ERROR:aws_xray_sdk.core.context:cannot找到当前段/子段

Question

最近，我们将X射线添加到代码中，方法是：

from aws_xray_sdk.core import xray_recorder
from aws_xray_sdk.core import patch_all

patch_all()

虽然这在AWS上运行良好，但是在调用ElasticSearch期间尝试在本地运行时，我们得到了以下异常：

ERROR:aws_xray_sdk.core.context:cannot find the current segment/subsegment, please make sure you have a segment open
queryCustomers - DEBUG - Caught exception for <function search_customer at 0x10bfcf0d0>
Traceback (most recent call last):
  File "/Users/jameslin/virtualenvs/test-project/lib/python3.6/site-packages/chalice/app.py", line 659, in _get_view_function_response
    response = view_function(**function_args)
  File "/Users/jameslin/projects/test-project/src/app.py", line 57, in search_customer
    return query[0:size].execute().to_dict()['hits']['hits']
  File "/Users/jameslin/virtualenvs/test-project/lib/python3.6/site-packages/elasticsearch_dsl/search.py", line 639, in execute
    **self._params
  File "/Users/jameslin/virtualenvs/test-project/lib/python3.6/site-packages/elasticsearch/client/utils.py", line 73, in _wrapped
    return func(*args, params=params, **kwargs)
  File "/Users/jameslin/virtualenvs/test-project/lib/python3.6/site-packages/elasticsearch/client/__init__.py", line 632, in search
    doc_type, '_search'), params=params, body=body)
  File "/Users/jameslin/virtualenvs/test-project/lib/python3.6/site-packages/elasticsearch/transport.py", line 312, in perform_request
    status, headers, data = connection.perform_request(method, url, params, body, ignore=ignore, timeout=timeout)
  File "/Users/jameslin/virtualenvs/test-project/lib/python3.6/site-packages/elasticsearch/connection/http_requests.py", line 71, in perform_request
    prepared_request = self.session.prepare_request(request)
  File "/Users/jameslin/virtualenvs/test-project/lib/python3.6/site-packages/aws_xray_sdk/ext/requests/patch.py", line 38, in _inject_header
    inject_trace_header(headers, xray_recorder.current_subsegment())
  File "/Users/jameslin/virtualenvs/test-project/lib/python3.6/site-packages/aws_xray_sdk/core/recorder.py", line 251, in current_subsegment
    entity = self.get_trace_entity()
  File "/Users/jameslin/virtualenvs/test-project/lib/python3.6/site-packages/aws_xray_sdk/core/recorder.py", line 316, in get_trace_entity
    return self.context.get_trace_entity()
  File "/Users/jameslin/virtualenvs/test-project/lib/python3.6/site-packages/aws_xray_sdk/core/context.py", line 93, in get_trace_entity
    return self.handle_context_missing()
  File "/Users/jameslin/virtualenvs/test-project/lib/python3.6/site-packages/aws_xray_sdk/core/context.py", line 118, in handle_context_missing
    raise SegmentNotFoundException(MISSING_SEGMENT_MSG)
aws_xray_sdk.core.exceptions.exceptions.SegmentNotFoundException: cannot find the current segment/subsegment, please make sure you have a segment open

我不知道他的方法是什么，也不知道如何摆脱它，我的google尝试给出的相关结果不多，我也尝试在本地运行x射线守护进程，但仍然有相同的问题：

./xray_mac -o -n ap-southeast-2

Answer 1

当您的代码在启用跟踪的AWS Lambda上运行时，Lambda容器将生成一个表示整个函数调用的段。它还将上下文设置为环境变量，以便SDK可以将函数中创建的任何子段链接回父段。

如果您在本地运行相同的代码，SDK仍然尝试为实际的函数代码创建子段，但是它找不到任何上下文，从而抛出您发布的错误。

要解决这个问题，您需要设置一些环境变量，以确保SDK具有与实际Lambda容器上运行的信息相同的信息。

1. 确保SDK认为它运行在Lambda容器上，方法是用您想要的任何值设置LAMBDA_TASK_ROOT (只有关键问题的存在)。您可以在这里看到源代码：launcher.py
2. 设置LAMBDA_TRACE_HEADER_KEY，以便该函数具有跟踪上下文。该值必须是跟踪头，您可以在这里看到更多详细信息：https://docs.aws.amazon.com/lambda/latest/dg/lambda-x-ray.html

这种解决方法并不理想，因为它需要用户方进行额外的代码更改。我们希望提供更好的客户经验，以测试X射线仪器的Lambda功能在当地.您介意分享更多关于您是如何进行本地测试的细节吗?以及您希望X射线跟踪在这样的测试环境中如何工作，这样我们就可以更好地改进您的用例吗？