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backpressure.check.js
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backpressure.check.js
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var Timedsource = require('./timedsource');
var tilelive = require('..');
var progress = require('progress-stream');
var util = require('util');
var setConcurrency = require('../lib/stream-util').setConcurrency;
var max = 9;
var readSpeed = 100;
var readsPerWrite = 10;
var numReads = 0;
var numWrites = 0;
var numDrains = 0;
var writesQueued = 0;
var writeConcurrency = 0;
var writeHighWater = 2 * setConcurrency();
console.log('Calculated concurrency: %s', setConcurrency());
function report() {
util.print(
util.format(
'\r\033[KReads: %s - Writes: %s - Queued: %s - Drains: %s - Write concurrency: %s',
numReads, numWrites, writesQueued, numDrains, writeConcurrency
)
);
}
var readsource = new Timedsource({ time: readSpeed, maxzoom: max });
var read = tilelive.createReadStream(readsource, { type: 'scanline' });
var readProgress = progress({
objectMode: true,
length: Math.pow(4, max),
time: 1
}, function(prog) {
if (prog.transferred > numReads) {
numReads = prog.transferred;
report();
}
});
var writesource = new Timedsource({ time: readSpeed * readsPerWrite, maxzoom: max });
var write = tilelive.createWriteStream(writesource, { highWaterMark: writeHighWater });
write.on('_write', function() {
numWrites++;
writeConcurrency = write._multiwriting;
writesQueued = write._writableState.buffer.length;
report();
});
write.on('drain', function() {
numDrains++;
writeConcurrency = write._multiwriting;
writesQueued = write._writableState.buffer.length;
report();
});
read.pipe(readProgress).pipe(write).on('stop', function() {
console.log('finished');
});