An oplog based realtime sync tool for MongoDB written in Go.
Source should be a replica set and destination could be a mongod/mongos instance or member of replica set.

• initial sync including collections and indexes
• oplog based increment sync
• concurrent oplog replaying

• the following databases are ignored: 'admin', 'local'
• collections that starts with 'system.' are ignored, e.g.: 'system.users', 'system.profile'

# ./go-mongo-sync --help
Usage of ./go-mongo-sync:
  -from="": source, a member of replica-set, value should be a hostportstr like 'host:port'
  -to="": destination, a mongos or mongod instance, value should be a hostportstr like 'host:port'
  -ignore-index=false: not create index for collections
  -oplog=false: replay oplog only
  -upsert=false: upsert documents in initial sync, insert documents if not set

• support authentication for source and destination
• specify startOptime in '--oplog' mode