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> Note that GET requests should be side-effect free. Not quite. If a GET request is side-effect free then it won't be logged (since that is a side effect). GE

• nybble41 5y ago
  Logging is stateful, though the state usually isn't observable via HTTP requests. Of course the same is true of the light bulb, unless another API is provided to read its status, and a similar API could be provided for the log files. Or a script could toggle a light bulb in response to the logging. Perhaps a better way to express this is that user agents are permitted to turn one GET request into N GET requests (N >= 1), and can also issue GET requests without user interaction (e.g. for preloading). When this happens the system should still meet its (customer / end-user) requirements. The requirements related to logging are that every request is logged, so it makes sense to record each GET request separately. The requirements for the light bulb are that one user interaction (not one GET request) equals one state change, so updating the state in response to each GET request doesn't meet the requirements. Even if the API were explicitly "turn on" or "turn off" rather than "toggle" you still wouldn't want the state to be affected by preloading, and you could get odd results if opposing requests were repeated (interleaved).