c++ - SQL table event store as a queue in Qt App -



c++ - SQL table event store as a queue in Qt App -

i need advice on qt app using qt classes. can take qtnetwork , qsql modules solutions not "3rd party" tools such rabbitmq etc.

i'm using "event store queue" (see greg young page 46) cqrs event sourcing. have simple sql table storing events unique sequential id. thus, can track "event store pointer" used "chasing process".

goal: run multiple processes handle events "pop them queue" ensuring treated once....

at stage have interprocess communication via db (mysql,sqlite) , setup shared table doing ttl (time live) heard beat list. "top" process acting worker. if dies ttl times out , next 1 takes over. top worker cleans out "stale processes". has delay equal @ to the lowest degree ttl eg. 5s not optimal situation.

i allow other processes take on work. alter "top" role worker dispatcher need communication other processes give work (eg. process events 100-200). going via db dispatch not thought in terms of performance can signal event ids via qtcp** classes...not real problem. but, brings other questions mind: happens when dispatcher dies? practice 1 process play worker , dispatcher? fail-over? redundancy? scalability?

i'm sure there must simple solution without breaking head. load balancer? same questions apply. load-balancer dispatcher. seems need maintain heartbeat between processes via tcp. faster....implementing raft protocol overkill @ stage! not sure if other distributed design patterns or protocols apply. have rest framework... maybe atom? pubsubhubhub , webhooks? no websockets since need persist tcp connections...

thought, ideas, suggestions welcome!

you're trying implement queueing mechanism on top of db worth it? see scheme can not afford loosing messages, 1 time have ttl looks don't need it.

"goal: run multiple processes handle events "pop them queue" ensuring treated once." - http://www.eaipatterns.com/competingconsumers.html simple solution, each worked have running should consume way: - getting message "queue", mark retrieved consumption , can in such state defined period of time. - consume. - alter status of message in queue , (re)move it.

have workers running in different vms , collect statistics each of them implementing http://arnon.me/soa-patterns/service-watchdog/

c++ qt distributed cqrs event-sourcing

Comments

Post a Comment

Popular posts from this blog

assembly - What is the addressing mode for ld, add, and rjmp instructions? -

assembly - What is the addressing mode for ld, add, and rjmp instructions? - hey guys know ldi (load immediate) addressing mode set immediate , st instruction addressing mode set index. however, have no thought others curious are! thanks :) the addressing modes explained in instruction set, in first few pages. in table of instructions see operands instruction determine addressing mode. mode indicated arguments assembly instruction. for example, ld had several different ways of operating, depending on arguments. 1 of them ld rd,x d number of register, such ld r3,x . ld r3,-z else (although both indirect addressing). rjmp k relative addressing, jumping pc + k + 1. add rr,rd direct register addressing. result contained in rd. assembly avr instructions
Read more

vowpalwabbit - Interpreting Vowpal Wabbit results: Why are some lines appended by "h"? -

vowpalwabbit - Interpreting Vowpal Wabbit results: Why are some lines appended by "h"? - below part of log training vw model. why of these lines followed h? you'll notice that's true of "average loss" line in summary @ end. i'm not sure means, or if should care. ... average since illustration illustration current current current loss lastly counter weight label predict features 1.000000 1.000000 1 1.0 -1.0000 0.0000 15 0.500000 0.000000 2 2.0 1.0000 1.0000 15 1.250000 2.000000 4 4.0 -1.0000 1.0000 9 1.167489 1.084979 8 8.0 -1.0000 1.0000 29 1.291439 1.415389 16 16.0 1.0000 1.0000 45 1.096302 0.901166 32 32.0 -1.0000 -1.0000 21 1.299807 1.503312 64 64.0 -1.0000 1.0000 ...
Read more

Is there a way to convert an HTML page styled with Bootstrap CSS into email-compatible html? -

Is there a way to convert an HTML page styled with Bootstrap CSS into email-compatible html? - is there way convert html page styled bootstrap css html email compatible form? see there exclusively different css frameworks, ink, creating email compatible html, there flow creating email doesn't require utilize of different css framework? there html -> pdf -> email html flow? or other flow? no, couple of reasons... first, there no reliable css or html email. clients on place in terms of css back upwards & how render html, structural/semantic problem. isn't converting classes much altering html structure. as explained in this css tricks post, typical solution ol-skool techniques table-based layouts, requiring exclusively restructure existing html. have add together client-specific hacks. second, , more importantly, shouldn't send everything on existing page email. if it's newsletter subscribers, people won't read it. instead, create ...
Read more