Enable javax.mail logging from watcher

[masseyke]

Description

Javax.mail and com.sun.mail.smtp log to stdout, but only if there is a mail.debug property set to true when the javax.mail.Session is created. As far as I can tell, watcher does not provide a way to set this property so you cannot turn on verbose logging for the email library used within watcher. Here is where we create the properties that we send to the Session. And here is where the Session reads that property to enable debug logging. You can see more at https://javaee.github.io/javamail/docs/api/javax/mail/package-summary.html.

[elasticsearchmachine]

Pinging @elastic/es-data-management (Team:Data Management)

[joegallo]

@masseyke and I just talked through this, and I think we're closer to having this working than we realized.

If you take a look at this code, you'll see that the debug flag controls whether to log to standard out (or whatever the debug logger is), but that it also uses normal old java.util.logging to log the messages, too: https://github.com/javaee/javamail/blob/8106b9dd15e917da63e96c33f8c6aea1cad40045/mail/src/main/java/com/sun/mail/util/MailLogger.java#L231-L242

It might be the case that we just need to add the jul-to-slf4j jar to the right place and then everything would be squared away.

[joegallo]

diff --git a/server/build.gradle b/server/build.gradle
index 8c5c1735c13..a83e2b0c298 100644
--- a/server/build.gradle
+++ b/server/build.gradle
@@ -66,6 +66,7 @@ dependencies {
   // logging
   api "org.apache.logging.log4j:log4j-api:${versions.log4j}"
   api "org.apache.logging.log4j:log4j-core:${versions.log4j}"
+  api "org.apache.logging.log4j:log4j-jul:${versions.log4j}"

   // access to native functions
   implementation project(':libs:elasticsearch-native')
diff --git a/server/src/main/java/org/elasticsearch/common/logging/LogConfigurator.java b/server/src/main/java/org/elasticsearch/common/logging/LogConfigurator.java
index a1ccfd30cba..dff08e35bc2 100644
--- a/server/src/main/java/org/elasticsearch/common/logging/LogConfigurator.java
+++ b/server/src/main/java/org/elasticsearch/common/logging/LogConfigurator.java
@@ -125,6 +125,7 @@ public class LogConfigurator {
             // whether or not the error listener check failed we can remove the listener now
             StatusLogger.getLogger().removeListener(ERROR_LISTENER);
         }
+        System.setProperty("java.util.logging.manager", "org.apache.logging.log4j.jul.LogManager");
         configureESLogging();
         configure(environment.settings(), environment.configFile(), environment.logsFile(), useConsole);
         initializeStatics();

Seems like it's working:

[2024-03-06T12:25:21,614][CONFIG][j.mail                   ] [runTask-0] Jakarta Mail version 1.6.4
[2024-03-06T12:25:21,616][CONFIG][j.mail                   ] [runTask-0] successfully loaded resource: /META-INF/javamail.default.providers
[2024-03-06T12:25:21,616][CONFIG][j.mail                   ] [runTask-0] Tables of loaded providers

when used with:

PUT _cluster/settings
{
  "persistent": {
    "logger.com.sun.mail.smtp": "TRACE",
    "logger.javax.mail": "TRACE"
  }
}

So maybe there is something there worth tidying up and turning into a pull request. 🤷