How do I get an attached file from CosmosDB using Nodejs SDK? - node.js

Question

I'm trying to work with CosmosDB in Nodejs. I have created some Documents in a collection and have added a couple attachments to one of the documents like so:
let dbds = new azure(dbEndpoint, {"masterKey":dbKey})
fs.open("c:/temp/capture.png", "r", (err, fd) => {
if(err) console.log(err);
else{
dbds.createAttachmentAndUploadMedia(documentLink, fs, {contentType:"image/png", partitionKey: partitionKey}, (err, result) =>{
fs.close(fd);
if(err) console.log(err);
else console.log(result);
}
}
}
Now when I read that attachments for that document, I get 2 attachments:
dbds.readAttachments(documentLink, {"partitionKey":partitionKey}).toArray((err, result) => {
if(err) console.log(err);
else {
console.log(result.length); //2
result.forEach(i => console.log(i.id);) //id of each attachment
}
}
Now I need to be able to read the document back and store it locally. There doesn't seem to be any documentation that I can find for doing this in Nodejs. I've tried the following:
let attachment = result[0]; //from result of toArray() above -- first attachment from list
let mediaURI = `${attachment._self}${attachment.media}`
dbds.readMedia(mediaURI, (err, result) => {
if(err) console.log(JSON.parse(err.body).message); //Request url is invalid
else {
//try to write result to file
}
}
How do I create a valid URI to the media in order to download it?
Edit
Based on comments below, I updated my code as follows:
let attachment = result[0]
let mediaURI = attachment.media //here is the change
dbds.readMedia(mediaURI, (err, result) => {
if(err) console.log(JSON.parse(err.body).message);
else {
//try to store the data
}
})
I no longer get an error but instead get a JSON object:
"{"constants":{"O_RDONLY":0,"O_WRONLY":1,"O_RDWR":2,"S_IFMT"‌​:61440,"S_IFREG":327‌​68,"S_IFDIR":16384,"‌​S_IFCHR":8192,"S_IFL‌​NK":40960,"O_CREAT":‌​256,"O_EXCL":1024,"O‌​_TRUNC":512,"O_APPEN‌​D":8,"F_OK":0,"R_OK"‌​:4,"W_OK":2,"X_OK":1‌​},"F_OK":0,"R_OK":4,‌​"W_OK":2,"X_OK":1}"

Answer 1

I got help from some folks at Microsoft on this.
The primary issue was that I wasn't writing the file correctly.
Instead of this
let dbds = new azure(dbEndpoint, {"masterKey":dbKey})
fs.open("c:/temp/capture.png", "r", (err, fd) => {
if(err) console.log(err);
else{
dbds.createAttachmentAndUploadMedia(documentLink, fs, {contentType:"image/png", partitionKey: partitionKey}, (err, result) =>{
fs.close(fd);
if(err) console.log(err);
else console.log(result);
}
}
}
With fs.open fs is not a filestream -- which is what createAttachmentAndUploadMedia is looking for. I had mistakenly assumed that fs was a fs.open created a filestream.
What I wound up doing was the following:
fs.readFile("c:/temp/myimage.jpg",(err, data) => {
if(err) reject(err);
else dbds.svc.createAttachmentAndUploadMedia(docPath,data,{contentType: "image/jpeg"
, partitionKey: "Key"}, (err, result) =>{..}
})

Answer 2

In your example, the mediaURI should just be ${attachment.media} not concatenated with the ${attachment._self}.
Here is an snippet:
return new Promise<any>((resolve, reject) => {
this.documentDbClient.readAttachment(docLink, options, (err, result) => {
if (err)
return reject(err);
resolve(result.media);
});
}).then((medialink) => {
return new Promise<any>((resolve, reject) => {
this.documentDbClient.readMedia(medialink, (err, result) => {
if (err)
return reject(err);
// buffered data
const data = [];
result.on('data', (chunk) => data.push(chunk));
result.on('end', () => {
resolve(data.join(''));
});
// if not buffered
// resolve(result.toString());
});
});
});