feat(zipkin) static tags (#84)

Implements #3

kong/plugins/zipkin/handler.lua

@@ -131,6 +131,14 @@ if subsystem == "http" then
     request_span:set_tag("http.method", method)
     request_span:set_tag("http.path", req.get_path())
 
+    local static_tags = conf.static_tags
+    if type(static_tags) == "table" then
+      for i = 1, #static_tags do
+        local tag = static_tags[i]
+        request_span:set_tag(tag.name, tag.value)
+      end
+    end
+
     ctx.zipkin = {
       request_span = request_span,
       header_type = header_type,
@@ -205,6 +213,14 @@ elseif subsystem == "stream" then
 
     request_span:set_tag("lc", "kong")
 
+    local static_tags = conf.static_tags
+    if type(static_tags) == "table" then
+      for i = 1, #static_tags do
+        local tag = static_tags[i]
+        request_span:set_tag(tag.name, tag.value)
+      end
+    end
+
     ctx.zipkin = {
       request_span = request_span,
       proxy_span = nil,

kong/plugins/zipkin/schema.lua

@@ -1,4 +1,44 @@
 local typedefs = require "kong.db.schema.typedefs"
+local Schema = require "kong.db.schema"
+
+local PROTECTED_TAGS = {
+  "error",
+  "http.method",
+  "http.path",
+  "http.status_code",
+  "kong.balancer.state",
+  "kong.balancer.try",
+  "kong.consumer",
+  "kong.credential",
+  "kong.node.id",
+  "kong.route",
+  "kong.service",
+  "lc",
+  "peer.hostname",
+}
+
+local static_tag = Schema.define {
+  type = "record",
+  fields = {
+    { name = { type = "string", required = true, not_one_of = PROTECTED_TAGS } },
+    { value = { type = "string", required = true } },
+  },
+}
+
+local validate_static_tags = function(tags)
+  if type(tags) ~= "table" then
+    return true
+  end
+  local found = {}
+  for i = 1, #tags do
+    local name = tags[i].name
+    if found[name] then
+      return nil, "repeated tags are not allowed: " .. name
+    end
+    found[name] = true
+  end
+  return true
+end
 
 return {
   name = "zipkin",
@@ -15,6 +55,8 @@ return {
           { 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" } } },
+          { static_tags = { type = "array", elements = static_tag,
+                            custom_validator = validate_static_tags } }
         },
     }, },
   },

spec/schema_spec.lua

@@ -0,0 +1,22 @@
+local schema_def = require "kong.plugins.zipkin.schema"
+local v = require("spec.helpers").validate_plugin_config_schema
+
+describe("Plugin: Zipkin (schema)", function()
+  it("rejects repeated tags", function()
+    local ok, err = v({
+      http_endpoint = "http://example.dev",
+      static_tags = {
+        { name = "foo", value = "bar" },
+        { name = "foo", value = "baz" },
+      },
+    }, schema_def)
+
+    assert.is_falsy(ok)
+    assert.same({
+      config = {
+        static_tags = "repeated tags are not allowed: foo"
+      }
+    }, err)
+  end)
+end)
+

spec/zipkin_spec.lua

@@ -160,6 +160,9 @@ describe("http integration tests with zipkin server [#"
         sample_ratio = 1,
         http_endpoint = fmt("http://%s:%d/api/v2/spans", ZIPKIN_HOST, ZIPKIN_PORT),
         traceid_byte_count = traceid_byte_count,
+        static_tags = {
+          { name = "static", value = "ok" },
+        }
       }
     })
 
@@ -239,7 +242,8 @@ describe("http integration tests with zipkin server [#"
       ["http.method"] = "GET",
       ["http.path"] = "/",
       ["http.status_code"] = "200", -- found (matches server status)
-      lc = "kong"
+      lc = "kong",
+      static = "ok",
     }, request_tags)
     local consumer_port = request_span.remoteEndpoint.port
     assert_is_integer(consumer_port)
@@ -312,7 +316,8 @@ describe("http integration tests with zipkin server [#"
       ["http.method"] = "POST",
       ["http.path"] = "/hello.HelloService/SayHello",
       ["http.status_code"] = "200", -- found (matches server status)
-      lc = "kong"
+      lc = "kong",
+      static = "ok",
     }, request_tags)
     local consumer_port = request_span.remoteEndpoint.port
     assert_is_integer(consumer_port)
@@ -393,7 +398,10 @@ describe("http integration tests with zipkin server [#"
     local request_tags = request_span.tags
     assert.truthy(request_tags["kong.node.id"]:match("^[%x-]+$"))
     request_tags["kong.node.id"] = nil
-    assert.same({ lc = "kong" }, request_tags)
+    assert.same({
+      lc = "kong",
+      static = "ok",
+    }, request_tags)
     local consumer_port = request_span.remoteEndpoint.port
     assert_is_integer(consumer_port)
     assert.same({
@@ -484,7 +492,8 @@ describe("http integration tests with zipkin server [#"
       ["http.method"] = "GET",
       ["http.path"] = "/foobar",
       ["http.status_code"] = "404", -- note that this was "not found"
-      lc = "kong"
+      lc = "kong",
+      static = "ok",
     }, request_tags)
     local consumer_port = request_span.remoteEndpoint.port
     assert_is_integer(consumer_port)