Attribute Requirement Levels
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.
The following attribute requirement levels are specified:
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
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.
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
defined by such convention. For example, the presence of the
attribute on a span can be used as an indication that the span follows database
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.
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
Opt-In requirement level on the attribute.
Conditionally Required by the
Database convention 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.
Instrumentations SHOULD add the attribute by default if it’s readily available and can be efficiently populated. Instrumentations MAY offer a configuration option to disable Recommended attributes.
Instrumentations that decide not to populate
Recommended attributes due to
performance, 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
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
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.
Here are several examples of expensive operations to be avoided by default:
- DNS lookups to populate
server.addresswhen 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.routecalculation before the HTTP framework calculates it
- reading response stream to find
Content-Lengthheader is not available