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Throttle repeated packet-parse error logs in FullPacketParser #179

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Throttle repeated packet-parse error logs in FullPacketParser #179

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16 changes: 14 additions & 2 deletions src/serializer.js
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Original file line number Diff line number Diff line change
@@ -1,5 +1,15 @@
const Transform = require('readable-stream').Transform

// A malformed stream can make the same packet fail to parse for every frame it sends -- thousands
// of identical stacks a minute. Log the first occurrence of each in full, then only at 1, 2, 4, 8,
// ... so a persistent fault stays O(log n) instead of unbounded. Keyed per parser instance.
function logThrottled (counts, key, full) {
const n = (counts.get(key) || 0) + 1
counts.set(key, n)
if (n === 1) console.log(full)
else if ((n & (n - 1)) === 0) console.log(`${key} (repeated ${n} times)`)
}

class Serializer extends Transform {
constructor (proto, mainType) {
super({ writableObjectMode: true })
Expand Down Expand Up @@ -62,6 +72,7 @@ class FullPacketParser extends Transform {
this.proto = proto
this.mainType = mainType
this.noErrorLogging = noErrorLogging
this.errorCounts = new Map()
}

parsePacketBuffer (buffer) {
Expand All @@ -73,13 +84,14 @@ class FullPacketParser extends Transform {
try {
packet = this.parsePacketBuffer(chunk)
if (packet.metadata.size !== chunk.length && !this.noErrorLogging) {
console.log('Chunk size is ' + chunk.length + ' but only ' + packet.metadata.size + ' was read ; partial packet : ' +
logThrottled(this.errorCounts, 'chunk size mismatch',
'Chunk size is ' + chunk.length + ' but only ' + packet.metadata.size + ' was read ; partial packet : ' +
JSON.stringify(packet.data) + '; buffer :' + chunk.toString('hex'))
}
} catch (e) {
if (e.partialReadError) {
if (!this.noErrorLogging) {
console.log(e.stack)
logThrottled(this.errorCounts, e.stack.split('\n')[0], e.stack)
}
return cb()
} else {
Expand Down
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