X
XXX +------Projection------+
X Balance View| Balance Sheet |
XXXXXXX <-----------+"XX1"-------------1400+<-------------+
X |"XX2"-------------2333| |
X | | |
XXX +----------------------+ |
XX XX |
XX XX +-----------+ |
X X |Deposit |
| |
+ | |
| | |
| | |
| | |
|Withdraw v |
| +------Bus/Handler-----+ |
| | | |
+---------------->+ Account Handler | |New Events
| | |
+--+----------------+--+ |
^ | |
| | |
| | |
Event Stream| |New Events |
| | |
| | |
| | |
| | |
| v |
+-----+---Event-Store--+-----+ |
|AccountCredited "XX1", 1000 | |
|AccountCredited "XX5", 2000 | |
|AccountDebited "XX1", 300 | |
|AccountCredited "XX1", 100 +-----------+
|AccountDebited "XX1", 200 |
|AccountCredited "XX5", 333 |
|............................|
+----------------------------+
Sample event store saves events into dictionary. Nice features:
- Saves events
- Loads event stream
- Provides events for projection
Event store does not publish events - projections need to poll for new events themselves
Command Handler and Command Bus as one thing for the sake of simplicity. Nice features:
- Deposits money
- Withdraws money
Projection which downloads new events from Event Store and updates balance documents. Nice features:
- Provides with balances of all the accounts
- Checks event store for update per your request
Run app with Python 3 to perform example operations with accounts and print balances
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