Merge pull request vespa-engine#3345 from vespa-engine/bratseth/releases

Moved from frontpage

en/releases.html

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+---
+# Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+title: "Releases"
+---
+
+<p>
+    Vespa is released every Monday through Thursday. Each public release has passed all
+    functional and performance tests, and is already running the applications on our
+    public cloud service.
+</p>
+<br/>
+<p>
+    For each Vespa release, the following artifacts are provided:
+</p>
+<ul class="list">
+    <li><a href="https://search.maven.org/artifact/com.yahoo.vespa/parent">Java artifacts for building Vespa applications on Maven Central</a></li>
+    <li><a href="https://copr.fedorainfracloud.org/coprs/g/vespa/vespa/">Vespa RPMs on Fedora Copr</a></li>
+    <li><a href="https://hub.docker.com/repository/docker/vespaengine/vespa">Container images on Docker Hub</a></li>
+</ul>
+<br/>
+<p>
+    Releases:
+</p>
+<ul class="list">
+    <li><a href="https://docs.vespa.ai/en/vespa7-release-notes.html">Vespa 7</a></li>
+    <li><a href="https://docs.vespa.ai/en/vespa8-release-notes.html">Vespa 8</a></li>
+</ul>
+<br/>
+<p>
+    Use the <a href="https://factory.vespa.oath.cloud/releases">Vespa Factory</a>
+    to inspect the commits in each release:
+</p>
+<img src="/assets/commits-release.png" alt="Screenshot of commit list diff per release"/>
+
+
+<h2 id="versions">Versions</h2>
+<p>
+    Vespa uses <a href="https://semver.org/">semantic versioning</a>.
+    Each release is backwards compatible and supports live migration on running systems, provided they
+    are running a version which is less than 2 months old.
+    It is therefore a minor version number change. All new features are released on such minor versions.
+    Every second year or so we make a major version change which removes previously deprecated
+    functionality.
+</p>
+<p>
+    Java APIs, web service APIs and all application package constructs are supported through a major release
+    and only removed on a new release if they are already marked deprecated.
+</p>
+<p>
+    Use of deprecated Java APIs will cause a warning on compilation,
+    and use of deprecated application package constructs will cause a deprecation warning on deployment.
+    Note that Java APIs come in two categories:
+</p>
+<ul class="list">
+    <li><em>Public APIs</em> carry the compatibility guarantee and are visible from your code
+        as well as in the javadoc</li> <!-- ToDo javadoc - link to something here if possible -->
+    <li><em>Exported APIs</em> are also visible from your code,
+        but is not in the public Javadoc and carry no compatibility guarantee</li>
+</ul>
+<p>
+    Check the Javadoc list to verify that you are using public packages.
+</p>
+<p>
+    In addition, some public Java classes and methods are marked with the com.yahoo.api.annotations.Beta tag.
+    These are under development and may still change before they stabilize.
+</p>
+
+
+
+<h2 id="stored-data">Stored Data</h2>
+
+<p>
+    Data written to Vespa is compatible between adjacent releases.
+    For self-hosted systems, it may be necessary to upgrade through each
+    minor release rather than in larger leaps to ensure Vespa can read existing data.
+    This is a good practice in any case.
+</p>