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5 changes: 5 additions & 0 deletions CHANGELOG.md
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### Metrics

- Add optional configuration for Prometheus exporters to promote resource attributes to metric attributes
([#3761](https://github.com/open-telemetry/opentelemetry-specification/pull/3761))

### Logs

- Add definition for standard output log record exporter.
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- Rename/replace `(client|server).socket.(address|port)` attributes with `network.(peer|local).(address|port)`.
([#3713](https://github.com/open-telemetry/opentelemetry-specification/pull/3713))
- Add `console` as an exporter type that is supported via environment variable configuration.
([#3742](https://github.com/open-telemetry/opentelemetry-specification/pull/3742))

### Supplementary Guidelines

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4 changes: 2 additions & 2 deletions specification/common/README.md
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Expand Up @@ -53,9 +53,9 @@ indices that are kept in sync (e.g., two attributes `header_keys` and `header_va
both containing an array of strings to represent a mapping
`header_keys[i] -> header_values[i]`).

See [Attribute Naming](attribute-naming.md) for naming guidelines.
See [Attribute Naming](https://github.com/open-telemetry/semantic-conventions/blob/main/docs/general/attribute-naming.md) for naming guidelines.

See [Requirement Level](attribute-requirement-level.md) for requirement levels guidelines.
See [Requirement Level](https://github.com/open-telemetry/semantic-conventions/blob/main/docs/general/attribute-requirement-level.md) for requirement levels guidelines.

See [this document](attribute-type-mapping.md) to find out how to map values obtained
outside OpenTelemetry into OpenTelemetry attribute values.
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156 changes: 2 additions & 154 deletions specification/common/attribute-naming.md
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# Attribute Naming

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

<details>
<summary>Table of Contents</summary>

<!-- toc -->

- [Name Pluralization guidelines](#name-pluralization-guidelines)
- [Name Reuse Prohibition](#name-reuse-prohibition)
- [Recommendations for OpenTelemetry Authors](#recommendations-for-opentelemetry-authors)
- [Recommendations for Application Developers](#recommendations-for-application-developers)
- [otel.* Namespace](#otel-namespace)

<!-- tocstop -->

</details>

_This section applies to Resource, Span, Log, and Metric attribute names (also
known as the "attribute keys"). For brevity within this section when we use the
term "name" without an adjective it is implied to mean "attribute name"._

Every name MUST be a valid Unicode sequence.

_Note: we merely require that the names are represented as Unicode sequences.
This specification does not define how exactly the Unicode sequences are
encoded. The encoding can vary from one programming language to another and from
one wire format to another. Use the idiomatic way to represent Unicode in the
particular programming language or wire format._

Names SHOULD follow these rules:

- Use namespacing to avoid name clashes. Delimit the namespaces using a dot
character. For example `service.version` denotes the service version where
`service` is the namespace and `version` is an attribute in that namespace.

- Namespaces can be nested. For example `telemetry.sdk` is a namespace inside
top-level `telemetry` namespace and `telemetry.sdk.name` is an attribute
inside `telemetry.sdk` namespace.
Note: the fact that an entity is located within another entity is typically
not a sufficient reason for forming nested namespaces. The purpose of a
namespace is to avoid name clashes, not to indicate entity hierarchies. This
purpose should primarily drive the decision about forming nested namespaces.

- For each multi-word dot-delimited component of the attribute name separate the
words by underscores (i.e. use snake_case). For example `http.response.status_code`
denotes the status code in the http namespace.

- Names SHOULD NOT coincide with namespaces. For example if
`service.instance.id` is an attribute name then it is no longer valid to have
an attribute named `service.instance` because `service.instance` is already a
namespace. Because of this rule be careful when choosing names: every existing
name prohibits existence of an equally named namespace in the future, and vice
versa: any existing namespace prohibits existence of an equally named
attribute key in the future.

## Name Pluralization guidelines

- When an attribute represents a single entity, the attribute name SHOULD be singular.
Examples: `host.name`, `db.user`, `container.id`.

- When attribute can represent multiple entities, the attribute name SHOULD be pluralized
and the value type SHOULD be an array. E.g. `process.command_args` might include multiple
values: the executable name and command arguments.

- When an attribute represents a measurement,
[Metric Name Pluralization Guidelines](https://github.com/open-telemetry/semantic-conventions/blob/main/docs/general/metrics.md#pluralization)
SHOULD be followed for the attribute name.

## Name Reuse Prohibition

A new attribute MUST NOT be added with the same name as an attribute that
existed in the past but was renamed (with a corresponding schema file).

When introducing a new attribute name check all existing schema files to make
sure the name does not appear as a key of any "rename_attributes" section (keys
denote old attribute names in rename operations).

## Recommendations for OpenTelemetry Authors

- All names that are part of OpenTelemetry semantic conventions SHOULD be part
of a namespace.

- When coming up with a new semantic convention make sure to check existing
namespaces ([Semantic Conventions](https://github.com/open-telemetry/semantic-conventions/blob/main/docs/README.md))
to see if the new name fits.

- When a new namespace is necessary consider whether it should be a top-level
namespace (e.g. `service`) or a nested namespace (e.g. `service.instance`).

- Semantic conventions exist for four areas: for Resource, Span, Log, and Metric
attribute names. In addition, for spans we have two more areas: Event and Link
attribute names. Identical namespaces or names in all these areas MUST have
identical meanings. For example the `http.request.method` span attribute name denotes
exactly the same concept as the `http.request.method` metric attribute, has the same
data type and the same set of possible values (in both cases it records the
value of the HTTP protocol's request method as a string).

- Semantic conventions MUST limit names to printable Basic Latin characters
(more precisely to
[U+0021 .. U+007E](https://en.wikipedia.org/wiki/Basic_Latin_(Unicode_block)#Table_of_characters)
subset of Unicode code points). It is recommended to further limit names to
the following Unicode code points: Latin alphabet, Numeric, Underscore, Dot
(as namespace delimiter).

## Recommendations for Application Developers

As an application developer when you need to record an attribute first consult
existing [semantic conventions](https://github.com/open-telemetry/semantic-conventions/blob/main/docs/README.md).
If an appropriate name does not exists you will need to come up with a new name.
To do that consider a few options:

- The name is specific to your company and may be possibly used outside the
company as well. To avoid clashes with names introduced by other companies (in
a distributed system that uses applications from multiple vendors) it is
recommended to prefix the new name by your company's reverse domain name, e.g.
`com.acme.shopname`.

- The name is specific to your application that will be used internally only. If
you already have an internal company process that helps you to ensure no name
clashes happen then feel free to follow it. Otherwise it is recommended to
prefix the attribute name by your application name, provided that
the application name is reasonably unique within your organization (e.g.
`myuniquemapapp.longitude` is likely fine). Make sure the application name
does not clash with an existing semantic convention namespace.

- It is not recommended to use existing OpenTelemetry semantic convention namespace
as a prefix for a new company- or application-specific attribute name. Doing so
may result in a name clash in the future, if OpenTelemetry decides to use that
same name for a different purpose or if some other third party instrumentation
decides to use that exact same attribute name and you combine that instrumentation
with your own.

- The name may be generally applicable to applications in the industry. In that
case consider submitting a proposal to this specification to add a new name to
the semantic conventions, and if necessary also to add a new namespace.

It is recommended to limit names to printable Basic Latin characters
(more precisely to
[U+0021 .. U+007E](https://en.wikipedia.org/wiki/Basic_Latin_(Unicode_block)#Table_of_characters)
subset of Unicode code points).

## otel.* Namespace

Attribute names that start with `otel.` are reserved to be defined by
OpenTelemetry specification. These are typically used to express OpenTelemetry
concepts in formats that don't have a corresponding concept.

For example, the `otel.scope.name` attribute is used to record the
instrumentation scope name, which is an OpenTelemetry concept that is natively
represented in OTLP, but does not have an equivalent in other telemetry formats
and protocols.

Any additions to the `otel.*` namespace MUST be approved as part of
OpenTelemetry specification.
This page has moved to
[github.com/open-telemetry/semantic-conventions/docs/general/attribute-naming.md](https://github.com/open-telemetry/semantic-conventions/blob/main/docs/general/attribute-naming.md).
76 changes: 2 additions & 74 deletions specification/common/attribute-requirement-level.md
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# Attribute Requirement Levels for Semantic Conventions

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

<details>
<summary>Table of Contents</summary>

<!-- toc -->

- [Required](#required)
- [Conditionally Required](#conditionally-required)
- [Recommended](#recommended)
- [Opt-In](#opt-in)
- [Performance suggestions](#performance-suggestions)

<!-- tocstop -->

</details>

_This section applies to Log, Metric, Resource, and Span, and describes requirement levels for attributes defined in semantic conventions._

Attribute requirement levels apply to the [instrumentation library](../glossary.md#instrumentation-library).

The following attribute requirement levels are specified:

- [Required](#required)
- [Conditionally Required](#conditionally-required)
- [Recommended](#recommended)
- [Opt-In](#opt-in)

The requirement level for an attribute is specified by semantic conventions depending on attribute availability across instrumented entities, performance, security, and other factors. When specifying requirement levels, a semantic convention MUST take into account signal-specific requirements.

For example, Metric attributes that may have high cardinality can only be defined with `Opt-In` level.

A semantic convention that refers to an attribute from another semantic convention MAY modify the requirement level within its own scope. Otherwise, requirement level from the referred semantic convention applies.

<!-- TODO(jsuereth) - make examples not break on changes to semconv -->
For example, [Database semantic convention](https://github.com/open-telemetry/semantic-conventions/blob/main/docs/database/README.md) references `network.transport` attribute defined in [General attributes](https://github.com/open-telemetry/semantic-conventions/blob/main/docs/general/README.md) with `Conditionally Required` level on it.

## Required

All instrumentations MUST populate the attribute. A semantic convention defining a Required attribute expects an absolute majority of instrumentation libraries and applications are able to efficiently retrieve and populate it, and can additionally meet requirements for cardinality, security, and any others specific to the signal defined by the convention. `http.request.method` is an example of a Required attribute.

_Note: Consumers of telemetry can detect if a telemetry item follows a specific semantic convention by checking for the presence of a `Required` attribute defined by such convention. For example, the presence of the `db.system` attribute on a span can be used as an indication that the span follows database semantics._

## Conditionally Required

All instrumentations MUST populate the attribute when the given condition is satisfied. The semantic convention of a `Conditionally Required` attribute MUST clarify the condition under which the attribute is to be populated.

`http.route` is an example of a conditionally required attribute that is populated when the instrumented HTTP framework provides route information for the instrumented request. Some low-level HTTP server implementations do not support routing and corresponding instrumentations can't populate the attribute.

When a `Conditionally Required` attribute's condition is not satisfied, and there is no requirement to populate the attribute, semantic conventions MAY provide special instructions on how to handle it. If no instructions are given and if instrumentation can populate the attribute, instrumentation SHOULD use the `Opt-In` requirement level on the attribute.

<!-- TODO(jsuereth) - make examples not break on changes to semconv -->
For example, `server.address` is `Conditionally Required` by the [Database convention](https://github.com/open-telemetry/semantic-conventions/blob/main/docs/database/README.md) when available. When `network.peer.address` is available instead, instrumentation can do a DNS lookup, cache and populate `server.address`, but only if the user explicitly enables the instrumentation to do so, considering the performance issues that DNS lookups introduce.

## Recommended

Instrumentations SHOULD add the attribute by default if it's readily available and can be [efficiently populated](#performance-suggestions). Instrumentations MAY offer a configuration option to disable Recommended attributes.

Instrumentations that decide not to populate `Recommended` attributes due to [performance](#performance-suggestions), security, privacy, or other consideration by default, SHOULD allow for users to
opt-in to emit them as defined for the `Opt-In` requirement level (if the attributes are logically applicable).

## Opt-In

Instrumentations SHOULD populate the attribute if and only if the user configures the instrumentation to do so. Instrumentation that doesn't support configuration MUST NOT populate `Opt-In` attributes.

This attribute requirement level is recommended for attributes that are particularly expensive to retrieve or might pose a security or privacy risk. These should therefore only be enabled explicitly by a user making an informed decision.

## Performance suggestions

Here are several examples of expensive operations to be avoided by default:

- DNS lookups to populate `server.address` when only an IP address is available to the instrumentation. Caching lookup results does not solve the issue for all possible cases and should be avoided by default too.
- forcing an `http.route` calculation before the HTTP framework calculates it
- reading response stream to find `http.response.body.size` when `Content-Length` header is not available
This page has moved to
[github.com/open-telemetry/semantic-conventions/docs/general/attribute-requirement-level.md](https://github.com/open-telemetry/semantic-conventions/blob/main/docs/general/attribute-requirement-level.md).
45 changes: 0 additions & 45 deletions specification/common/url.md

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10 changes: 5 additions & 5 deletions specification/compatibility/prometheus_and_openmetrics.md
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In SDK Prometheus (pull) exporters, resource attributes SHOULD be converted to
a single [`target_info` metric](https://github.com/OpenObservability/OpenMetrics/blob/main/specification/OpenMetrics.md#supporting-target-metadata-in-both-push-based-and-pull-based-systems)
if the resource is not [empty](../resource/sdk.md#the-empty-resource);
otherwise, they MUST be dropped, and MUST NOT be attached as labels to other
metric families. The target_info metric MUST be an info-typed metric whose
labels MUST include the resource attributes, and MUST NOT include any other
labels. There MUST be at most one target_info metric exposed on an SDK
if the resource is not [empty](../resource/sdk.md#the-empty-resource).
The resource attributes MAY be copied to labels of exported metric families
if required by the exporter configuration, or MUST be dropped. The target_info metric MUST be an info-typed
metric whose labels MUST include the resource attributes, and MUST NOT include
any other labels. There MUST be at most one target_info metric exposed on an SDK
Prometheus endpoint.

In the Collector's Prometheus pull and push (remote-write) exporters, it is
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