Apache Stable Version

[Kristin Dampeer]

ApacheTomcat is an open source software implementation of asubset of the Jakarta EE (formally Java EE) technologies. Different versions ofApache Tomcat are available for different versions of the specifications. Themapping betweenthespecifications and the respective Apache Tomcat versions is:

Tomcat should also work on any Java early access build that meets therequirements of the final column in the table above. For example, users weresuccessfully running Tomcat 8 on Java 8 many months before the first stable Java8 release. However, users of early access builds should be aware of thefollowing:

Please note that although we offer downloads and documentation of olderreleases, such as Apache Tomcat 7.x, we strongly encourage users to use thelatest stable version of Apache Tomcat whenever possible. We recognize thatupgrading across major versions may not be a trivial task, and some support isstill offered on the mailing list for users of old versions. However, becauseof the community-driven support approach, the older your version, fewer peoplewill be interested or able to support you.

When voting for a release, reviewers specify the stability level that theyconsider the release has reached. Initial releases of a new major versiontypically process from Alpha, through Beta to Stable over a period of severalmonths. However, the Stable level is only available once the Java specificationsthe release implements have been finalised. This means a release that in allother respects is considered stable, may still be labelled as Beta if thespecifications are not final.

Stability is a subjective judgement and you should always read carefully therelease notes for any version you intend to make use of. If you are an earlyadopter of a release, we would love to hear your opinion about its stability aspart of the vote: it takes place on the development mailinglist.

Alpha releases may contain large amounts of untested/missingfunctionality required by the specification and/or significant bugs and are notexpected to run stably for any length of time.

It was created in March 2016 as a fork from Tomcat 9.0.0.M4 (alpha)milestone release. It provides HTTP/2 support and other features fromTomcat 9.x codebase, while being compatible with Tomcat 8.0 runtime andspecification requirements. (A stable release of Tomcat 9.0 could not becreated at that time, as Java EE specifications targeted by Tomcat 9 werefinalized only a few years later).

Apache Tomcat 5.5.x supports the same Servlet and JSPSpecification versions as Apache Tomcat 5.0.x. There are significant changesin many areas under the hood, resulting in improved performance, stability,and total cost of ownership. Please refer to the Apache Tomcat 5.5 Changelogfor details.

Apache Tomcat 4.0.x. Apache Tomcat 4.0.6 is the old productionquality release. The 4.0 servletcontainer (Catalina) has been developed from the ground up for flexibility andperformance. Version 4.0 implements the final released versions of the Servlet2.3 and JSP 1.2 specifications. As required by the specifications, Apache Tomcat 4.0also supports web applications built for the Servlet 2.2 and JSP 1.1specifications with no changes.

All Apache Tomcat 3.x releases trace their heritage back to theoriginal Servlet and JSP implementations that Sun donated to the ApacheSoftware Foundation. The 3.x versions all implement the Servlet2.2 and JSP 1.1 specifications.

Apache Tomcat 3.3.x. Version 3.3.2 is the current productionquality release. It continues the refactoring that was begun in version 3.2 andcarries it to its logical conclusion. Version 3.3 provides a much more modulardesign and allows the servlet container to be customized by adding and removingmodules that control the processing of servlet requests. This version alsocontains many performance improvements.

Apache Tomcat 3.2.x. Version 3.2 added few new featuressince 3.1; the major effort was a refactoring of the internals to improveperformance and stability. The 3.2.1 release, like 3.1.1, was a securitypatch. Version 3.2.2 fixed a large number of bugs and all knownspecification compliance issues. Version 3.2.3 was a security update thatcloses a serious security hole. Version 3.2.4 is a minor bug fix release.All users of Apache Tomcat versions prior to 3.2.3 should upgrade as soon aspossible. With the exception of fixes for critical security related bugs,development on the Apache Tomcat 3.2.x branch has stopped.

Apache Tomcat 3.1.x. The 3.1 release contained severalimprovements over Apache Tomcat 3.0, including servlet reloading, WAR filesupport and added connectors for the IIS and Netscape web servers. Thelatest maintenance release, 3.1.1, contained fixes for security problems.There is no active development ongoing for Apache Tomcat 3.1.x. Users of Apache Tomcat3.1 should update to 3.1.1 to close the security holes and they arestrongly encouraged to migrate to the current production release, Apache Tomcat3.3.

The Apache ZooKeeper community supports two release branches at a time: stable and current. The stable version of ZooKeeper is 3.8.x and the current version is 3.9.x. Once a new minor version is released, the stable version is expected to be decommissioned soon and in approximately half a year will be announced as End-of-Life. During the half year grace period only security and critical fixes are expected to be released for the version. After EoL is announced no further patches are provided by the community. All ZooKeeper releases will remain accessible from the official Apache Archives.

ZooKeeper clients from 3.5.x onwards are fully compatible with 3.9.x servers.

The upgrade from 3.7.x and 3.8.x can be executed as usual, no particular additional upgrade procedure is needed.

ZooKeeper 3.9.x clients are compatible with 3.5.x, 3.6.x, 3.7.x and 3.8.x servers as long as you are not using new APIs not present these versions.

Latest released version of Apache ZooKeeper 3.6 (currently 3.6.4) will be available on the download page for another year (until 30th of December, 2023), after that it will be accessible among other historical versions from Apache Archives.

Latest released version of Apache ZooKeeper 3.5 (currently 3.5.9) will be available on the download page for another year (until 1st of June, 2023), after that it will be accessible among other historical versions from Apache Archives.

ZooKeeper clients from 3.5.x onwards are fully compatible with 3.8.x servers.

The upgrade from 3.6.x and 3.7.x can be executed as usual, no particular additional upgrade procedure is needed.

ZooKeeper 3.8.x clients are compatible with 3.5.x, 3.6.x and 3.7.x servers as long as you are not using new APIs not present these versions.

ZooKeeper clients from the 3.5 and 3.6 branches are fully compatible with 3.7 servers.

The upgrade from 3.6.x to 3.7.0 can be executed as usual, no particular additional upgrade procedure is needed.

ZooKeeper 3.7.0 clients are compatible with 3.5 and 3.6 servers as long as you are not using new APIs not present these versions.

This is a bugfix release for 3.5 branch.

It fixes 24 issues, including third party CVE fixes, several leader-election related fixes and a compatibility issue with applications built against earlier 3.5 client libraries (by restoring a few non public APIs).

This is the second release for 3.6 branch.

It is a bugfix release and it fixes a few compatibility issues with applications built for ZooKeeper 3.5. The upgrade from 3.5.7 to 3.6.1 can be executed as usual, no particular additional upgrade procedure is needed. ZooKeeper 3.6.1 clients are compatible with 3.5 servers as long as you are not using new APIs not present in 3.5.

This is the first release for 3.6 branch.

It comes with lots of new features and improvements around performance and security. It is also introducing new APIS on the client side.

ZooKeeper clients from 3.4 and 3.5 branch are fully compatible with 3.6 servers. The upgrade from 3.5.7 to 3.6.0 can be executed as usual, no particular additional upgrade procedure is needed. ZooKeeper 3.6.0 clients are compatible with 3.5 servers as long as you are not using new APIs not present in 3.5.

First stable version of 3.5 branch. This release is considered to be the successor of 3.4 stable branch and recommended for production use.

It contains 950 commits, resolves 744 issues, fixes 470 bugs and includes the following new features:

This is a bugfix release. It fixes 8 issues, mostly build / unit tests issues, dependency updates flagged by OWASP, NPE and a name resolution problem. Among these it also supports experimental Maven build and Markdown based documentation generation. See ZooKeeper 3.4.14 Release Notes for details.

This is a bugfix release. It fixes 17 issues, including issues such as ZOOKEEPER-2959 that could cause data loss when observer is used, and ZOOKEEPER-2184 that prevents ZooKeeper Java clients working in dynamic IP (container / cloud) environment. See ZooKeeper 3.4.13 Release Notes for details.

Release 3.5.3 added a new feature ZOOKEEPER-2169 "Enable creation of nodes with TTLs". There was a major oversight when TTL nodes were implemented. The session ID generator for each server is seeded with the configured Server ID in the high byte. TTL Nodes were using the highest bit to denote a TTL node when used in the ephemeral owner. This meant that Server IDs > 127 that created ephemeral nodes would have those nodes always considered TTL nodes (with the TTL being essentially a random number). ZOOKEEPER-2901 fixes the issue. By default TTL is disabled and must now be enabled in zoo.cfg. When TTL Nodes are enabled, the max Server ID changes from 255 to 254. See the documentation for TTL in the administrator guide (or the referenced JIRAs) for more details.

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