ZooKeeper provides Access Control to its data via an Access Control List (ACL) mechanism. When data is written to ZooKeeper, NiFi will provide an ACL that indicates that any user is allowed to have full permissions to the data, or an ACL that indicates that only the user that created the data is allowed to access the data. Which ACL is used depends on the value of the Access Control property for the ZooKeeperStateProvider (see the Configuring State Providers section for more information).

In order to use an ACL that indicates that only the Creator is allowed to access the data, we need to tell ZooKeeper who the Creator is. There are two mechanisms for accomplishing this. The first mechanism is to provide authentication using Kerberos. See Kerberizing NiFi's ZooKeeper Client for more information.

The second option is to use a user name and password. This is configured by specifying a value for the Username and a value for the Password properties for the ZooKeeperStateProvider (see the Configuring State Providers section for more information). The important thing to keep in mind here, though, is that ZooKeeper will pass around the password in plain text. This means that using a user name and password should not be used unless ZooKeeper is running on localhost as a one-instance cluster, or if communications with ZooKeeper occur only over encrypted communications, such as a VPN or an SSL connection. ZooKeeper will be providing support for SSL connections in version 3.5.0.