This feature is available in SDK version 4.12.0 and later.
This feature works fully with with DQL Strict Mode disabled. DQL_STRICT_MODE=falseRead more about STRICT MODE and upcoming v5 behavior
The system:data_sync_info collection provides real-time information about synchronization status between your device and other peers in the Ditto mesh network.

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What You Can Monitor

  • Connection status with peers and cloud servers
  • Sync progress using commit IDs
  • Last update timing from each peer

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Document Structure

Each document in system:data_sync_info represents one peer connection: 
{
  "_id": "peer-123",
  "is_ditto_server": true,
  "documents": {
    "sync_session_status": "Connected",
    "synced_up_to_local_commit_id": 1500,
    "last_update_received_time": 1703123456
  }
}

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Key Fields

  • _id - Unique peer identifier
  • is_ditto_server - true for cloud servers, false for other devices
  • sync_session_status - "Connected", "Not Connected", or "Disabled"
  • synced_up_to_local_commit_id - Latest commit ID synced to this peer
  • last_update_received_time - Unix timestamp of last data received

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Basic Queries

The examples in this document assume DQL Strict Mode is disabled.If DQL Strict Mode is enabled the collection definition must be provided.COLLECTION system:data_sync_info (documents MAP)Read more about STRICT MODE and upcoming v5 behavior

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Get All Peers

SELECT * FROM system:data_sync_info

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Get Only Cloud Servers

SELECT * FROM system:data_sync_info WHERE is_ditto_server = true

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Get Connected Peers Only

SELECT * FROM system:data_sync_info WHERE documents.sync_session_status = 'Connected'

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Get Specific Fields

SELECT _id, documents.sync_session_status, documents.synced_up_to_local_commit_id 
FROM system:data_sync_info

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Example in Code

// Get all sync info
let result = try await ditto.store.execute(
  query: "SELECT * FROM system:data_sync_info"
)

result.items.forEach { item in
  let peer = item.value
  let status = (peer["documents"] as? [String: Any])?["sync_session_status"] as? String ?? "Unknown"
  print("Peer \(peer["_id"] ?? ""): \(status)")
}

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Observing Changes

Observers on system:data_sync_info result in the callback triggering every 500ms even when the result remains the same. This frequency can be configured using the live_query_system_collection_refresh_interval system parameter.
Use registerObserver to monitor sync status changes in real-time: 
let observer = ditto.store.registerObserver(
  query: "SELECT * FROM system:data_sync_info"
) { result in
  result.items.forEach { item in
    let peer = item.value
    let status = (peer["documents"] as? [String: Any])?["sync_session_status"] as? String ?? "Unknown"
    print("Peer \(peer["_id"] ?? ""): \(status)")
  }
}

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Using Commit IDs

Every data modification returns a commit ID that you can use to track sync progress: 
// Every mutation returns a commit ID
let result = try await ditto.store.execute(
  query: "UPDATE cars SET color = 'blue' WHERE _id = '123'"
)
print("Commit ID: \(result.commitID ?? -1)")
Compare this commit ID with synced_up_to_local_commit_id to see if a peer has received your change.

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Important Notes

Sync status information is local-only and never synchronizes between peers. Each peer maintains its own view of sync status.
  • Commit IDs are monotonic (always increasing) but not necessarily sequential
  • Multiple cloud servers may appear due to load balancing or failover
  • Local-only data - this collection exists only on your device
  • Minimal performance impact - observing sync status is lightweight

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Supported APIs

API/FeatureIndex Support
execute SDK API✅ Supported
registerObserver SDK API✅ Supported
registerSubscription SDK API❌ Not Supported
Big Peer HTTP API❌ Not Supported
SDKs with in-memory storage (e.g. web browser)❌ Not Supported