consistency

I can not find the documentation for this. I know there is a consistency command in cqlsh, but there is no distinction between read and write consistency. How would I set different consistency levels for read and write? Furthermore, there is a mention of a "default" consistency level. Where is that default set? and is it for read or write? bechbd By default, the Consistency Level is ONE for all R/W Operations. Setting CL is done on a per query (read or upsert) basis by adding the CONSISTENCY XXXX syntax on the query as seen here: https://cassandra.apache.org/doc/latest/cql/dml.html#insert and

Lets say I've created a keyspace and table: CREATE KEYSPACE IF NOT EXISTS keyspace_rep_0 WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 0}; CREATE TABLE IF NOT EXISTS some_table ( some_key ascii, some_data ascii, PRIMARY KEY (some_key) ); I don't want any replica of this data. I can insert into this table with consistency level ANY . But I couldn't select any data from this table. I got the following errors when querying with consistency levels ANY and ONE , respectively: message="ANY ConsistencyLevel is only supported for writes" message="Cannot achieve consistency level

In the context of correctness of concurrent programs, Sequential consistency is stronger condition than quiescent consistency according to The art of multiprocessor programming by Maurice Herlihy and Nir Shavit(chapter 3) Authors also mention in 3.4.1 that there are sequentially consistent executions that are not quiescently consistent. I don't understand how. Could somebody throw a light or provide sample execution ? ewernli Consider a queue (FIFO) to which you enqueue and dequeue elements. From this dissertation about concurrency, I read (p.20): An example of a scenario that is allowed in

I'm trying to understand what is the right approach for this following scenario : Multiplayer game,each game structured only with two players. Each game/match will be completely randomized Lets assume 5 users "logs" the same time into my app, each one of them "searching" for a match. Each user hold a property named opponent which equal the the opponent uniqueID (initial value equal "" . so far so good. assuming user 1 matched with user 3. user 1 will update his own oppoent value to user 3 uniqueID and will do the same to user 3 Problem 1) What if at the same moment, user 2 tried to to the same

I am looking for a good, up to date and "decision helping" explanation on how to choose a NoSQL database engine for storing all the events in a CQRS designed application. I am currently a newcomer to all things around NoSQL (but learning): please be clear and do not hesitate to explain your point of view in an (almost too much) precise manner. This post may deserve other newcomers like me. This database will: Be able to insert 2 to 10 rows per updates asked by the front view (in my case, updates are frequent). Think of thousand of updates per minute, how would it scale? Critically need to be

Are there any algorithms that are commonly used for achieving eventual consistency in distributed systems? There are algorithms that have been developed for ACID transactions in distributed systems, Paxos in particular, but is there a similar body of theory that has been developed for BASE scenarios, with weaker consistency guarantees? Edit: This appears to be an area of academic research that is only beginning to be developed. Mcdowella's answer shows that there has been at least some work in this area. If "Anti-entropy protocols for repairing replicated data, which operate by comparing

I have taken a database class this semester and we are studying about maintaining cache consistency between the RDBMS and a cache server such as memcached. The consistency issues arise when there are race conditions. For example: Suppose I do a get(key) from the cache and there is a cache miss. Because I get a cache miss, I fetch the data from the database, and then do a put(key,value) into the cache. But, a race condition might happen, where some other user might delete the data I fetched from the database. This delete might happen before I do a put into the cache. Thus, ideally the put into