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Declare freeze of Trace API Specification 1.0 (open-telemetry#1121)
* Declare freeze of Trace Specification 1.0 We want to freeze Trace specification 1.0 so that we no longer accept substantial changes (unless a fundamental problem is found in the spec). Resolves open-telemetry/opentelemetry-specification#1120
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# Attribute and Label Naming | ||
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<details> | ||
<summary> | ||
Table of Contents | ||
</summary> | ||
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- [Name Pluralization Guidelines](#name-pluralization-guidelines) | ||
- [Recommendations for OpenTelemetry Authors](#recommendations-for-opentelemetry-authors) | ||
- [Recommendations for Application Developers](#recommendations-for-application-developers) | ||
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</details> | ||
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_This section applies to Resource, Span and Log attribute names (also known as | ||
the "attribute keys") and to keys of Metric labels. For brevity within this | ||
section when we use the term "name" without an adjective it is implied to mean | ||
"attribute name or metric label key"._ | ||
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Every name MUST be a valid Unicode sequence. | ||
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_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._ | ||
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Names SHOULD follow these rules: | ||
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- 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. | ||
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- 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. | ||
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- For each multi-word dot-delimited component of the attribute name separate the | ||
words by underscores (i.e. use snake_case). For example `http.status_code` | ||
denotes the status code in the http namespace. | ||
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- 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 or label key in the future. | ||
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## Name Pluralization guidelines | ||
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- When an attribute represents a single entity, the attribute name SHOULD be singular. | ||
Examples: `host.name`, `db.user`, `container.id`. | ||
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- 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. | ||
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- When an attribute represents a measurement, | ||
[Metric Name Pluralization Guidelines](../metrics/semantic_conventions/README.md#pluralization) | ||
SHOULD be followed for the attribute name. | ||
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## Recommendations for OpenTelemetry Authors | ||
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- All names that are part of OpenTelemetry semantic conventions SHOULD be part | ||
of a namespace. | ||
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- When coming up with a new semantic convention make sure to check existing | ||
namespaces for | ||
[Resources](../resource/semantic_conventions/README.md), | ||
[Spans](../trace/semantic_conventions/README.md), | ||
and | ||
[Metrics](../metrics/semantic_conventions/README.md) | ||
to see if the new name fits. | ||
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- 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`). | ||
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- Semantic conventions exist for four areas: for Resource, Span and Log | ||
attribute names as well as Metric label keys. 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.method` | ||
span attribute name denotes exactly the same concept as the `http.method` | ||
metric label, 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). | ||
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- 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). | ||
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## Recommendations for Application Developers | ||
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As an application developer when you need to record an attribute or a label | ||
first consult existing semantic conventions for | ||
[Resources](../resource/semantic_conventions/README.md), | ||
[Spans](../trace/semantic_conventions/README.md), | ||
and | ||
[Metrics](../metrics/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: | ||
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- 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`. | ||
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- 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 or label key 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. | ||
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- 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. | ||
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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). |
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