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Get CouchDB to return HTTP 304 when getting attachments, using Express and Nano on Node.js.
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| var app = express(); | |
| app.get('/:username/image', function (req, res) { | |
| db.getImage(req.params.username, req.headers["if-none-match"], res, function (err) { | |
| if (err) { | |
| // We don't have to do anything, here, as the db | |
| // pipe takes care of 404s and whatnot. | |
| // Log if you want. | |
| // console.log(err); | |
| } | |
| }); | |
| }); |
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| :-) |
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| var nanoDb = "..."; // nano(dbUrl); | |
| var databaseName = "..."; | |
| var cookieToken = "..."; // see below | |
| // docId - the _id of the Couch doc | |
| // attachmentName - ... | |
| // headers - req.headers from express | |
| // res - the connect / express response | |
| // callback - for handling errors | |
| var streamImageAttachment = function (docId, attachmentName, etag, res, callback) { | |
| // If you have authentication going, you need to set | |
| // your cookie token for your call to relax, below. | |
| // | |
| // Getting a cookie token is beyond the scope of this Gist, | |
| // but basically deal with headers['set-cookie'] from CouchDB, | |
| // and see the nano docs. | |
| var headers = {}; | |
| headers["X-CouchDB-WWW-Authenticate"] = "Cookie"; | |
| headers["cookie"] = cookieToken; | |
| // The 'If-None-Match' header that was specified by the | |
| // browser is what CouchDB uses to compare against the ETag, | |
| // which determines whether http 304 or http 200 (plus data) | |
| // is returned. | |
| headers["if-none-match"] = etag; | |
| var opts = { | |
| db: databaseName, | |
| headers: headers, | |
| method: "GET", | |
| doc: docId, | |
| att: attachmentName, | |
| encoding: null | |
| }; | |
| // We use the relax method because nano's | |
| // db.attachment.get method doesn't have a | |
| // headers parameter. | |
| var readStream = nanoDb.relax(opts, function (err) { | |
| if (err) { | |
| callback(err); | |
| } | |
| }); | |
| // Stream the image to 'res' | |
| res.type("image/jpeg"); // hard-coded because this a Gist | |
| readStream.pipe(res); | |
| }; | |
| var getDocId = function (username) { | |
| // an exercise for the reader | |
| }; | |
| var getImage = function (username, etag, res, callback) { | |
| streamImageAttachment(getDocId(username), "something.jpg", etag, res, callback); | |
| }; |
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| <html> | |
| <img src="/someone/image"/> | |
| </html> |
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