We have identified a blocking call with the help of Blockhound while trying to perform HTTP operations with reactor-netty.

We have tested this scenario enabling Blockhound and identified the blocking call with OpenJDK 11 and 17.

Attached the stack trace of the blocking call exception here : blocking_call_log.txt

On analysing the blocking call trace and the OpenJDK changes, the blocking call is happening while,

• The ResteasyJackson2Provider trying to write the request body which internally tries whitelist the classes for deserialisation via WhiteListPolymorphicTypeValidatorBuilder class.
• This class tried to load the baseType and subType properties from Configuration object(ConfigurationFactory.getInstance()) loaded via ServiceLoader.
• The ServiceLoader prior to OpenJDK 9, uses ServiceLoader.LazyIterator to iterate and load the providers
• After OpenJDK 9, the above step is done via ServiceLoader.LazyClassPathLookupIterator which is the main flow for causing the blocking call

Reproduced the blocking call with a test case (MonoTest.testMonoMap()) in rest-easy under this repo : https://github.com/anthochristen/resteasy/tree/blocking-write-issue