Saturday, 15 June 2019

Scalability | Proxies


Proxy server
A proxy server is a dedicated computer or a software system running on a computer that acts as an intermediate server between the client and the back-end server. The proxy server may exist in the same machine as a firewall server or it may be on a separate server, which forwards requests through the firewall.

Typically, proxies are used to filter requests, log requests, or sometimes transform requests (by adding/removing headers, encrypting/decrypting, or compressing a resource). Another advantage of a proxy server is that its cache can serve all users. If one or more Internet sites are frequently requested, these are likely to be in the proxy's cache and serve it to all the clients without going to the remote server, which will improve user response time. A proxy can also log its interactions, which can be helpful for troubleshooting.

Proxy Server Types

Proxies can reside on the client’s local server or anywhere between the client and the remote servers. Here are a few famous types of proxy servers:

Open Proxy
An open proxy is a proxy server that is accessible by any Internet user. Generally, the proxy server only allows users within a networking group (i.e. a closed proxy) to store and forward Internet services such as DNS or web pages to reduce and control the bandwidth used by the group. With an open proxy, however, any user on the Internet is able to use this forwarding service. There two famous open proxy types:

1. Anonymous Proxy
This proxy reveals its identity as а server but does not disclose the іnіtіаl IP address. Though this proxy server can be discovered easily at can be benefіcіаl for some users as at hides their IP address.

2. Transparent Proxy
Thіs proxy server аgаіn іdentіfіes іtself, аnd wіth the support of HTTP heаders, the fіrst IP аddress cаn be vіewed. The mаіn benefіt of usіng thіs sort of server іs іts аbіlіty to cаche the websіtes.

Reverse Proxy

A reverse proxy retrieves resources on behalf of a client from one or more servers. These resources are then returned to the client, appearing as if they originated from the proxy server itself. Reverse proxies are typically implemented to help increase security, performance, and reliability.

Benefits of a reverse proxy

Load balancing
A reverse proxy can provide a load balancing solution which will distribute the incoming traffic evenly among the different servers to prevent any single server from becoming overloaded. In the event that a server fails completely, other servers can step up to handle the traffic.

Protection from attacks
With a reverse proxy in place, a web site or service never needs to reveal the IP address of their origin server(s). This makes it much harder for attackers to leverage a targeted attack against them, such as a DDoS attack. Instead of the attackers will only be able to target the reverse proxy, such as Cloudflare’s CDN, which will have tighter security and more resources to fend off a cyber attacks.

Global Server Load Balancing (GSLB)
In this form of load balancing, a website can be distributed on several servers around the globe and the reverse proxy will send clients to the server that’s geographically closest to them. This decreases the distances that requests and responses need to travel, minimizing load times.

Caching
A reverse proxy can also cache content, resulting in faster performance. For example, if a user in Mumbai visits a reverse-proxied website with web servers in Los Angeles, the user might actually connect to a local reverse proxy server in Mumbai, which will then have to communicate with an origin server in Los Angeles. The proxy server can then cache (or temporarily save) the response data. Subsequent Mumbai’s users who browse the site will then get the locally cached the version from the Mumbai's reverse proxy server, resulting in much faster performance.

SSL encryption
Encrypting and decrypting SSL (or TLS) communications for each client can be computationally expensive for an origin server. A reverse proxy can be configured to decrypt all incoming requests and encrypt all outgoing responses, freeing up valuable resources on the origin server.

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