Realm Sync Configuration Files

On this page

Partition-Based Sync Configuration

Flexible Sync Configuration

You can configure Realm sync for your application in the sync directory:

app/
└── sync/
    └── config.json

Partition-Based Sync Configuration

When you use Partition-Based Sync, your Realm app uses this Sync configuration:

sync/config.json

{
  "state": <"enabled" | "disabled">,
  "development_mode_enabled": <Boolean>,
  "service_name": "<Data Source Name>",
  "database_name": "<Development Mode Database Name>",
  "partition": {
    "key": "<Partition Key Field Name>",
    "type": "<Partition Key Type>",
    "permissions": {
      "read": { <JSON Expression> },
      "write": { <JSON Expression> }
    }
  },
  "last_disabled": <Number>,
  "client_max_offline_days": <Number>
}

Field	Description
`state` String	The current state of the sync protocol for the application. Valid Options: `"enabled"` `"disabled"`
`service_name` String	The name of the MongoDB data source to sync. You cannot use sync with a serverless instance or data lake.
`development_mode_enabled` Boolean	If `true`, Development Mode is enabled for the application. While enabled, Realm automatically stores synced objects in a specific database (specified in `database_name`) and mirrors objects types in that database's collection schemas.
`database_name` String	The name of a database in the synced cluster where Realm stores data in Development Mode. Realm automatically generates a schema for each synced type and maps each object type to a collection within the database.
`partition.key` String	The field name of your app's partition key. This field must be defined in the schema for object types that you want to sync.
`partition.type` String	The value type of the partition key field. This must match the type defined in the object schema. Valid Options: `"string"` `"objectId"` `"long"`
`partition.permissions.read` JSON Expression	An expression that evaluates to `true` when a user has permission to read objects in a partition. If the expression evaluates to `false`, Realm does not allow the user to read an object or its properties.
`partition.permissions.write` JSON Expression	An expression that evaluates to `true` when a user has permission to write objects in a partition. If the expression evaluates to `false`, Realm does not allow the user to modify an object or its properties. Write permission requires read permission. A user cannot write to a document that they cannot read.
`last_disabled` Number	The date and time that sync was last paused or disabled, represented by the number of seconds since the Unix epoch (January 1, 1970, 00:00:00 UTC).
`client_max_offline_days` Number	Controls how long the backend compaction process waits before aggressively pruning metadata that some clients require to synchronize from an old version of a realm.

Flexible Sync Configuration

When you use Flexible Sync, your Realm app uses this Sync configuration:

sync/config.json

{
  "type": "flexible",
  "development_mode_enabled": <Boolean>,
  "service_name": "<Data Source Name>",
  "database_name": "<Development Mode Database Name>",
  "state": <"enabled" | "disabled">,
  "permissions": {
    "rules": {
      "<Collection Name>": [
        {
          "name": <String>,
          "applyWhen": { <JSON Expression> },
          "read": { <JSON Expression> },
          "write": { <JSON Expression> }
        }
      ]
    },
    "defaultRoles": [
      {
        "name": <String>,
        "applyWhen": { <JSON Expression> },
        "read": <JSON Expression>,
        "write": <JSON Expression>
      }
    ]
  },
  "queryable_fields_names": [
    <Array of String Field Names>
  ]
}

Field	Description
`type` String	The Sync Mode for the application. Valid Options: `"flexible"`
`development_mode_enabled` Boolean	If `true`, Development Mode is enabled for the application. While enabled, Realm automatically stores synced objects in a specific database (specified in `database_name`) and mirrors objects types in that database's collection schemas.
`service_name` String	The name of the Atlas cluster data source to sync. You cannot use sync with a serverless instance.
`database_name` String	The name of a database in the synced cluster where Realm stores data in Development Mode. Realm automatically generates a schema for each synced type and maps each object type to a collection within the database.
`state` String	The current state of the Sync protocol for the application. Valid Options: `"enabled"` `"disabled"`
`permissions.rules.<Coll>` String	You can define rules that apply to a single collection by specifying the collection name. Realm apps apply rules in order from the beginning of the array, so start with the most specific rules first.
`rules.<Coll>.name` String	The name of the specific rule in the rules array. You might use a descriptive name to make it easier to parse the rules, such as "adminReadWrite" or "employeeReadOnly".
`rules.<Coll>.applyWhen` JSON Expression	An expression that evaluates to `true` when the rule should be applied. An example might be `{"%%user.custom_data.isGlobalAdmin": true}`. This reads the value of the `isGlobalAdmin` bool from the user's custom data, and applies the rule when the value of this bool is `true`.
`rules.<Coll>.read` JSON Expression	An expression that evaluates to `true` when a user has permission to read objects in the collection. If the expression evaluates to `false`, Realm does not allow the user to read an object or its properties.
`rules.<Coll>.write` JSON Expression	An expression that evaluates to `true` when a user has permission to write objects in the collection. If the expression evaluates to `false`, Realm does not allow the user to modify an object or its properties. Write permission requires read permission. A user cannot write to a document that they cannot read.
`permissions.defaultRoles` String	Your Realm app evaluates `defaultRoles` after `rules`. If no collection-specific rule applies to a user's attempt to access data through a Realm app, Realm proceeds to evaluate `defaultRoles` until it finds a set of permissions that apply to the user. This may occur when a collection does not have a specific set of rules defined, or when none of the rules defined for a collection apply to a user. You can have more than one `defaultRole`, and they apply across all the collections that your Realm app can access, even when you have more specific collection rules defined.
`defaultRoles.name` String	The name of the specific role in the defaultRoles array. You might use a descriptive name to make it easier to parse the roles, such as "adminReadWrite" or "employeeReadOnly".
`defaultRoles.applyWhen` JSON Expression	An expression that evaluates to `true` when the role should be applied. An example might be `{"%%user.custom_data.isGlobalAdmin": true}`. This reads the value of the `isGlobalAdmin` bool from the user's custom data, and applies the role when the value of this bool is `true`.
`defaultRoles.read` JSON Expression	An expression that evaluates to `true` when a user has permission to read objects in the collection. If the expression evaluates to `false`, Realm does not allow the user to read an object or its properties.
`defaultRoles.write` JSON Expression	An expression that evaluates to `true` when a user has permission to write objects in the collection. If the expression evaluates to `false`, Realm does not allow the user to modify an object or its properties.
`queryable_fields_names` Array of Strings	The names of the fields that your client application can query to determine which data to synchronize.
`last_disabled` Number	The date and time that sync was last paused or disabled, represented by the number of seconds since the Unix epoch (January 1, 1970, 00:00:00 UTC).
`client_max_offline_days` Number	Controls how long the backend compaction process waits before aggressively pruning metadata that some clients require to synchronize from an old version of a realm.

← MongoDB Data Source Configuration Files Function Configuration Files →