[Bug Report]The destruction process in sync is asynchronous, leading to the lock file being locked when the sync is triggered.

[jackzhhuang]

Bug Report

In sync, when the block fetcher tries to get a block from the remote, if it fails and the retry time gets over limit, the sync process will end in failure and sends a notification to clear the state of sync. But this action is asynchronous, if the sync is triggered, for example, a new block notification comes, the sync will try restart. At this moment, the release of last sync process is not done, making the new process fails at trying to lock the sync database file.

To solve this, the handle of the sync database should be held by the sync service not the thread of sync.

Starcoin version:

Current behavior:

Expected behavior:

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