Remove lazy Event and Link API from Span interface (open-telemetry#840)

* Remove lazy Event and Link API from Span interface

* Recommend existing lazy API implementations to be removed in the changelog

CHANGELOG.md

@@ -18,13 +18,15 @@ Updates:
 
 - Add semantic convention for NGINX custom HTTP 499 status code.
 - Adapt semantic conventions for the span name of messaging systems ([#690](https://github.com/open-telemetry/opentelemetry-specification/pull/690))
+- Remove lazy Event and Link API from Span interface ([#840](https://github.com/open-telemetry/opentelemetry-specification/pull/840))
 - Provide clear definitions for readable and read/write span interfaces in the SDK ([#669](https://github.com/open-telemetry/opentelemetry-specification/pull/669))
   * SpanProcessors must provide read/write access at least in OnStart.
 - Specify how `Probability` sampler is used with `ParentOrElse` sampler.
 - Clean up api-propagators.md, by extending documentation and removing redundant sections ([#577](https://github.com/open-telemetry/opentelemetry-specification/pull/577))
 - Rename HTTPText propagator to TextMap ([#793](https://github.com/open-telemetry/opentelemetry-specification/pull/793))
 - Rename ParentOrElse sampler to ParentBased and add multiple delegate samplers ([#610](https://github.com/open-telemetry/opentelemetry-specification/pull/610))
 - Rename ProbabilitySampler to TraceIdRatioBasedSampler and add requirements ([#611](https://github.com/open-telemetry/opentelemetry-specification/pull/611))
+  * SIGs are recommended to remove any existing implementation of the lazy APIs to avoid conflicts/breaking changes in case they will be reintroduced to the spec in future.
 
 ## v0.6.0 (07-01-2020)
 

specification/trace/api.md

@@ -337,8 +337,8 @@ The parent should be selected in the following order of precedence:
 
 #### Add Links
 
-During the `Span` creation user MUST have the ability to record links to other `Span`s. Linked
-`Span`s can be from the same or a different trace. See [Links
+During the `Span` creation user MUST have the ability to record links to other `Span`s.
+Linked `Span`s can be from the same or a different trace. See [Links
 description](../overview.md#links-between-spans).
 
 A `Link` is defined by the following properties:
@@ -348,17 +348,10 @@ A `Link` is defined by the following properties:
 
 The `Link` SHOULD be an immutable type.
 
-The Span creation API should provide:
+The Span creation API MUST provide:
 
 - An API to record a single `Link` where the `Link` properties are passed as
   arguments. This MAY be called `AddLink`.
-- An API to record a single `Link` whose attributes or attribute values are
-  lazily constructed, with the intention of avoiding unnecessary work if a link
-  is unused. If the language supports overloads then this SHOULD be called
-  `AddLink` otherwise `AddLazyLink` MAY be considered. In some languages, it might
-  be easier to defer `Link` or attribute creation entirely by providing a wrapping
-  class or function that returns a `Link` or formatted attributes. When providing
-  a wrapping class or function it SHOULD be named `LinkFormatter`.
 
 Links SHOULD preserve the order in which they're set.
 
@@ -437,13 +430,6 @@ The Span interface MUST provide:
 
 - An API to record a single `Event` where the `Event` properties are passed as
   arguments. This MAY be called `AddEvent`.
-- An API to record a single `Event` whose attributes or attribute values are
-  lazily constructed, with the intention of avoiding unnecessary work if an event
-  is unused. If the language supports overloads then this SHOULD be called
-  `AddEvent` otherwise `AddLazyEvent` MAY be considered. In some languages, it
-  might be easier to defer `Event` or attribute creation entirely by providing a
-  wrapping class or function that returns an `Event` or formatted attributes. When
-  providing a wrapping class or function it SHOULD be named `EventFormatter`.
 
 Events SHOULD preserve the order in which they're set. This will typically match
 the ordering of the events' timestamps.
@@ -680,13 +666,9 @@ SpanBuilder is used by more than one thread/coroutine.
 
 **Span** - All methods of Span are safe to be called concurrently.
 
-**Event** - Events are immutable and safe to be used concurrently. Lazy
-initialized events must be thread safe. This is the responsibility of the
-implementer of these events.
+**Event** - Events are immutable and safe to be used concurrently.
 
-**Link** - Links are immutable and is safe to be used concurrently. Lazy
-initialized links must be thread safe. This is the responsibility of the
-implementer of these links.
+**Link** - Links are immutable and safe to be used concurrently.
 
 ## Included Propagators