Jul 18, 2022

[Django_Rest_Framework] Dynamic serializer fields

Dynamic fields in serializer can retrieve the required fields from the model, and speed up the serializing if the query doesn’t need to retrieve all fields. Setup the dynamic serializer class DynamicSerializer(serializers.ModelSerializer): first= FirstSerializer() second = SecondSerializer() third = ThirdSerializer() def __init__(self, *args, **kwargs): required_fields = kwargs.get("context", {}).get("fields") super(DynamicSerializer, self).__init__(*args, **kwargs) if required_fields: required = set(required_fields) existed = set(self.fields) for field in existed - required: self.fields.pop(field)

Django

1 min read

Django

1 min read

[Django_Rest_Framework] Dynamic serializer fields

Dynamic fields in serializer can retrieve the required fields from the model, and speed up the serializing if the query doesn’t need to retrieve all fields.

Setup the dynamic serializer

class DynamicSerializer(serializers.ModelSerializer):
    first= FirstSerializer()
    second = SecondSerializer()
    third = ThirdSerializer()    def __init__(self, *args, **kwargs):
        required_fields = kwargs.get("context", {}).get("fields")

        super(DynamicSerializer, self).__init__(*args, **kwargs)

        if required_fields:
            required = set(required_fields)
            existed = set(self.fields)

            for field in existed - required:
               self.fields.pop(field)

Usage in view

fields = ["first", "third"]queryset = Model.objects.all()data = DynamicSerializer(queryset, context={"fields": fields}).data

Jul 17, 2022

[Django_Rest_Framework] Eager loading

Straightforward usage of the Django REST Framework and its nested serializers can kill performance of API endpoints. The database is queried inside a loop, and the problem is called the N+1 selects problem. straightforward class Account(models.Model): id = models.AutoField(primary_key=True) name = models.CharField(max_length=32, null=True) class Product(models.Model): id =…

Django

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Django

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Jul 16, 2022

[Web] Nginx introduction

Nginx is a web server that support forward proxy, reverse proxy, caching, load balancing, etc. Forward proxy

Web

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Web

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[Web] Nginx introduction

Nginx is a web server that support forward proxy, reverse proxy, caching, load balancing, etc.

Forward proxy

May 9, 2022

[Web] WSGI introduction

WSGI (Web Server Gateway Interface) is an interface specification between web server and Python web frameworks/applications, and forward requests from web servers to web frameworks/applications. Gunicorn Gunicorn is one of WSGI server, so that it can run Python web applications which implement the WSGI specification. Manage running multiple instances of web application, and make sure the instances are healthy and restart them if needed.

Wsgi

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Wsgi

1 min read

[Web] WSGI introduction

WSGI (Web Server Gateway Interface) is an interface specification between web server and Python web frameworks/applications, and forward requests from web servers to web frameworks/applications.

Gunicorn

Gunicorn is one of WSGI server, so that it can run Python web applications which implement the WSGI specification.
Manage running multiple instances of web application, and make sure the instances are healthy and restart them if needed.
Distribute incoming requests between instances of web application, and communicate with the web server.

Apr 6, 2022

[Kubernetes] Node architecture with service

Kubelet Take responsibility for pods management and communication with master node. If Kubelet receive order from master node, it will create pods. Kube-Proxy Kube-Proxy updates the latest information of pods to iptables, and ensure pods can be accessed by other objects in cluster. Kube-Proxy generates iptables rules to control routing inside a cluster. If pods are created, Kube-Proxy will update these pods information to iptables.

Kubernetes

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Kubernetes

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Mar 21, 2022

[Docker] Container network models

None docker container run --network=none alpine Docker engine will setup a network namespace, which don’t have the network. Can apply if your components in container no need to have network, or need to isolate from the network. Host docker container run --network=host alpine

Docker

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Docker

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Mar 11, 2022

[Docker] RUN/CMD/ENTRYPOINT

Forms of Dockerfile Shell Form RUN pip3 install -r requirements.txt CMD echo Hello world ENTRYPOINT echo Hello world # In image generation, will transfer to exec form as below RUN /bin/sh -c pip3 install -r requirements.txt CMD ["/bin/sh" "-c" "echo Hello world"] ENTRYPOINT ["/bin/sh" "-c" "echo Hello world"] Exec Form …

Docker

3 min read

Docker

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Feb 22, 2022

[Python] Shallow copy/Deep copy

Assignment l1 = [[0], 1, 2, 3] l2 = l1 print(id(l1), id(l1[0]), l1) # 111, 000, [[0], 1, 2, 3] print(id(l2), id(l2[0]), l2) # 222, 000, [[0], 1, 2, 3] l1.append(4) print(id(l1), id(l1[0]), l1) # 111, 000, [[0], 1, 2, 3, 4] print(id(l2), id(l2[0]), l2) # 222, 000, [[0]…

Python

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Python

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Feb 20, 2022

[Python] Instance/Static/Class/Abstract methods

Instance method class User: static_var = "Static Variable" def func(self): print("Func") print(self.static_var) if __name__ == "__main__": User.func() # Error: TypeError user = User() user.func() # Func # Static Variable Can only use instance of class to call. Need to use instance(self) as parameter. Can use instance(self) to access static variables…

Python

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Python

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Feb 20, 2022

[Python] Private members

There are no strict private mechanism in Python, but we can follow the convention to simulate non-public mechanism. The non-public mechanism help to improve code stability and readability, which can reduce problems in collaborated development. Basic usage class User: is_anonymous = True __is_admin = False def func1(): print("Func1") def __func2()…

Python

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Python

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