Precompute hex encodings of SpanID and TraceID (#874)

* Use `binary:encode_hex/2` instead of `io_lib:format/2`

`io_lib:format/2` has very significant overhead over
`binary:encode_hex/2`.

* Precompute hex trace and span ids

* Prefill hex IDs in remaining span_ctx constructors

---------

Co-authored-by: Tristan Sloughter <[email protected]>

Author: kzemek

apps/opentelemetry/src/otel_span_ets.erl

@@ -102,7 +102,9 @@ get_ctx(#span{trace_id=TraceId,
               tracestate=TraceState,
               is_recording=IsRecording}) ->
     #span_ctx{trace_id=TraceId,
+              hex_trace_id=otel_utils:encode_hex(<<TraceId:128>>),
               span_id=SpanId,
+              hex_span_id=otel_utils:encode_hex(<<SpanId:64>>),
               tracestate=TraceState,
               is_recording=IsRecording}.
 

apps/opentelemetry/src/otel_span_utils.erl

@@ -87,12 +87,20 @@ new_span_ctx(Ctx, IdGeneratorModule) ->
             {root_span_ctx(IdGeneratorModule), undefined, undefined};
         ParentSpanCtx=#span_ctx{span_id=ParentSpanId, is_remote=ParentIsRemote} ->
             %% keep the rest of the parent span ctx, simply need to update the span_id
-            {ParentSpanCtx#span_ctx{span_id=IdGeneratorModule:generate_span_id()}, ParentSpanId, ParentIsRemote}
+            SpanId = IdGeneratorModule:generate_span_id(),
+            HexSpanId = otel_utils:encode_hex(<<SpanId:64>>),
+            {ParentSpanCtx#span_ctx{span_id=SpanId, hex_span_id=HexSpanId}, ParentSpanId, ParentIsRemote}
     end.
 
 root_span_ctx(IdGeneratorModule) ->
-    #span_ctx{trace_id=IdGeneratorModule:generate_trace_id(),
-              span_id=IdGeneratorModule:generate_span_id(),
+    TraceId = IdGeneratorModule:generate_trace_id(),
+    HexTraceId = otel_utils:encode_hex(<<TraceId:128>>),
+    SpanId = IdGeneratorModule:generate_span_id(),
+    HexSpanId = otel_utils:encode_hex(<<SpanId:64>>),
+    #span_ctx{trace_id=TraceId,
+              hex_trace_id=HexTraceId,
+              span_id=SpanId,
+              hex_span_id=HexSpanId,
               is_valid=true,
               trace_flags=0}.
 

apps/opentelemetry/test/opentelemetry_SUITE.erl

@@ -1101,6 +1101,17 @@ no_exporter(_Config) ->
 
     ok.
 
+
+generate_trace_id() -> 41394.
+generate_span_id() -> 50132.
+pregenerate_hex_ids(_Config) ->
+    HexTraceId = <<"0000000000000000000000000000a1b2">>,
+    HexSpanId = <<"000000000000c3d4">>,
+    SpanCtx = otel_span_utils:root_span_ctx(?MODULE),
+    ?assertEqual(HexTraceId, SpanCtx#span_ctx.hex_trace_id),
+    ?assertEqual(HexSpanId, SpanCtx#span_ctx.hex_span_id),
+    ok.
+
 %%
 
 assert_all_exported(Tid, SpanCtxs) ->

apps/opentelemetry_api/include/opentelemetry.hrl

@@ -49,8 +49,12 @@
 -record(span_ctx, {
           %% 128 bit int trace id
           trace_id          :: opentelemetry:trace_id(),
+          %% 128 bit int trace id encoded as hex binary string
+          hex_trace_id      :: opentelemetry:hex_trace_id(),
           %% 64 bit int span id
           span_id           :: opentelemetry:span_id(),
+          %% 64 bit int span id encoded as hex binary string
+          hex_span_id       :: opentelemetry:hex_span_id(),
           %% 8-bit integer, lowest bit is if it is sampled
           trace_flags = 0   :: integer(),
           %% Tracestate represents tracing-system specific context in a list of key-value pairs.

apps/opentelemetry_api/src/otel_span.erl

@@ -126,22 +126,12 @@ hex_span_ctx(_) ->
     #{}.
 
 -spec hex_trace_id(opentelemetry:span_ctx()) -> opentelemetry:hex_trace_id().
-hex_trace_id(#span_ctx{trace_id=TraceId}) ->
-    case otel_utils:format_binary_string("~32.16.0b", [TraceId]) of
-        {ok, Binary} ->
-            Binary;
-        _ ->
-            <<>>
-    end.
+hex_trace_id(#span_ctx{hex_trace_id=HexTraceId}) ->
+    HexTraceId.
 
 -spec hex_span_id(opentelemetry:span_ctx()) -> opentelemetry:hex_span_id().
-hex_span_id(#span_ctx{span_id=SpanId}) ->
-    case otel_utils:format_binary_string("~16.16.0b", [SpanId]) of
-        {ok, Binary} ->
-            Binary;
-        _ ->
-            <<>>
-    end.
+hex_span_id(#span_ctx{hex_span_id=HexSpanId}) ->
+    HexSpanId.
 
 -spec tracestate(opentelemetry:span_ctx() | undefined) -> otel_tracestate:t().
 tracestate(#span_ctx{tracestate=Tracestate}) ->

apps/opentelemetry_api/src/otel_tracer.erl

@@ -90,7 +90,9 @@ with_span(Ctx, Tracer={Module, _}, SpanName, Opts, Fun) when is_atom(Module) ->
                         -> opentelemetry:span_ctx().
 non_recording_span(TraceId, SpanId, Traceflags) ->
     #span_ctx{trace_id=TraceId,
+              hex_trace_id=otel_utils:encode_hex(<<TraceId:128>>),
               span_id=SpanId,
+              hex_span_id=otel_utils:encode_hex(<<SpanId:64>>),
               is_recording=false,
               trace_flags=Traceflags}.
 
@@ -100,7 +102,9 @@ non_recording_span(TraceId, SpanId, Traceflags) ->
                       -> opentelemetry:span_ctx().
 from_remote_span(TraceId, SpanId, Traceflags) ->
     #span_ctx{trace_id=TraceId,
+              hex_trace_id=otel_utils:encode_hex(<<TraceId:128>>),
               span_id=SpanId,
+              hex_span_id=otel_utils:encode_hex(<<SpanId:64>>),
               is_valid=true,
               is_recording=false,
               is_remote=true,

apps/opentelemetry_api/src/otel_tracer_noop.erl

@@ -28,7 +28,9 @@
 -include("otel_tracer.hrl").
 
 -define(NOOP_SPAN_CTX, #span_ctx{trace_id=0,
+                                 hex_trace_id= <<"00000000000000000000000000000000">>,
                                  span_id=0,
+                                 hex_span_id= <<"0000000000000000">>,
                                  trace_flags=0,
                                  tracestate=otel_tracestate:new(),
                                  is_valid=false,

apps/opentelemetry_api/src/otel_utils.erl

@@ -20,7 +20,8 @@
          format_binary_string/2,
          format_binary_string/3,
          assert_to_binary/1,
-         unicode_to_binary/1]).
+         unicode_to_binary/1,
+         encode_hex/1]).
 
 -if(?OTP_RELEASE >= 24).
 format_exception(Kind, Reason, StackTrace) ->
@@ -55,3 +56,15 @@ unicode_to_binary(String) ->
         _ ->
             {error, bad_binary_conversion}
     end.
+
+-spec encode_hex(binary()) -> binary().
+-if(?OTP_RELEASE >= 26).
+encode_hex(Bin) ->
+    binary:encode_hex(Bin, lowercase).
+-elif(?OTP_RELEASE >= 24).
+encode_hex(Bin) ->
+    string:lowercase(binary:encode_hex(Bin)).
+-else.
+encode_hex(Bin) ->
+    string:lowercase(<< <<Enc>> || <<HByte:4>> <= Bin, Enc <- integer_to_list(HByte, 16) >>).
+-endif.

apps/opentelemetry_api/test/opentelemetry_api_SUITE.erl

@@ -249,7 +249,7 @@ noop_with_span(_Config) ->
 hex_trace_ids(_Config) ->
     HexTraceId = <<"0000000000000000000000000000a1b2">>,
     HexSpanId = <<"000000000000c3d4">>,
-    SpanCtx=#span_ctx{trace_id=41394, span_id=50132},
+    SpanCtx=#span_ctx{trace_id=41394, hex_trace_id=HexTraceId, span_id=50132, hex_span_id=HexSpanId},
     ?assertEqual(HexTraceId, otel_span:hex_trace_id(SpanCtx)),
     ?assertEqual(HexSpanId, otel_span:hex_span_id(SpanCtx)),
     ?assertEqual(#{otel_trace_id => HexTraceId,

apps/opentelemetry_api/test/otel_propagators_SUITE.erl

@@ -70,7 +70,9 @@ rewrite(_Config) ->
     otel_ctx:clear(),
 
     RecordingSpanCtx = #span_ctx{trace_id=21267647932558653966460912964485513216,
+                                 hex_trace_id= <<"10000000000000000000000000000000">>,
                                  span_id=1152921504606846976,
+                                 hex_span_id= <<"1000000000000000">>,
                                  is_valid=true,
                                  is_recording=true},
     otel_tracer:set_current_span(RecordingSpanCtx),
@@ -117,7 +119,9 @@ invalid_span_no_sdk_propagation(_Config) ->
     otel_ctx:clear(),
 
     InvalidSpanCtx = #span_ctx{trace_id=0,
+                               hex_trace_id= <<"00000000000000000000000000000000">>,
                                span_id=0,
+                               hex_span_id= <<"0000000000000000">>,
                                trace_flags=0,
                                is_valid=false,
                                is_recording=false},
@@ -142,7 +146,9 @@ nonrecording_no_sdk_propagation(_Config) ->
     otel_ctx:clear(),
 
     NonRecordingSpanCtx = #span_ctx{trace_id=21267647932558653966460912964485513216,
+                                    hex_trace_id= <<"10000000000000000000000000000000">>,
                                     span_id=1152921504606846976,
+                                    hex_span_id= <<"1000000000000000">>,
                                     is_valid=true,
                                     is_recording=false},
     ?set_current_span(NonRecordingSpanCtx),