Change OTLP/HTTP port from 4317 to 4318 (#1839) (#1970)

Related to #1816
Fixes #1835
Fixes #1920

Some historical context: we wanted to make grpc and http use the same port and we
had an open issue in the Collector to do so:
open-telemetry/opentelemetry-collector#1256

The conclusion is that there are technical hurdles that make it unfeasible:
open-telemetry/opentelemetry-collector#1256 (comment)

Because of that we need to keep grpc and http ports separate. This means we need to
change the spec to say that otlp/http uses port 4318. Once this PR is merged we
will also need to submit for port 4318 registration with IANA like we did previously
with port 4317:
#1148 (comment)

There was also a draft PR to merge the ports in the Collector but it was not completed:
open-telemetry/opentelemetry-collector#3765

Note that this change was initially submitted in PR #1839
and then reverted in PR #1847
because we hoped that the merging could be successfully done. We believe that we should
no longer pursue this and should consider the ports separate from now on.

Note 2: we consider this a spec bug fix (spec was impossible to implement), rather than a 
functionality change, that's why we believe this is an allowed change.

CHANGELOG.md

@@ -66,6 +66,7 @@ release.
   ([#1923](https://github.com/open-telemetry/opentelemetry-specification/pull/1923))
 - Clarify OTLP server components MUST support none/gzip compression
   ([#1955](https://github.com/open-telemetry/opentelemetry-specification/pull/1955))
+- Change OTLP/HTTP port from 4317 to 4318 ([#1970](https://github.com/open-telemetry/opentelemetry-specification/pull/1970))
 
 ### SDK Configuration
 

specification/protocol/exporter.md

@@ -10,7 +10,7 @@ The following configuration options MUST be available to configure the OTLP expo
 
 | Configuration Option | Description                                                  | Default           | Env variable                                                 |
 | -------------------- | ------------------------------------------------------------ | ----------------- | ------------------------------------------------------------ |
-| Endpoint (OTLP/HTTP) | Target to which the exporter is going to send spans or metrics. The endpoint MUST be a valid URL with scheme (http or https) and host, and MAY contain a port and path. A scheme of https indicates a secure connection. When using `OTEL_EXPORTER_OTLP_ENDPOINT`, exporters SHOULD follow the collector convention of appending the version and signal to the path (e.g. `v1/traces` or `v1/metrics`), if not present already. The per-signal endpoint configuration options take precedence and can be used to override this behavior. See the [OTLP Specification][otlphttp-req] for more details. | `https://localhost:4317` | `OTEL_EXPORTER_OTLP_ENDPOINT` `OTEL_EXPORTER_OTLP_TRACES_ENDPOINT` `OTEL_EXPORTER_OTLP_METRICS_ENDPOINT` |
+| Endpoint (OTLP/HTTP) | Target to which the exporter is going to send spans or metrics. The endpoint MUST be a valid URL with scheme (http or https) and host, and MAY contain a port and path. A scheme of https indicates a secure connection. When using `OTEL_EXPORTER_OTLP_ENDPOINT`, exporters SHOULD follow the collector convention of appending the version and signal to the path (e.g. `v1/traces` or `v1/metrics`), if not present already. The per-signal endpoint configuration options take precedence and can be used to override this behavior. See the [OTLP Specification][otlphttp-req] for more details. | `https://localhost:4318` | `OTEL_EXPORTER_OTLP_ENDPOINT` `OTEL_EXPORTER_OTLP_TRACES_ENDPOINT` `OTEL_EXPORTER_OTLP_METRICS_ENDPOINT` |
 | Endpoint (OTLP/gRPC) | Target to which the exporter is going to send spans or metrics. The endpoint SHOULD accept any form allowed by the underlying gRPC client implementation. Additionally, the endpoint MUST accept a URL with a scheme of either `http` or `https`. A scheme of `https` indicates a secure connection and takes precedence over the `insecure` configuration setting. If the gRPC client implementation does not support an endpoint with a scheme of `http` or `https` then the endpoint SHOULD be transformed to the most sensible format for that implementation. | `https://localhost:4317` | `OTEL_EXPORTER_OTLP_ENDPOINT` `OTEL_EXPORTER_OTLP_TRACES_ENDPOINT` `OTEL_EXPORTER_OTLP_METRICS_ENDPOINT` |
 | Insecure             | Whether to enable client transport security for the exporter's gRPC connection. This option only applies to OTLP/gRPC - OTLP/HTTP always uses the scheme provided for the `endpoint`. Implementations MAY choose to not implement the `insecure` option if it is not required or supported by the underlying gRPC client implementation. | `false` | `OTEL_EXPORTER_OTLP_INSECURE` `OTEL_EXPORTER_OTLP_SPAN_INSECURE` `OTEL_EXPORTER_OTLP_METRIC_INSECURE` |
 | Certificate File     | The trusted certificate to use when verifying a server's TLS credentials. Should only be used for a secure connection. | n/a               | `OTEL_EXPORTER_OTLP_CERTIFICATE` `OTEL_EXPORTER_OTLP_TRACES_CERTIFICATE` `OTEL_EXPORTER_OTLP_METRICS_CERTIFICATE` |

specification/protocol/otlp.md

@@ -478,7 +478,7 @@ connections SHOULD be configurable.
 
 #### OTLP/HTTP Default Port
 
-The default network port for OTLP/HTTP is 4317.
+The default network port for OTLP/HTTP is 4318.
 
 ## Implementation Recommendations