Question

我正在查询一个像这样工作的数据集：每次查询它时都会生成不同的Bytes_Written和Bytes_Read值。我似乎无法完成的是从前一个值中减去当前值并继续每秒执行此操作。

以下是数据的样子：

{
  "Number of Devices": 2,
  "Block Devices": {
    "bdev0": {
      "Backend_Device_Path": "/dev/disk/by-path/ip-192.168.26.1:3260-iscsi-iqn.2010-10.org.openstack:volume-d1c8e7c6-8c77-444c-9a93-8b56fa1e37f2-lun-010.0.0.142",
      "Capacity": "2147483648",
      "Guest_Device_Name": "vdb",
      "IO_Operations": "97069",
      "Bytes_Written": "34410496",
      "Bytes_Read": "363172864"
    },
    "bdev1": {
      "Backend_Device_Path": "/dev/disk/by-path/ip-192.168.26.1:3260-iscsi-iqn.2010-10.org.openstack:volume-b27110f9-41ba-4bc6-b97c-b5dde23af1f9-lun-010.0.0.146",
      "Capacity": "2147483648",
      "Guest_Device_Name": "vdb",
      "IO_Operations": "93",
      "Bytes_Written": "0",
      "Bytes_Read": "380928"
    }
  }
}

查询数据的代码：

def counterVolume_one():
    #Get data 
    url = 'http://url:8080/vrio/blk'
    r = requests.get(url)
    data = r.json()

wanted = {'Bytes_Written', 'Bytes_Written', 'IO_Operation'}
for d in data['Block Devices'].itervalues():
    values = {k: v for k, v in d.iteritems() if k in wanted}
    print json.dumps(values)

counterVolume_one()

我想获得输出的方式是：

{"IO_Operations": "97069", "Bytes_Read": "363172864", "Bytes_Written": "34410496"}
{"IO_Operations": "93", "Bytes_Read": "380928", "Bytes_Written": "0"}

这是我想要完成的事情：

first time query = first set of values
after 1 sec
second time query = first set of values-second set of values
after 1 sec
third time query = second set of  values-third set of values

预期输出将是一个json对象，如下所示

{'bytes-read': newvalue, 'bytes-written': newvalue, 'io_operations': newvalue}

Answer 1

最简单的修复方法可能是修改counterVolume_one()函数，使其接受定义当前状态的参数，并在收集数据时更新。例如，以下代码从JSON文档中收集和总结您感兴趣的字段：

FIELDS = ('Bytes_Written', 'Bytes_Read', 'IO_Operation')

def counterVolume_one(state):
    url = 'http://url:8080/vrio/blk'
    r = requests.get(url)
    data = r.json()

    for field in FIELDS:
        state[field] += data[field]
    return state

state = {"Bytes_Written": 0, "Bytes_Read": 0, "IO_Operation": 0}
while True:
    counterVolume_one(state)
    time.sleep(1)
    for field in FIELDS:
        print("{field:s}: {count:d}".format(field=field,
                                            count=state[field]))

更正确的修复可能是使用类来保存状态，并且有一个更新状态的方法。但是，我认为遵循上述想法可以最快地为您提供解决方案。

如何创建一个函数，每次调用时都会从前一个值中减去当前值

1 个答案: