Azure repository is missing log4j-slf4j-impl dependency

[pgomulka]

Elasticsearch Version

8.0

Installed Plugins

repository_azure

Java Version

bundled

OS Version

macos

Problem Description

ES never had a dependency on slf4j, however azure repository does. This plugin default to no op logger implementation and emits a warning into logs

[2022-01-28T15:35:44,847][WARN ][stderr                   ] [runTask-0] SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
[2022-01-28T15:35:44,848][WARN ][stderr                   ] [runTask-0] SLF4J: Defaulting to no-operation (NOP) logger implementation
[2022-01-28T15:35:44,849][WARN ][stderr                   ] [runTask-0] SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.

The stacktrace for this warning is

bind:135, LoggerFactory (org.slf4j)
performInitialization:108, LoggerFactory (org.slf4j)
getILoggerFactory:279, LoggerFactory (org.slf4j)
getLogger:252, LoggerFactory (org.slf4j)
<init>:58, ClientLogger (com.azure.core.util.logging)
<init>:48, ClientLogger (com.azure.core.util.logging)
<init>:49, JacksonAdapter (com.azure.core.util.serializer)
createDefaultSerializerAdapter:112, JacksonAdapter (com.azure.core.util.serializer)
<clinit>:55, AzureRepositoryPlugin (org.elasticsearch.repositories.azure)
newInstance0:-1, NativeConstructorAccessorImpl (jdk.internal.reflect)
newInstance:77, NativeConstructorAccessorImpl (jdk.internal.reflect)
newInstance:45, DelegatingConstructorAccessorImpl (jdk.internal.reflect)
newInstanceWithCaller:499, Constructor (java.lang.reflect)
newInstance:480, Constructor (java.lang.reflect)
loadPlugin:762, PluginsService (org.elasticsearch.plugins)
loadBundle:709, PluginsService (org.elasticsearch.plugins)
loadBundles:492, PluginsService (org.elasticsearch.plugins)
<init>:165, PluginsService (org.elasticsearch.plugins)
<init>:377, Node (org.elasticsearch.node)
<init>:277, Node (org.elasticsearch.node)
<init>:234, Bootstrap$5 (org.elasticsearch.bootstrap)
setup:234, Bootstrap (org.elasticsearch.bootstrap)
init:358, Bootstrap (org.elasticsearch.bootstrap)
init:166, Elasticsearch (org.elasticsearch.bootstrap)
execute:157, Elasticsearch (org.elasticsearch.bootstrap)
execute:77, EnvironmentAwareCommand (org.elasticsearch.cli)
mainWithoutErrorHandling:112, Command (org.elasticsearch.cli)
main:77, Command (org.elasticsearch.cli)
main:122, Elasticsearch (org.elasticsearch.bootstrap)
main:80, Elasticsearch (org.elasticsearch.bootstrap)

The problem become visible since #81870 made repository_azure a module (an always loaded plugin). Hence we can observe this warning on very startup when modules are loaded.

Should we add log4j-slf4j-impl dependency?
or Should we ignore this, "strip"/hide those warnings? From what I see in ClientLogger from azure-core it would just use System.out.println for logging.

        logger = initLogger instanceof NOPLogger ? new DefaultLogger(className) : initLogger;

Steps to Reproduce

checkout any revision after 29349f4 and start ES

Logs (if relevant)

No response

[elasticmachine]

Pinging @elastic/es-core-infra (Team:Core/Infra)

[elasticmachine]

Pinging @elastic/es-delivery (Team:Delivery)