Hi! I just recently learned that this design would also help on recovering from a disaster.
Cassandra can be easily replicated so the risk of loosing all the Cassandra nodes is relatively small. And even if that happens you only loose the commands that are not executed yet (not a huge problem since any command could fail after it is issued). Postgres can also be replicated but at one point the database (and replica) could become corrupt. So you restore it from the recent backup but you face the problem that the backup is probably at least several hours old. To solve the issue you could replay the commands in Cassandra to bring the database restored fromt the backup to the lasest state. The current problem however is that there are some commands that when they get executed, they create other commands as a result (when you replay such a command you will create a command again - although it exists already) So there should be a mechanism in place in Fineract-CN to identify such commands so one could skip executing them during replay (or some other stattegy to deal with this). Juhan Kontakt Victor Romero (<[email protected]>) kirjutas kuupäeval N, 24. oktoober 2019 kell 17:28: > Yes it is. > > > https://cwiki.apache.org/confluence/display/FINERACT/Fineract+CN+Project+Structure#FineractCNProjectStructure-cassandra > > El 24 de octubre de 2019 a las 08:11 AM Niklas Uhrberg < > [email protected]> escribió: > > > Hi! > > I didn't pay much attention to the Cassandra database when looking at > Fineract CN, but now I read > https://cwiki.apache.org/confluence/display/FINERACT/CQRS+in+Fineract+CN > and I conclude from this documentation that the only usage of Cassandra is > to persist the commands. > > Furthermore that one and the same database is used in the processing of > the commands , i.e. the state changes in the Postgres db as a consequence > of a command being processed occur in the same Postgres database used to > serve read style requests (since there is only one Postgres db) > > Is this correctly understood? > > Best regards Niklas > > > > > Niklas Uhrberg > Konsult > IT Development | Loans & Credit > > > > > Resurs Bank AB > > > > > Växel: +46 42 38 20 00 > E-post: [email protected] > Webb: www.resursbank.se > > > > > > >
