==================
Read at 0x00c421abe390 by goroutine 1415:
  reflect.Value.Len()
      /usr/local/go/src/reflect/value.go:1050 +0x19f
  encoding/json.isEmptyValue()
      /usr/local/go/src/encoding/json/encode.go:309 +0x1d5
  encoding/json.(*structEncoder).encode()
      /usr/local/go/src/encoding/json/encode.go:628 +0x319
  encoding/json.(*structEncoder).(encoding/json.encode)-fm()
      /usr/local/go/src/encoding/json/encode.go:653 +0x7b
  encoding/json.(*structEncoder).encode()
      /usr/local/go/src/encoding/json/encode.go:639 +0x2dc
  encoding/json.(*structEncoder).(encoding/json.encode)-fm()
      /usr/local/go/src/encoding/json/encode.go:653 +0x7b
  encoding/json.(*ptrEncoder).encode()
      /usr/local/go/src/encoding/json/encode.go:780 +0x127
  encoding/json.(*ptrEncoder).(encoding/json.encode)-fm()
      /usr/local/go/src/encoding/json/encode.go:785 +0x7b
  encoding/json.(*structEncoder).encode()
      /usr/local/go/src/encoding/json/encode.go:639 +0x2dc
  encoding/json.(*structEncoder).(encoding/json.encode)-fm()
      /usr/local/go/src/encoding/json/encode.go:653 +0x7b
  encoding/json.(*ptrEncoder).encode()
      /usr/local/go/src/encoding/json/encode.go:780 +0x127
  encoding/json.(*ptrEncoder).(encoding/json.encode)-fm()
      /usr/local/go/src/encoding/json/encode.go:785 +0x7b
  encoding/json.(*encodeState).reflectValue()
      /usr/local/go/src/encoding/json/encode.go:325 +0x93
  encoding/json.interfaceEncoder()
      /usr/local/go/src/encoding/json/encode.go:611 +0xed
  encoding/json.(*structEncoder).encode()
      /usr/local/go/src/encoding/json/encode.go:639 +0x2dc
  encoding/json.(*structEncoder).(encoding/json.encode)-fm()
      /usr/local/go/src/encoding/json/encode.go:653 +0x7b
  encoding/json.(*arrayEncoder).encode()
      /usr/local/go/src/encoding/json/encode.go:761 +0x128
  encoding/json.(*arrayEncoder).(encoding/json.encode)-fm()
      /usr/local/go/src/encoding/json/encode.go:768 +0x7b
  encoding/json.(*sliceEncoder).encode()
      /usr/local/go/src/encoding/json/encode.go:735 +0xe1
  encoding/json.(*sliceEncoder).(encoding/json.encode)-fm()
      /usr/local/go/src/encoding/json/encode.go:747 +0x7b
  encoding/json.(*structEncoder).encode()
      /usr/local/go/src/encoding/json/encode.go:639 +0x2dc
  encoding/json.(*structEncoder).(encoding/json.encode)-fm()
      /usr/local/go/src/encoding/json/encode.go:653 +0x7b
  encoding/json.(*ptrEncoder).encode()
      /usr/local/go/src/encoding/json/encode.go:780 +0x127
  encoding/json.(*ptrEncoder).(encoding/json.encode)-fm()
      /usr/local/go/src/encoding/json/encode.go:785 +0x7b
  encoding/json.(*encodeState).reflectValue()
      /usr/local/go/src/encoding/json/encode.go:325 +0x93
  encoding/json.(*encodeState).marshal()
      /usr/local/go/src/encoding/json/encode.go:298 +0xb2
  encoding/json.(*Encoder).Encode()
      /usr/local/go/src/encoding/json/stream.go:200 +0xd7
  github.com/cockroachdb/cockroach/pkg/kv.GRPCTransportFactory.func1()
      /go/src/github.com/cockroachdb/cockroach/pkg/kv/transport_race.go:129 +0x21f
  github.com/cockroachdb/cockroach/pkg/util/stop.(*Stopper).RunAsyncTask.func1()
      /go/src/github.com/cockroachdb/cockroach/pkg/util/stop/stopper.go:324 +0xf3

Previous write at 0x00c421abe390 by goroutine 828:
  github.com/cockroachdb/cockroach/pkg/roachpb.(*EndTransactionRequest).SetHeader()
      /go/src/github.com/cockroachdb/cockroach/pkg/roachpb/api.go:358 +0x80
  github.com/cockroachdb/cockroach/pkg/kv.(*txnSeqNumAllocator).SendLocked()
      /go/src/github.com/cockroachdb/cockroach/pkg/kv/txn_interceptor_sequence_nums.go:55 +0x20c
  github.com/cockroachdb/cockroach/pkg/kv.(*txnHeartbeat).SendLocked()
      /go/src/github.com/cockroachdb/cockroach/pkg/kv/txn_interceptor_heartbeat.go:230 +0x1cb
  github.com/cockroachdb/cockroach/pkg/kv.(*TxnCoordSender).Send()
      /go/src/github.com/cockroachdb/cockroach/pkg/kv/txn_coord_sender.go:643 +0x6ba
  github.com/cockroachdb/cockroach/pkg/internal/client.(*DB).sendUsingSender()
      /go/src/github.com/cockroachdb/cockroach/pkg/internal/client/db.go:623 +0x123
  github.com/cockroachdb/cockroach/pkg/internal/client.(*Txn).Send()
      /go/src/github.com/cockroachdb/cockroach/pkg/internal/client/txn.go:838 +0x1cf
  github.com/cockroachdb/cockroach/pkg/internal/client.(*Txn).commit()
      /go/src/github.com/cockroachdb/cockroach/pkg/internal/client/txn.go:525 +0x30e
  github.com/cockroachdb/cockroach/pkg/internal/client.(*Txn).Commit()
      /go/src/github.com/cockroachdb/cockroach/pkg/internal/client/txn.go:573 +0x4c
  github.com/cockroachdb/cockroach/pkg/internal/client.(*Txn).exec()
      /go/src/github.com/cockroachdb/cockroach/pkg/internal/client/txn.go:743 +0x466
  github.com/cockroachdb/cockroach/pkg/internal/client.(*DB).Txn()
      /go/src/github.com/cockroachdb/cockroach/pkg/internal/client/db.go:585 +0x15d
  github.com/cockroachdb/cockroach/pkg/sql/distsqlrun.WriteResumeSpan()
      /go/src/github.com/cockroachdb/cockroach/pkg/sql/distsqlrun/backfiller.go:243 +0x24d
  github.com/cockroachdb/cockroach/pkg/sql/distsqlrun.(*backfiller).mainLoop()
      /go/src/github.com/cockroachdb/cockroach/pkg/sql/distsqlrun/backfiller.go:142 +0xba4
  github.com/cockroachdb/cockroach/pkg/sql/distsqlrun.(*backfiller).Run()
      /go/src/github.com/cockroachdb/cockroach/pkg/sql/distsqlrun/backfiller.go:82 +0x239
  github.com/cockroachdb/cockroach/pkg/sql/distsqlrun.(*columnBackfiller).Run()
      <autogenerated>:1 +0x61