确定 django 中会话的年龄

Question

如何确定 django 中会话对象的年龄？

Answer 1

好的，这就是我的想法。好多了。我认为这与在 Session 对象上使用 post_save 一样便宜：

from django.db import models
from people.models import Member
from django.contrib.sessions.models import Session
from django.contrib.sessions.backends.db import SessionStore


from django.db.models import *
from django.db.models.signals import post_save, pre_delete, post_init
from datetime import datetime

class SessionInfo(models.Model):
    #note: a OneToOneField with the name 'session' has been added as part of the inheritance
    created = models.DateTimeField(auto_now_add=True) #joined field is auto initialized with creation time
    session = models.OneToOneField(Session)
    def age(self):
        return (datetime.now() - self.created)


def session_create_listener(instance, **kwargs):
    store = SessionStore(session_key=instance.session_key)

    if '_auth_user_id' in store:
        try:
            instance.sessioninfo
        except SessionInfo.DoesNotExist:
            sessioninfo = SessionInfo(session=instance) 
            sessioninfo.save()        

post_save.connect(session_create_listener, sender=Session)

Answer 2

这就是我最终所做的而不是托马斯的建议。请注意，我拒绝使用接收器装饰器，因此它在 1.3 之前仍然可以工作。

（这需要认真纠正）。

from django.db import models
from people.models import Member
from django.contrib.sessions.models import Session
from django.contrib.sessions.backends.db import SessionStore


from django.db.models import *
from django.db.models.signals import post_save, pre_delete, post_init
#from django.dispatch import receiver
from datetime import datetime

class SessionInfo(models.Model):
    #note: a OneToOneField with the name 'session' has been added as part of the inheritance
    created = models.DateTimeField(auto_now_add=True) #joined field is auto initialized with creation time
    session = models.OneToOneField(Session)
    def age(self):
        return (datetime.now() - self.created)


def session_create_listener(instance, **kwargs):
    store = SessionStore(session_key=instance.session_key)

    if '_auth_user_id' in store:
        try:
            sessioninfo = SessionInfo.objects.get(session=instance)
        except SessionInfo.DoesNotExist:
            sessioninfo = SessionInfo(session=instance) 
            sessioninfo.save()
            store['anonymous'] = False
            store.save()
    else:
        try:
            store['anonymous']
        except KeyError:
            store['anonymous'] = True 
            store.save()

post_save.connect(session_create_listener, sender=Session)

我希望有人能为我纠正这个问题，因为我不相信这是最有效的方法。

首先也是最重要的，每次修改会话时，这都会增加两次额外的数据库命中（第一次尝试：sessioninfo = SessionInfo.objects.get(session=instance)）。

第一个显然是在查找过程中。第二种发生在保存发生时，再次触发整个过程。

该怎么办呢？

Answer 3

您需要挂钩来自 django.contrib.sessions.models.Session 的 post_init 信号才能收到会话开始（或结束）的通知，然后将该信息保存到您自己的应用程序中的模型中。例如

from django.contrib.sessions.models import Session
from django.db.models import *
from django.db.models.signals import post_init, pre_delete
from django.dispatch import receiver
from datetime import datetime

class SessionTimer(Session):
    #note: a OneToOneField with the name 'session' has been added as part of the inheritance
    created = DateTimeField(auto_now_add=True) #joined field is auto initialized with creation time
    def age(self):
        return (datetime.now() - self.created)

@receiver(post_init, sender=Session)
def session_create_listener(instance, **kwargs):
    created_session = instance
    timer_entry = SessionTimer(session=created_session)
    timer_entry.save()

@receiver(pre_delete, sender=Session)
def session_destroy_listener(instance, **kwargs):
    SessionTimer.objects.get(session=instance).delete() # short version

，当您需要知道会话的年龄时，请使用session.sessiontimer.age()。这将返回一个代表会话年龄的 TimeDelta 对象。