- Introduced a `fastRecovery` flag in the Raft structure and configuration to enable fast recovery mode.
- Updated `NewRaft` to initialize `fastRecovery` from the configuration.
- Added `persistCommitIndex` function to store the commit index when fast recovery is enabled.
- Modified `processLogs` to persist the commit index before updating `lastApplied`.
- Documented the `FastRecovery` option in the config.

- Implemented `recoverFromCommitedLogs` function to recover the Raft node from committed logs.
- If `fastRecovery` is enabled and the log store implements `CommitTrackingLogStore`, the commit index is read from the store, avoiding the need to replay logs.
- Logs between the last applied and commit index are fed into the FSM for faster recovery.

…ency

- Refactor `ReadCommitIndex` to `GetCommitIndex` across `LogStore` and `InmemCommitTrackingStore`.
- Introduce `InmemCommitTrackingStore` to track commit index in memory for testing purposes.
- Add locking mechanism to safely read/write commit index in `InmemCommitTrackingStore`.

…m persist store

…ntil the next StoreLogs call and then write it out on disk along with the log data.

…mmittedLogs`

- Implemented commit tracking logs in the Raft cluster configuration.
- Added tests for restoring snapshots on startup with commit tracking logs.
- Introduced a fast recovery test to ensure logs are applied correctly after restart.
- Updated `MakeClusterOpts` to include `CommitTrackingLogs` option.

…tore implement

Updated the function name from `persistCommitIndex` to `tryPersistCommitIndex` to better reflect its behavior. This function now updates the commit index in the persistent store only if fast recovery is enabled and if the log store implements `CommitTrackingLogStore`. Adjusted references to this function in `dispatchLogs` and `appendEntries`.

…clarity

…ence

- Rename SetCommitIndex to StagCommitIndex in CommitTrackingLogStore interface
- Add detailed documentation for StagCommitIndex method
- Update raft.go to use StagCommitIndex instead of SetCommitIndex
- Optimize commit index staging in appendEntries using min(lastNewIndex, leaderCommitIndex)

This change ensures commit index updates are only persisted atomically
with the following StoreLogs call, preventing inconsistencies between the
commit index and log entries in case of crashes. It also optimizes the
staged commit index to be as up-to-date as possible without exceeding the
last new entry index, reducing commit index lag in the CommitTrackingStore.
The contract for implementations is clarified, specifying that GetCommitIndex
must never return a value higher than the last index in the log.

- Rename SetCommitIndex to StageCommitIndex in InmemCommitTrackingStore
- Fix typo in CommitTrackingLogStore interface (StagCommitIndex to StageCommitIndex)
- Update error message in tryStageCommitIndex for consistency
- Ensure CommitTrackingLogStore extends LogStore interface

…idation

- Add error logging and panic for critical errors during recovery
- Replace lastApplied check with lastIndex comparison
- Ensure commitIndex does not exceed lastIndex
- Improve code structure and readability

…type

This commit adds a compile-time interface check for InmemCommitTrackingStore
to ensure it implements the CommitTrackingLogStore interface. It also changes
the return type of NewInmemCommitTrackingStore to be more specific.

- Add interface check: var _ CommitTrackingLogStore = &InmemCommitTrackingStore{}
- Change NewInmemCommitTrackingStore return type from CommitTrackingLogStore to *InmemCommitTrackingStore

This commit enhances the type assertion for CommitTrackingLogStore in the
TestRaft_FastRecovery function, adding explicit error handling for better
test reliability and clarity.

- Add explicit type assertion check for CommitTrackingLogStore interface
- Introduce new variable 'store' to hold the asserted CommitTrackingLogStore
- Add error handling to fail the test if the type assertion is unsuccessful

This commit adds a warning log message when fast recovery is enabled but
the log store does not support the CommitTrackingLogStore interface. This
provides better visibility into potential configuration issues.

- Add warning log in recoverFromCommittedLogs when log store doesn't
  implement CommitTrackingLogStore
- Include the type of the log store in the warning message for easier debugging

This commit renames the FastRecovery feature to RestoreCommittedLogs for
better clarity and consistency. This is a breaking change as it modifies
public API elements.

- Rename Config.FastRecovery to Config.RestoreCommittedLogs
- Rename Raft.fastRecovery to Raft.RestoreCommittedLogs
- Update all references to fastRecovery in the codebase
- Rename TestRaft_FastRecovery to TestRaft_RestoreCommittedLogs
- Update comments to reflect the new terminology
- Refactor tryStageCommitIndex to accept commitIndex as a parameter

BREAKING CHANGE: Config.FastRecovery has been renamed to Config.RestoreCommittedLogs

…ed comments

- Add a notice in the Config struct documentation for RestoreCommittedLogs
- Specify that Raft will fail to start with ErrIncompatibleLogStore if the
  requirement is not met

- Update makeCluster to return (*cluster, error)
- Modify MakeCluster, MakeClusterNoBootstrap, and MakeClusterCustom to return error
- Update all test cases to handle potential errors from cluster creation
- Replace t.Fatalf() calls with t.Logf() and error returns in makeCluster

BREAKING CHANGE: MakeCluster, MakeClusterNoBootstrap, and MakeClusterCustom
now return an additional error value, which needs to be handled in existing tests.

This reverts commit cfffcb5.

- Add PropagateError option to MakeClusterOpts
- Update makeCluster to return (*cluster, error)
- Modify MakeCluster, MakeClusterNo

…face

- Specify that GetCommitIndex should not return a value higher than the last
  index in the log
- Clarify that if a higher value is returned, the last index in the log will
  be used instead
- Add instruction to return (0, nil) when no commit index is found in the
  log store