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This article will explain in detail what the Routes module in Python is. The editor thinks it is very practical, so I share it for you as a reference. I hope you can get something after reading this article.

Routes is a Rails routes system re-implemented by python to map the urls to the application-specific action and, conversely, generate a url. Since Routes is the python implementation of Rails routes system, and there are few documents about Routes on the Internet, we can understand the Routes library well from rails's routes system.

First of all, look at a simple example to understand the role of routes

For example, the browser receives the following HTTP request, and the routing request of GET / instances/1 Rails is responsible for parsing the request to a specific function in the dispatch code to complete the call, such as returning the information of the virtual machine.

The first part: explain the call entry (paste) of wsgi.

WSGI (Web Server Gateway Interface) in python is an interface between Python application or framework and Web server, which defines a set of excuses to implement the communication specification between server and application. According to a set of specifications, the application side wants to communicate simply by implementing a python object that accepts two parameters, contains the _ _ call__ method and returns a traverable python object with zero or more string results.

On the server side, for each http request, the protocol that invokes the application side "registration" once specifies the object that the application must implement, and then returns the corresponding response message. The only task of WSGI Server is to receive the request from client, then pass the request to application, and finally pass the response of application to client. Some things that exist in the middle need to be dealt with by middleware.

Paste Deployment is the system used to discover and configure WSGI appliaction and server. For WSGI application, the user provides a separate function (loadapp) to load WSGI application from a configuration file or python egg. Because WSGI application provides a single, simple access entry, application does not need to expose the internal implementation details of application.

Paste.Deploy is mainly used to load Web App in WSGI, and its core function is loadapp ().

The following will take the nova of openstack as an example to explain how paste loads and starts the nova service (that is, publishing routes API to provide calls to the upper layer)

1. Nova-- start with debug list:

The main purpose of the command is to send two url requests: (the first is sent to keystone authorization, which gets the list of virtual machines by sending it to nova)

Token and parameter values are included in url

The following figure shows that the request for url is successful and returns 200.

2. Next, we will explain in detail how to send the following url, how to map to the v2 version of nova API in the background, and how to configure permission authentication.

Http://192.168.1.120: 8774/v2/c865d5a3760348a4b8a92cf657a9176d/servers/detail

3. Each url mapping is parsed by a paste module. The entry of the paste module is the * .ini configuration file. The following shows the paste entry profile controlled by all url mappings throughout openstack.

Find / etc/ | xargs grep paste-- color=auto finds all the ini configuration files for paste.

4. Explain it with the api-paste.ini configuration file of nova.

Start by introducing several concepts in the paste configuration file:

A configuration file is suffixed with ini, and the content is divided into many section. Paste.depoly only cares about segments with prefixes, such as [app:main] or [filter:errors]. Generally speaking, the identity of a section is [type:name], and section that is not of this type will be ignored.

The content of a section is marked with a key = value. # is a comment. In the definition of a segment, there are the following categories:

[app:main]: define an WSGI application. Main means there is only one application. If there are multiple applications, main will be changed to the application name.

[server:main]: a server that defines a WSGI.

[composite:xxx]: indicates that you need to dispatched a request to multiple applications or applications. The following is a simple example, in which composite is used to load multiple applications through urlmap.

[fliter:]: define a "filter" to further encapsulate the application.

[DEFAULT]: define some default variable values.

Vim / etc/nova/api-paste.ini

Where use = call:nova.api.auth:pipeline_factory of openstack_compute_api_v2 indicates that the specific application to be used is selected by the url visited.

According to http://192.168.1.120:8774/v2/c865d5a3760348a4b8a92cf657a9176d/servers/detail, by matching rules, the next call

/ v2: openstack_compute_api_v2 application.

This Application corresponds to three parameters: noauth,keystone and keystone_nolimit. We can see that the concrete implementation of Application here is pipeline_factory. We can see that several applications are integrated in the parameters noauth,keystone and keystone_nolimit. In fact, the final Application of each parameter is the last one, that is, osapi_compute_app_v2,osapi_compute_app_v2 and osapi_compute_app_v2, and the Application in front of it acts as the filter of the last Application. We take the parameter keystone as an example. The Application that implements the parameter keystone is osapi_compute_app_v2, and the faultwrap sizelimit authtoken keystonecontext and other applications in front of it are all its filters. The implementation process is faultwrap (authtoken (keystonecontext (osapi_compute_app_v2). The specific calling process is osapi_compute_app_v2- > keystonecontext- > authtoken- > sizelimit- > faultwrap. The execution result of the previous method is used as the input parameter of the later method. The final running result is taken as the value of the parameter keystone. It can be explained that the values of the three parameters noauth,keystone and keystone_nolimit are all obtained in this way.

Detailed explanation:

The following three sentences respectively correspond to different configurations in the configuration file to perform an impassable filtering process, and eventually all three will be returned to the osapi_compute_app_v2 application.

Use = call:nova.api.auth:pipeline_factory code:

The purpose of the pipeline_factory function is to read the authentication policies defined in the parsing configuration file (/ etc/nova/nova.conf): noauth, keystone, keystone_nolimit.

If auth_strategy=keystone is configured in the configuration file nova.conf, then match:

Keystone_nolimit = faultwrap sizelimit authtoken keystonecontext osapi_compute_app_v2

The faultwrap sizelimit filter will not be explained in further detail. If you are interested, please follow up the code by yourself. 5. Analyze the authtoken filter:

Find the corresponding code: as can be seen from the above code, authorization corresponds to the filter authtoken, which is operated in the _ _ call__ function of the AuthProtocol class. Please analyze the above functions for the details of authorization, and do not explain too much again. Note: with the knowledge of paste, every factory will have a _ _ call__ function. This function is called when the factory is called.

6. Next, analyze the keystonecontext filter:

Corresponding code:

The above code function: when authorizing the filter authtoken in the previous step, some necessary information was obtained from keystone. For example, X_USER_ID, X_TENANT_NAME, X_ROLES, token values, and so on, and then assemble a request of http to request the corresponding url information.

From the command execution results, we can also see the respective functions and interaction process of the two filters authtoken, and keystonecontext.

Authtoken filter execution process: (curl-I sends a url request, INFO is followed by parameters requested from the keystone module, which are passed to the keystonecontext filter

According to these parameters, the keystonecontext filter assembles the corresponding http request and requests the corresponding url)

Keystonecontext filter execution process:

7. After the implementation of the filter, we will focus on the analysis of the osapi_compute_app_v2 application:

Keystone_nolimit = faultwrap sizelimit authtoken keystonecontext osapi_compute_app_v2

Find the corresponding entry code:

The above APIRouter class is where paste loads the OSPI _ compute_app_v2 application and then publishes the routing rules.

Class APIRouter (nova.api.openstack.APIRouter):

Find the parent class nova.api.openstack.APIRouter:

8. Print router information:

Vim / usr/lib/python2.6/site-packages/nova/api/openstack/__init__.py

Restart the openstack-nova-api service

Service openstack-nova-api restart

Tailf / var/log/nova/api.log

This is the end of the article on "what is the Routes module in Python". I hope the above content can be of some help to you, so that you can learn more knowledge. if you think the article is good, please share it for more people to see.

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