a transform stream that buffers up to N items, discarding on further writes
npm install discard-streamA transform stream that passes through writes by default, but only buffers up
to a certain number of pending writes when backpressure is applied. New writes
will push old writes out of the buffer, so no more than N writes can be pending
at a time.
This is especially useful for logging or metrics situations, where:
1. the data generated is of less value than keeping the process healthy,
2. and it is difficult or meaningless to apply backpressure to the generation of the data.
``javascript
var discardStream = require('discard-stream')
var myLogs = discardStream({
maxBacklog: 100,
objectMode: true
})
myLogs.pipe(fs.createWriteStream('some/slow/logs'))
myHighPerformanceWebserver.on('request', function (req, res) {
myLogs.write(metrics)
})
`
`
// or use it as a transform:
someVeryFastMetricsStream()
.pipe(discardStream(10))
.pipe(someSlowTCPConnection())
#### discardStream(options) → DiscardStream
Create a discard stream using the provided [stream options][stream-opts].
An additional options key, maxBacklog, is required. maxBacklog determinesmaxBacklog
the maximum number of written values to be retained during backpressure — any
writes _over_ will result in an old buffered value being discarded.
options.highWaterMark will be ignored — it is always set to 0.
DiscardStream's will never apply backpressure upstream. They act as
infinite sinks for data.
#### discardStream(number) → DiscardStream
A shorthand for creating a discard stream with the following options:
`
discardStream({
maxBacklog: number,
highWaterMark: 0,
objectMode: true
})
#### DiscardStream#backlog
Get the backlog of queued writes as an array.
#### "discard" (data)
Emitted when an old write is discarded in favor of a more recent write.
This is the last chance the user has to do something with data`.
ISC
[stream-opts]: https://iojs.org/api/stream.html#stream_new_stream_readable_options