This is a tool for automatic replication of documents from one MongoDB cluster to another.

• -s, --source: Connection string for source server or cluster. Required.
• -d, --destination: Connection string for destination server or cluster. Required.
• -c, --config: YAML file with configuration. Required.
• -r, --runs: How many transition cycles should tool do. Zero value will result in infinite cycle. Default: 0.
• --verbose: Log debug information into console.
• --dry: Run tool without inserting or updating records.
• --logs: Directory for storing logs. By default they will be stored in current directory.
• -n, --notify: Notification interval in seconds. Default: 3.
• -w, --workers: Degree of parallelization for inserts, value is amount per each CPU (core). Default: 4.
• -b, --batchSize: Batch size for insertion. Default: 1000.

YAML config file contains array of settings for each collection to be transferred.

Example:

- name: TestCollection
  database: Test
  iterativeOptions:
    field: LastModified
    forcedCheckpoint: 2021-03-15T16:00:00.894Z
    offsetInMinutes: 60
  shardKey:
    fields:
    - UserId
    - _id
    fromDestination: false
  noUpsert: false

Description:

• name: collection name.
• database: database name.
• iterativeOptions: options for iterative transfer, i.e. when tool transfer data only from last known point-in-time.
  • field: name of the field, which contains checkpoint (version) value. Currently only UTC date values are supported.
  • forcedCheckpoint: option for making a transfer from specified point in time.
  • offsetInMinutes: time offset that is subtracted from last checkpoint value.
• shardKey: options dedicated to work with sharded cluster.
  • fields: an array of keys, that should be included in update filter. Useful when you restore collection with some unique index or a sharded collection.
  • fromDestination: when performing an upsert, load values for update filter not from source, but from destination. Useful when you are changing you shard key value - if not specified, it will cause duplicate key exception, cause it won't find document with new keys and perform insertion. WARNING: currently this behavior is not supported.
• noUpsert: disable upsert and perform regular update.