如何处理文档更新冲突时使用CouchDB客户端摇篮为Node.js

Question

100000个客户端同时尝试使用flatiron/cradle更新couchdb文档。如何处理所有的更新冲突?

Answer 1

解决方案:

var cradle = require('cradle');
var c = new(cradle.Connection)({cache: true} )   ;
var db = c.database('ml');
function asyncLoop(iterations, func, callback) {
    var index = 0;
    var done = false;
    var loop = {
        next: function() {
            if (done) {
                return;
            }
            if (index < iterations) {
                index++;
                func(loop);
            } else {
                done = true;
                callback();
            }
        },
        iteration: function() {
            return index - 1;
        },
        break: function() {
            done = true;
            callback();
        }
    };
    loop.next();
    return loop;
}
//----------------------------------------
function revloop(game,gamenumber, callback){
    db.get('testdocument', function (err, doc) {

        if (err) {
            // Handle error
        } else {
            // Handle success
            db.save('testdocument', doc._rev ,{
                game:game,
                gamenumber:gamenumber
            }, function (err, res) {
                if (err) {
                    console.log(err);
                    if(err.reason=='Document update conflict.')
                    {callback(0);}
                    else{console.log('other errror');callback(1)}
                } else {
                    console.log('new game created');
                    callback(1);
                    // Handle success

                }// success save opengames end bracket
            });
        }
    });
}
//-----------------------------------
asyncLoop(100 ,function(loop){
    revloop('b-against-c',3,function(callback){
        if(callback == 0){
            loop.next();
        }
        else{loop.break();}
    });
} , function(){  console.log('loop finished')});

这个解决方案使用了Ivo Wetzel的异步循环。

下面是一个测试，有9个更新冲突是由向_rev: 添加字符串引起的

var cradle = require('cradle');
var c = new(cradle.Connection)({cache: true} )   ;
var db = c.database('ml');
function asyncLoop(iterations, func, callback) {
    var index = 0;
    var done = false;
    var loop = {
        next: function() {
            if (done) {
                return;
            }
            if (index < iterations) {
                index++;
                func(loop);
            } else {
                done = true;
                callback();
            }
        },
        iteration: function() {
            return index - 1;
        },
        break: function() {
            done = true;
            callback();
        }
    };
    loop.next();
    return loop;
}
//----------------------------------------
var revchanger= 0;
function revloop(game,gamenumber, callback){
    revchanger ++;
    var addstuff = revchanger== 10? '':'123';// this will cause nine update conflicts
    db.get('testdocument', function (err, doc) {

        if (err) {
            // Handle error
        } else {
            // Handle success
            db.save('testdocument', doc._rev+addstuff ,{
                game:game,
                gamenumber:gamenumber
            }, function (err, res) {
                if (err) {
                    console.log(err);
                    if(err.reason=='Document update conflict.')
                    {callback(0);}
                    else{console.log('other errror');callback(1)}
                } else {
                    console.log('new game created');
                    callback(1);
                    // Handle success

                }// success save opengames end bracket
            });
        }
    });
}
//-----------------------------------
asyncLoop(100 ,function(loop){
    revloop('a-against-b',2,function(callback){
        if(callback == 0){
            loop.next();
        }
        else{loop.break();}
    });
} , function(){  console.log('loop finished')});

创建数据库:createml.js:

var cradle = require('cradle');
var c = new(cradle.Connection)    ;
var db = c.database('ml');
db.create();

创建testdocumentcreatetestdocument.js:

var cradle = require('cradle');
var db= new(cradle.Connection)().database('ml');
db.save('testdocument' , {
    game: 'gamename1',
    gamenumber:1
}, function (err, res) {
    if (err) {
        // Handle error
    } else {
        // Handle success
    }
});

在浏览器中查看:

http://localhost:5984/ml/testdocument

Answer 2

我建议将couchdb与redis一起使用，因为redis是原子的。