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log catastrophic errors in getIndex, clean up comments

This commit is contained in:
ansuz 2019-08-23 12:43:05 +02:00
parent 62c23a29a7
commit 7642ee9584
1 changed files with 15 additions and 17 deletions
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32
historyKeeper.js
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@ -229,9 +229,10 @@ module.exports.create = function (cfg) {
as an added bonus:
if the channel exists but its index does not then it caches the index
*/
const indexQueue = {};
const indexQueues = {};
const getIndex = (ctx, channelName, cb) => {
const chan = ctx.channels[channelName];
// if there is a channel in memory and it has an index cached, return it
if (chan && chan.index) {
// enforce async behaviour
return void setTimeout(function () {
@ -239,38 +240,35 @@ module.exports.create = function (cfg) {
});
}
// make a queue of callbacks in case getIndex is called before you
// compute and cache the index
// if a call to computeIndex is already in progress for this channel
// then add the callback for the latest invocation to the queue
// and wait for it to complete
if (indexQueue[channelName]) {
indexQueue.channelName.push(cb);
if (Array.isArray(indexQueues[channelName])) {
indexQueues[channelName].push(cb);
return;
}
// if computeIndex is not already in progress, make an array
// with the current call first in line, so additional calls
// can add their callbacks to the queue
indexQueue[channelName] = (indexQueue[channelName] || []).push(cb);
// otherwise, make a queue for any 'getIndex' calls made before the following 'computeIndex' call completes
var queue = indexQueues[channelName] = (indexQueues[channelName] || [cb]);
computeIndex(channelName, (err, ret) => {
// keep a local reference to this channel's queue
let queue = indexQueue[channelName];
if (!Array.isArray(queue)) {
// something is very wrong if there's no callback array
return void Log.error("E_INDEX_NO_CALLBACK", channelName);
}
// but remove it from the map of queues and not worry about cleaning up
// as long as computeIndex always calls back this won't be a memory leak
delete indexQueue[channelName];
// clean up the queue that you're about to handle, but keep a local copy
delete indexQueues[channelName];
// this is most likely an unrecoverable filesystem error
if (err) {
// call back every pending function with the error
return void queue.forEach(function (_cb) {
_cb(err);
});
}
// if there's a channel to use as a cache, store the result
// for future use
// cache the computed result if possible
if (chan) { chan.index = ret; }
// call back every pending function with the result