Dropbox 400 Error in JavaScript Datastore API Request

Question

I'm attempting to post a large number of records (2000-ish) to Dropbox via the Datastore JS API. I'm getting this error:

POST https://api12.dropbox.com/1/datastores/put_delta 400 (Bad Request)

...and it references: api12.dropbox.com/1/datastores/put_delta:1

That's not a lot of info to use when debugging, but I'm guess it's because I'm over the size limit.

Any ideas how I can fix this or at least debug it further?

Update

I used the XHR inspector in Chrome to get this response:

{"error": 
  {
  "size_limit": "Error: put_delta of delta (size 4138335) exceeds size limit 2097152 bytes",
  "object_type": "delta", 
  "limit": 2097152, 
  "size": 4138335
 }
}

Is there anything in the body of the response? I believe it should contain more useful information about the error. — Greg
– Greg, Commented Dec 3, 2014 at 21:25
I looked again and found the response JSON (see above). If I don't know what the size of the POST will be in my app. Is there a way for me to break up the request into chunks? Is there a way to "sync" periodically like there is in the iOS SDK to keep the request size down? — Clifton Labrum
– Clifton Labrum, Commented Dec 3, 2014 at 23:31

user94559 · Accepted Answer · 2014-12-05 18:18:00Z

1

In the JS SDK, there's an implicit "sync" every time your code yields control back to the browser. So if you write a for loop entering a lot of data, that will all go into a single delta. You can break things up by writing in smaller chunks. For example, something like this (untested, sorry if there's an off-by-one error or the like):

var LIMIT = 100; // how many things to write in a single delta

function writeThings(arrayOfThings) {

    // write up to LIMIT things
    for (var i = 0; i < arrayOfThings.length && i < LIMIT; i++) {
        writeSingleThing(arrayOfThings[i]);
    }

    if (i < arrayOfThings.length) {
        // more to write

        window.setTimeout(function () {
            // after a tick, continue from where we left off
            writeThings(arrayOfThings.slice(i));
        }, 1);
    } else {
        // done writing
    }

}

edited Dec 5, 2014 at 18:18

answered Dec 3, 2014 at 23:56

user94559

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4 Comments

Clifton Labrum Over a year ago

This is interesting and helpful, thanks. Is the if/else statement supposed to be inside the for loop so it can reference i?

user94559 Over a year ago

No, the if/else is where it's supposed to be. i should still be in scope. Why, are you seeing an error?

Clifton Labrum Over a year ago

You're right, it still is in scope (JavaScript is weird). :) I found my real issue. The setTimeout function needs the function to be the first parameter, and the timeout interval to be the second parameter. This is working great for me now. I can upload large datasets without hitting the delta limit. Thank you!

user94559 Over a year ago

Cool! I updated the answer to match the right use for window.setTimeout.

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