I have a utility (written in Scala and built with SBT) that includes a logback.xml: <configuration debug="true"> <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender"> <encoder class="ch.qos.logback.classic.encoder.PatternLayoutEncoder"> <pattern>%d{ISO8601} | %-5level | %thread | %logger{1} | %m%n</pattern> </encoder> </appender> <logger name="com.typesafe.sslconfig.ssl.ConfigSSLContextBuilder" level="ERROR" /> <logger name="com.typesafe.sslconfig.ssl.AlgorithmChecker" level="ERROR" /> <root level="ERROR"> <appender-ref ref="STDOUT" /> </root> </configuration> I added the ‘debug=“true”’ to help me diagnose why, despite the <logger/> elements that attempt to set the loglevel of log messages from the packages defined in the “name” attribute to “ERROR”, I’m seeing “WARN” messages in the console output when I run the command. I fragment of the first few lines of output appears below: java -jar xxx.jar <arguments> [WARN] [07/25/2017 17:05:59.490] [main] [com.typesafe.sslconfig.ssl.ConfigSSLContextBuilder] validateStore: Skipping certificate with weak key size in thawtepremiumserverca: Certificate failed: cert = "1.2.840.113549.1.9.1=#16197072656d69756d2d736572766572407468617774652e636f6d,CN=Thawte Premium Server CA,OU=Certification Services Division,O=Thawte Consulting cc,L=Cape Town,ST=Western Cape,C=ZA" failed on constraint RSA keySize < 2048, algorithm = RSA, keySize = 1024 [WARN] [07/25/2017 17:05:59.490] [main] [com.typesafe.sslconfig.ssl.ConfigSSLContextBuilder] validateStore: Skipping certificate with weak key size in thawteserverca: Certificate failed: cert = "1.2.840.113549.1.9.1=#16177365727665722d6365727473407468617774652e636f6d,CN=Thawte Server CA,OU=Certification Services Division,O=Thawte Consulting cc,L=Cape Town,ST=Western Cape,C=ZA" failed on constraint RSA keySize < 2048, algorithm = RSA, keySize = 1024 …. [WARN] [07/25/2017 17:05:59.500] [main] [com.typesafe.sslconfig.ssl.ConfigSSLContextBuilder] validateStore: Skipping certificate with weak key size in verisignclass1g2ca: Certificate failed: cert = "OU=VeriSign Trust Network,OU=(c) 1998 VeriSign\, Inc. - For authorized use only,OU=Class 1 Public Primary Certification Authority - G2,O=VeriSign\, Inc.,C=US" failed on constraint RSA keySize < 2048, algorithm = RSA, keySize = 1024 17:05:59,530 |-INFO in ch.qos.logback.classic.LoggerContext[default] - Could NOT find resource [logback.groovy] 17:05:59,530 |-INFO in ch.qos.logback.classic.LoggerContext[default] - Could NOT find resource [logback-test.xml] 17:05:59,530 |-INFO in ch.qos.logback.classic.LoggerContext[default] - Found resource [logback.xml] at [jar:file:/Users/eswenson/Projects/Modulus/ws/modulus-shared-libraries/modules/dataset-client-cli/target/scala-2.11/dataset-client-cli-assembly-1.0.dev.jar!/logback.xml] 17:05:59,540 |-INFO in ch.qos.logback.core.joran.spi.ConfigurationWatchList@257cc1fc - URL [jar:file:/Users/eswenson/Projects/Modulus/ws/modulus-shared-libraries/modules/dataset-client-cli/target/scala-2.11/dataset-client-cli-assembly-1.0.dev.jar!/logback.xml] is not of type file 17:05:59,584 |-INFO in ch.qos.logback.core.joran.action.AppenderAction - About to instantiate appender of type [ch.qos.logback.core.ConsoleAppender] 17:05:59,586 |-INFO in ch.qos.logback.core.joran.action.AppenderAction - Naming appender as [STDOUT] 17:05:59,616 |-INFO in ch.qos.logback.classic.joran.action.LoggerAction - Setting level of logger [com.typesafe.sslconfig.ssl.ConfigSSLContextBuilder] to ERROR 17:05:59,617 |-INFO in ch.qos.logback.classic.joran.action.LoggerAction - Setting level of logger [com.typesafe.sslconfig.ssl.AlgorithmChecker] to ERROR 17:05:59,617 |-INFO in ch.qos.logback.classic.joran.action.RootLoggerAction - Setting level of ROOT logger to ERROR 17:05:59,617 |-INFO in ch.qos.logback.core.joran.action.AppenderRefAction - Attaching appender named [STDOUT] to Logger[ROOT] 17:05:59,617 |-INFO in ch.qos.logback.classic.joran.action.ConfigurationAction - End of configuration. 17:05:59,618 |-INFO in ch.qos.logback.classic.joran.JoranConfigurator@5a67e962 - Registering current configuration as safe fallback point [WARN] [07/25/2017 17:05:59.830] [main] [com.typesafe.sslconfig.ssl.ConfigSSLContextBuilder] validateStore: Skipping certificate with weak key size in thawtepremiumserverca: Certificate failed: cert = "1.2.840.113549.1.9.1=#16197072656d69756d2d736572766572407468617774652e636f6d,CN=Thawte Premium Server CA,OU=Certification Services Division,O=Thawte Consulting cc,L=Cape Town,ST=Western Cape,C=ZA" failed on constraint RSA keySize < 2048, algorithm = RSA, keySize = 1024 … <command output> There of two things of note in the output above: there are log messages that appear BEFORE we see the logging output due to the logback “debug=true” option. Second, we see many of these WARN messages from com.typesafe.sslconfig.ssl.ConfigSSLContextBuilder both before and after the logback debug output. Why is logback not suppressing the [WARN] messages? The com.typesafe.sslconfig.ssl code uses akka.event.Logging. I’ve tried to look into this code, and quickly got lost. I’m not sure what low-level logging this package is using, but whatever it is, it isn’t being captured by logback. I suspect I need to use some logback bridge, although I’ve tried various and get errors that I have multiple slf4j providers and it makes no difference to the logging output. How do I track down what is going on here?