Scala getting started guide fails with logging config error when run with read-only workspace directory

[edmorley]

This is similar to #655, except the image is being run with a read-only filesystem mount, rather than a separate Linux user.

Currently if the Scala getting started guide is run with a read-only filesystem (with only /tmp and /home/heroku set to writable), by using docker run --read-only --tmpfs /tmp --tmpfs /home/heroku ..., then the following error occurs:

Picked up JAVA_TOOL_OPTIONS: -XX:MaxRAMPercentage=80.0 -Dfile.encoding=UTF-8
08:08:50,128 |-INFO in ch.qos.logback.classic.LoggerContext[default] - Could NOT find resource [logback-test.xml]
Oops, cannot start the server.
java.nio.file.FileSystemException: /workspace/target/universal/stage/RUNNING_PID: Read-only file system
	at java.base/sun.nio.fs.UnixException.translateToIOException(UnixException.java:100)
	at java.base/sun.nio.fs.UnixException.rethrowAsIOException(UnixException.java:106)
	at java.base/sun.nio.fs.UnixException.rethrowAsIOException(UnixException.java:111)
	at java.base/sun.nio.fs.UnixFileSystemProvider.newByteChannel(UnixFileSystemProvider.java:218)
	at java.base/java.nio.file.spi.FileSystemProvider.newOutputStream(FileSystemProvider.java:484)
	at java.base/java.nio.file.Files.newOutputStream(Files.java:228)
	at play.core.server.ProdServerStart$.createPidFile(ProdServerStart.scala:147)
	at play.core.server.ProdServerStart$.start(ProdServerStart.scala:45)
	at play.core.server.ProdServerStart$.main(ProdServerStart.scala:29)
	at play.core.server.ProdServerStart.main(ProdServerStart.scala)
08:08:50,128 |-INFO in ch.qos.logback.classic.LoggerContext[default] - Found resource [logback.xml] at [file:/workspace/target/universal/stage/conf/logback.xml]
08:08:50,180 |-INFO in ch.qos.logback.classic.joran.action.ConfigurationAction - debug attribute not set
08:08:50,181 |-INFO in ch.qos.logback.core.joran.action.AppenderAction - About to instantiate appender of type [ch.qos.logback.core.FileAppender]
08:08:50,190 |-INFO in ch.qos.logback.core.joran.action.AppenderAction - Naming appender as [FILE]
08:08:50,198 |-INFO in ch.qos.logback.core.joran.action.NestedComplexPropertyIA - Assuming default type [ch.qos.logback.classic.encoder.PatternLayoutEncoder] for [encoder] property
08:08:50,250 |-INFO in ch.qos.logback.core.FileAppender[FILE] - File property is set to [./logs/application.log]
08:08:50,251 |-ERROR in ch.qos.logback.core.FileAppender[FILE] - Failed to create parent directories for [/workspace/target/universal/stage/./logs/application.log]
08:08:50,251 |-ERROR in ch.qos.logback.core.FileAppender[FILE] - openFile(./logs/application.log,true) call failed. java.io.FileNotFoundException: ./logs/application.log (No such file or directory)
	at java.io.FileNotFoundException: ./logs/application.log (No such file or directory)
	at 	at java.base/java.io.FileOutputStream.open0(Native Method)
	at 	at java.base/java.io.FileOutputStream.open(FileOutputStream.java:319)
	at 	at java.base/java.io.FileOutputStream.<init>(FileOutputStream.java:259)
	at 	at ch.qos.logback.core.recovery.ResilientFileOutputStream.<init>(ResilientFileOutputStream.java:26)
	at 	at ch.qos.logback.core.FileAppender.openFile(FileAppender.java:204)
	at 	at ch.qos.logback.core.FileAppender.start(FileAppender.java:127)
	at 	at ch.qos.logback.core.joran.action.AppenderAction.end(AppenderAction.java:90)
	at 	at ch.qos.logback.core.joran.spi.Interpreter.callEndAction(Interpreter.java:309)
	at 	at ch.qos.logback.core.joran.spi.Interpreter.endElement(Interpreter.java:193)
	at 	at ch.qos.logback.core.joran.spi.Interpreter.endElement(Interpreter.java:179)
	at 	at ch.qos.logback.core.joran.spi.EventPlayer.play(EventPlayer.java:62)
	at 	at ch.qos.logback.core.joran.GenericConfigurator.doConfigure(GenericConfigurator.java:165)
	at 	at ch.qos.logback.core.joran.GenericConfigurator.doConfigure(GenericConfigurator.java:152)
	at 	at ch.qos.logback.core.joran.GenericConfigurator.doConfigure(GenericConfigurator.java:110)
	at 	at ch.qos.logback.core.joran.GenericConfigurator.doConfigure(GenericConfigurator.java:53)
	at 	at ch.qos.logback.classic.util.ContextInitializer.configureByResource(ContextInitializer.java:64)
	at 	at ch.qos.logback.classic.util.ContextInitializer.autoConfig(ContextInitializer.java:134)
	at 	at org.slf4j.impl.StaticLoggerBinder.init(StaticLoggerBinder.java:84)
	at 	at org.slf4j.impl.StaticLoggerBinder.<clinit>(StaticLoggerBinder.java:55)
	at 	at org.slf4j.LoggerFactory.bind(LoggerFactory.java:150)
	at 	at org.slf4j.LoggerFactory.performInitialization(LoggerFactory.java:124)
	at 	at org.slf4j.LoggerFactory.getILoggerFactory(LoggerFactory.java:417)
	at 	at org.slf4j.LoggerFactory.getLogger(LoggerFactory.java:362)
	at 	at org.slf4j.LoggerFactory.getLogger(LoggerFactory.java:388)
	at 	at play.api.Logger$.<clinit>(Logger.scala:265)
	at 	at play.api.Configuration$.<clinit>(Configuration.scala:168)
	at 	at play.core.server.ProdServerStart$.readServerConfigSettings(ProdServerStart.scala:102)
	at 	at play.core.server.ProdServerStart$.start(ProdServerStart.scala:42)
	at 	at play.core.server.ProdServerStart$.main(ProdServerStart.scala:29)
	at 	at play.core.server.ProdServerStart.main(ProdServerStart.scala)

(see https://github.com/heroku/cnb-builder-images/actions/runs/9299142531/job/25592522803)

This is presumably due to the logs location being configured here:
https://github.com/heroku/scala-getting-started/blob/61340fc2b557cb8bcf365c7bd7f05042cc9768f0/conf/logback.xml#L4-L5

...so perhaps this is specific to the getting started guide and needs fixing there, by making the logs write to /tmp instead?

However, I'm filing against the buildpack for now in case there is something the buildpack could/should be doing. (Feel free to use the GitHub issue transfer feature to move the issue over if preferred.)