RaftStorage: add method get_log_state() -> Result<(Option<LogId>, Option<LogId>, StorageError> to return the first and last log id in the store

[drmingdrmer]

RaftStorage: add method get_log_state() -> Result<(Option<LogId>, Option<LogId>, StorageError> to return the first and last log id in the store.

Then remove first_id_in_log() and last_id_in_log().

This way to simplify the trait API users need to impl.

openraft/openraft/src/storage.rs

Lines 173 to 180 in 9b00e7c

	async fn first_id_in_log(&self) -> Result<Option<LogId>, StorageError>;
	async fn first_known_log_id(&self) -> Result<LogId, StorageError>;
	/// Returns the last log id in log.
	///
	/// The impl should not consider the applied log id in state machine.
	async fn last_id_in_log(&self) -> Result<LogId, StorageError>;

[github-actions]

👋 Thanks for opening this issue!

Get help or engage by:

• /help : to print help messages.
• /assignme : to assign this issue to you.

[YangKian]

/assignme

[YangKian]

Hi, I have a question, the old last_id_in_log method will return a LogId，not an Option<LogId>, but the new one we should return an Option. I found I need to call unwrap_or_default() every time I want to get the last_log_id. Shall we replace the return type of get_log_state method to Result<(Option<LogId>, LogId), StorageError> ? @drmingdrmer

[drmingdrmer]

There are some corner cases with using LogId for last_log_id.
E.g., when there is no log at all, using LogId, it returns (0,0), which will confuse the caller.

• unwrap() everywhere, for now, is not a big deal. As soon as the main branch merges Make last_log_id an Option<LogId>, or it can not express an uninitialized state #49 , it will work smoothly altogether.

[YangKian]

get~ thanks XD

[Veeupup]

@YangKian hi, this issue may have a strong connection with #49 , it seems difficult to finish each one alone, so do you want to combine these two issues into one pr to fix them or any other advice?

[YangKian]

@Veeupup Sorry for the late reply. Is it blocking something on your side? It seems to be working fine on my side, at least the tests passed after the changes were made, if I'm not missing something. I'll fill the pr later, and if my side is blocking your progress, it's ok to leave it to me XD

[Veeupup]

@YangKian yeah, u can finish it later. from my side, it will make nonsense if last_id_in_log() and some function return LogId ranther than Option<LogId>.

[YangKian]

@Veeupup Ok, let me handle it~