以 sudo 運行時 python3 腳本失敗

Question

當我使用 pi 用戶在樹莓派上運行下面的 python 腳本時，它運行良好。

#!/usr/bin/python3

from prometheus_client import start_http_server, Summary, Gauge
import random
import time
import subprocess
import json

# Create a metric to track time spent and requests made.
REQUEST_TIME = Summary('request_processing_seconds', 'Time spent processing request')


# use Gauge to record the metrics
labels = ['server_name', 'server_id']
latencyGauge = Gauge('ping_latency', 'Ping Latency in ms', labels)
downloadGauge = Gauge('download_speed', 'Download speed in bytes', labels)
uploadGauge = Gauge('upload_speed', 'Upload speed in bytes', labels)

# launch a subprocess running the speedtest command
# Decorate function with metric.
@REQUEST_TIME.time()
def process_request(id, t):
    comp = subprocess.run(['speedtest', '-s', id, '-f', 'json'], stdout=subprocess.PIPE, stderr=subprocess.PIPE, universal_newlines=True)
#    print(comp)
    output_str = comp.stdout
#    print(output_str)
    res = json.loads(output_str)
    ping = res["ping"]["latency"]
    upload = res["upload"]["bandwidth"]
    download = res["download"]["bandwidth"]
    server_name = res["server"]["name"]
    print("Result for %s (%s): %d, %d, %d" % (id, server_name, ping, download, upload))
    latencyGauge.labels(server_name, id).set(ping)
    uploadGauge.labels(server_name, id).set(upload)
    downloadGauge.labels(server_name, id).set(download)

    time.sleep(t)



if __name__ == '__main__':
    # Start up the server to expose the metrics.
    start_http_server(8000)
    # Generate some requests.
    while True:
        process_request("1686", 120)

但是，如果我使用 sudo 運行它，它會失敗並出現以下錯誤。

pi@raspberrypi:~/speedtest $ sudo ./speedtest.py
Traceback (most recent call last):
  File "./speedtest.py", line 46, in <module>
    process_request("1686", 120)
  File "<decorator-gen-1>", line 2, in process_request
  File "/usr/local/lib/python3.7/dist-packages/prometheus_client/context_managers.py", line 66, in wrapped
    return func(*args, **kwargs)
  File "./speedtest.py", line 27, in process_request
    res = json.loads(output_str)
  File "/usr/lib/python3.7/json/__init__.py", line 348, in loads
    return _default_decoder.decode(s)
  File "/usr/lib/python3.7/json/decoder.py", line 337, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "/usr/lib/python3.7/json/decoder.py", line 355, in raw_decode
    raise JSONDecodeError("Expecting value", s, err.value) from None
json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)

在 sudo 中運行腳本的原因是我希望它通過編輯 /etc/rc.local 自動啟動

可能是什么原因？

Answer 1

解決。

問題的根本原因是，在第一次使用 speedtest 軟件時，用戶需要通過輸入兩次“是”（或拒絕）來接受，然后才能繼續。

由於腳本需要 JSON 回復，因此初始運行時顯示的文本破壞了 JSON 解析。

因此，解決方案是使用 sudo 至少運行一次不帶任何選項（默認）的速度測試，如下所示。