Opencensus Python gRPC的“异常迭代请求”

Question

我正试图通过gRPC将OpenCensus跨度发送给使用python的OpenCensus收集器，如下所示：

from opencensus.proto.agent.trace.v1.trace_service_pb2 import ExportTraceServiceRequest
from opencensus.proto.agent.trace.v1.trace_service_pb2_grpc import TraceServiceStub
import grpc


def export(spans, endpoint):
    channel = grpc.insecure_channel(endpoint)
    client = TraceServiceStub(channel=channel)
    rq = ExportTraceServiceRequest(spans = spans)
    responses = client.Export(rq)
    print(list(responses))

spans参数包含类型opencensus.proto.trace.v1.trace_pb2.Span的列表。 我希望这会将列表中的所有跨度导出到opencensus收集器，该收集器在endpoint侦听。但是，我没有看到任何数据到达，响应对象包含

<_MultiThreadedRendezvous of RPC that terminated with:
    status = StatusCode.UNKNOWN
    details = "Exception iterating requests!"
    debug_error_string = "None"
>