From cb9601774ceb5d97366f2607f14c5edce02ad632 Mon Sep 17 00:00:00 2001
From: Andrew Selder <andrew.selder@pepsico.com>
Date: Thu, 3 Dec 2020 13:51:11 -0800
Subject: [PATCH] Encode logger metadata as string.

This avoid a potential issue where JSON logs are parsed and numbers are
treated as floats. This can lead to the trace and span ids losing
precision when read from JSON.

If you look at the DataDog docs for other languages, you can see this.
See: https://docs.datadoghq.com/tracing/connect_logs_and_traces/ruby/
---
 lib/spandex.ex                 | 8 ++++----
 test/plug/add_context_test.exs | 4 ++--
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/lib/spandex.ex b/lib/spandex.ex
index c5f184a..c4de405 100644
--- a/lib/spandex.ex
+++ b/lib/spandex.ex
@@ -453,7 +453,7 @@ defmodule Spandex do
     adapter = opts[:adapter]
 
     with {:ok, top_span} <- span(name, opts, span_context, adapter) do
-      Logger.metadata(trace_id: span_context.trace_id, span_id: top_span.id)
+      Logger.metadata(trace_id: to_string(span_context.trace_id), span_id: to_string(top_span.id))
 
       trace = %Trace{
         id: span_context.trace_id,
@@ -483,7 +483,7 @@ defmodule Spandex do
 
     with {:ok, span} <- Span.child_of(current_span, name, adapter.span_id(), adapter.now(), opts),
          {:ok, _trace} <- strategy.put_trace(opts[:trace_key], %{trace | stack: [span | trace.stack]}) do
-      Logger.metadata(span_id: span.id, trace_id: trace.id)
+      Logger.metadata(span_id: to_string(span.id), trace_id: to_string(trace.id))
       {:ok, span}
     end
   end
@@ -495,7 +495,7 @@ defmodule Spandex do
 
     with {:ok, span} <- span(name, opts, span_context, adapter),
          {:ok, _trace} <- strategy.put_trace(opts[:trace_key], %{trace | stack: [span]}) do
-      Logger.metadata(span_id: span.id, trace_id: trace_id)
+      Logger.metadata(span_id: to_string(span.id), trace_id: to_string(trace_id))
       {:ok, span}
     end
   end
@@ -507,7 +507,7 @@ defmodule Spandex do
     span_context = %SpanContext{trace_id: trace_id}
 
     with {:ok, span} <- span(name, opts, span_context, adapter) do
-      Logger.metadata(trace_id: trace_id, span_id: span.id)
+      Logger.metadata(trace_id: to_string(trace_id), span_id: to_string(span.id))
       trace = %Trace{spans: [], stack: [span], id: trace_id}
       strategy.put_trace(opts[:trace_key], trace)
     end
diff --git a/test/plug/add_context_test.exs b/test/plug/add_context_test.exs
index b92d921..0b681c0 100644
--- a/test/plug/add_context_test.exs
+++ b/test/plug/add_context_test.exs
@@ -50,8 +50,8 @@ defmodule Spandex.Plug.AddContextTest do
 
       assert {:ok, expected_span} = Tracer.start_span("foobar")
 
-      assert Keyword.fetch!(Logger.metadata(), :trace_id) == tid
-      assert Keyword.fetch!(Logger.metadata(), :span_id) == expected_span.id
+      assert Keyword.fetch!(Logger.metadata(), :trace_id) == to_string(tid)
+      assert Keyword.fetch!(Logger.metadata(), :span_id) == to_string(expected_span.id)
 
       {:ok, _} = Tracer.finish_trace()