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docs/_build/html/_sources/class21/modules/module1.rst.txt

@@ -17,31 +17,270 @@ Objective - 1.1 Given a scenario identify when to use NGINX
 
 **1.1 - Describe NGINX as a web server**
 
-*TODO*
+https://nginx.org/en/
+
+https://docs.nginx.com/nginx/admin-guide/web-server/web-server/
+
+Slide 11 https://f5u.csod.com/ui/lms-learning-details/app/course/f62cdc17-e0df-4117-820c-6270100981a2
+
+**NGINX handling web protocols**
+
+One of NGINX's key feature is its web server functionality. NGINX software
+indeed implements many features related to the HTTP (web) protocol and can be
+configured to serve web content, making it describable as a web server. At a
+high level, configuring NGINX Plus as a web server is a matter of defining
+which URLs it handles and how it processes HTTP requests for resources at those
+URLs. At a lower level, the configuration defines a set of virtual servers that
+control the processing of requests for particular domains or IP addresses.
+
+The most basic web server feature that can be handled by NGINX is serving
+static content. The following snippet shows a basic example of NGINX
+configuration file for serving static web content:
+
+.. code-block:: NGINX
+
+    http {
+        server {
+            root /www/data;
+
+            location / {
+            }
+
+        }
+    }
+
+Receiving this configuration file, NGINX would listen to the HTTP port 80 on
+the host machine for incoming connections. Upon receiving HTTP request, it
+would serve content from the host's `/www/data` directory (for example, a
+`/www/data/index.html` file).
 
 |
 
 **1.1 - Describe NGINX as a reverse proxy**
 
-*TODO*
+https://www.cloudflare.com/learning/cdn/glossary/reverse-proxy/
+
+https://docs.nginx.com/nginx/admin-guide/web-server/reverse-proxy/
+
+https://nginx.org/en/docs/http/ngx_http_proxy_module.html
+
+Slide 8 and 13 https://f5u.csod.com/ui/lms-learning-details/app/course/f62cdc17-e0df-4117-820c-6270100981a2
+
+**What is reverse proxying and why do so**
+
+A reverse proxy is a server that sits in front of web servers and forwards
+client (e.g. web browser) requests to those web servers. Reverse proxies are
+typically implemented to help increase security, performance, and reliability.
+
+Proxying is typically used to distribute the load among several servers,
+seamlessly show content from different websites, or pass requests for
+processing to application servers over protocols other than HTTP.
+
+.. image:: /_static/n1-n4/reverse_proxy_flow.jpg
+    :alt: Reverse proxy flow
+
+Reverse proxy flow illustrated. A reverse proxy sits just before the
+application servers in the classic client-server network architecture. (from
+https://www.cloudflare.com/learning/cdn/glossary/reverse-proxy/).
+
+**How can NGINX be a reverse proxy**
+
+When NGINX proxies a request, it sends the request to a specified proxied
+server, fetches the response, and sends it back to the client. It is possible
+to proxy requests to an HTTP server (another NGINX server or any other server)
+or a non-HTTP server (which can run an application developed with a specific
+framework, such as PHP or Python) using a specified protocol. Supported
+protocols include FastCGI, uwsgi, SCGI, and memcached.
+
+To pass a request to an HTTP proxied server, the proxy_pass directive is
+specified inside a location.
+
+.. code-block:: NGINX
+
+    location /some/path/ {
+        proxy_pass http://www.example.com/link/;
+    }
+
+This example configuration results in passing all requests processed in this
+location to the proxied server at the specified address. This address can be
+specified as a domain name or an IP address.
 
 |
 
 **1.1 - Describe NGINX as a load balancer**
 
+https://www.cloudflare.com/learning/performance/what-is-load-balancing/
+
+https://nginx.org/en/docs/http/load_balancing.html
+
+https://docs.nginx.com/nginx/admin-guide/load-balancer/
+
+Slide 14 https://f5u.csod.com/ui/lms-learning-details/app/course/f62cdc17-e0df-4117-820c-6270100981a2
+
+**What is load balancing in the context of networking and web server**
+
+Load balancing is the practice of distributing computational workloads between
+two or more computers. On the Internet, load balancing is often employed to
+divide network traffic among several servers. This reduces the strain on each
+server and makes the servers more efficient, speeding up performance and
+reducing latency. Load balancing is essential for most Internet applications to
+function properly.
+
+.. image:: /_static/n1-n4/without_load_balancing_diagram.png
+    :alt: Without load balancing diagram
+    :height: 500px
+
+.. image:: /_static/n1-n4/with_load_balancing_diagram.png
+    :alt: With load balancing diagram
+    :height: 500px
+
+**How can NGINX be seen as a load balancer**
+
+It is possible to use nginx as a very efficient HTTP load balancer to
+distribute traffic to several application servers and to improve performance,
+scalability and reliability of web applications with nginx.
+
+The simplest configuration for load balancing with nginx may look like the
+following:
+
+.. code-block:: NGINX
+
+    http {
+        upstream myapp1 {
+            server srv1.example.com;
+            server srv2.example.com;
+            server srv3.example.com;
+        }
+
+        server {
+            listen 80;
+
+            location / {
+                proxy_pass http://myapp1;
+            }
+        }
+    }
+
+In the example above, there are 3 instances of the same application running on
+srv1-srv3. When the load balancing method is not specifically configured, it
+defaults to round-robin. All requests are proxied to the server group myapp1,
+and nginx applies HTTP load balancing to distribute the requests.
+
 *TODO*
 
 |
 
 **1.1 - Describe NGINX as a caching solution**
 
-*TODO*
+https://aws.amazon.com/caching/
+
+https://docs.nginx.com/nginx/admin-guide/content-cache/content-caching/
+
+https://nginx.org/en/docs/http/ngx_http_proxy_module.html#proxy_cache
+
+https://www.f5.com/company/events/webinars/content-caching-nginx-plus
+
+**Caching in the context of the web**
+
+Caching is a general concept referring to storing data in a high-speed storage
+so that this data can be retrieved faster than possible when reaching its
+original location. In the context of web, caching is crucial and is present at
+many layers between the actual client software (e.g. web browser) and the
+backend server or database, storing the content.
+
+.. image:: /_static/n1-n4/diagram_caching.png
+    :alt: Caching on the web diagram
+    :height: 250px
+
++---------------+--------------------------------------+---------------+----------------------------------------------------------------------------+--------------------------------------+------------------------------------------+
+| Layer         | Client-Side                          | DNS           | Web                                                                        | App                                  | Database                                 |
++===============+======================================+===============+============================================================================+======================================+==========================================+
+|| Use Case     || Accelerate retrieval of web content || Domain to IP || Accelerate retrieval of web content from web/app servers. Manage Web      || Accelerate application performance  || Reduce latency associated with database |
+||              || from websites (browser or device)   || Resolution   || Sessions (server side) web/app servers. Manage Web Sessions (server side) || and data access                     || query requests                          |
++---------------+--------------------------------------+---------------+----------------------------------------------------------------------------+--------------------------------------+------------------------------------------+
+|| Technologies || HTTP Cache Headers, Browsers        || DNS Servers  || HTTP Cache Headers, CDNs, Reverse Proxies, Web Accelerators,              || Key/Value data stores, Local caches || Database buffers, Key/Value data stores |
+||              ||                                     ||              || Key/Value Stores                                                          ||                                     ||                                         |
++---------------+--------------------------------------+---------------+----------------------------------------------------------------------------+--------------------------------------+------------------------------------------+
+
+The above representation comes from the AWS article about caching
+(https://aws.amazon.com/caching/) and depicts various levels at which caching
+has influence in the context of web content serving.
+
+**How NGINX can be seen as a caching solution**
+
+NGINX leverages the caching capabilities of the web in multiple ways. Indeed,
+NGINX as a reverse proxy or web server sits in a crucial place of web content
+retrieval pipeline:
+
+- Client-Side caching: NGINX can set and add HTTP headers helping the client
+  side to use caching.
+- Web and App content: NGINX can, through its `proxy_cache` directive, cache
+  the results of requests to the backend servers. These cached results can be
+  directly served to new clients, preventing making additional requests to the
+  backend servers. NGINX content caching can be fine-tuned, allowing to best
+  match the application logic. For example, highly dynamic pages may not be
+  cached to make sure the most up-to-date content is served to the clients,
+  while static files can be cached for longer time to prevent requesting the
+  backend server multiple times for identical files.
+- Web and App connections: another useful caching technique sits at the
+  transport layer. Thanks to its `keepalive` directives, NGINX can prevent
+  closing TCP sockets too early and reuse existing sockets instead of
+  re-negotiating a new connection. For the Transport Layer Security, NGINX also
+  has directives to cache SSL sessions and prevent re-negotiating keys and
+  certificates and reuse existing parameters with clients.
+
+These put together allow NGINX to vastly influence the caching of the web
+content served by an application when it acts as a reverse proxy.
 
 |
 
 **1.1 - Describe NGINX as an API gateway**
 
-*TODO*
+https://www.redhat.com/en/topics/api/what-does-an-api-gateway-do
+
+https://www.f5.com/company/blog/nginx/deploying-nginx-plus-as-an-api-gateway-part-1
+
+**What is an API gateway**
+
+An API gateway is an API management tool that sits between a client and a
+collection of backend services. In this case, a client is the application on a
+user's device and the backend services are those on an enterprise's servers.
+API stands for application programming interface, which is a set of definitions
+and protocols for building and integrating application software.
+
+An API gateway is a component of application delivery (the combination of
+services that serve an application to users) and acts as a reverse proxy to
+accept all application programming interface (API) calls, aggregate the various
+services required to fulfil them, and return the appropriate result. In
+simpler terms, an API gateway is a piece of software that intercepts API calls
+from a user and routes them to the appropriate backend service.
+
+**How can NGINX be used as an API gateway**
+
+NGINX can be configured as a perfect API gateway through various configuration
+aspects:
+
+- Load balancing and upstream definition. As seen before, NGINX can be
+  configured with an upstream servers pool and perform load balancing between
+  the different API servers. This allows to ensure that the API service can
+  scale and match different needs.
+- API routes definition. NGINX can be used to define the different API routes
+  available in the same way it defines static web content serving routes. This
+  allows to define broad (using REGEX matching URIs) and precise (using exact
+  matching URIs) endpoints, and control the private or restricted endpoint's
+  access.
+- Request interception and rewriting for handling breaking changes. NGINX can,
+  for example, handle the redirection from legacy API routes to the new ones
+  through HTTP redirect and content rewriting.
+- Handling errors. NGINX can interpret HTTP errors received from the backend
+  and display the desired error pages or messages.
+- Authenticating endpoints. NGINX can handle restricting access to some
+  endpoints using authentication methods such as API keys or JSON Web Tokens.
+- Rate limiting and logging. NGINX can help to secure and enforcing policies on
+  endpoints by using its rate limiting or advanced logging features.
+
+All these aspects make NGINX an efficient and complete solution for placing it
+as an API gateway.
 
 |
 |

docs/_build/html/class21/class21.html

@@ -14,7 +14,7 @@
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-  <meta name="updated_date"  content="2024-05-23 09:50:21"/>
+  <meta name="updated_date"  content="2024-05-27 01:56:36"/>
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