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76 changes: 38 additions & 38 deletions docs/general/attribute-naming.md
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Expand Up @@ -11,7 +11,7 @@
- [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)
- [otel.\* Namespace](#otel-namespace)

<!-- tocstop -->

Expand All @@ -37,15 +37,15 @@ Names SHOULD follow these rules:

- 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.
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.
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`service.instance.id` is an attribute name then it is no longer valid to have
Expand All @@ -57,16 +57,16 @@ Names SHOULD follow these rules:

## Name Pluralization guidelines

- When an attribute represents a single entity, the attribute name SHOULD be singular.
Examples: `host.name`, `db.user`, `container.id`.
- 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 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](./metrics.md#pluralization)
SHOULD be followed for the attribute name.
[Metric Name Pluralization Guidelines](./metrics.md#pluralization) SHOULD be
followed for the attribute name.

## Name Reuse Prohibition

Expand All @@ -83,33 +83,32 @@ denote old attribute names in rename operations).
of a namespace.

- When coming up with a new semantic convention make sure to check existing
namespaces ([Semantic Conventions](./README.md))
to see if the new name fits.
namespaces ([Semantic Conventions](./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).
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)
[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](./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:
existing [semantic conventions](./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
Expand All @@ -120,28 +119,28 @@ To do that consider a few options:
- 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.
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.
- 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)
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
## otel.\* Namespace

Attribute names that start with `otel.` are reserved to be defined by
OpenTelemetry specification. These are typically used to express OpenTelemetry
Expand All @@ -155,4 +154,5 @@ and protocols.
Any additions to the `otel.*` namespace MUST be approved as part of
OpenTelemetry specification.

[DocumentStatus]: https://github.com/open-telemetry/opentelemetry-specification/tree/v1.26.0/specification/document-status.md
[DocumentStatus]:
https://github.com/open-telemetry/opentelemetry-specification/tree/v1.26.0/specification/document-status.md
89 changes: 69 additions & 20 deletions docs/general/attribute-requirement-level.md
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Expand Up @@ -17,9 +17,11 @@

</details>

_This section applies to Log, Metric, Resource, and Span, and describes requirement levels for attributes defined in semantic conventions._
_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](https://github.com/open-telemetry/opentelemetry-specification/tree/v1.26.0/specification/glossary.md#instrumentation-library).
Attribute requirement levels apply to the
[instrumentation library](https://github.com/open-telemetry/opentelemetry-specification/tree/v1.26.0/specification/glossary.md#instrumentation-library).

The following attribute requirement levels are specified:

Expand All @@ -28,51 +30,98 @@ The following attribute requirement levels are specified:
- [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.
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.
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.
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](../database/README.md) references `network.transport` attribute defined in [General attributes](./README.md) with `Conditionally Required` level on it.

For example, [Database semantic convention](../database/README.md) references
`network.transport` attribute defined in [General attributes](./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.
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._
_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.
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.
`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.
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](../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.

For example, `server.address` is `Conditionally Required` by the
[Database convention](../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 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).
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.
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.
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.
- 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
- reading response stream to find `http.response.body.size` when
`Content-Length` header is not available

[DocumentStatus]: https://github.com/open-telemetry/opentelemetry-specification/tree/v1.26.0/specification/document-status.md
[DocumentStatus]:
https://github.com/open-telemetry/opentelemetry-specification/tree/v1.26.0/specification/document-status.md

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