Motivation
With Azure SDKs for a wide variety of programming languages, why should anybody want to learn about the Azure Storage REST API?
Maybe there is no SDK for your favourite language, which was my case. Maybe the official SDK do not support the latest API version, which could mean it is not possible to communicate with JSON in Table Storage. Maybe you are just courios.
This blog post is based on my work on GoHaveAzureStorage, and hopefully you will also gain from challenges I have had the Azure Storage.
Request break down
A REST call looks like this:
GET https://myaccount.table.core.windows.net/Tables HTTP/1.1
This request is used to get all tables for an storage account. There is 2 mandatory http header fields, and an additional optional which I recommend, which you must send for every request to make it work. They are
GET https://myaccount.table.core.windows.net/Tables HTTP/1.1
This request is used to get all tables for an storage account. There is 2 mandatory http header fields, and an additional optional which I recommend, which you must send for every request to make it work. They are
- x-ms-date - time for the request.
- x-ms-version - Which API version is the request targeting
- authorization - Which is a security digest
The first 2 header will be explained in this post, while the Authorization will be explained in part 2.
The URL
First the easy part. It is possible to use either HTTP or HTTPS, else it is more or less straight forward.
The x-ms-date header field
This field is used by Azure for validation and authorization. A valid request must be maximum 15 minutes old, and it must not be dated in the future. It can be expressed as:
current time =< x-ms-date < current time - 15
Pro tip
As it is close to impossible to be complete time synchronized with Azure, it is recommend to substract a few minutes from current time, when sending request.
One important last ting, Azure only understands time in RFC1123 format and GMT +0
If you have: Thu, 12 Feb 2015 21:16:45 UTC in a +1 time zone
It must converted to: Thu, 12 Feb 2015 20:16:45 GMT
The x-ms-version header field (Pro tip)
This an optional field, but you should prefer to set it, or else you will hit an earlier version of the Azure Storage API. you might experience challenges with JSON in table storage or with Shared Access Keys if not using the latest version.
The versions are defined as date, The date which the API version is released. I'm not sure wether this a good solution, because I find dates hard to remember after a while compared to versions. So I have to look up once in a while here: https://msdn.microsoft.com/en-us/library/azure/dd894041.aspx
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