Add minItems recommendation for array properties

CONTRIBUTING.md

@@ -192,6 +192,14 @@ Another example:
 
 `oneOf` is used to specify that the `value` property matches the [Attribute AnyValue](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/common/README.md#anyvalue) definition, and is either a primitive or array of primitives. This type of use is acceptable but should be used judiciously.
 
+### Array minItems
+
+Because properties of type `array` are not candidates for [env var substitution], it typically does not make sense to allow the array to be empty. In some cases, an empty array likely corresponds to an accidental misconfiguration which should be detected and reported as an error. In other cases, an empty array is simply meaningless and the user is better off omitting the property altogether.
+
+For these reasons, [`minItems`](https://json-schema.org/understanding-json-schema/reference/array#length) is typically set to `1`.
+
+NOTE: there are some valid cases where an empty array is semantically meaningful, such as when setting `ExplicitBucketHistogram.boundaries`.
+
 ### Annotations - title and description
 
 The JSON schema [`title` and `description` annotations](https://json-schema.org/understanding-json-schema/reference/annotations) are keywords which are not involved in validation. Instead, they act as a mechanism to help schemas be self-documenting, and may be used by code generation tools.

examples/sdk-config.yaml

@@ -96,9 +96,6 @@ tracer_provider:
             # Value must be non-negative. A value of 0 indicates no limit (infinity).
             # If omitted or null, 10000 is used.
             timeout: 10000
-            # Configure headers. Entries have higher priority than entries from .headers_list.
-            # If an entry's .value is null, the entry is ignored.
-            headers: []
   # Configure span limits. See also attribute_limits.
   limits:
     # Configure max attribute value size. Overrides .attribute_limits.attribute_value_length_limit. 
@@ -199,9 +196,6 @@ meter_provider:
             # Value must be non-negative. A value of 0 indicates no limit (infinity).
             # If omitted or null, 10000 is used.
             timeout: 10000
-            # Configure headers. Entries have higher priority than entries from .headers_list.
-            # If an entry's .value is null, the entry is ignored.
-            headers: []
             # Configure temporality preference.
             # Values include: cumulative, delta, low_memory. For behavior of values, see https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/sdk_exporters/otlp.md.
             # If omitted or null, cumulative is used.
@@ -264,9 +258,6 @@ logger_provider:
             # Value must be non-negative. A value of 0 indicates no limit (infinity).
             # If omitted or null, 10000 is used.
             timeout: 10000
-            # Configure headers. Entries have higher priority than entries from .headers_list.
-            # If an entry's .value is null, the entry is ignored.
-            headers: []
   # Configure log record limits. See also attribute_limits.
   limits:
     # Configure max attribute value size. Overrides .attribute_limits.attribute_value_length_limit. 

examples/sdk-migration-config.yaml

@@ -69,10 +69,6 @@ attribute_limits:
 # Configure text map context propagators.
 # If omitted, a noop propagator is used.
 propagator:
-  # Configure the propagators in the composite text map propagator. Entries from .composite_list are appended to the list here with duplicates filtered out.
-  # Built-in propagator keys include: tracecontext, baggage, b3, b3multi, jaeger, ottrace. Known third party keys include: xray. 
-  # If the resolved list of propagators (from .composite and .composite_list) is empty, a noop propagator is used.
-  composite: []
   # Configure the propagators in the composite text map propagator. Entries are appended to .composite with duplicates filtered out.
   # The value is a comma separated list of propagator identifiers matching the format of OTEL_PROPAGATORS. See https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/configuration/sdk-environment-variables.md#general-sdk-configuration for details.
   # Built-in propagator identifiers include: tracecontext, baggage, b3, b3multi, jaeger, ottrace. Known third party identifiers include: xray. 
@@ -128,9 +124,6 @@ tracer_provider:
             # Value must be non-negative. A value of 0 indicates no limit (infinity).
             # If omitted or null, 10000 is used.
             timeout: ${OTEL_EXPORTER_OTLP_TRACES_TIMEOUT:-10000}
-            # Configure headers. Entries have higher priority than entries from .headers_list.
-            # If an entry's .value is null, the entry is ignored.
-            headers: []
             # Configure headers. Entries have lower priority than entries from .headers.
             # The value is a list of comma separated key-value pairs matching the format of OTEL_EXPORTER_OTLP_HEADERS. See https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/protocol/exporter.md#configuration-options for details.
             # If omitted or null, no headers are added.
@@ -237,9 +230,6 @@ meter_provider:
             # Value must be non-negative. A value of 0 indicates no limit (infinity).
             # If omitted or null, 10000 is used.
             timeout: ${OTEL_EXPORTER_OTLP_METRICS_TIMEOUT:-10000}
-            # Configure headers. Entries have higher priority than entries from .headers_list.
-            # If an entry's .value is null, the entry is ignored.
-            headers: []
             # Configure headers. Entries have lower priority than entries from .headers.
             # The value is a list of comma separated key-value pairs matching the format of OTEL_EXPORTER_OTLP_HEADERS. See https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/protocol/exporter.md#configuration-options for details.
             # If omitted or null, no headers are added.
@@ -306,9 +296,6 @@ logger_provider:
             # Value must be non-negative. A value of 0 indicates no limit (infinity).
             # If omitted or null, 10000 is used.
             timeout: ${OTEL_EXPORTER_OTLP_LOGS_TIMEOUT:-10000}
-            # Configure headers. Entries have higher priority than entries from .headers_list.
-            # If an entry's .value is null, the entry is ignored.
-            headers: []
             # Configure headers. Entries have lower priority than entries from .headers.
             # The value is a list of comma separated key-value pairs matching the format of OTEL_EXPORTER_OTLP_HEADERS. See https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/protocol/exporter.md#configuration-options for details.
             # If omitted or null, no headers are added.