fix: trace id mismatch (#84)

Some 128-bit w3c trace IDs in the wild contain a zero-padded
64-bit portion. This commit sets the default high part of the
trace ID to 0, ensuring the check passes correctly.

Resolves #83

* add unit tests

Author: dmehala

kong/plugins/ddtrace/datadog_propagation.lua

@@ -56,7 +56,6 @@ local function extract_datadog(get_header, max_header_size)
     end
 
     -- other headers are expected but aren't provided in all cases
-    local trace_id = { high = nil, low = trace_id_low }
     local parent_id = parse_uint64(get_header("x-datadog-parent-id"), 10)
     local sampling_priority = tonumber(get_header("x-datadog-sampling-priority"))
     local origin = get_header("x-datadog-origin")
@@ -74,24 +73,25 @@ local function extract_datadog(get_header, max_header_size)
         end
     end
 
+    local trace_id_high = 0
     local tid = dd_tags["_dd.p.tid"]
     if tid then
         if #tid ~= 16 then
             dd_tags["_dd.propagation_error"] = "malformed_tid " .. tid
             dd_tags["_dd.p.tid"] = nil
         else
-            local trace_id_high, err = parse_uint64(tid, 16)
+            local high, err = parse_uint64(tid, 16)
             if err then
                 dd_tags["_dd.propagation_error"] = "malformed_tid " .. tid
                 dd_tags["_dd.p.tid"] = nil
             else
-                trace_id.high = trace_id_high
+                trace_id_high = high
             end
         end
     end
 
     return {
-        trace_id = trace_id,
+        trace_id = { high = trace_id_high, low = trace_id_low },
         parent_id = parent_id,
         sampling_priority = sampling_priority,
         origin = origin,

kong/plugins/ddtrace/w3c_propagation.lua

@@ -81,14 +81,15 @@ local function extract(get_header, _)
         return nil, "0 is an invalid parent ID"
     end
 
-    local trace_id = { high = 0, low = 0 }
+    local high
+    local low
 
-    trace_id.high, err = parse_uint64(string.sub(hex_trace_id, 1, 16), 16)
+    high, err = parse_uint64(string.sub(hex_trace_id, 1, 16), 16)
     if err then
         return nil, "failed to parse trace ID: " .. err
     end
 
-    trace_id.low, err = parse_uint64(string.sub(hex_trace_id, 17, 32), 16)
+    low, err = parse_uint64(string.sub(hex_trace_id, 17, 32), 16)
     if err then
         return nil, "failed to parse trace ID: " .. err
     end
@@ -137,7 +138,7 @@ local function extract(get_header, _)
     end
 
     return {
-        trace_id = trace_id,
+        trace_id = { high = high, low = low },
         parent_id = parent_id,
         sampling_priority = sampling_priority,
         origin = dd_state["origin"],

spec/01-unit-tests/03_propagation_spec.lua

@@ -1,9 +1,12 @@
 local new_span = require("kong.plugins.ddtrace.span").new
 local new_propagator = require("kong.plugins.ddtrace.propagation").new
 
+local last_warning
 _G.kong = {
     log = {
-        warn = function() end,
+        warn = function(msg)
+            last_warning = msg
+        end,
     },
 }
 
@@ -76,11 +79,45 @@ describe("trace propagation", function()
 
             local span = multi_propagator:extract_or_create_span(request, default_span_opts)
 
-            local expected_trace_id = { high = nil, low = 12345678901234567890ULL }
+            local expected_trace_id = { high = 0, low = 12345678901234567890ULL }
             local expected_parent_id = 9876543210987654321ULL
             assert.same(expected_trace_id, span.trace_id)
             assert.same(expected_parent_id, span.parent_id)
         end)
+
+        it("64-bit and 128-bit match", function()
+            local datadog_first = { "datadog", "tracecontext" }
+            local multi_propagator = new_propagator(datadog_first, datadog_first, default_max_header_size)
+            local request = {
+                get_header = make_getter({
+                    traceparent = "00-0000000000000000a3ce929d0e0e4736-00f067aa0ba902b7-01",
+                    tracestate = "fizz=buzz:fizzbuzz,dd=s:2;o:rum;p:00f067aa0ba902b7;t.dm:-5",
+                    ["x-datadog-trace-id"] = "11803532876627986230",
+                    ["x-datadog-parent-id"] = "67667974448284343",
+                }),
+            }
+
+            last_warning = nil
+            local _ = multi_propagator:extract_or_create_span(request, default_span_opts)
+            assert.is_nil(last_warning)
+        end)
+
+        it("mismatch trace ID log a warning", function()
+            local datadog_first = { "datadog", "tracecontext" }
+            local multi_propagator = new_propagator(datadog_first, datadog_first, default_max_header_size)
+            local request = {
+                get_header = make_getter({
+                    traceparent = "00-4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-01",
+                    tracestate = "fizz=buzz:fizzbuzz,dd=s:2;o:rum;p:00f067aa0ba902b7;t.dm:-5",
+                    ["x-datadog-trace-id"] = "12345678901234567890",
+                    ["x-datadog-parent-id"] = "9876543210987654321",
+                }),
+            }
+
+            last_warning = nil
+            local _ = multi_propagator:extract_or_create_span(request, default_span_opts)
+            assert.is_not_nil(last_warning)
+        end)
     end)
 
     describe("inject", function()

spec/01-unit-tests/06_datadog_propagation_spec.lua

@@ -44,7 +44,7 @@ describe("trace propagation", function()
             assert.is_nil(err)
             assert.is_not_nil(extracted)
 
-            local expected_trace_id = { high = nil, low = 12345678901234567890ULL }
+            local expected_trace_id = { high = 0, low = 12345678901234567890ULL }
             assert.same(expected_trace_id, extracted.trace_id)
             assert.equal(9876543210987654321ULL, extracted.parent_id)
             assert.equal(1, extracted.sampling_priority)