Add tracing (#846)

Signed-off-by: andylokandy <[email protected]>

proto/coprocessor.proto

@@ -6,7 +6,6 @@ import "kvrpcpb.proto";
 import "gogoproto/gogo.proto";
 import "rustproto.proto";
 import "metapb.proto";
-import "span.proto";
 
 option (gogoproto.marshaler_all) = true;
 option (gogoproto.sizer_all) = true;
@@ -57,7 +56,8 @@ message Response {
     bool is_cache_hit = 7;
     uint64 cache_last_version = 8;
     bool can_be_cached = 9;
-    repeated span.SpanSet spans = 10;
+
+    reserved 10;
 }
 
 message RegionInfo {

proto/kvrpcpb.proto

@@ -6,6 +6,7 @@ import "errorpb.proto";
 import "gogoproto/gogo.proto";
 import "rustproto.proto";
 import "deadlock.proto";
+import "trace.proto";
 
 option (gogoproto.marshaler_all) = true;
 option (gogoproto.sizer_all) = true;
@@ -712,6 +713,9 @@ message Context {
     // Read request should read through locks belonging to these transactions because these
     // transactions are committed and theirs commit_ts <= read request's start_ts.
     repeated uint64 committed_locks = 22;
+
+    // The informantion to trace a request to TiKV.
+    trace.TraceContext trace_context = 23;
 }
 
 // The API version the server and the client is using.

proto/trace.proto

@@ -0,0 +1,52 @@
+syntax = "proto3";
+package trace;
+
+service TraceRecordPubSub {
+    // Subscribe the tracing records generated on this service. The service will periodically (e.g. per minute)
+    // publishes tracing records to clients via gRPC stream.
+    rpc Subscribe(TraceRecordRequest) returns (stream TraceRecord) {}
+}
+
+message TraceRecordRequest {}
+
+// The necessary information to trace a request.
+// Setting any field to 0 will disable tracing on the RPC server.
+message TraceContext {
+    // The id that is able to identify a unique request. It's usually a UUID.
+    uint64 trace_id = 1;
+    // The span that represents the caller's calling procedural.
+    uint64 parent_id = 2;
+}
+
+message TraceRecord {
+    oneof record_oneof {
+        SpanSet spans = 1;
+    }
+}
+
+// The spans for a request on a service.
+message SpanSet {
+    // The id that is able to identify a unique request.
+    uint64 trace_id = 1;
+    // The span that represents the caller's calling procedural.
+    // Set to 0 when reporting to indicate that it's the root service of the entire trace.
+    uint64 parent_id = 2;
+    repeated Span spans = 3;
+}
+
+message Span {
+    // The unique span id within a `SpanSet`.
+    uint32 span_id = 1;
+    // The parent span within a `SpanSet`.
+    // Set to 0 to indicate that it's the root span within a `SpanSet`.
+    uint32 parent_id = 2;
+    uint64 begin_unix_ns = 3;
+    uint64 duration_ns = 4;
+    string event = 5;
+    repeated Property properties = 6;
+}
+
+message Property {
+    string key = 1;
+    string value = 2;
+}