Add tracing hooks for existing connections

Previously the redis/go-redis library would call newTracingHook with
no connString as default tracing, but that was recently removed in 9.8.0
which has caused our clients to lose oteltracing if connections are
created before tracing can be instrumented.

Author: AllanGuigou

extra/redisotel/tracing.go

@@ -21,7 +21,7 @@ const (
 	instrumName = "github.com/redis/go-redis/extra/redisotel"
 )
 
-func InstrumentTracing(rdb redis.UniversalClient, opts ...TracingOption) error {
+func InstrumentTracing(ctx context.Context, rdb redis.UniversalClient, opts ...TracingOption) error {
 	switch rdb := rdb.(type) {
 	case *redis.Client:
 		opt := rdb.Options()
@@ -36,6 +36,13 @@ func InstrumentTracing(rdb redis.UniversalClient, opts ...TracingOption) error {
 			connString := formatDBConnString(opt.Network, opt.Addr)
 			rdb.AddHook(newTracingHook(connString, opts...))
 		})
+
+		rdb.ForEachShard(ctx, func(ctx context.Context, rdb *redis.Client) error {
+			opt := rdb.Options()
+			opts = addServerAttributes(opts, opt.Addr)
+			connString := formatDBConnString(opt.Network, opt.Addr)
+			rdb.AddHook(newTracingHook(connString, opts...))
+		})
 		return nil
 	case *redis.Ring:
 		rdb.OnNewNode(func(rdb *redis.Client) {
@@ -44,6 +51,13 @@ func InstrumentTracing(rdb redis.UniversalClient, opts ...TracingOption) error {
 			connString := formatDBConnString(opt.Network, opt.Addr)
 			rdb.AddHook(newTracingHook(connString, opts...))
 		})
+
+		rdb.ForEachShard(ctx, func(ctx context.Context, rdb *redis.Client) error {
+			opt := rdb.Options()
+			opts = addServerAttributes(opts, opt.Addr)
+			connString := formatDBConnString(opt.Network, opt.Addr)
+			rdb.AddHook(newTracingHook(connString, opts...))
+		})
 		return nil
 	default:
 		return fmt.Errorf("redisotel: %T not supported", rdb)