The Apache Tomcat Servlet/JSP Container

Apache Tomcat 7

Version 7.0.26, Feb 23 2012
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The Manager Component

Table of Contents
Introduction

The Manager element represents the session manager that will be used to create and maintain HTTP sessions as requested by the associated web application.

A Manager element MAY be nested inside a Context component. If it is not included, a default Manager configuration will be created automatically, which is sufficient for most requirements, — see Standard Manager Implementation below for the details of this configuration.

Attributes
Common Attributes

All implementations of Manager support the following attributes:

AttributeDescription
className

Java class name of the implementation to use. This class must implement the org.apache.catalina.Manager interface. If not specified, the standard value (defined below) will be used.

distributable

Set to true to ask the session manager to enforce the restrictions described in the Servlet Specification on distributable applications (primarily, this would mean that all session attributes must implement java.io.Serializable). Set to false (the default) to not enforce these restrictions.

NOTE - The value for this property is inherited automatically based on the presence or absence of the <distributable> element in the web application deployment descriptor (/WEB-INF/web.xml).

maxActiveSessions

The maximum number of active sessions that will be created by this Manager, or -1 (the default) for no limit.

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 60 seconds 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. The default is 16.

Standard Implementation

Tomcat provides two standard implementations of Manager for use — the default one stores active sessions, while the optional one stores active sessions that have been swapped out (in addition to saving sessions across a restart of Tomcat) in a storage location that is selected via the use of an appropriate Store nested element.

Standard Manager Implementation

The standard implementation of Manager is org.apache.catalina.session.StandardManager. It supports the following additional attributes (in addition to the common attributes listed above):

AttributeDescription
pathname

Absolute or relative (to the work directory for this Context) pathname of the file in which session state will be preserved across application restarts, if possible. The default is "SESSIONS.ser".
See Persistence Across Restarts for more information. This persistence may be disabled by setting this attribute to an empty string.

processExpiresFrequency

Frequency of the session expiration, and related manager operations. Manager operations will be done once for the specified amount of backgrondProcess 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.

Persistent Manager Implementation

NOTE: You must set either the org.apache.catalina.session.StandardSession.ACTIVITY_CHECK or org.apache.catalina.STRICT_SERVLET_COMPLIANCE system properties to true for the persistent manager to work correctly.

The persistent implementation of Manager is org.apache.catalina.session.PersistentManager. In addition to the usual operations of creating and deleting sessions, a PersistentManager has the capability to swap active (but idle) sessions out to a persistent storage mechanism, as well as to save all sessions across a normal restart of Tomcat. The actual persistent storage mechanism used is selected by your choice of a Store element nested inside the Manager element - this is required for use of PersistentManager.

This implementation of Manager supports the following attributes in addition to the Common Attributes described earlier.

AttributeDescription
className

It has the same meaning as described in the Common Attributes above. You must specify org.apache.catalina.session.PersistentManager to use this manager implementation.

maxIdleBackup

The time interval (in seconds) since the last access to a session before it is eligible for being persisted to the session store, or -1 to disable this feature. By default, this feature is disabled.

maxIdleSwap

The time interval (in seconds) since the last access to a session before it should be persisted to the session store, and passivated out of the server's memory, or -1 to disable this feature. If this feature is enabled, the time interval specified here should be equal to or longer than the value specified for maxIdleBackup. By default, this feature is disabled.

minIdleSwap

The time interval (in seconds) since the last access to a session before it will be eligible to be persisted to the session store, and passivated out of the server's memory, or -1 for this swapping to be available at any time. If specified, this value should be less than that specified by maxIdleSwap. By default, this value is set to -1.

processExpiresFrequency

It is the same as described above for the org.apache.catalina.session.StandardManager class.

saveOnRestart

Should all sessions be persisted and reloaded when Tomcat is shut down and restarted (or when this application is reloaded)? By default, this attribute is set to true.

secureRandomClass

It is the same as described above for the org.apache.catalina.session.StandardManager class.

secureRandomProvider

It is the same as described above for the org.apache.catalina.session.StandardManager class.

secureRandomAlgorithm

It is the same as described above for the org.apache.catalina.session.StandardManager class.

In order to successfully use a PersistentManager, you must nest inside it a <Store> element, as described below.

Nested Components

Standard Manager Implementation

If you are using the Standard Manager Implementation as described above, no elements may be nested inside your <Manager> element.

Persistent Manager Implementation

If you are using the Persistent Manager Implementation as described above, you MUST nest a <Store> element inside, which defines the characteristics of the persistent data storage. Two implementations of the <Store> element are currently available, with different characteristics, as described below.

File Based Store

The File Based Store implementation saves swapped out sessions in individual files (named based on the session identifier) in a configurable directory. Therefore, you are likely to encounter scalability problems as the number of active sessions increases, and this should primarily be considered a means to easily experiment.

To configure this, add a <Store> nested inside your <Manager> element with the following attributes:

AttributeDescription
checkInterval

The interval (in seconds) between checks for expired sessions among those sessions that are currently swapped out. By default, this interval is set to 60 seconds (one minute).

className

Java class name of the implementation to use. This class must implement the org.apache.catalina.Store interface. You must specify org.apache.catalina.session.FileStore to use this implementation.

directory

Absolute or relative (to the temporary work directory for this web application) pathname of the directory into which individual session files are written. If not specified, the temporary work directory assigned by the container is utilized.

JDBC Based Store

The JDBC Based Store implementation saves swapped out sessions in individual rows of a preconfigured table in a database that is accessed via a JDBC driver. With large numbers of swapped out sessions, this implementation will exhibit improved performance over the File Based Store described above.

To configure this, add a <Store> nested inside your <Manager> element with the following attributes:

AttributeDescription
checkInterval

The interval (in seconds) between checks for expired sessions among those sessions that are currently swapped out. By default, this interval is set to 60 seconds (one minute).

className

Java class name of the implementation to use. This class must implement the org.apache.catalina.Store interface. You must specify org.apache.catalina.session.JDBCStore to use this implementation.

connectionURL

The connection URL that will be handed to the configured JDBC driver to establish a connection to the database containing our session table.

dataSourceName

Name of the JNDI resource for a JDBC DataSource-factory. If this option is given and a valid JDBC resource can be found, it will be used and any direct configuration of a JDBC connection via connectionURL and driverName will be ignored. Since this code uses prepared statements, you might want to configure pooled prepared statements as shown in the JNDI resources HOW-TO.

driverName

Java class name of the JDBC driver to be used.

sessionAppCol

Name of the database column, contained in the specified session table, that contains the Engine, Host, and Web Application Context name in the format /Engine/Host/Context.

sessionDataCol

Name of the database column, contained in the specified session table, that contains the serialized form of all session attributes for a swapped out session. The column type must accept a binary object (typically called a BLOB).

sessionIdCol

Name of the database column, contained in the specified session table, that contains the session identifier of the swapped out session. The column type must accept character string data of at least as many characters as are contained in session identifiers created by Tomcat (typically 32).

sessionLastAccessedCol

Name of the database column, contained in the specified session table, that contains the lastAccessedTime property of this session. The column type must accept a Java long (64 bits).

sessionMaxInactiveCol

Name of the database column, contained in the specified session table, that contains the maxInactiveInterval property of this session. The column type must accept a Java integer (32 bits).

sessionTable

Name of the database table to be used for storing swapped out sessions. This table must contain (at least) the database columns that are configured by the other attributes of this element.

sessionValidCol

Name of the database column, contained in the specified session table, that contains a flag indicating whether this swapped out session is still valid or not. The column type must accept a single character.

Before attempting to use the JDBC Based Store for the first time, you must create the table that will be used to store swapped out sessions. Detailed SQL commands vary depending on the database you are using, but a script like this will generally be required:

create table tomcat_sessions (
  session_id     varchar(100) not null primary key,
  valid_session  char(1) not null,
  max_inactive   int not null,
  last_access    bigint not null,
  app_name       varchar(255),
  session_data   mediumblob,
  KEY kapp_name(app_name)
);

In order for the JDBC Based Store to successfully connect to your database, the JDBC driver you configure must be visible to Tomcat's internal class loader. Generally, that means you must place the JAR file containing this driver into the $CATALINA_HOME/lib directory.

Special Features
Persistence Across Restarts

Whenever Apache Tomcat is shut down normally and restarted, or when an application reload is triggered, the standard Manager implementation will attempt to serialize all currently active sessions to a disk file located via the pathname attribute. All such saved sessions will then be deserialized and activated (assuming they have not expired in the mean time) when the application reload is completed.

In order to successfully restore the state of session attributes, all such attributes MUST implement the java.io.Serializable interface. You MAY cause the Manager to enforce this restriction by including the <distributable> element in your web application deployment descriptor (/WEB-INF/web.xml).

Disable Session Persistence

As documented above, every web application by default has standard manager implementation configured, and it performs session persistence across restarts. To disable this persistence feature, create a Context configuration file for your web application and add the following element there:

<Manager pathname="" />

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