Logging in code

LOGS IN CODE
MODEN APPLICATION
Jannarong Wadthong

1/Sept/2020

▸ Part I — Software Development and S.O.L.I.D ~ 10 mins

▸ Part II — Logs in Code ~ 30 mins

▸ Part III — Logs in Architecture ~ 15 mins

▸ Part IV — Log Framework ~ xx mins

SOFTWARE DEVELOPMENT
AND S.O.L.D
PART I

TEXT
MAINTAINABILITY CAN BE QUANTIFIED:
▸ Extensibility — how hard is it to add features

▸ Stability — how hard is it to make changes?

▸ Understandability — how hard is it for someone else to pick
up your code?

12 PRINCIPLES BEHIND THE AGILE MANIFESTO

HOW TO AVOID TECHNICAL DEBT?
▸ Avoid code smells as you go, and practice regular
refactoring. Don’t Repeat Yourself (DRY), use clear &
consistent variable & method names, practice Test Driven
Development (TDD), follow the Single Responsibility
Principle (SRP), avoid long/complex methods, and
maintain thin interfaces / don’t hard-code

▸ Conduct code reviews.

▸ Use automated testing.

PUBLIC VS INTERNAL BANKING API
▸ Transfer Money API

▸ Deposit Money API

▸ Withdrawal Money API

TEXT
PUBLIC TRANSFER MONEY FLOW
CONTROLLER ACCEPTS
REQUEST
CONTROLLER ACK BACK TO USER
CHECK BALANCE WITHDRAW DEPOSIT
CHECK
AUTHORISATION

TEXT
INTERNAL TRANSFER MONEY FLOW
CONTROLLER ACCEPTS
REQUEST
CONTROLLER ACK BACK TO USER
CHECK BALANCE WITHDRAW DEPOSIT

INTERNAL TRANSFER
void transfer(Account fromAcc, Account toAcc, int amount) throws Exception {

if (fromAcc.getBalance() < amount)

throw new InsufficientFundsException();

fromAcc.withdraw(amount);

toAcc.deposit(amount);

}

PUBLIC TRANSFER
void transfer(Account fromAcc, Account toAcc, int amount, User user) throws Exception {

if (!isUserAuthorised(user, fromAcc)) {

logger.info("User has no permission.");

throw new UnauthorisedUserException();

}

if (fromAcc.getBalance() < amount) {

logger.info("Insufficient funds.");


}



}

PUBLIC TRANSFER WITH PERFORMANCE LOGGING

long startTime = currentTime();

if (!isUserAuthorised(user, fromAcc)) {

logger.info("User has no permission.");

throw new UnauthorisedUserException();

}

if (fromAcc.getBalance() < amount) {

logger.info("Insufficient funds.");


}



long endTime = currentTime();

logger.info("Execution time:" + (endTime - startTime);

}

TEXT
WITHDRAW MONEY
CONTROLLER
CHECK BALANCE
DO WITHDRAW
CHECK AUTHORISATION
CONTROLLER
CHECK BALANCE
DO WITHDRAW
START TIME
END TIME
START TIME
END TIME

TEXT
DEPOSIT MONEY
CONTROLLER
DO DEPOSIT
CHECK AUTHORISATION
CONTROLLER
DO DEPOSIT
START TIME
END TIME
START TIME
END TIME

TEXT
TRANSFER MONEY
CONTROLLER
CHECK BALANCE
WITHDRAW
CHECK AUTHORISATION
DEPOSIT
START TIME
END TIME
CONTROLLER
CHECK BALANCE
WITHDRAW
DEPOSIT
START TIME
END TIME

TEXT
WITHDRAW MONEY
CONTROLLER
CHECK BALANCE
DO WITHDRAW
CHECK AUTHORISATION
CONTROLLER
CHECK BALANCE
DO WITHDRAW
START TIME
END TIME
START TIME
END TIME
DO WITHDRAW

TEXT
DEPOSIT MONEY
CONTROLLER
DO DEPOSIT
CHECK AUTHORISATION
CONTROLLER
DO DEPOSIT
START TIME
END TIME
START TIME
END TIME
DO DEPOSIT

ALL PUBLIC API
WITHDRAW
CONTROLLER
CHECK BALANCE
DO WITHDRAW
CHECK AUTHORISATION
START TIME
END TIME
CONTROLLER
CHECK BALANCE
DO WITHDRAW
CHECK AUTHORISATION
START TIME
END TIME
CONTROLLER
DO DEPOSIT
CHECK AUTHORISATION
START TIME
END TIME
CONTROLLER
CHECK BALANCE
WITHDRAW
CHECK AUTHORISATION
DEPOSIT
START TIME
END TIME
DEPOSIT TRANSFER

ALL PUBLIC API
WITHDRAW
CONTROLLER
CHECK BALANCE
DO WITHDRAW
CHECK AUTHORISATION
START TIME
END TIME
CONTROLLER
CHECK BALANCE
DO WITHDRAW
CHECK AUTHORISATION
START TIME
END TIME
CONTROLLER
DO DEPOSIT
CHECK AUTHORISATION
START TIME
END TIME
CONTROLLER
CHECK BALANCE
WITHDRAW
CHECK AUTHORISATION
DEPOSIT
START TIME
END TIME
DEPOSIT TRANSFER
PERFORMANCE LOGGING CONCERN

ALL PUBLIC API
WITHDRAW
CONTROLLER
CHECK BALANCE
DO WITHDRAW
CHECK AUTHORISATION
START TIME
END TIME
CONTROLLER
CHECK BALANCE
DO WITHDRAW
CHECK AUTHORISATION
START TIME
END TIME
CONTROLLER
DO DEPOSIT
CHECK AUTHORISATION
START TIME
END TIME
CONTROLLER
CHECK BALANCE
WITHDRAW
CHECK AUTHORISATION
DEPOSIT
START TIME
END TIME
DEPOSIT TRANSFER
PERFORMANCE LOGGING CONCERN SECURITY CONCERN

CODE TANGLING AND CODE SCATTERING
WITHDRAW
CONTROLLER
CHECK BALANCE
DO WITHDRAW
CHECK AUTHORISATION
START TIME
END TIME
CONTROLLER
CHECK BALANCE
DO WITHDRAW
CHECK AUTHORISATION
START TIME
END TIME
CONTROLLER
DO DEPOSIT
CHECK AUTHORISATION
START TIME
END TIME
CONTROLLER
CHECK BALANCE
WITHDRAW
CHECK AUTHORISATION
DEPOSIT
START TIME
END TIME
DEPOSIT TRANSFER
PERFORMANCE LOGGING CONCERN SECURITY CONCERN

CODE TANGLING AND CODE SCATTERING
WITHDRAW
CONTROLLER
CHECK BALANCE
DO WITHDRAW
CONTROLLER
CHECK BALANCE
DO WITHDRAW
CONTROLLER
DO DEPOSIT
CONTROLLER
CHECK BALANCE
WITHDRAW
DEPOSIT
DEPOSIT TRANSFER
PERFORMANCE LOGGING ASPECT SECURITY ASPECT

WE WANT THIS
@LogExecutionTime

@Authorize


checkBalance(fromAcc);



}

TEXT
AOP IMPLEMENTATION: DYNAMIC PROXY
@Aspect
 
Performance Logging Proxy

1.start time

2.end time
ATMController Target Service
+ transfer()

+ withdraw()

+ deposit()
As you can see from that diagram, the proxy has one job.
• Opening and closing times.
• And then delegating to the real target service, the one we wrote.
• And ATMController will never know that they are talking to a proxy, and not the real thing.
2 MARKERS: @BEFORE AND @AFTER
OR 1 MARKER: @AROUND

TEXT
AOP IMPLEMENTATION
@Aspect
 
Authorisation Proxy

1.check if user is valid

ATMController Real ATMService
+ transfer()

+ withdraw()

+ deposit()
1 MARKER: @BEFORE

TEXT
ASPECT
@Aspect
public class PerformanceAspect {
@Around("@annotation(LogExecutionTime)")
public Object logExecutionTime(ProceedingJoinPoint joinPoint) throws Throwable {
long start = System.currentTimeMillis();
Object proceed = joinPoint.proceed();
long executionTime = System.currentTimeMillis() - start;
log.info(joinPoint.getSignature() + " executed in " + executionTime + "ms");
return proceed;
}
}

This slide is intentionally left blank :)

TEXT
LOGS IN ACTION
▸ Troubleshooting

▸ Law

▸ User behaviours

TEXT
PUBLIC TRANSFER MONEY FLOW

TEXT
LOG FRAMEWORK: IMPLEMENTATION
LOG
HARDDISK
STOUT REST API
DATABASE
TEXT FILE
PROMETHEUS GRAFANA

SUMMARY
Begin/End Transaction

Transaction Error Hand

Logging in code

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