Steps of addEntry (bookie side)

When a client adds an entry to a ledger, it sends requests to write that entry to all bookies in a quorum. Once the request reaches the bookie, the bookie processes it as follows:

1. It checks that the master password matches. If not, the operation is not executed;
2. It adds the entry to the transaction log (log device of the bookie);
3. It adds the entry identifier to the ledger index cache. This is a memory operation;
4. It queues the entry and flushes the entries in the queue in batches to make the writes more efficient. Such writes are asynchronous, and a response to the client is not dependent upon success of the ledger device write.