opencensus: deprecate Zipkin configuration.

Prefer to have operators use Envoy's native Zipkin tracer, since Zipkin
implies libcurl in opencensus. Once we complete a deprecation cycle
here, we should be able to remove this source of libcurl dependency.

Part of envoyproxy#11816.

Risk level: Low
Testing: bazel test //test/...

Signed-off-by: Harvey Tuch <htuch@google.com>

api/envoy/config/trace/v3/http_tracer.proto

@@ -58,7 +58,7 @@ message Tracing {
     // See the trace drivers for examples:
     //
     // - :ref:`LightstepConfig <envoy_api_msg_config.trace.v3.LightstepConfig>`
-    // - :ref:`ZipkinConfig <envoy_api_msg_config.trace.v3.ZipkinConfig>`
+    // - :ref:`ZipkinConfig <envoy_v3_api_msg_config.trace.v3.ZipkinConfig>`
     // - :ref:`DynamicOtConfig <envoy_api_msg_config.trace.v3.DynamicOtConfig>`
     // - :ref:`DatadogConfig <envoy_api_msg_config.trace.v3.DatadogConfig>`
     // - :ref:`OpenCensusConfig <envoy_api_msg_config.trace.v3.OpenCensusConfig>`

api/envoy/config/trace/v3/opencensus.proto

@@ -72,11 +72,14 @@ message OpenCensusConfig {
   core.v3.GrpcService stackdriver_grpc_service = 13;
 
   // Enables the Zipkin exporter if set to true. The url and service name must
-  // also be set.
-  bool zipkin_exporter_enabled = 5;
-
-  // The URL to Zipkin, e.g. "http://127.0.0.1:9411/api/v2/spans"
-  string zipkin_url = 6;
+  // also be set. This is deprecated, prefer to use Envoy's :ref:`native Zipkin
+  // tracer <envoy_v3_api_msg_config.trace.v3.ZipkinConfig>`.
+  bool zipkin_exporter_enabled = 5 [deprecated = true];
+
+  // The URL to Zipkin, e.g. "http://127.0.0.1:9411/api/v2/spans". This is
+  // deprecated, prefer to use Envoy's :ref:`native Zipkin tracer
+  // <envoy_v3_api_msg_config.trace.v3.ZipkinConfig>`.
+  string zipkin_url = 6 [deprecated = true];
 
   // Enables the OpenCensus Agent exporter if set to true. The ocagent_address or
   // ocagent_grpc_service must also be set.

docs/root/version_history/current.rst

@@ -113,3 +113,4 @@ Deprecated
 * logging: the `--log-format-prefix-with-location` option is removed.
 * ratelimit: the :ref:`dynamic metadata <envoy_v3_api_field_config.route.v3.RateLimit.Action.dynamic_metadata>` action is deprecated in favor of the more generic :ref:`metadata <envoy_v3_api_field_config.route.v3.RateLimit.Action.metadata>` action.
 * stats: the `--use-fake-symbol-table` option is removed.
+* tracing: OpenCensus :ref:`Zipkin configuration <envoy_api_field_config.trace.v2.OpenCensusConfig.zipkin_exporter_enabled>` is now deprecated, the preferred Zipkin export is via Envoy's :ref:`native Zipkin tracer <envoy_v3_api_msg_config.trace.v3.ZipkinConfig>`.