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implement per-channel fifo queues for metadata and channel writes

This commit is contained in:
ansuz 2019-09-04 11:51:33 +02:00
parent 41c86bb6bc
commit 4902554a61
3 changed files with 107 additions and 96 deletions
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126
historyKeeper.js
View File

@ -7,6 +7,7 @@ const Nacl = require('tweetnacl');
const Crypto = require('crypto');
const Once = require("./lib/once");
const Meta = require("./lib/metadata");
const WriteQueue = require("./lib/write-queue");
let Log;
const now = function () { return (new Date()).getTime(); };
@ -302,88 +303,59 @@ module.exports.create = function (cfg) {
* the fix is to use callbacks and implement queueing for writes
* to guarantee that offset computation is always atomic with writes
*/
const storageQueues = {};
const storeQueuedMessage = function (ctx, queue, id) {
if (queue.length === 0) {
delete storageQueues[id];
return;
}
const first = queue.shift();
const msgBin = first.msg;
const optionalMessageHash = first.hash;
const isCp = first.isCp;
// Store the message first, and update the index only once it's stored.
// store.messageBin can be async so updating the index first may
// result in a wrong cpIndex
nThen((waitFor) => {
store.messageBin(id, msgBin, waitFor(function (err) {
if (err) {
waitFor.abort();
Log.error("HK_STORE_MESSAGE_ERROR", err.message);
// this error is critical, but there's not much we can do at the moment
// proceed with more messages, but they'll probably fail too
// at least you won't have a memory leak
// TODO make it possible to respond to clients with errors so they know
// their message wasn't stored
storeQueuedMessage(ctx, queue, id);
return;
}
}));
}).nThen((waitFor) => {
getIndex(ctx, id, waitFor((err, index) => {
if (err) {
Log.warn("HK_STORE_MESSAGE_INDEX", err.stack);
// non-critical, we'll be able to get the channel index later
// proceed to the next message in the queue
storeQueuedMessage(ctx, queue, id);
return;
}
if (typeof (index.line) === "number") { index.line++; }
if (isCp) {
index.cpIndex = sliceCpIndex(index.cpIndex, index.line || 0);
for (let k in index.offsetByHash) {
if (index.offsetByHash[k] < index.cpIndex[0]) {
delete index.offsetByHash[k];
}
}
index.cpIndex.push(({
offset: index.size,
line: ((index.line || 0) + 1)
} /*:cp_index_item*/));
}
if (optionalMessageHash) { index.offsetByHash[optionalMessageHash] = index.size; }
index.size += msgBin.length;
// handle the next element in the queue
storeQueuedMessage(ctx, queue, id);
}));
});
};
const queueStorage = WriteQueue();
const storeMessage = function (ctx, channel, msg, isCp, optionalMessageHash) {
const id = channel.id;
const msgBin = new Buffer(msg + '\n', 'utf8');
if (Array.isArray(storageQueues[id])) {
return void storageQueues[id].push({
msg: msgBin,
hash: optionalMessageHash,
isCp: isCp,
});
}
const queue = storageQueues[id] = (storageQueues[id] || [{
msg: msgBin,
hash: optionalMessageHash,
}]);
storeQueuedMessage(ctx, queue, id);
queueStorage(id, function (next) {
// Store the message first, and update the index only once it's stored.
// store.messageBin can be async so updating the index first may
// result in a wrong cpIndex
nThen((waitFor) => {
store.messageBin(id, msgBin, waitFor(function (err) {
if (err) {
waitFor.abort();
Log.error("HK_STORE_MESSAGE_ERROR", err.message);
// this error is critical, but there's not much we can do at the moment
// proceed with more messages, but they'll probably fail too
// at least you won't have a memory leak
// TODO make it possible to respond to clients with errors so they know
// their message wasn't stored
return void next();
}
}));
}).nThen((waitFor) => {
getIndex(ctx, id, waitFor((err, index) => {
if (err) {
Log.warn("HK_STORE_MESSAGE_INDEX", err.stack);
// non-critical, we'll be able to get the channel index later
return void next();
}
if (typeof (index.line) === "number") { index.line++; }
if (isCp) {
index.cpIndex = sliceCpIndex(index.cpIndex, index.line || 0);
for (let k in index.offsetByHash) {
if (index.offsetByHash[k] < index.cpIndex[0]) {
delete index.offsetByHash[k];
}
}
index.cpIndex.push(({
offset: index.size,
line: ((index.line || 0) + 1)
} /*:cp_index_item*/));
}
if (optionalMessageHash) { index.offsetByHash[optionalMessageHash] = index.size; }
index.size += msgBin.length;
// handle the next element in the queue
next();
}));
});
});
};
var CHECKPOINT_PATTERN = /^cp\|(([A-Za-z0-9+\/=]+)\|)?/;

40
lib/write-queue.js Normal file
View File

@ -0,0 +1,40 @@
/*
var q = Queue();
q(id, function (next) {
// whatever you need to do....
// when you're done
next();
});
*/
var fix1 = function (f, x) {
return function () { f(x); };
};
module.exports = function () {
var map = {};
var next = function (id) {
if (map[id] && map[id].length === 0) { return void delete map[id]; }
var task = map[id].shift();
task(fix1(next, id));
};
return function (id, task) {
// support initialization with just a function
if (typeof(id) === 'function' && typeof(task) === 'undefined') {
task = id;
id = '';
}
// ...but you really need to pass a function
if (typeof(task) !== 'function') { throw new Error("Expected function"); }
// if the intended queue already has tasks in progress, add this one to the end of the queue
if (map[id]) { return void map[id].push(task); }
// otherwise create a queue containing the given task
map[id] = [task];
next(id);
};
};

37
rpc.js
View File

@ -18,7 +18,7 @@ const nThen = require("nthen");
const getFolderSize = require("get-folder-size");
const Pins = require("./lib/pins");
const Meta = require("./lib/metadata");
const WriteQueue = require("./lib/write-queue");
var RPC = module.exports;
@ -340,8 +340,7 @@ var getMetadata = function (Env, channel, cb) {
value: value
}
*/
// XXX global saferphore may cause issues here, a queue "per channel" is probably better
var metadataSem = Saferphore.create(1);
var queueMetadata = WriteQueue();
var setMetadata = function (Env, data, unsafeKey, cb) {
var channel = data.channel;
var command = data.command;
@ -349,16 +348,15 @@ var setMetadata = function (Env, data, unsafeKey, cb) {
if (!command || typeof (command) !== 'string') { return void cb ('INVALID_COMMAND'); }
if (Meta.commands.indexOf(command) === -1) { return void('UNSUPPORTED_COMMAND'); }
metadataSem.take(function (give) {
var g = give();
queueMetadata(channel, function (next) {
getMetadata(Env, channel, function (err, metadata) {
if (err) {
g();
return void cb(err);
cb(err);
return void next();
}
if (!(metadata && Array.isArray(metadata.owners))) {
g();
return void cb('E_NO_OWNERS');
cb('E_NO_OWNERS');
return void next();
}
// Confirm that the channel is owned by the user in question
@ -372,13 +370,13 @@ var setMetadata = function (Env, data, unsafeKey, cb) {
|| !Array.isArray(data.value)
|| data.value.length !== 1
|| data.value[0] !== unsafeKey) {
g();
return void cb('INSUFFICIENT_PERMISSIONS');
cb('INSUFFICIENT_PERMISSIONS');
return void next();
}
} else if (metadata.owners.indexOf(unsafeKey) === -1) {
g();
return void cb('INSUFFICIENT_PERMISSIONS');
cb('INSUFFICIENT_PERMISSIONS');
return void next();
}
// Add the new metadata line
@ -387,22 +385,23 @@ var setMetadata = function (Env, data, unsafeKey, cb) {
try {
changed = Meta.handleCommand(metadata, line);
} catch (e) {
g();
return void cb(e);
cb(e);
return void next();
}
// if your command is valid but it didn't result in any change to the metadata,
// call back now and don't write any "useless" line to the log
if (!changed) {
g();
return void cb(void 0, metadata);
cb(void 0, metadata);
return void next();
}
Env.msgStore.writeMetadata(channel, JSON.stringify(line), function (e) {
g();
if (e) {
return void cb(e);
cb(e);
return void next();
}
cb(void 0, metadata);
next();
});
});
});