Using native image with javax.mail and logback variables

[adamkobor]

Hey there,
I'm kind of stuck with two separate issues regarding GraalVM and native images. I have a pet project, called Kuvasz, you can find the public repo here: https://github.com/kuvasz-uptime/kuvasz

The first problem is about logback and environment variables. As you can see here, I'm using a variable like this in my logback.xml:

<variable name="communicationLogLevel" value="${HTTP_COMMUNICATION_LOG_LEVEL:-INFO}"/>

The default value can be overridden in a "regular" docker image, but it doesn't work inside a native image (there is no exception, or anything suspicious, it just always uses the default value).

The second problem is about javax.mail. I'm using simple-java-mailer to send emails through a pre-configured SMTP host. There were issues about build-time class initialization and missing resources, but I already solved them (or at least I think so, because there are no build time errors). However, when I try to run the native image with a valid SMTP configuration, I get this at the bottom of the stacktrace:

kuvasz_1  | Caused by: javax.mail.NoSuchProviderException: smtp
kuvasz_1  |     at javax.mail.Session.getService(Session.java:842)
kuvasz_1  |     at javax.mail.Session.getTransport(Session.java:772)
kuvasz_1  |     at javax.mail.Session.getTransport(Session.java:713)
kuvasz_1  |     at javax.mail.Session.getTransport(Session.java:693)
kuvasz_1  |     at javax.mail.Session.getTransport(Session.java:673)
kuvasz_1  |     at org.simplejavamail.mailer.internal.util.TransportRunner.runOnSessionTransport(TransportRunner.java:74)
kuvasz_1  |     at org.simplejavamail.mailer.internal.util.TransportRunner.connect(TransportRunner.java:60)
kuvasz_1  |     at org.simplejavamail.mailer.internal.TestConnectionClosure.executeClosure(TestConnectionClosure.java:54)

(The mentioned part of the code in Session.java is using reflection heavily, and trying to instantiate a class with a ClassLoader)

In both cases I've tried to run the native image agent, but I can't get closer to the solution. (I've also attached the output of the agent.)

native-image-agent-output-kuvasz.zip

Any help appreciated 🙏

Micronaut version: 2.0.1
GraalVM version: graalvm-ce:20.2.0-java11

[fernando-valdez]

Hello @adamkobor, regarding the second problem:
The error javax.mail.NoSuchProviderException: smtp could mean that some JDK classes are not included in the native image by default, and that is intended.
We have caller-based filters you can use with the native-image-agent to get the proper configuration files. If you want to know more about this see https://github.com/oracle/graal/blob/master/substratevm/CONFIGURE.md#caller-based-filters
I would recommend you to initially use this filter:

{
    "rules": [
      {"includeClasses": "javax.mail.**"}
    ]
}

You will need to save it to a file, and then use native-image-agent like this:
java -agentlib:native-image-agent=config-output-dir=$CONFIG_DIR,caller-filter-file=$FILTER_FILE_PATH
Note the addition of caller-filter-file= for the filter path.

[adamkobor]

Thanks, will check it 🙏

[adamkobor]

Hey @fernando-valdez, it worked like a charm 🤗 Actually, I've ended up with the following reflect-config.json to make it work: https://github.com/kuvasz-uptime/kuvasz/blob/main/src/main/resources/META-INF/native-image/com.kuvaszuptime/kuvasz-application/reflect-config.json

[fernando-valdez]

Awesome! Thanks for reporting back!

[darren7690]

Hey there,
I also had a problem about javax.mail. I'm using simple-java-mailer to send emails through a pre-configured SMTP host. There was issue about encoding for Chinese charactor: it works well in java jar; However, when I try to run the native image ,the Chinese charactors in email content shows garbage code as ‘？’

Any help appreciated 🙏

[ilopmar]

@adamkobor regarding the logback issue. Have you tried asking/opening an issue in their tracker? Maybe it's something logback doesn't support yet, but they are not aware.

With the email thing, as @fernando-valdez recommended, use the native image tracing agent. More info here: https://medium.com/graalvm/introducing-the-tracing-agent-simplifying-graalvm-native-image-configuration-c3b56c486271

[adamkobor]

Thank you Iván, I'll check it tomorrow, and will also take a look at logback's GitHub.

[adamkobor]

A quick update: I've also tried to set this variable programmatically through logback's context, but I didn't succeed, so I'll head to the logback guys with the issue. Thanks for your help anyway!