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mongosync States
mongosync enters different states depending on the requests it
receives. mongosync can only be in a single state at a given time.
The current mongosync states determines which API operations you can
run.
This page describes mongosync states.
View the Current State
To view the current state of mongosync, use the /progress. endpoint. The /progress
endpoint returns the state in the state field.
State Descriptions
The following table describes each state and lists the permitted operations in that state.
State | Description | Possible API Operations |
|---|---|---|
| mongosync is initialized and ready for a sync job to
begin. | |
RUNNING | The sync process is currently running. In this state, data is
initially synced to the destination cluster. Subsequent writes to
the source cluster are applied to the destination cluster. | |
PAUSED | The sync process is paused. To resume the sync process, send a
request to the /resume endpoint. | |
| The cutover for the sync process has started. The time it takes
to transition to the COMMITTED phase depends on
lagTimeSeconds. To monitor lagTimeSeconds or to see if
mongosync has finished committing, use the /progress endpoint. |
|
COMMITTED | The cutover for the sync process is complete. |
|
Read Operations
Read operations on the source cluster are always permitted.
When the /progress endpoint reports canWrite is true, the
data on the source and destination clusters is consistent.
Write Operations
To see what state mongosync is in, call the /progress API endpoint. The /progress output includes a
boolean value, canWrite.
When
canWriteistrue, it is safe to write to the destination cluster.When
canWriteisfalse, do not write to the destination cluster.
You can safely write to the source cluster while mongosync is
syncing. Do not write to the destination cluster unless canWrite is
true.
Write-blocking
When write-blocking is enabled, mongosync blocks writes:
On the destination cluster during sync
On the source cluster while committing
To enable write-blocking, use the start API
to set enableUserWriteBlocking to true. You cannot enable
write-blocking after the sync starts.
To set enableUserWriteBlocking, the mongosync user must have a
role that includes the setUserWriteBlockMode and
bypassWriteBlockingMode ActionTypes.
Note
When using enableUserWriteBlocking, writes are only blocked for users
that do not have the bypassWriteBlockingMode ActionType. Users
who have this ActionType are able to perform writes.