feat/request tags (#102)

kong-plugin-zipkin-1.2.0-1.rockspec

@@ -26,5 +26,6 @@ build = {
     ["kong.plugins.zipkin.span"] = "kong/plugins/zipkin/span.lua",
     ["kong.plugins.zipkin.tracing_headers"] = "kong/plugins/zipkin/tracing_headers.lua",
     ["kong.plugins.zipkin.schema"] = "kong/plugins/zipkin/schema.lua",
+    ["kong.plugins.zipkin.request_tags"] = "kong/plugins/zipkin/request_tags.lua",
   },
 }

kong/plugins/zipkin/handler.lua

@@ -2,6 +2,8 @@ local new_zipkin_reporter = require "kong.plugins.zipkin.reporter".new
 local new_span = require "kong.plugins.zipkin.span".new
 local utils = require "kong.tools.utils"
 local tracing_headers = require "kong.plugins.zipkin.tracing_headers"
+local request_tags = require "kong.plugins.zipkin.request_tags"
+
 
 local subsystem = ngx.config.subsystem
 local fmt = string.format
@@ -102,8 +104,10 @@ if subsystem == "http" then
   initialize_request = function(conf, ctx)
     local req = kong.request
 
+    local req_headers = req.get_headers()
+
     local header_type, trace_id, span_id, parent_id, should_sample, baggage =
-      tracing_headers.parse(req.get_headers())
+      tracing_headers.parse(req_headers)
     local method = req.get_method()
 
     if should_sample == nil then
@@ -139,6 +143,17 @@ if subsystem == "http" then
       end
     end
 
+    local req_tags, err = request_tags.parse(req_headers[conf.tags_header])
+    if err then
+      -- log a warning in case there were erroneous request tags. Don't throw the tracing away & rescue with valid tags, if any
+      kong.log.warn(err)
+    end
+    if req_tags then
+      for tag_name, tag_value in pairs(req_tags) do
+        request_span:set_tag(tag_name, tag_value)
+      end
+    end
+
     ctx.zipkin = {
       request_span = request_span,
       header_type = header_type,

kong/plugins/zipkin/request_tags.lua

@@ -0,0 +1,82 @@
+-- Module for parsing Zipkin span tags introduced by requests with a special header
+-- by default the header is called Zipkin-Tags
+--
+-- For example, the following http request header:
+--
+--   Zipkin-Tags: foo=bar; baz=qux
+--
+-- Will add two tags to the request span in Zipkin
+
+
+local split = require "kong.tools.utils".split
+
+local match = string.match
+
+local request_tags = {}
+
+
+-- note that and errors is an output value; we do this instead of
+-- a return in order to be more efficient (allocate less tables)
+local function parse_tags(tags_string, dest, errors)
+  local items = split(tags_string, ";")
+  local item
+
+  for i = 1, #items do
+    item = items[i]
+    if item ~= "" then
+      local name, value = match(item, "^%s*(%S+)%s*=%s*(.*%S)%s*$")
+      if name then
+        dest[name] = value
+
+      else
+        errors[#errors + 1] = item
+      end
+    end
+  end
+end
+
+
+-- parses req_headers into extra zipkin tags
+-- returns tags, err
+-- note that both tags and err can be non-nil when the request could parse some tags but rejects others
+-- tag can be nil when tags_header is nil. That is not an error (err will be empty)
+function request_tags.parse(tags_header)
+  if not tags_header then
+    return nil, nil
+  end
+
+  local t = type(tags_header)
+  local tags, errors = {}, {}
+
+  -- "normal" requests are strings
+  if t == "string" then
+    parse_tags(tags_header, tags, errors)
+
+  -- requests where the tags_header_name header is used more than once get an array
+  --
+  -- example - a request with the headers:
+  --   zipkin-tags: foo=bar
+  --   zipkin-tags: baz=qux
+  --
+  -- will get such array. We have to transform that into { foo=bar, baz=qux }
+  elseif t == "table" then
+    for i = 1, #tags_header do
+      parse_tags(tags_header[i], tags, errors)
+    end
+
+  else
+    return nil,
+           string.format("unexpected tags_header type: %s (%s)",
+                         tostring(tags_header), t)
+  end
+
+  if next(errors) then
+    errors = "Could not parse the following Zipkin tags: " .. table.concat(errors, ", ")
+  else
+    errors = nil
+  end
+
+  return tags, errors
+end
+
+return request_tags

kong/plugins/zipkin/schema.lua

@@ -57,6 +57,7 @@ return {
                             one_of = { "preserve", "b3", "b3-single", "w3c", "jaeger" } } },
           { default_header_type = { type = "string", required = true, default = "b3",
                                     one_of = { "b3", "b3-single", "w3c", "jaeger" } } },
+          { tags_header = { type = "string", required = true, default = "Zipkin-Tags" } },
           { static_tags = { type = "array", elements = static_tag,
                             custom_validator = validate_static_tags } },
         },

spec/request_tags_spec.lua

@@ -0,0 +1,46 @@
+local parse = require("kong.plugins.zipkin.request_tags").parse
+
+describe("request_tags", function()
+  describe("parse", function()
+    it("parses simple case, swallowing spaces", function()
+      assert.same({ foo = "bar" }, parse("foo=bar"))
+      assert.same({ foo = "bar" }, parse("foo=  bar"))
+      assert.same({ foo = "bar" }, parse("foo =bar"))
+      assert.same({ foo = "bar" }, parse("foo  =  bar"))
+      assert.same({ foo = "bar" }, parse("   foo =  bar"))
+      assert.same({ foo = "bar" }, parse("foo = bar   "))
+      assert.same({ foo = "bar" }, parse("  foo = bar   "))
+    end)
+    it("rejects invalid tags, keeping valid ones", function()
+      local tags, err = parse("foobar;foo=;=bar;keep=true;=")
+      assert.same(tags, {keep = "true"})
+      assert.equals("Could not parse the following Zipkin tags: foobar, foo=, =bar, =", err)
+    end)
+    it("allows spaces on values, but not on keys", function()
+      assert.same({ foo = "bar baz" }, parse("foo=bar baz"))
+      local tags, err = parse("foo bar=baz")
+      assert.same(tags, {})
+      assert.equals("Could not parse the following Zipkin tags: foo bar=baz", err)
+    end)
+    it("parses multiple tags separated by semicolons, swallowing spaces", function()
+      assert.same({ foo = "bar", baz = "qux" }, parse("foo=bar;baz=qux"))
+      assert.same({ foo = "bar", baz = "qux" }, parse("foo  =bar;baz=qux"))
+      assert.same({ foo = "bar", baz = "qux" }, parse("foo=  bar;baz=qux"))
+      assert.same({ foo = "bar", baz = "qux" }, parse("  foo=bar  ;baz=qux"))
+      assert.same({ foo = "bar", baz = "qux" }, parse("foo  =  bar  ;baz=qux"))
+      assert.same({ foo = "bar", baz = "qux" }, parse("  foo  =  bar  ;baz=qux"))
+      assert.same({ foo = "bar", baz = "qux" }, parse("  foo  =  bar  ;baz =qux"))
+      assert.same({ foo = "bar", baz = "qux" }, parse("  foo  =  bar  ;baz  = qux"))
+      assert.same({ foo = "bar", baz = "qux" }, parse("  foo  =  bar  ;baz  =  qux"))
+    end)
+    it("swallows empty tags between semicolons silently", function()
+      local tags, err = parse(";;foo=bar;;;;baz=qux;;")
+      assert.same({ foo = "bar", baz = "qux" }, tags)
+      assert.is_nil(err)
+    end)
+    it("parses multiple tags separated by semicolons, in an array", function()
+      assert.same({ foo = "bar", baz = "qux", quux = "quuz" },
+                  parse({"foo=bar;baz=qux", "quux=quuz"}))
+    end)
+  end)
+end)

spec/zipkin_spec.lua

@@ -5,7 +5,7 @@ local to_hex = require "resty.string".to_hex
 
 local fmt = string.format
 
-local ZIPKIN_HOST = "zipkin"
+local ZIPKIN_HOST = os.getenv("ZIPKIN_HOST") or "zipkin"
 local ZIPKIN_PORT = 9411
 local GRPCBIN_HOST = "grpcbin"
 local GRPCBIN_PORT = 9000
@@ -226,6 +226,7 @@ describe("http integration tests with zipkin server [#"
       headers = {
         ["x-b3-sampled"] = "1",
         host  = "http-route",
+        ["zipkin-tags"] = "foo=bar; baz=qux"
       },
     })
     assert.response(r).has.status(200)
@@ -245,6 +246,8 @@ describe("http integration tests with zipkin server [#"
       ["http.status_code"] = "200", -- found (matches server status)
       lc = "kong",
       static = "ok",
+      foo = "bar",
+      baz = "qux",
     }, request_tags)
     local consumer_port = request_span.remoteEndpoint.port
     assert_is_integer(consumer_port)
@@ -475,6 +478,7 @@ describe("http integration tests with zipkin server [#"
       headers = {
         ["x-b3-traceid"] = trace_id,
         ["x-b3-sampled"] = "1",
+        ["zipkin-tags"] = "error = true"
       },
     })
     assert.response(r).has.status(404)
@@ -495,6 +499,7 @@ describe("http integration tests with zipkin server [#"
       ["http.status_code"] = "404", -- note that this was "not found"
       lc = "kong",
       static = "ok",
+      error = "true",
     }, request_tags)
     local consumer_port = request_span.remoteEndpoint.port
     assert_is_integer(consumer_port)