CODEWITHSUNDEEP
cassandradatastaxcassandra-2.1
Naresh
Naresh

Reputation: 5407

Avoid dirty read and write in cassandra

I am using Cassandra 2.1.12 to store the event data in a column family. Below is the c# code for creating the client for the .net which manage connections from Cassandra. Now the problem is rate of insert/update data is very high. So, now let's say i increment a column value in Cassandra on subsequent request. But as i said rate of insert/update is very high. So in my 3 node cluster if first time i write value of the column would be 1 then in next request i will read the value of this column and update it to 2. But if the value if fetched from other node where the value has not been initialized to 1. Then again value would be stored as 1. So, now to solve this problem i have also kept the value of consistency to be QUORUM. But still the problem persists. Can any one tell me the possible solution for this ? 

     private static ISession _singleton;

        public static ISession GetSingleton()
        {
            if (_singleton == null)
            {
                Cluster cluster = Cluster.Builder().AddContactPoints(ConfigurationManager.AppSettings["cassandraCluster"].ToString().Split(',')).Build();
                ISession session = cluster.Connect(ConfigurationManager.AppSettings["cassandraKeySpace"].ToString());
                _singleton = session;
            }
            return _singleton;
        }

Upvotes: 1

Views: 1536

Answers (1)

Jaya Ananthram
Jaya Ananthram

Reputation: 3463

No, It is not possible to achieve your goal in cassandra. The reason is, every distributed application falls within the CAP theorem. According to that, cassandra does not have Consistency.

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So in your scenario, you are trying to update a same partition key for many time in multi threaded environment, So it is not guaranteed to see latest data in all the threads. If you try with small interval gap then you might see latest data in all the threads. If your requirement is to increment/decrement the integers then you can go with cassandra counters. But however cassandra counter does not support to retrieve the updated value with in a single request. Which means you can have a request to increment the counter and have a separate request to get the updated value. It is not possible to increment and to get the incremented value in a single request. If you requirement is to only incrementing the value (like counting the number of times a page is viewed) then you can go with cassandra counters. Cassandra counters will not miss any increments/decrements. You can see actual data at last. Hope it helps.

Upvotes: 2

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