eventual-consistency | 易学教程

Read Operation in Cassandra at Consistency level of Quorum?

阅读更多关于 Read Operation in Cassandra at Consistency level of Quorum?

问题 I am reading this post on read operations and consistency level in Cassandra. According to this post: For example, in a cluster with a replication factor of 3, and a read consistency level of QUORUM, 2 of the 3 replicas for the given row are contacted to fulfill the read request. Supposing the contacted replicas had different versions of the row, the replica with the most recent version would return the requested data. In the background, the third replica is checked for consistency with the

AWS DynamoDB read after write consistency - how does it work theoretically?

阅读更多关于 AWS DynamoDB read after write consistency - how does it work theoretically?

问题 Most of the nosql solution only use eventually consistency, and given that DynamoDB replicate the data into three datacenter, how does read after write consistency is being maintained? What would be generic approach to this kind of problem? I think it is interesting since even in MySQL replication data is replicated asynchronously. 回答1: I'll use MySQL to illustrate the answer, since you mentioned it, though, obviously, neither of us is implying that DynamoDB runs on MySQL. In a single network

Enforce strict consistency spanning multiple aggregates

阅读更多关于 Enforce strict consistency spanning multiple aggregates

问题 Consider the following business requirements: We have players which can play games. A player can play only one game at a time. A game needs two players. The system will contain millions of players, and games take about two minutes. Concurrency issues are likely to emerge. We want to comply to the rule that a single transaction involves a single aggregate . Further, eventual consistency must not lead to accepted games which must be cancelled afterwards (even if a short period of time) due to

How to achieve immediate consistency in microservice architecture?

阅读更多关于 How to achieve immediate consistency in microservice architecture?

问题 For example amazon.com; they rely on microservice architecture and probably order and payment are seperate micro services but when you checkout order on amazon.com you can finally see the order id and details.If it's not eventual consistency approach what is it? Maybe 2PC? I'm generalizing my question; what if eventual consistency is not appropriate for business transaction(end user should see the result end of transaction) but seperate microservices is meaningful(like order and payment) how

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

阅读更多关于 Are there any general algorithms for achieving eventual consistency in distributed systems?

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

Google Datastore Strong consistency and Entity Group max size

阅读更多关于 Google Datastore Strong consistency and Entity Group max size

In a shared expenses app that shows payments dues and shared expenses details for each group. As a financial application, so many operations are transactional, which requires strong consistency to ensure data integrity. We used Entity Groups and ancestor queries which seems to have solved the issue of strong consistency, this caused the entity group to be large in size. As the shared 'group' is now the parent of members, expenses, payments, dues..etc. Until now we don't see a problem, but we are worried as this scales, expenses and/or payments can scale to the order of 10~100K entities. After

Does mySQL replication have immediate data consistency?

阅读更多关于 Does mySQL replication have immediate data consistency?

问题 I am considering a noSQL solution for a current project, but I'm hesitant about the 'eventual consistency' clause in many of these databases. Is eventual consistency different than dealing with a mySQL database where replication lags? One solution I have used in the past with lagging replication is to read from the master when immediate data consistency is needed. However, I am confused then as to why relational database claim to have strong data consistency. I guess I should use transactions

CQRS - Eventual Consistency

阅读更多关于 CQRS - Eventual Consistency

I have the following scenario which I need to implement following the CQRS pattern: a user logs in the user enters some insurance details the user ask for a decision to be applied the user views the result of the decision This seems fairly straightforward, however my problem is between step 3 and 4, on step 3 I send a ApplyForDecision command which will get a decision from a underwriting service, an event with the result of that decision is then sent to the BUS for the read store to later consume it and update the view tables with the decision result. The problem is on the UI, how do I let the

Read-your-own-writes consistency in Mongodb

阅读更多关于 Read-your-own-writes consistency in Mongodb

first, here is what is said in Pymongo Documentation By default, PyMongo starts a request for each thread when the thread first runs an operation on MongoDB. This guarantees **read-your-writes consistency . Within a request, the thread will continue to use the same socket exclusively, and no other thread will use this socket, until the thread calls end_request() or it terminates. At that point, the socket is returned to the connection pool for use by other threads. so when using an async library to Mongodb (like Asyncmongo, Motor), will the user have a consistency like the one in blocking

Does using NoSQL make sense for a non-distributed system? (trying to understand eventual consistency)

阅读更多关于 Does using NoSQL make sense for a non-distributed system? (trying to understand eventual consistency)

I have been reading and learning about NoSQL and MongoDB, CouchDB, etc, for the last two days, but I still can't tell if this is the right kind of storage for me. What worries me is the eventual consistency thing. Does that type of consistency only kick in when using clusters? (I'm hosting my sites in a single dedicated server, so I don't know if I can benefit from NoSQL) For which kind of applications is OK to have eventual consistency (instead of ACID), and for which ones it isn't? Can you give me some examples? What's the worst thing that can happen in an application for which is OK to have