我已经设计了一个使用Django框架的本地网络网站，最近遇到了我直到最近才遇到的问题。 我们正在本地网络上进行实验，收集各种测量值，我建立了这个网站，以确保我们在同一个地方收集所有数据。
我设置了一个PostGreSQL数据库并使用django在接收测量值时动态填充它。执行该操作的脚本如下所示：
**ladrLogger.py**
#various imports
import django
from django.db import IntegrityError
os.environ.setdefault("DJANGO_SETTINGS_MODULE", "mysite.settings")
django.setup()
from logger.models import Measurement, Device, Type , Room, Experiment, ExperimentData
def logDevice(self,port):
# Callback function executed each time I receive data to log it in the database
deviceData = port.data # get the data
# Do a bunch of tests and checks
# ....
# Get all measurement to add to the database
# measurements is a list of measurement as defined in my django models
measurements = self.prepareMeasurement(...)
self.saveMeasurements(measurements)
print "Saved measurements successfully."
def saveMeasurements(self,meas):
if not meas:
return
elif type(meas) is list:
for m in meas:
self.saveMeasurements(m)
elif type(meas) is Measurement:
try:
meas.save()
except IntegrityError as e:
if 'unique constraint' in e.message:
print "Skipping... Measurement already existed for device " + meas.device.name
else:
print "Skipping measurement due to error: " + e.message
def prepareMeasurement(self,nameDevice, typeDevice, time, data):
### Takes the characteristics of measurement (device, name and type) and creates the appropriate measurements.
measurements = []
m = Measurement()
m.device = Device.objects.get(name=nameDevice)
m.date = time
# Bunch of tests
# .....
for idv,v in enumerate(value):
if v in data:
m = Measurement()
m.device = something
m.date = something else
m.value = bla
m.quantity = blabla
measurements.append(m)
return measurements
# Bunch of other methods
请注意，此脚本始终在运行，并等待执行logDevice回调的更多测量。
编辑：基于YARP的基于自定义的库负责回调处理。创建回调的代码如下所示：
portid = self.createPort(quer.group(1),True,True) #creates a port
pyarp.connect(desc[0], self.fullPortPath(portid)) #establishes connection to talking port
self.listenToPort(portid, lambda port: self.logDevice(port)) #tells him to execute that callback when he receives messages'
回调完全在后台处理。
另一方面，我有我的django网站，有各种视图显示设备，测量，绘图等等。 我遇到的问题是我正在记录我的测量结果（有时候每秒大约几（2-3）次，通常更少）我可以看到记录似乎很好。但是当我调用我的观点时，例如询问设备x的最新测量值，我得到一个旧的测量值。代码的一个例子：
def latestTemp(request,device_id):
# Creates a csv file with the latest temperature measured
#### for now does not check what measurements are actually available
dev = get_object_or_404(Device, pk=device_id)
tz = pytz.timezone('Europe/Zurich')
# Create the HttpResponse object with the appropriate CSV header.
response = HttpResponse(content_type='text/csv')
response['Content-Disposition'] = 'attachment; filename="%s.csv"' %dev.name
#get measurement
lastMeas = Measurement.objects.filter(device=dev, quantity=Type.objects.get(quantity='Temperature')).latest('date')
writer = csv.writer(response)
# Form list of required timesteps
date = lastMeas.date.astimezone(tz)
writer.writerow([date.strftime('%Y-%m-%d'),date.strftime('%H:%M'),lastMeas.value])
return response
编辑（更精确）： 我已经记录了几个小时的数据，但网站只向我展示了几个小时后的东西。随着我不断要求这些数据，它变得越来越近，好像它已被缓存到某个地方并且现在变得缓慢是网站可见的地方，直到一切都恢复正常。另一方面，如果我终止了日志记录过程，数据似乎永远丢失了。但奇怪的是logDevice方法完成了，我可以看到meas.save（）命令已经执行了。我还尝试为Django信号post.save添加一个监听器，并且我正确地捕获它们。
几乎没有信息：
- 我正在使用postgresql后端
- 我在专用的Mac机器上运行所有这些
- 让我知道其他任何有用的知识
我的问题是：
- 你有没有可能发生的任何理由（以前不会发生这种情况，所以我猜它可能与数据库变大，4Gb现在有关）
- 作为一个附带问题，但可能是相关的，我怀疑我在数据库中推送新元素的方式并不是很好，因为代码完全独立于django网站本身运行。有关如何改进的任何建议？我认为ladrLogger代码可以向创建新元素的专用视图发送请求，但这可能更重，无用。
编辑：添加我的models.py
class Room(models.Model):
fullName = models.CharField(max_length=20, unique=True)
shortName = models.CharField(max_length=5, unique=True, default = "000")
nickName = models.CharField(max_length=20, default="Random Room")
def __unicode__(self):
return self.fullName
class Type(models.Model):
quantity = models.CharField(max_length=100, default="Temperature", unique = True)
unit = models.CharField(max_length=5, default="C", blank=True)
VALUE_TYPES = (
('float', 'float'),
('boolean', 'boolean'),
('integer', 'integer'),
('string', 'string'),
)
value_type = models.CharField(max_length=20, choices=VALUE_TYPES, default = "float")
def __unicode__(self):
return self.quantity
class Device(models.Model):
name = models.CharField(max_length=30, default="Unidentified Device",unique=True)
room = models.ForeignKey(Room)
description = models.CharField(max_length=500, default="", blank=True,)
indigoId = models.CharField(max_length=30,default="000")
def __unicode__(self):
#r = Room.objects.get(pk = self.room)
return self.name #+ ' in room ' + r.name
def latestMeasurement(self,*args):
if len(args)==0:
#No argument so just return latest argument
meas = Measurement.objects.filter(device=self).latest('date')
else:
#Use first argument as the type
meas = Measurement.objects.filter(device=self, quantity=args[0]).latest('date')
if not meas:
return None
else:
return meas
def typeList(self):
return Type.objects.filter(measurement__device=self).distinct()
class Measurement(models.Model):
device = models.ForeignKey(Device)
date = models.DateTimeField(db_index=True)
value = models.CharField(max_length=100,default="")
quantity = models.ForeignKey(Type)
class Meta:
unique_together = ('date','device','quantity',)
index_together = ['date', 'device']
def __unicode__(self):
t = self.quantity
return str(self.value) + " " + self.quantity.unit
# return str(self.value)