post: HAProxy Implementation Case Study | review 01

src/content/blog/haproxy_case_study.md

@@ -1,12 +1,12 @@
 ---
 title: "HAProxy Implementation Case Study"
-description: "This article covers the HAProxy deployment on firewall and SELinux-enabled CentOS 7 systems."
+description: "This article discusses setting up HAProxy on CentOS 7 systems that have both a firewall and SELinux enabled."
 pubDate: "Feb 10 2018"
 heroImage: 'https://bizkt.imgix.net/posts/hap-case-study/hap-case-study.jpg'
 badge: "RETRO"
 ---
 
-This tutorial covers the HAProxy deployment on firewall and SELinux-enabled CentOS 7 systems.
+This article discusses setting up HAProxy on CentOS 7 systems that have both a firewall and SELinux enabled.
 
 > The content of this article is migrated from the old blog post, so the information might be subject to updates.
 
@@ -26,35 +26,35 @@ From Cloudflare, all requests to `mycompany.com` will be forwarded to our public
 
 > **Note**: All HTTPS connections should terminate at HAProxy. Please see my post "HTTPS for HAProxy".
 
-In this chapter, we will explore load balancing and ACL-based traffic routing between IIS web servers.
-
-As the first step, I will add host entries to my hosts file:
+As the first step, lets add host entries to my hosts file (in HAProxy server):
 
 ```bash
-vi /etc/hosts
+# vi /etc/hosts
 10.0.3.121 iiswebsrv01
 10.0.3.131 iiswebsrv02
 ```
 
 You may do a ping and verify the connectivity between the HAProxy server and your web servers.
 
-To download and enable the EPEL Repositories and install HAProxy:
+### Installation
+
+Let's download and enable the EPEL Repositories and install HAProxy:
 
 ```bash
 wget http://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm
 rpm -ivh epel-release-latest-7.noarch.rpm
 yum -y install haproxy
 ```
 
-After the successful installation of HAProxy, you can start its configuration. Before editing the configuration file, it's recommended to keep a backup of the existing HAProxy configuration file:
+After the successful installation of HAProxy, we can start its configuration. **Before editing the configuration file, it's recommended to keep a backup of the existing HAProxy configuration file.**
 
 ```bash
 cp /etc/haproxy/haproxy.cfg /etc/haproxy/haproxy.cfg_bak
 ```
 
 ### HAProxy Configurations
 
-Now, let's examine our HAProxy configurations. The HAProxy configuration file contains four types of sections:
+Now, let's examine our HAProxy configurations. The HAProxy configuration file contains four sections:
 
 1. **Global Section**: Contains global configurations.
 2. **Default Section**: Provides default configurations.
@@ -74,7 +74,7 @@ global
     tune.ssl.default-dh-param 2048
 ```
 
-- In the `global` section, we configure where to store our HAProxy logs. In this case, our HAProxy logs will be stored using the local rsyslog server.
+- In the `global` section, we can configure where to store our HAProxy logs. In this case, our HAProxy logs will be stored using the local syslog server.
 - `maxconn 1024` specifies the maximum connection count that the HAProxy server should accommodate.
 - The `user` and `group` directives define the HAProxy user and group, respectively, which were created during installation.
 - The `daemon` directive indicates that HAProxy should run as a daemon process.
@@ -83,7 +83,7 @@ global
 
 #### Default
 
-It's time to begin our configurations for HAProxy's Default Configuration. In the default section, we set the default parameters for both frontend and backend sections:
+Let's focus on HAProxy's Default Configuration. In the default section, we set the default parameters for both frontend and backend sections.
 
 ```conf
 defaults
@@ -98,9 +98,9 @@ defaults
     timeout server 500000ms
 ```
 
-- `log global`: This directive defines the log mode to use, which we have already set in the Global configuration.
-- `option tcplog`: This enables logging at the TCP (Layer 4) level. Note that you can also use httplog if you wish to log at the HTTP level.
-- `option dontlognull`: This directive filters the log entries, keeping your logs clean. By default, even a simple port probe produces a log. With this option, HAProxy avoids logging such entries.
+- `log global`: This directive defines which log mode to use, which we have already set in the Global configuration.
+- `option tcplog`: This enables logging at the TCP (Layer 4) level. Note that we can also use `httplog` if we wish to log at the HTTP level.
+- `option dontlognull`: This directive filters the log entries, keeping our logs clean. By default, even a simple port probe produces a log. With this option, HAProxy avoids logging such entries.
 - `retries 3`: Sets the number of retries after failed attempts to the server.
 - `option redispatch`: If a server designated by a cookie is down, clients may still attempt to connect because they can't flush the cookie. This option allows HAProxy to break their persistence and redistribute them to a working server.
 - `maxconn 1024`: Defines the maximum connection count.
@@ -110,7 +110,7 @@ Finally, the frontend and backend configurations
 
 #### Frontend
 
-In the frontend section, HAProxy accepts traffic from public entities, processes them, and forwards the traffic to the relevant backend. In the following frontend section, I will demonstrate how to read HTTP headers, process them with basic ACLs, and forward them to the corresponding backend sections.
+In the frontend section, HAProxy receive the traffic, processes them, and forwards the traffic to the relevant backend. In the following frontend section, we will discuss how to read HTTP headers, process them with basic ACLs, and forward them to the corresponding backend sections.
 
 ```conf
 frontend http_handler
@@ -130,12 +130,11 @@ frontend http_handler
 
 - The frontend will accept all HTTP and HTTPS requests and process them using an ACL.
 - To accept traffic from port 80 (HTTP) and 443 (HTTPS), we bind both ports to a frontend. For HTTPS traffic, an SSL certificate is required. For this tutorial, I've created an SSL certificate using [Let's Encrypt](https://letsencrypt.org).
-- Since our primary objective is to read the HTTP headers and forward the traffic accordingly, we use `mode http`. If you use TCP mode instead, load balancing will be based on Layer 4, and you won't be able to read the HTTP header in your ACL.
+- Since we are required to read the HTTP headers and forward the traffic accordingly, we use `mode http`. If we use TCP mode instead, load balancing will be based on Layer 4, and we won't be able to read the HTTP header in your ACL.
 - I've enabled HTTP logging of HTTP/HTTPS requests using option `httplog`.
 - `log global` adds logs to the global syslog service.
-- In HAProxy, an ACL is defined using the `acl` keyword. ACLs can be defined in either the backend or frontend sections. In our scenario, ACLs are defined in the frontend section. Two ACLs are created: one for London (`acl_london`) and one for Chicago (`acl_chicago`). These ACLs read the HTTP headers and forward traffic based on the content of these headers.
-- The `use_backend` directive switches backends depending on the ACL output. For instance, if `acl_london` is true, traffic is sent to the London backend (be_london).
-Traffic arriving at our frontends is tested against the ACLs, so it's essential to define our backends to accommodate HTTP requests and forward them to the intended destination.
+- In HAProxy, an ACL is defined using the `acl` keyword. ACLs can be defined in either in the backend or frontend sections. In our scenario, ACLs are defined in the frontend section. Two ACLs are created: one for London (`acl_london`) and one for Chicago (`acl_chicago`). These ACLs process the HTTP headers and forward traffic based on the content of these headers.
+- The `use_backend` directive switches backends depending on the ACL output. For instance, if `acl_london` is true, traffic is sent to the London backend (be_london). Traffic received by the frontend is tested against the ACLs, so it's essential to define our backends to accommodate HTTP requests and forward them to the intended destination.
 
 #### Backend
 
@@ -157,11 +156,10 @@ backend be_london
 ```
 
 - `balance leastconn`: This directive specifies the load balancing algorithm to use. The `leastconn` algorithm selects the server with the fewest number of connections. It's recommended for longer sessions.
-- `redirect scheme https if !{ ssl_fc }`: For security reasons, we prefer to use HTTPS. In the backend, this directive filters traffic to use only HTTPS. If a connection isn't secure, it redirects to HTTPS.
+- `redirect scheme https if !{ ssl_fc }`: For security reasons, it is preferred to use HTTPS. If a connection isn't secure HTTP, it redirects to HTTPS.
 - `option forwardfor`: Enables the `X-Forwarding` for HTTP connections. When HAProxy acts as a reverse proxy, the server only sees the IP address of the HAProxy server as the client address. `X-Forwarding` allows HAProxy to append the original IP address of the client to the requests sent to the server.
 - `stick match src` and `stick-table type ip size 200k expire 30m`: Configures the stickiness. Stick tables store learned data from the connection in memory. _*Note that restarting the service will remove these entries.*_
 - `mode http`: Specifies that the backend will operate at the HTTP level.
-- `reqadd X-Forwarded-Proto:\ http`: Adds a header to all HTTP requests passing through this backend.
 - `cookie SERVERID insert indirect nocache`: Adds cookie values to HTTP requests.
 - `option httpchk GET /check.aspx?testsrv=londonsrv01:8080` and `http-check expect string 200\ OK`: Before forwarding traffic to destination servers, HAProxy checks the availability of those servers using HTTP Check. If the server responds with `200 OK`, HAProxy considers it ready to serve.
 - `server london_01 iiswebsrv01:94 cookie L01 check` and `server london_02 iiswebsrv02:94 cookie L02 check`: Define the backend servers. The check parameter tests the availability based on the aforementioned HTML script.
@@ -174,7 +172,7 @@ To validate the configuration after completing the HAProxy setup:
 haproxy -f /etc/haproxy/haproxy.cfg -c
 ```
 
-To restart HAProxy:
+To restart HAProxy server:
 
 ```bash
 systemctl restart haproxy
@@ -189,7 +187,7 @@ semanage port --add --type http_port_t --proto tcp <port>
 To open firewall ports:
 
 ```bash
-firewall-cmd --permanent --add-port= cp
+firewall-cmd --permanent --add-port=\\tcp
 firewall-cmd --reload
 ```