Week 4 - Web layer continued

Question 1

Example of a proxy Just read

Answer 1

Okay, let me try to explain the proxy concept with a simple example:
Imagine you’re browsing the web on your laptop at home. When you type in a website address, like www.example.com, your web browser doesn’t actually connect directly to that website’s server. Instead, it first connects to a proxy server.
The proxy server sits between your laptop (the client) and the actual example.com server. When your browser sends a request to the proxy for www.example.com, here’s what happens:

The proxy receives your request for www.example.com.
The proxy first checks its own cache to see if it has a copy of the website content that it can quickly serve back to your browser. This is called a “cache hit” - the proxy can satisfy your request without needing to contact the actual example.com server.
If the content is not in the proxy’s cache (a “cache miss”), then the proxy will forward your request on to the example.com server. It will take the response from example.com, and send that back to your browser, translating it through the HTTP protocol.

So in summary, the proxy acts as an intermediary, receiving requests from you (the client) and trying to satisfy those requests as quickly as possible, either from its own cache or by contacting the actual server on your behalf. This can improve performance and save bandwidth compared to your browser talking directly to the website’s server.
The key benefit of using a proxy is that it can optimize and manage the communication between many clients and many servers, caching content and controlling the traffic flow.

Question 2

example i provided above in relation to the slides

Answer 2

The slide states that a “proxy” is an intermediary selected by the client, usually via local configuration rules. In the example, the web browser on the user’s laptop is configured to route its requests through the proxy server, rather than connecting directly to the web server.

The slide mentions that the proxy “receives requests for URLs and attempts to satisfy those requests via translation through the HTTP interface.” In the example, when the user’s browser sends a request to www.example.com, the proxy receives that request.

The slide explains that the proxy will first check if it can satisfy the request using its own cache. In the example, this is where the proxy checks its cache to see if it has a cached copy of the example.com website content that it can quickly return to the browser, instead of forwarding the request to the actual server.
If the content is not in the proxy’s cache, the slide states that the proxy will forward the request to the actual server. In the example, if the content is not in the proxy’s cache, it will then pass the request along to the example.com web server.

Finally, the slide mentions that proxies are often used in organizations to group and manage HTTP requests through a common intermediary, which can be for reasons like security, annotation services, or shared caching. In the example, the proxy is serving this centralized role, optimizing and managing the communication between multiple clients and servers.

Question 3

Forward ( regular) proxy

Answer 3

Forward Proxy:

Sits in front of CLIENTS
Example benefits:

Hides client IP addresses from the internet
Controls what websites employees can visit
Monitors internet usage
Can block malicious websites
Caches common requests to save bandwidth

Question 4

Reverse Proxy:

Answer 4

Sits in front of SERVERS
Example benefits:

Load balancing across servers
SSL encryption handling
Protection from attacks
Caching to reduce server load

Question 5

Safe

Answer 5

Read only operation

Question 6

Idempotent

Answer 6

Can be repeated with SAME effect

eg Put is idempotent -
2 updates that are the same will have same effect

|
PUT /users/123
{name: “John”, age: 30}

Do this once: User 123 becomes {name: “John”, age: 30}
Do this five times: User 123 is still {name: “John”, age: 30}

eg POST is NOT idempotent as you are creating 2 different resources

Question 7

cacheable

Answer 7

response can be cached

Question 8

summary of everything i learned for the week

Answer 8

look in laptop ins for week 4 too

Here’s a comprehensive overview of REST, Proxies, Cookies, and URI design:

REST Architecture Basics:

Transfers representations of resources, not actual resources
Uses standard formats (JSON, XML, etc.)
Stateless: each request contains all needed information
Server doesn’t remember previous requests
Client must remember resource URLs

Proxies:
Forward Proxy:

Sits in front of CLIENTS
Protects/represents clients
Features:

Monitor internet usage
Block websites
Cache content
Hide client IPs

Reverse Proxy:

Sits in front of SERVERS
Protects/represents servers
Features:

Load balancing
SSL handling
Security
Caching

State Management:
Stateless Architecture:

State distributed between client/server
Each request independent
Server crash doesn’t lose session data
Client remembers URLs
Resource data in database

Stateful Architecture:

State saved on server
Server remembers sessions
Server crash loses session data
More vulnerable to failures

Cookies:
Purpose:

Small data pieces server sends to browser
Browser stores and returns with future requests
Helps identify returning clients

Issues with REST:

Creates site-wide state (non-RESTful)
Affects all requests to entire site
Can create state mismatches
Browser-specific storage

URI Design:
Hierarchical Structure:

General → Specific
Example: /category/subcategory/item/id

Best Practices:

Clear domain naming
Logical structure
Consistent patterns
Self-descriptive
Human-readable

Types:

Public Sector: /transport/road/M5/junction/24
Supply Chain: /gtin/productcode
General Use: /users/username/posts/date

Key Points to Remember:

REST is about resource representations
Proxies serve different purposes based on placement
State should be carefully managed
Cookies can conflict with REST principles
URIs should be well-structured and meaningful