How to read Media from Attachment using REST API - azure-cosmosdb

Question

I have created an Attachment with image:
{
"_rid": "xD4vALTE7QBAAwAAAAAAAA==",
"Attachments": [
{
"contentType": "image/jpeg",
"id": "10b91d7d-2e5e-466e-a896-3ee54baff4dc",
"media": "/media/xD4vALTE7QBAAwAAAAAAALobDgYB",
"_rid": "xD4vALTE7QBAAwAAAAAAALobDgY=",
"_self": "dbs/xD4vAA==/colls/xD4vALTE7QA=/docs/xD4vALTE7QBAAwAAAAAAAA==/attachments/xD4vALTE7QBAAwAAAAAAALobDgY=",
"_etag": "\"00000d37-0000-0000-0000-5a09602a0000\"",
"_ts": 1510563882
}
],
"_count": 1
}
What is the url to the Media object?
When I use the Cosmos .NET SDK method DocumentClient.ReadMediaAsync(string mediaLink) where mediaLink is /media/xD4vALTE7QBAAwAAAAAAALobDgY= then I can get the Media stream and display the image. But this only works when connecting to Cosmos Db Emulator, when doing the same on the Azure Cosmos DB instance, then I get this error:
Unknown server error occurred when processing this request. ActivityId: 53508de6-2456-4213-947e-4361a8118574, Microsoft.Azure.Documents.Common/1.17.99.1, documentdb-dotnet-sdk/1.19.0 Host/32-bit MicrosoftWindowsNT/6.2.9200.0
The Attachment creation with Medial upload works.
I was thinking to try to query the CosmosDB using the Postman, but I cannot figure out the url to get the Media object.

Answer 1

The url to the Media object is: https://[YOUR-DOCDB-HOST]/media/xD4vALTE7QBAAwAAAAAAALobDgYB
I call this as a GET request in Postman with the following Pre-Request Script:
// store our master key for documentdb
var mastKey = [YOUR-DOCUMENTDB-KEY-HERE];
console.log("mastKey = " + mastKey);
// store our date as RFC1123 format for the request
var today = new Date();
var UTCstring = today.toUTCString();
postman.setEnvironmentVariable("RFC1123time", UTCstring);
// define resourceId/Type now so we can assign based on the amount of levels
var resourceId = "[YOUR-RID-HERE]"; // _rid in attachment document
var resType = "media";
// assign our verb
var verb = request.method.toLowerCase();
// assign our RFC 1123 date
var date = UTCstring.toLowerCase();
// parse our master key out as base64 encoding
var key = CryptoJS.enc.Base64.parse(mastKey);
console.log("key = " + key);
// build up the request text for the signature so can sign it along with the key
var text = (verb || "").toLowerCase() + "\n" +
(resType || "").toLowerCase() + "\n" +
(resourceId || "").toLowerCase() + "\n" +
(date || "").toLowerCase() + "\n" +
"" + "\n";
console.log("text = " + text);
// create the signature from build up request text
var signature = CryptoJS.HmacSHA256(text, key);
console.log("sig = " + signature);
// back to base 64 bits
var base64Bits = CryptoJS.enc.Base64.stringify(signature);
console.log("base64bits = " + base64Bits);
// format our authentication token and URI encode it.
var MasterToken = "master";
var TokenVersion = "1.0";
auth = encodeURIComponent("type=" + MasterToken + "&ver=" + TokenVersion + "&sig=" + base64Bits);
console.log("auth = " + auth);
// set our auth token enviornmental variable.
postman.setEnvironmentVariable("authToken", auth);
There are two variables: [YOUR-DOCUMENTDB-KEY-HERE] and [YOUR-RID-HERE]. The kicker is, you need to query attachment meta data first to get the _rid value to use in the token when requesting the media.
The authToken and RFC1123time postman variables are used in the Authorization header: