feat: ignore existing trace

kong/plugins/zipkin/handler.lua

@@ -102,8 +102,16 @@ if subsystem == "http" then
   initialize_request = function(conf, ctx)
     local req = kong.request
 
-    local header_type, trace_id, span_id, parent_id, should_sample, baggage =
-      tracing_headers.parse(req.get_headers())
+    local header_type = conf.default_header_type
+    local trace_id, span_id, parent_id, should_sample, baggage
+
+    -- If header_type is set to `ignore`, then the default_header_type will
+    -- be used to initiate a new trace.
+    if conf.header_type ~= "ignore" then
+      header_type, trace_id, span_id, parent_id, should_sample, baggage =
+        tracing_headers.parse(req.get_headers())
+    end
+
     local method = req.get_method()
 
     if should_sample == nil then

kong/plugins/zipkin/schema.lua

@@ -54,7 +54,7 @@ return {
           { include_credential = { type = "boolean", required = true, default = true } },
           { traceid_byte_count = { type = "integer", required = true, default = 16, one_of = { 8, 16 } } },
           { header_type = { type = "string", required = true, default = "preserve",
-                            one_of = { "preserve", "b3", "b3-single", "w3c", "jaeger" } } },
+                            one_of = { "preserve", "ignore", "b3", "b3-single", "w3c", "jaeger" } } },
           { default_header_type = { type = "string", required = true, default = "b3",
                                     one_of = { "b3", "b3-single", "w3c", "jaeger" } } },
           { static_tags = { type = "array", elements = static_tag,

kong/plugins/zipkin/tracing_headers.lua

@@ -337,7 +337,10 @@ end
 local function set(conf_header_type, found_header_type, proxy_span, conf_default_header_type)
   local set_header = kong.service.request.set_header
 
+  -- If conf_header_type is set to `preserve`, found_header_type is used over default_header_type;
+  -- if conf_header_type is set to `ignore`, found_header_type is not set, thus default_header_type is used.
   if conf_header_type ~= "preserve" and
+     conf_header_type ~= "ignore" and
      found_header_type ~= nil and
      conf_header_type ~= found_header_type
   then