Apache Tomcat 8 Configuration Reference (8.0.21) - The ClusterManager object
Author: Filip Hanik

## The ClusterManager object

### Table of Contents

- Introduction
- The <Manager>
- Attributes
  1. Common Attributes
  2. org.apache.catalina.ha.session.DeltaManager Attributes
  3. org.apache.catalina.ha.session.BackupManager Attributes
- Nested Components

### Introduction

A cluster manager is an extension to Tomcat's session manager interface, `org.apache.catalina.Manager`. A cluster manager must implement the `org.apache.catalina.ha.ClusterManager` and is solely responsible for how the session is replicated.
There are currently two different managers, the `org.apache.catalina.ha.session.DeltaManager` replicates deltas of session data to all members in the cluster. This implementation is proven and works very well, but has a limitation as it requires the cluster members to be homogeneous, all nodes must deploy the same applications and be exact replicas. The `org.apache.catalina.ha.session.BackupManager` also replicates deltas but only to one backup node. The location of the backup node is known to all nodes in the cluster. It also supports heterogeneous deployments, so the manager knows at what locations the web application is deployed.

### The <Manager>

The `<Manager>` element defined inside the `<Cluster>` element is the template defined for all web applications that are marked `<distributable/>` in their `web.xml` file. However, you can still override the manager implementation on a per web application basis, by putting the `<Manager>` inside the `<Context>` element either in the `context.xml` file or the `server.xml` file.

### Attributes

#### Common Attributes

Attribute | Description
--- | ---
`className` |
`name` | The name of this cluster manager, the name is used to identify a session manager on a node. The name might get modified by the `Cluster` element to make it unique in the container.
`notifyListenersOnReplication` | Set to `true` if you wish to have session listeners notified when session attributes are being replicated or removed across Tomcat nodes in the cluster.
`sessionAttributeFilter` | A regular expression used to filter, which session attributes will be replicated. An attribute will only be replicated, if its name matches this pattern. If the pattern is not set (default), all attributes are eligible for replication. As an example, the value `^(userName|sessionHistory)$` will only replicate the two session attributes named `userName` and `sessionHistory`.
`maxInactiveInterval` | The initial maximum time interval, in seconds, between client requests before a session is invalidated. A negative value will result in sessions never timing out. If the attribute is not provided, a default of 1800 seconds (30 minutes) is used. This attribute provides the initial value whenever a new session is created, but the interval may be dynamically varied by a servlet via the `setMaxInactiveInterval` method of the `HttpSession` object.
`sessionIdLength` | The length of session ids created by this Manager, measured in bytes, excluding subsequent conversion to a hexadecimal string and excluding any JVM route information used for load balancing. This attribute is deprecated. Set the length on a nested SessionIdGenerator element instead.
`processExpiresFrequency` | Frequency of the session expiration, and related manager operations. Manager operations will be done once for the specified amount of backgroundProcess calls (i.e., the lower the amount, the more often the checks will occur). The minimum value is 1, and the default value is 6.
`secureRandomClass` | Name of the Java class that extends `java.security.SecureRandom` to use to generate session IDs. If not specified, the default value is `java.security.SecureRandom`.
`secureRandomProvider` | Name of the provider to use to create the `java.security.SecureRandom` instances that generate session IDs. If an invalid algorithm and/or provider is specified, the Manager will use the platform default provider and the default algorithm. If not specified, the platform default provider will be used.
`secureRandomAlgorithm` | Name of the algorithm to use to create the `java.security.SecureRandom` instances that generate session IDs. If an invalid algorithm and/or provider is specified, the Manager will use the platform default provider and the default algorithm. If not specified, the default algorithm of SHA1PRNG will be used. If the default algorithm is not supported, the platform default will be used. To specify that the platform default should be used, do not set the secureRandomProvider attribute and set this attribute to the empty string.

#### org.apache.catalina.ha.session.DeltaManager Attributes

Attribute | Description
--- | ---
`expireSessionsOnShutdown` | When a web application is being shutdown, Tomcat issues an expire call to each session to notify all the listeners. If you wish for all sessions to expire on all nodes when a shutdown occurs on one node, set this value to `true`. Default value is `false`.
`maxActiveSessions` | The maximum number of active sessions that will be created by this Manager, or -1 (the default) for no limit. For this manager, all sessions are counted as active sessions irrespective if whether or not the current node is the primary node for the session.
`notifySessionListenersOnReplication` | Set to `true` if you wish to have session listeners notified when sessions are created and expired across Tomcat nodes in the cluster.
`notifyContainerListenersOnReplication` | Set to `true` if you wish to have container listeners notified across Tomcat nodes in the cluster.
`stateTransferTimeout` | The time in seconds to wait for a session state transfer to complete from another node when a node is starting up. Default value is `60` seconds.
`sendAllSessions` | Flag whether send sessions as split blocks. If set to `true`, send all sessions as one big block. If set to `false`, send sessions as split blocks. Default value is `true`.
`sendAllSessionsSize` | The number of sessions in a session block message. This value is effective only when `sendAllSessions` is `false`. Default is `1000`.
`sendAllSessionsWaitTime` | Wait time between sending of session block messages. This value is effective only when `sendAllSessions` is `false`. Default is `2000` milliseconds.
`stateTimestampDrop` | When this node sends a `GET_ALL_SESSIONS` message to other node, all session messages that are received as a response are queued. If this attribute is set to `true`, the received session messages (except any `GET_ALL_SESSIONS` sent by other nodes) are filtered by their timestamp. A message is dropped if it is not a `GET_ALL_SESSIONS` message and its timestamp is earlier than the timestamp of our `GET_ALL_SESSIONS` message. If set to `false`, all queued session messages are handled. Default is `true`.

#### org.apache.catalina.ha.session.BackupManager Attributes

Attribute | Description
--- | ---
`mapSendOptions` | The backup manager uses a replicated map, this map is sending and receiving messages. You can setup the flag for how this map is sending messages, the default value is `6`(synchronous). Note that if you use asynchronous messaging it is possible for update messages for a session to be processed by the receiving node in a different order to the order in which they were sent.
`maxActiveSessions` | The maximum number of active sessions that will be created by this Manager, or -1 (the default) for no limit. For this manager, only sessions where the current node is the primary node for the session are considered active sessions.
`rpcTimeout` | Timeout for RPC message used for broadcast and transfer state from another map. Default value is `15000` milliseconds.
`terminateOnStartFailure` | Set to true if you wish to terminate replication map when replication map fails to start. If replication map is terminated, associated context will fail to start. If you set this attribute to false, replication map does not end. It will try to join the map membership in the heartbeat. Default value is `false` .

### Nested Components

### All Manager Implementations

All Manager implementations allow nesting of a <SessionIdGenerator> element. It defines the behavior of session id generation. All implementations of the SessionIdGenerator allow the following attributes:

Attribute | Description
--- | ---
`sessionIdLength` | The length of the session ID may be changed with the sessionIdLength attribute.

### Comments

Notice: This comments section collects your suggestions on improving documentation for Apache Tomcat.
If you have trouble and need help, read Find Help page and ask your question on the tomcat-users mailing list. Do not ask such questions here. This is not a Q&A section.
The Apache Comments System is explained here. Comments may be removed by our moderators if they are either implemented or considered invalid/off-topic.