NewDocumentReader creates reader with mongodb url

RecordDuplicatedOplog Write dup oplog in DB APPConflictDatabase

use by full sync

CheckFcv read the given file and parse the fcv do comparison

GetDbNamespace return db namespace. return: @[]NS: namespace list, e.g., []{"a.b", "a.c"} @map[string][]string: db->collection map. e.g., "a"->[]strin

IsAbort is true if the oplog entry had the abort command.

IsCommit is true if the oplog entry was an abort command or was the final entry of an unprepared transaction.

* * tunnel name */

NewBuffer initializes a transaction oplog buffer.

PurgeTxn closes any transaction streams in progress and deletes all oplog entries associated with a transaction. Must not be called concurrently with

addIntoBatchGroup isBarrier Barrier Oplogs(like DDL or Transaction) must execute sequentially and separately, send to batchGroup[0]

checkpoint calculate and update current checkpoint value. `flush` means whether force calculate & update checkpoint. if inputTs is given(> 0), use thi

sendErrAndClose is a utility for putting an error on a channel before closing.

deserializer: fetch oplog from pending queue, parsed and then add into logs queue.

Concurrency notes: We require that AddOp, GetTxnStream and PurgeTxn be called serially as part of orchestrating replay of oplog entries. The only me

ExtractInnerNs is used to extract the inner namespace of the txn PS: here only check the first inner op

ExtractInnerOps doc.applyOps[i].ts（Let ckpt use the last ts to judge complete） doc.applyOps[0 - n-1].ts = doc.ts - 1 doc.applyOps[n-1].ts = doc.ts

InitialLogger initialize logger verbose: where log goes to: 0 - file，1 - file+stdout，2 - stdout

IsFinal is true if the oplog entry is the closing entry of a transaction, i.e. if IsAbort or IsCommit is true.

var Metric *ReplicationMetric

** * write the real tunnel message to tunnel. * * return the right ACK offset value with positive number. if AckRequired is set * this ACk off

SetOplogDiskFinishTs OplogDiskQueueFinishTs and OplogDiskQueue won't take effect immediately, will be inserted in the next Update call.