consistency

how to set cassandra read and write consistency

由 房东的猫 提交于 2019-12-10 10:09:06
问题 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? 回答1: 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

How to keep long running NHibernate Session data consistent?

由 不羁的心 提交于 2019-12-09 19:22:50
问题 I have NHibernate sessions cached in the ASP.NET session. I came across a situation where a user edited an object so it's in their first level cache in the ISession. Another user then edited the same object. At this point User1 still sees their original version of their edits where as User2 sees the correct state of the object? What is the correct way to handle this without manually calling session.Refresh(myObj) explicitly for every single object all the time? I also have a 2nd level cache

What are the differences between sequential consistency and quiescent consistency?

由 风格不统一 提交于 2019-12-09 08:30:25
问题 Can anyone explain me the definitions and differences between sequential consistency and quiescent consistency? In the most dumb form possible :| I did read this: Example of execution which is sequentially consistent but not quiescently consistent But I am not able to understand Sequential and quiescent consistency itself :( 回答1: Sequential consistency requires that the operations should appear to take effect in the order they are specified in each program. Basically it enforces program order

Google AppEngine DataStore constistency

由 此生再无相见时 提交于 2019-12-08 01:59:28
问题 My current understanding of Google AppEngine's High Replication DataStore is the following: Gets and puts of individual entities are always strongly consistent, i.e. once a put of this entry completes, no later get will ever return a version earlier than the completed put . Or, more precisely, as soon as any one get returns the new version, no later get will ever return the old version again. Gets and puts of multiple entities are strongly consistent, if they belong to the same ancestor group

How to check SQLite file consistency (health check)

由 走远了吗. 提交于 2019-12-08 00:05:40
问题 I am using a SQLite database file in my Android application that is created from several pieces stored in the assets folder by using the following approach: ReignDesign - Using your own SQLite database in Android applications On completion of the assemby process I would like to check if the database was correctly merged. The following approaches crossed my mind: MD5 hash comparison Checking table existence and entry counts Which approach would you recommend? Is there a better way? Thanks,

Cassandra - Select without replication

由 送分小仙女□ 提交于 2019-12-07 09:14:42
问题 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

Example of execution which is sequentially consistent but not quiescently consistent

由 半腔热情 提交于 2019-12-07 02:22:55
问题 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 ? 回答1: Consider a queue (FIFO) to which you enqueue and dequeue elements.

FireBase - maintain/guarantee data consistency

由 北城以北 提交于 2019-12-06 14:50:26
问题 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

How to check SQLite file consistency (health check)

由 淺唱寂寞╮ 提交于 2019-12-06 13:31:55
I am using a SQLite database file in my Android application that is created from several pieces stored in the assets folder by using the following approach: ReignDesign - Using your own SQLite database in Android applications On completion of the assemby process I would like to check if the database was correctly merged. The following approaches crossed my mind: MD5 hash comparison Checking table existence and entry counts Which approach would you recommend? Is there a better way? Thanks, Philipp I had a similar situation in an application I'm developing. There are a variety of ways of doing

Are there any general algorithms for achieving eventual consistency in distributed systems?

由 家住魔仙堡 提交于 2019-12-06 03:21:04
问题 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
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