Add jaeger remote sampler to SDK configuration

Signed-off-by: Pavol Loffay <[email protected]>

CHANGELOG.md

@@ -11,6 +11,7 @@ release.
 
 ### Traces
 
+- Adding SDK configuration for Jaeger remote sampler ([#1791](https://github.com/open-telemetry/opentelemetry-specification/pull/1791))
 - Adding environment variables for event and link attribute limits. ([#1751](https://github.com/open-telemetry/opentelemetry-specification/pull/1751))
 
 ### Metrics

specification/sdk-environment-variables.md

@@ -56,12 +56,16 @@ Known values for `OTEL_TRACES_SAMPLER` are:
 - `"parentbased_always_on"`: `ParentBased(root=AlwaysOnSampler)`
 - `"parentbased_always_off"`: `ParentBased(root=AlwaysOffSampler)`
 - `"parentbased_traceidratio"`: `ParentBased(root=TraceIdRatioBased)`
+- `"jaeger_remote"`: `JaegerRemoteSampler`
 
 Depending on the value of `OTEL_TRACES_SAMPLER`, `OTEL_TRACES_SAMPLER_ARG` may be set as follows:
 
 - For `traceidratio` and `parentbased_traceidratio` samplers: Sampling probability, a number in the [0..1] range, e.g. "0.25". Default is 1.0 if unset.
-
-## Batch Span Processor
+- For `jaeger_remote`: The value is a comma separated list:
+  - `endpoint`: the endpoint of gRPC server that serves the sampling strategy for the service ([sampling.proto](https://github.com/jaegertracing/jaeger-idl/blob/master/proto/api_v2/sampling.proto)).
+  - `pollingIntervalMs`:  in milliseconds indicating how often the sampler will poll the backend for updates to sampling strategy.
+  - `initialSamplingRate`:  in the [0..1] range, which is used as the sampling probability when the backend cannot be reached to retrieve a sampling strategy. This value stops having an effect once a sampling strategy is retrieved successfully, as the remote strategy will be used until a new update is retrieved.
+  - Example: `endpoint:localhost:14250,pollingIntervalMs:5000,initialSamplingRate:0.25`
 
 **Status**: [Stable](document-status.md)