This document critically reviews the existing APIs, highlighting the perceived pros and cons of each.

Amazon EC2

• Well accepted, de-facto standard

Cons:

• Intellectual property minefield (copyright, patent and trademark concerns raised)
• RPC-style API
• Flat namespace
• Many different functions to implement/remember (design shows legacy of development: e.g. starting a server with a static IP and persistent storage is 3 calls, since both of these features were added independently later)

Elastic Hosts

• Very simple key-value pairs used (big plus)

Cons:

• Limited extensibility
• Limited verifiability of formats (no schemas)
• Limited security beyond HTTPS and HTTP Basic Auth (e.g. no signatures)

Flexi Scale

Not yet assessed.

Go Grid

• Includes support for load balancers
• Handles jobs/requests ("A Job is an asynchronous command issued to the system by either a user or system workflow. These asynchronous commands are processed into actions that modify the environment.")
• Supports multiple formats (CSV, JSON, XML)
• Multiple client implementations (Java, PHP, Python, Perl, Ruby, C#, Bash)
• Uses HTTP errors (but extends them with structured data, for better or worse)
• Exposes billing information (including resource statistics)
• Credential (username/password) management
• Simple request format (HTML forms: application/x-www-form-urlencoded)

Cons:

• Uses request signing unnecessarily (may be dangerous e.g. Amazon EC2 vulnerability)
• REST/RPC hybrid ("REST-like Query interface" with parametrised procedures like "/grid/server/delete")
• Rudimentary filtering options for large numbers of resources (grid.image.list returns "a list of all server images available to you" for example)
• Stops/Restarts are always hard (no ACPI options etc.)

Sun

Pros:

• Mostly RESTful
• Exposes Sun Cloud functionality as simply as possible

Cons:

• Still in development
• Hybrid RPC-REST
• Limited extensibility