Name: read-async-bson
Owner: P'unk Avenue
Description: Read a stream of BSON documents, passing each one to a callback and waiting patiently until that callback is finished with its work.
Created: 2015-03-07 16:05:34.0
Updated: 2015-03-07 16:49:57.0
Pushed: 2015-03-07 16:49:57.0
Homepage: null
Size: 140
Language: JavaScript
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Let's read a stream of BSON documents from standard input, passing each one through a callback and waiting patiently until that callback is finished with its work:
reader = require('read-async-bson');
rn reader(
from: process.stdin },
nction(item, callback) {
// One BSON document, converted as a JavaScript object
console.log(item);
return callback(null);
nction(err) {
// Called on error or at end of stream
if (!err) {
console.log('end of stream');
} else {
console.error(err);
}
read-async-bson reads incoming BSON documents from any node stream, and invokes a callback for each one. Documents are delivered one at a time. The next document will not be delivered until you invoke a callback to signal that you have handled the previous one.
When an error occurs, or the end of the stream is reached, a final callback is invoked.
Documents in the BSON format, concatenated end to end.
That is already easy without any help from me:
bson = require('bson');
BSON = bson.BSONPure.BSON;
stream = process.stdout;
data = [ ... tons and tons of objects ... ]
.forEach(function(item) {
ream.write(BSON.serialize(item, false, true, false));
For more information, see the BSON npm module docs.
This implementation is extremely fast because it is designed to avoid allocating memory too often. It is especially fast in raw mode (see below).
from specifies the input stream. If you do not specify from, then process.stdin is assumed.
raw: normally BSON documents are parsed into JavaScript objects for you. If raw is true, then raw buffers containing BSON documents are delivered to your callback, which is much, much faster if you plan to just hand them to the mongodb driver. (Note that you must specify raw mode in your insert call.)
maxDocumentSize: by default BSON documents may be up to 16,777,216 bytes in length. This is MongoDB's limit. If you wish you may specify a different limit. Mostly useful for testing and low-memory environments.
When you just want to handle incoming objects in a strict order, streams just make things complicated and introduce bugs. We've had no end of trouble with node object streams that don't respect pause() in the streams1 interface, or stall out without emitting readable again in the streams2 interface, or… wait, why are we using these again?
mongo-dump-stream covers that use case nicely. Check it out.
read-async-bson was created at P'unk Avenue for use in many projects built with Apostrophe, an open-source content management system built on node.js. If you like read-async-bson you should definitely check out apostrophenow.org.
Feel free to open issues on github.
Fixed package description.
Do not invoke the final callback on end-of-stream unless we have actually consumed all of the data in our buffer.
Initial release. Refactored from mongo-dump-stream. New tests written, covering more cases.
Copyright (c) 2015 P'unk Avenue LLC
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.