How to log JSON fields?¶

When using the --log-json option, the logs will be output in JSON format with the following fields:

time: Unix time when the log entry was created.
level: Log level (“debug”, “info”, “warn”, “error”).
message: Log message, if any.
error: Error message, if any.
s: Scope of the log entry.
ns: Namespace (database.collection format).
elapsed_secs: The duration in seconds for the specific operation to complete.

Example:

{ "level": "info",
  "s": "clone",
  "ns": "db_1.coll_1",
  "elapsed_secs": 0,
  "time": "2025-02-23 11:26:03.758",
  "message": "Cloned db_1.coll_1" }

{ "level": "info",
  "s": "plm",
  "elapsed_secs": 0,
  "time": "2025-02-23 11:26:03.857",
  "message": "Change replication stopped at 1740335163.1740335163 source cluster time" }

Last update: October 8, 2025
Created: October 8, 2025