How can ETags be utilized in fetching data?

Question

How can ETags be utilized in fetching data?

To prevent mid-air collisions caused by multiple users or processes modifying the same item in the database, I am considering using Etags for validation. Here is my proposed approach:

The client will call a RESTful API to obtain an Etag from the header, which will then be stored in the item object.
When a user attempts to make changes to the item, the Etag will be sent back to the RESTful API as an If-Match header. The API will validate this against the current record, saving it if valid or rejecting it with code 412 if not.
If the change is rejected, the client will display an error message instructing the user to refresh the page.

Questions:

Do you think this approach is effective?

How can I efficiently store the Etag value in the item object using fetch? Specifically, how can I merge the Etag received in the header with the data returned from response.json()?

Thank you!

javascript json header fetch etag

Answer 1

Answer №1

Is this method effective?

Absolutely, this is the correct and documented approach.

How can I neatly store it in the item object using fetch?

There are different opinions on this, but you could include the etag header along with your data and pass that whole object. Here's an example:

    fetch('/data.json')
        .then(r => ({
            etag: r.headers.get('etag'), 
            json: r.json()
        }))
        .then(data => { 
            // Manipulate the etag and data
            console.log(data.etag);
            data.json.then(console.log)
        })
        .catch(console.error.bind(console));

Check out this information about handling edit collisions using ETag and If-Match headers:

By utilizing the ETag and the If-Match headers, you can detect conflicts when editing content simultaneously.

For instance, when modifying a wiki page, the current content may be hashed and placed into an Etag header in the response:

ETag: "33a64df551425fcc55e4d42a148795d9f25f89d4" When saving edits to a wiki page (sending data), the POST request will contain the If-Match header with the ETag values for freshness validation.

If-Match: "33a64df551425fcc55e4d42a148795d9f25f89d4" If the hashes do not match, it indicates that the document was altered in the meantime, resulting in a 412 Precondition Failed error.

More information on ETag

Answer 2

Is this method effective?

Absolutely, this is the correct and documented approach.

How can I neatly store it in the item object using fetch?

There are different opinions on this, but you could include the etag header along with your data and pass that whole object. Here's an example:

    fetch('/data.json')
        .then(r => ({
            etag: r.headers.get('etag'), 
            json: r.json()
        }))
        .then(data => { 
            // Manipulate the etag and data
            console.log(data.etag);
            data.json.then(console.log)
        })
        .catch(console.error.bind(console));

Check out this information about handling edit collisions using ETag and If-Match headers:

By utilizing the ETag and the If-Match headers, you can detect conflicts when editing content simultaneously.

For instance, when modifying a wiki page, the current content may be hashed and placed into an Etag header in the response:

ETag: "33a64df551425fcc55e4d42a148795d9f25f89d4" When saving edits to a wiki page (sending data), the POST request will contain the If-Match header with the ETag values for freshness validation.

If-Match: "33a64df551425fcc55e4d42a148795d9f25f89d4" If the hashes do not match, it indicates that the document was altered in the meantime, resulting in a 412 Precondition Failed error.

More information on ETag

How can ETags be utilized in fetching data?

Answer №1

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