Now that JDK 14 is available, and we are bundling it, this commit
enables us to run with helpful null pointer exceptions, which will be a
great aid in debugging.
Change how we format exceptions to only wrap them as necessary. While
the config's overall philosophy is to put items one-per-line when
wrapping, in practice this is a little cumbersome for exception lists.
This commit introduces aarch64 packaging, including bundling an aarch64
JDK distribution. We had to make some interesting choices here:
- ML binaries are not compiled for aarch64, so for now we disable ML on
aarch64
- depending on underlying page sizes, we have to disable class data
sharing
When installing plugins from remote sources, either the Elastic download
service, or maven, a checksum file is downloaded and checked against the
downloaded zip. The current format for official plugins is to use a
sha512 checksum which includes the zip filename. This format matches
that from sha512sum, and allows using the --check argument there to
verify the checksum manually. However, when generating checksum files
with maven and gradle, the filename is not included.
This commit relaxes the requirement the filename existing within the
sha512 checksum file for maven plugins. We continue to strictly enforce
official plugins have the existing format of the file.
closes#52413
Back when the distribution launchers were compiled to target JDK 7, we
did not have access to the String#join method to space-delimit JVM
options. Since the launchers now target the same minimum JDK as
Elasticsearch itself, we now have access to this method and can replace
the use of spaceDelimitJvmOptions with String#join. This commit does
that.
This commit prepares the JvmOptionsParser to be more unit testable by
refactoring the class to have some input that it pulls from external
sources passed in as arguments. We do not change any functionality in
this commit, nor add any unit tests, we are only preparing the way.
Now that the FIPS 140 security provider is simply a test dependency
we don't need the thirdPartyAudit exceptions, but plugin-cli and
transport-netty4 do need jarHell disabled as they use the non fips
BouncyCastle security provider as a test dependency too.
This commit introduces the ability to override JVM options by adding
custom JVM options files to a jvm.options.d directory. This simplifies
administration of Elasticsearch by not requiring administrators to keep
the root jvm.options file in sync with changes that we make to the root
jvm.options file. Instead, they are not expected to modify this file but
instead supply their own in jvm.options.d. In Docker installations, this
means they can bind mount this directory in. In future versions of
Elasticsearch, we can consider removing the root jvm.options file
(instead, providing all options there as system JVM options).
This change changes the way to run our test suites in
JVMs configured in FIPS 140 approved mode. It does so by:
- Configuring any given runtime Java in FIPS mode with the bundled
policy and security properties files, setting the system
properties java.security.properties and java.security.policy
with the == operator that overrides the default JVM properties
and policy.
- When runtime java is 11 and higher, using BouncyCastle FIPS
Cryptographic provider and BCJSSE in FIPS mode. These are
used as testRuntime dependencies for unit
tests and internal clusters, and copied (relevant jars)
explicitly to the lib directory for testclusters used in REST tests
- When runtime java is 8, using BouncyCastle FIPS
Cryptographic provider and SunJSSE in FIPS mode.
Running the tests in FIPS 140 approved mode doesn't require an
additional configuration either in CI workers or locally and is
controlled by specifying -Dtests.fips.enabled=true
Adding back accidentally removed jvm option that is required to enforce
start of the week = Monday in IsoCalendarDataProvider.
Adding a `feature` to yml test in order to skip running it in JDK8
commit that removed it 398c802
commit that backports SystemJvmOptions c4fbda3
relates 7.x backport of code that enforces CalendarDataProvider use #48349
When installing multiple plugins at once, this commit changes the
behavior to report installed plugins as we go. In the case of failure,
we emit a message that we are rolling back any plugins that were
installed successfully, and also that they were successfully rolled
back. In the case a plugin is not successfully rolled back, we report
this clearly too, alerting the user that there might still be state on
disk they would have to clean up.
This commit allows the plugin installer to install multiple plugins in a
single invocation. The installation will be treated as a transaction, so
that all of the plugins are install successfully, or none of the plugins
are installed.
This fixes a regression introduced in #42042. The logic here was
mistakenly inverted such that we only run these tests in a FIPS JVM
which is the opposite of what we intend.
Backport of #48849. Update `.editorconfig` to make the Java settings the
default for all files, and then apply a 2-space indent to all `*.gradle`
files. Then reformat all the files.
This commit introduces a consistent, and type-safe manner for handling
global build parameters through out our build logic. Primarily this
replaces the existing usages of extra properties with static accessors.
It also introduces and explicit API for initialization and mutation of
any such parameters, as well as better error handling for uninitialized
or eager access of parameter values.
Closes#42042
* Always pass user-specified MaxDirectMemorySize
We had been testing whether a user had passed a value for
MaxDirectMemorySize by parsing the output of "java -XX:PrintFlagsFinal
-version". If MaxDirectMemorySize equals zero, we set it to half of max
heap. The problem is that on Windows with JDK 8, a JDK bug incorrectly
truncates values over 4g and returns multiples of 4g as zero. In order
to always respect the user-defined settings, we need to check our input
to see if an "-XX:MaxDirectMemorySize" value has been passed.
* Always warn for Windows/jdk8 ergo issue
Even if a user has set MaxDirectMemorySize, they aren't future-proof for
this JDK bug. With this change, we issue a general warning for the
windows/JDK8 issue, and a specific warning if MaxDirectMemorySize is
unset.
This commit moves JVM options that we are setting on behalf of the user
that we do not expect them to fiddle with out of the jvm.options
configuration file and into the JVM options parser. In this way, we
discourage fiddling with these settings, but more importantly, we ensure
that as we evolve or add to these settings that a user would pick these
pick instead of being left behind if they have a modified jvm.options
file and do not pick any new that come with the distribution.
Our JVM ergonomics extract max heap size from JDK PrintFlagsFinal output.
On JDK 8, there is a system-dependent bug where memory sizes are cast to
32-bit integers. On affected systems (namely, Windows), when 1/4 of physical
memory is more than the maximum integer value, the output of PrintFlagsFinal
will be inaccurate. In the pathological case, where the max heap size would
be a multiple of 4g, the test will fail.
The practical effect of this bug, beyond test failures, is that we may set
MaxDirectMemorySize to an incorrect value on Windows. This commit adds a
warning about this situation during startup.
This commit removes the option to change the netty system properties to
reenable the direct buffer pooling. It also removes the need for us to
disable the buffer pooling in the system properties file. Instead, we
programmatically craete an allocator that is used by our networking
layer.
This commit does introduce an Elasticsearch property which allows the
user to fallback on the netty default allocator. If they choose this
option, they can configure the default allocator how they wish using the
standard netty properties.
This test has been failing very frequently on Windows checks for 7.4. We've also seen it for 7.x as well as for the new 7.5 tests. I'm muting during investigation so we can see if this is masking any other issues.
Compilation was accidentally broken here when a backport used code from
JDK 9, which is not supported in 7.x. This commit addresses this by
using JDK 8 compatiable APIs.
This commit moves the ES_TMPDIR substitution that we do for JVM options
into the JVM options parser itself. This solves a problem where the fact
that the we do not make the substitution before ergonomics parsing can
lead to the JVM that we start for computing the ergonomic values failing
to start. Additionally, moving this substitution here enables us to
simplify the shell scripts since we do not need to implement this there,
and twice for Bash and Windows.
This is the Java side of https://github.com/elastic/ml-cpp/pull/593
with a fallback so that ml-cpp bundles with either the
new or old directory structure work for the time being.
A few days after merging the C++ changes a followup to
this change will be made that removes the fallback.
We currently configure io.netty.allocator.numDirectArenas to be 0 in the
jvm erconomics class. This is a config that we always want to set, so it
makes sense to move it to jvm.options.
Most of our CLI tools use the Terminal class, which previously did not provide methods for writing to standard output. When all output goes to standard out, there are two basic problems. First, errors and warnings are "swallowed" in pipelines, making it hard for a user to know when something's gone wrong. Second, errors and warnings are intermingled with legitimate output, making it difficult to pass the results of interactive scripts to other tools.
This commit adds a second set of print commands to Terminal for printing to standard error, with errorPrint corresponding to print and errorPrintln corresponding to println. This leaves it to developers to decide which output should go where. It also adjusts existing commands to send errors and warnings to stderr.
Usage is printed to standard output when it's correctly requested (e.g., bin/elasticsearch-keystore --help) but goes to standard error when a command is invoked incorrectly (e.g. bin/elasticsearch-keystore list-with-a-typo | sort).
Elasticsearch does not grant Netty reflection access to get Unsafe. The
only mechanism that currently exists to free direct buffers in a timely
manner is to use Unsafe. This leads to the occasional scenario, under
heavy network load, that direct byte buffers can slowly build up without
being freed.
This commit disables Netty direct buffer pooling and moves to a strategy
of using a single thread-local direct buffer for interfacing with sockets.
This will reduce the memory usage from networking. Elasticsearch
currently derives very little value from direct buffer usage (TLS,
compression, Lucene, Elasticsearch handling, etc all use heap bytes). So
this seems like the correct trade-off until that changes.
This commit applies a normalization process to environment paths, both
in how they are stored internally, also their settings values. This
normalization is done via two means:
- we make the paths absolute
- we remove redundant name elements from the path (what Java calls
"normalization")
This change ensures that when we compare and refer to these paths within
the system, we are using a common ground. For example, prior to the
change if the data path was relative, we would not compare it correctly
to paths from disk usage. This is because the paths in disk usage were
being made absolute.
* Mute failing test
tracked in #44552
* mute EvilSecurityTests
tracking in #44558
* Fix line endings in ESJsonLayoutTests
* Mute failing ForecastIT test on windows
Tracking in #44609
* mute BasicRenormalizationIT.testDefaultRenormalization
tracked in #44613
* fix mute testDefaultRenormalization
* Increase busyWait timeout windows is slow
* Mute failure unconfigured node name
* mute x-pack internal cluster test windows
tracking #44610
* Mute JvmErgonomicsTests on windows
Tracking #44669
* mute SharedClusterSnapshotRestoreIT testParallelRestoreOperationsFromSingleSnapshot
Tracking #44671
* Mute NodeTests on Windows
Tracking #44256
Today when checksumming a plugin zip during plugin install, we read all
of the bytes of the zip into memory at once. When trying to run the
plugin installer on a small heap (say, 64 MiB), this can lead to the
plugin installer running out of memory when checksumming large
plugins. This commit addresses this by reading the plugin bytes in 8 KiB
chunks, thus using a constant amount of memory independent of the size
of the plugin.
This change makes the process of verifying the signature of
official plugins FIPS 140 compliant by defaulting to use the
BouncyCastle FIPS provider and adding a dependency to bcpg-fips
that implement parts of openPGP in a FIPS compliant manner.
In already FIPS 140 enabled environments that use the
BouncyCastle FIPS provider, the bcfips dependency is redundant
but doesn't cause an issue as it will be added only in the classpath
of the cli-tools
This is a backport of #44224
Java 8 presents the JVM options slightly differently when displaying via
-XX:+PrintFlagsFinal. This commit adapts the JVM options parser for this
possibility.
Relates #42009
This commit removes manual parsing of JVM options when calculating
ergonomics. This is to avoid a situation that we parse values
differently than the JVM would. In fact, we already have a bug along
these lines today. It is possible to start the JVM with the same flag
multiple times on the command line. In this case, the last value
wins. For example, -Xmx1g -Xmx2g would start the JVM with a heap size of
two gigabytes. Our JVM ergonomics ignores this possibility and instead
the first value is winning!
Our strategy to avoid manual parsing of the JVM options is to start the
Java command line parser (without actually starting a JVM) by invoking
java with the same command line flags as presented and request that the
JVM tell us what values it would start with. This ensures that we have
the correct values when making ergonomic decisions.
Moreover, our strategy also is ignoring ES_JAVA_OPTS which could
override the heap size as well leading to incorrect ergonomic
choices. This commit address this issue too.
hamcrest has some improvements in newer versions, like FileMatchers
that make assertions regarding file exists cleaner. This commit upgrades
to the latest version of hamcrest so we can start using new and improved
matchers.
* Replace usages RandomizedTestingTask with built-in Gradle Test (#40978)
This commit replaces the existing RandomizedTestingTask and supporting code with Gradle's built-in JUnit support via the Test task type. Additionally, the previous workaround to disable all tasks named "test" and create new unit testing tasks named "unitTest" has been removed such that the "test" task now runs unit tests as per the normal Gradle Java plugin conventions.
(cherry picked from commit 323f312bbc829a63056a79ebe45adced5099f6e6)
* Fix forking JVM runner
* Don't bump shadow plugin version
This commit deprecates versions of Java prior to Java 11. This commit
will cause a warning to be printed to standard error when any command
line tool is invoked, or when Elasticsearch is started. Additionally, we
log a deprecation message when Elasticsearch is started.
* Testing conventions now checks for tests in main
This is the last outstanding feature of the old NamingConventionsTask,
so time to remove it.
* PR review
We added some special handling for installing and removing the
ingest-geoip and ingest-user-agent plugins when we converted them to
modules. This special handling was done to minimize breaking users in a
minor release. However, do not want to maintain this behavior forever so
this commit removes that special handling in the master branch so that
starting with 7.0.0 this special handling will be gone.
* Don't print download progress in batch mode
With this change we will no longer provide the progress bar in batch
mode.
Assuming that this is mode is mainly for consumption by tools which
will serialize the output, we shouldn't print a progress bar to be
for every percentile.
* PR review
In the long run we want to move all of startup to a Java program. This
will simplify our startup scripts and make maintenance of startup less
dependent on the underlying platform that we run on. This commit moves
the creation of the temporary directory off of system-dependent commands
and onto a simple Java program.
The list of official plugins accidentally included `qa` projects like,
well, `qa` and `amazon-ec2`. This changes the mechanism that we use to
build the list and adds a test to catch this.
Closes#35623
With this change, `Version` no longer carries information about the qualifier,
we still need a way to show the "display version" that does have both
qualifier and snapshot. This is now stored by the build and red from `META-INF`.
The main benefit of the upgrade for users is the search optimization for top scored documents when the total hit count is not needed. However this optimization is not activated in this change, there is another issue opened to discuss how it should be integrated smoothly.
Some comments about the change:
* Tests that can produce negative scores have been adapted but we need to forbid them completely: #33309Closes#32899
- third party audit detects jar hell with JDK so we disable it
- jdk non portable in forbiddenapis detects classes being used from the
JDK ( for fips ) that are not portable, this is intended so we don't
scan for it on fips.
- different exclusion rules for third party audit on fips
Closes#33179
Ensure our tests can run in a FIPS JVM
JKS keystores cannot be used in a FIPS JVM as attempting to use one
in order to init a KeyManagerFactory or a TrustManagerFactory is not
allowed.( JKS keystore algorithms for private key encryption are not
FIPS 140 approved)
This commit replaces JKS keystores in our tests with the
corresponding PEM encoded key and certificates both for key and trust
configurations.
Whenever it's not possible to refactor the test, i.e. when we are
testing that we can load a JKS keystore, etc. we attempt to
mute the test when we are running in FIPS 140 JVM. Testing for the
JVM is naive and is based on the name of the security provider as
we would control the testing infrastrtucture and so this would be
reliable enough.
Other cases of tests being muted are the ones that involve custom
TrustStoreManagers or KeyStoreManagers, null TLS Ciphers and the
SAMLAuthneticator class as we cannot sign XML documents in the
way we were doing. SAMLAuthenticator tests in a FIPS JVM can be
reenabled with precomputed and signed SAML messages at a later stage.
IT will be covered in a subsequent PR
With this commit we add the possibility to define further JVM options (and
system properties) based on the current environment. As a proof of concept, it
chooses Netty's allocator ergonomically based on the maximum defined heap size.
We switch to the unpooled allocator at 1GB heap size (value determined
experimentally, see #30684 for more details). We are also explicit about the
choice of the allocator in either case.
Relates #30684
This was silly; Bouncy Castle has an armored input stream for reading
keys in ASCII armor format. This means that we do not need to strip the
header ourselves and base64 decode the key. This had problems anyway
because of discrepancies in the padding that Bouncy Castle would produce
and the JDK base64 decoder was expecting. Now that we armor input/output
the whole way during tests, we fix all random failures in test cases
too.
The java version checker requires being written with java 7 APIs.
In order to use java 8 apis in other launcher utilities, this commit
moves the java version checker back to its own jar.
We no longer need animal sniffer because we use JDK functionality
(introduced in JDK 9) to target older versions of the JDK for
compilation. This functionality means that the JDK handles the problem
of ensuring that we do not use JDK APIs from the version that we are
compiling from that are not available in the version that we are
compiling to. A previous commit removed this for the REST client (where
we target JDK 7) but a few traces were left behind.
A previous commit added the public key used for signing artifacts to the
plugin CLI. This commit is an iteration on that to add the header and
footer to the key so that it is clear what the key is. Instead, we strip
the header/footer on read. With this change we simplify our test where
keys already in this format are generated and we had to strip on the
test side.
We sign our official plugins yet this is not well-advertised and not at
all consumed during plugin installation. For plugins that are installed
over the intertubes, verifying that the downloaded artifact is signed by
our signing key would establish both integrity and validity of the
downloaded artifact. The chain of trust here is simple: our installable
artifacts (archive and package distributions) so that if a user trusts
our packages via their signatures, and our plugin installer (which would
be executing trusted code) verifies the downloaded plugin, then the user
can trust the downloaded plugin too. This commit adds verification of
official plugins downloaded during installation. We do not add
verification for offline plugin installs; a user can download our
signatures and verify the artifacts themselves.
This commit also needs to solve a few interesting challenges. One of
these is that we want the bouncy castle JARs on the classpath only for
the plugin installer, but not for the runtime
Elasticsearch. Additionally, we want these JARs to not be present for
the JAR hell checks. To address this, we shift these JARs into a
sub-directory of lib (lib/tools/plugin-cli) that is only loaded for the
plugin installer, and in the plugin installer we filter any JARs in this
directory from the JAR hell check.
We post snapshot builds to snapshots.elastic.co yet the official plugin
installer will not let you install such plugins without manually
downloading them and installing them from a file URL. This commit adds
the ability for the plugin installer to use snapshots.elastic.co for
installing official plugins if a es.plugins.staging is set and the
current build is also a snapshot build. Otherwise, we continue to use
staging.elastic.co if the current build is a release build and
es.plugins.staging is set and, of course, use the release artifacts at
artifacts.elastic.co for release builds with es.plugins.staging unset.
Meta plugins existed only for a short time, in order to enable breaking
up x-pack into multiple plugins. However, now that x-pack is no longer
installed as a plugin, the need for them has disappeared. This commit
removes the meta plugins infrastructure.
X-Pack can no longer be installed as a plugin. This commit adds special
handling for when a user attempts to install X-Pack. This special
handling informs the user of the oss distribution that they should
download the default distribution and the user of the default
distribution that X-Pack does not require installation as it is included
by default.
This commit adds the distribution flavor (default versus oss) to the
build process which is passed through the startup scripts to
Elasticsearch. This change will be used to customize the message on
attempting to install/remove x-pack based on the distribution flavor.
This commit makes x-pack a module and adds it to the default
distrubtion. It also creates distributions for zip, tar, deb and rpm
which contain only oss code.
This commit fixes plugin warning confirmation to include native
controller confirmation when no security policy exists. The case was
already covered for meta plugins, but not for normal plugins. Tests are
also added for all cases.
Today we have a silent batch mode in the install plugin command when
standard input is closed or there is no tty. It appears that
historically this was useful when running tests where we want to accept
plugin permissions without having to acknowledge them. Now that we have
an explicit batch mode flag, this use-case is removed. The motivation
for removing this now is that there is another place where silent batch
mode arises and that is when a user attempts to install a plugin inside
a Docker container without keeping standard input open and attaching a
tty. In this case, the install plugin command will treat the situation
as a silent batch mode and therefore the user will never have the chance
to acknowledge the additional permissions required by a plugin. This
commit removes this silent batch mode in favor of using the --batch flag
when running tests and requiring the user to take explicit action to
acknowledge the additional permissions (either by leaving standard input
open and attaching a tty, or by passing the --batch flags themselves).
Note that with this change the user will now see a null pointer
exception when they try to install a plugin in a Docker container
without keeping standard input open and attaching a tty. This will be
addressed in an immediate follow-up, but because the implications of
that change are larger, they should be handled separately from this one.
Provide more actionable error message when installing an offline plugin
in the plugins directory, and the `plugins` directory for the node
contains plugin distribution.
Closes#27401
As we have factored Elasticsearch into smaller libraries, we have ended
up in a situation that some of the dependencies of Elasticsearch are not
available to code that depends on these smaller libraries but not server
Elasticsearch. This is a good thing, this was one of the goals of
separating Elasticsearch into smaller libraries, to shed some of the
dependencies from other components of the system. However, this now
means that simple utility methods from Lucene that we rely on are no
longer available everywhere. This commit copies IOUtils (with some small
formatting changes for our codebase) into the fold so that other
components of the system can rely on these methods where they no longer
depend on Lucene.
This commit removes the ability to specify that a plugin requires the
keystore and instead creates the keystore on package installation or
when Elasticsearch is started for the first time. The reason that we opt
to create the keystore on package installation is to ensure that the
keystore has the correct permissions (the package installation scripts
run as root as opposed to Elasticsearch running as the elasticsearch
user) and to enable removing the keystore on package removal if the
keystore is not modified.
This commit moves the semantic validation (like which version a plugin
was built for or which java version it is compatible with) from reading
a plugin descriptor, leaving the checks on the format of the descriptor
intact.
relates #28540
This commit removes the extra layer of all plugin files existing under
"elasticsearch" within plugin zips. This simplifies building plugin zips
and removes the need for special logic of modules vs plugins.
When elasticsearch was originally moved to gradle, the "provided" equivalent in maven had to be done through a plugin. Since then, gradle added the "compileOnly" configuration. This commit removes the provided plugin and replaces all uses with compileOnly.
Plugin descriptors currently contain an elasticsearch version,
which the plugin was built against, and a java version, which the plugin
was built with. These versions are read and validated, but not stored.
This commit keeps them in PluginInfo so they can be used later.
While seeing the elasticsearch version is less interesting (since it is
enforced to match that of the running elasticsearc node), the java
version is interesting since we only validate the format, not the actual
version. This also makes PluginInfo have full parity with the plugin
properties file.
We now read the plugin descriptor when removing an old plugin. This is
to check if we are removing a plugin that is extended by another
plugin. However, when reading the descriptor we enforce that it is of
the same version that we are. This is not the case when a user has
upgraded Elasticsearch and is now trying to remove an old plugin. This
commit fixes this by skipping the version enforcement when reading the
plugin descriptor only when removing a plugin.
Relates #28540
The `testMetaPluginPolicyConfirmation` needs to close the file streams it is
iterating over, otherwise some OSes (like Windows) might not be able to delete
all temporary folders, which in turn leads to test failures.
Closes#28415
This commit switches the internal format of the elasticsearch keystore
to no longer use java's KeyStore class, but instead encrypt the binary
data of the secrets using AES-GCM. The cipher key is generated using
PBKDF2WithHmacSHA512. Tests are also added for backcompat reading the v1
and v2 formats.
Currently meta plugins will ask for confirmation of security policy
exceptions for each bundled plugin. This commit collects the necessary
permissions of each bundled plugin, and asks for confirmation of all of
them at the same time.
Meta plugins move the unzipped plugin as is, but the inner plugins may
have a different directory name than their corresponding plugin
properties file specifies. This commit fixes installation to rename the
directory if necessary.
* This change makes sure that we don't detect a file path containing a ':' as
a maven coordinate (e.g.: `file:C:\path\to\zip`)
* restore test muted on master
This change modifies the installation for a meta plugin,
the content of the config and bin directory inside each bundled plugins are now moved in the meta plugin directory.
So instead of `$configDir/meta-plugin-name/bundled_plugin/name/` the content of the config
for a bundled plugin is now in `$configDir/meta-plugin-name`. Same applies for the bin directory.
This commit adds the ability to package multiple plugins in a single zip.
The zip file for a meta plugin must contains the following structure:
|____elasticsearch/
| |____ <plugin1> <-- The plugin files for plugin1 (the content of the elastisearch directory)
| |____ <plugin2> <-- The plugin files for plugin2
| |____ meta-plugin-descriptor.properties <-- example contents below
The meta plugin properties descriptor is mandatory and must contain the following properties:
description: simple summary of the meta plugin.
name: the meta plugin name
The installation process installs each plugin in a sub-folder inside the meta plugin directory.
The example above would create the following structure in the plugins directory:
|_____ plugins
| |____ <name_of_the_meta_plugin>
| | |____ meta-plugin-descriptor.properties
| | |____ <plugin1>
| | |____ <plugin2>
If the sub plugins contain a config or a bin directory, they are copied in a sub folder inside the meta plugin config/bin directory.
|_____ config
| |____ <name_of_the_meta_plugin>
| | |____ <plugin1>
| | |____ <plugin2>
|_____ bin
| |____ <name_of_the_meta_plugin>
| | |____ <plugin1>
| | |____ <plugin2>
The sub-plugins are loaded at startup like normal plugins with the same restrictions; they have a separate class loader and a sub-plugin
cannot have the same name than another plugin (or a sub-plugin inside another meta plugin).
It is also not possible to remove a sub-plugin inside a meta plugin, only full removal of the meta plugin is allowed.
Closes#27316
This commit adds the infrastructure to plugin building and loading to
allow one plugin to extend another. That is, one plugin may extend
another by the "parent" plugin allowing itself to be extended through
java SPI. When all plugins extending a plugin are finished loading, the
"parent" plugin has a callback (through the ExtensiblePlugin interface)
allowing it to reload SPI.
This commit also adds an example plugin which uses as-yet implemented
extensibility (adding to the painless whitelist).