several sentences in `sdk.md` only mentioned attributes removed *"by
aggregation or View configuration"*.

As surfaced in the `Attributes` advisory parameter implementation audit
(open-telemetry#3785 (comment)),
SDK implementations currently differ on this point:
* **Go** passes unfiltered measurement attributes to
`ExemplarReservoir`, so attributes filtered out by the `Attributes`
advisory parameter are recorded on Exemplars as `filtered_attributes`.
* **Java** applies its `AttributesProcessor` prior to offering
measurements to `ExemplarReservoir`, so attributes dropped by `Advice`
(or a View) are not included in `filtered_attributes`.

Because instrumentation (e.g., HTTP instrumentation) uses the
`Attributes` advisory parameter to filter high-cardinality contextual
span attributes out of metric streams, preserving those filtered
attributes on sampled Exemplars enables trace/metric correlation and
high-cardinality debugging while keeping metric stream cardinality
bounded.

* [x] Related issues open-telemetry#3785
* [ ] Related [OTEP(s)](https://github.com/open-telemetry/oteps) #
* [x] Links to the prototypes (when adding or changing features)
  * Go: open-telemetry/opentelemetry-go#8135
* [x]
[`CHANGELOG.md`](https://github.com/open-telemetry/opentelemetry-specification/blob/main/CHANGELOG.md)
file updated for non-trivial changes
* [ ] [Spec compliance
matrix](https://github.com/open-telemetry/opentelemetry-specification/blob/main/spec-compliance-matrix/template.yaml)
updated if necessary
* [ ] [Declarative config data
model](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/configuration/data-model.md#overview)
is updated if SDK config surface is changed