HTTP propagator: Better handling of invalid data

Signed-off-by: Marco Costa <marco.costa@datadoghq.com>

lib/datadog/tracing/distributed/b3_multi.rb

@@ -31,7 +31,7 @@ def inject!(digest, data = {})
 
           # DEV: We need these to be hex encoded
           data[@trace_id_key] = format('%032x', digest.trace_id)
-          data[@span_id_key] = format('%016x', digest.span_id)
+          data[@span_id_key] = format('%016x', digest.span_id || 0) # # Fall back to zero (invalid) if not present
 
           if digest.trace_sampling_priority
             sampling_priority = Helpers.clamp_sampling_priority(

lib/datadog/tracing/distributed/b3_single.rb

@@ -25,8 +25,10 @@ def initialize(fetcher:, key: B3_SINGLE_HEADER_KEY)
         def inject!(digest, env)
           return if digest.nil?
 
+          span_id = digest.span_id || 0 # Fall back to zero (invalid) if not present
+
           # DEV: We need these to be hex encoded
-          value = "#{format('%032x', digest.trace_id)}-#{format('%016x', digest.span_id)}"
+          value = "#{format('%032x', digest.trace_id)}-#{format('%016x', span_id)}"
 
           if digest.trace_sampling_priority
             sampling_priority = Helpers.clamp_sampling_priority(

lib/datadog/tracing/distributed/datadog.rb

@@ -42,7 +42,7 @@ def inject!(digest, data)
 
           data[@trace_id_key] = Tracing::Utils::TraceId.to_low_order(digest.trace_id).to_s
 
-          data[@parent_id_key] = digest.span_id.to_s
+          data[@parent_id_key] = digest.span_id.to_s if digest.span_id
           data[@sampling_priority_key] = digest.trace_sampling_priority.to_s if digest.trace_sampling_priority
           data[@origin_key] = digest.trace_origin.to_s if digest.trace_origin
 

lib/datadog/tracing/distributed/propagation.rb

@@ -32,7 +32,9 @@ def initialize(
 
         # inject! populates the env with span ID, trace ID and sampling priority
         #
-        # This method will never raise errors, but instead log them to `Datadog.logger`.
+        # This method will never raise errors.
+        # It can propagate partial data, if deemed useful, instead of failing.
+        # In case of unrecoverable errors, it will log them to `Datadog.logger`.
         #
         # DEV-2.0: inject! should work without arguments, injecting the active_trace's digest
         # DEV-2.0: and returning a new Hash with the injected data.
@@ -45,7 +47,7 @@ def initialize(
         # @param digest [TraceDigest]
         # @param data [Hash]
         # @return [Boolean] `true` if injected successfully, `false` if no propagation style is configured
-        # @return [nil] in case of error, see `Datadog.logger` output for details.
+        # @return [nil] in case of unrecoverable errors, see `Datadog.logger` output for details.
         def inject!(digest, data)
           if digest.nil?
             ::Datadog.logger.debug('Cannot inject distributed trace data: digest is nil.')
@@ -54,6 +56,11 @@ def inject!(digest, data)
 
           digest = digest.to_digest if digest.respond_to?(:to_digest)
 
+          if digest.trace_id.nil?
+            ::Datadog.logger.debug('Cannot inject distributed trace data: digest.trace_id is nil.')
+            return nil
+          end
+
           result = false
 
           # Inject all configured propagation styles

lib/datadog/tracing/distributed/trace_context.rb

@@ -107,7 +107,7 @@ def delete_prefix(prefix)
         def build_traceparent(digest)
           build_traceparent_string(
             digest.trace_id,
-            digest.span_id,
+            digest.span_id || 0, # Fall back to zero (invalid) if not present
             build_trace_flags(digest)
           )
         end
@@ -198,7 +198,8 @@ def build_tracestate(digest)
 
         def last_dd_parent_id(digest)
           if !digest.span_remote
-            "p:#{format('%016x', digest.span_id)};"
+            span_id = digest.span_id || 0 # Fall back to zero (invalid) if not present
+            "p:#{format('%016x', span_id)};"
           elsif digest.trace_distributed_tags&.key?(Tracing::Metadata::Ext::Distributed::TAG_DD_PARENT_ID)
             "p:#{digest.trace_distributed_tags[Tracing::Metadata::Ext::Distributed::TAG_DD_PARENT_ID]};"
           else

spec/datadog/tracing/distributed/b3_multi_spec.rb

@@ -93,6 +93,14 @@
         )
       end
     end
+
+    context 'with span_id nil' do
+      let(:digest) { Datadog::Tracing::TraceDigest.new(trace_id: 0xdef) }
+
+      it 'sets x-b3-spanid to all zeros' do
+        expect(data).to include('x-b3-spanid' => '0000000000000000')
+      end
+    end
   end
 
   describe '#extract' do

spec/datadog/tracing/distributed/b3_single_spec.rb

@@ -76,6 +76,18 @@
         expect(data).to eq(b3_single_header => 'aaaaaaaaaaaaaaaaffffffffffffffff-bbbbbbbbbbbbbbbb')
       end
     end
+
+    context 'with span_id nil' do
+      let(:digest) do
+        Datadog::Tracing::TraceDigest.new(
+          trace_id: 0xabcdef
+        )
+      end
+
+      it 'sets span component to all zeros' do
+        expect(data).to eq(b3_single_header => '00000000000000000000000000abcdef-0000000000000000')
+      end
+    end
   end
 
   describe '#extract' do

spec/datadog/tracing/distributed/datadog_spec.rb

@@ -242,6 +242,19 @@
           )
         end
       end
+
+      context 'with span_id nil' do
+        let(:digest) do
+          Datadog::Tracing::TraceDigest.new(
+            trace_id: 30000
+          )
+        end
+
+        it 'does not include the x-datadog-parent-id field' do
+          inject!
+          expect(data).to eq('x-datadog-trace-id' => '30000')
+        end
+      end
     end
   end
 

spec/datadog/tracing/distributed/propagation_spec.rb

@@ -56,6 +56,26 @@
         expect(data).to include('x-datadog-parent-id' => '9876543210')
       end
 
+      context 'when trace_id is nil' do
+        let(:trace_id) { nil }
+
+        before { skip('TraceOperation always has a trace_id') if trace.is_a?(Datadog::Tracing::TraceOperation) }
+
+        it 'does not inject the trace id' do
+          inject!
+          expect(data).to be_empty
+        end
+      end
+
+      context 'when span_id is nil' do
+        let(:span_id) { nil }
+
+        it 'includes an empty x-datadog-parent-id tag' do
+          inject!
+          expect(data).to_not have_key('x-datadog-parent-id')
+        end
+      end
+
       context 'when sampling priority is set' do
         let(:sampling_priority) { 0 }
 

spec/datadog/tracing/distributed/trace_context_spec.rb

@@ -311,6 +311,19 @@
           end
         end
       end
+
+      context 'with span_id nil' do
+        let(:digest) do
+          Datadog::Tracing::TraceDigest.new(
+            trace_id: 0xC0FFEE,
+            span_id: nil
+          )
+        end
+
+        it 'sets span component to all zeros' do
+          expect(traceparent).to eq('00-00000000000000000000000000c0ffee-0000000000000000-00')
+        end
+      end
     end
   end