Upgrade caffeine to 3.0.2, no more sun.misc.Unsafe

[bcmedeiros]

Possible solution to #4092

[laurit]

Caffeine 3 requires java 11 our agent aims to support java 8. Could you verify that the agent still works with jdk8. You can run test with jdk8 by adding -PtestJavaVersion=8 to gradle arguments, gradle will download jdk8 if needed.

[bcmedeiros]

Caffeine 3 requires java 11 our agent aims to support java 8. Could you verify that the agent still works with jdk8. You can run test with jdk8 by adding -PtestJavaVersion=8 to gradle arguments, gradle will download jdk8 if needed.

It obviously doesn't, completely missed that.

The release notes say that:

Highlights
Java 11 or above is required
Java 8 users can continue to use version 2.x, which will be supported

Any plans to support multiple releases? This is going to be very hard to fix if we need a single distribution targetting Java 8/11/17.

[laurit]

Any plans to support multiple releases? This is going to be very hard to fix if we need a single distribution targetting Java 8/11/17.

Although I haven't discussed with others I'm sure that everybody agrees that we want to continue providing a single distribution that works on all supported jvms. Having separate agents for different jvms is a hassle.
Luckily the way I see this issue is neither complex not serious enough to force us away from single agent.
We could just state that the agent depends on jdk.unsupported and we expect it to be available. Or we could shade caffeine 2&3 under different package names and use both. We only use a very small set of features from caffeine and all of our usages of caffeine go through a single builder class that could easily switch between caffeine 2&3 depending on jvm version. Though caffeine is the least of our problems in this Unsafe mess. Other usages of Unsafe in bytebuddy etc. seem more troublesome. We could try working with the authors of these frameworks or find replacements that we could use. Alternatively we could provide our own implementation of sun.misc.Unsafe that uses jdk.internal.misc.Unsafe, jdk11 also implements sun.misc.Unsafe this way. The last options would let the libraries that we use continue using sun.misc.Unsafe when running with module system without requiring adding dependency to jdk.unsupported.

[trask]

thanks @brunojcm! closing with alternative solution #4154