LockManager Synchronizing Runtime With Language Server

[radeusgd]

Summary

Once #1772 is fully implemented, both the Runtime's Compiler (when resolving imports) and the Language Server (on user's library/preinstall request) will be able to install libraries. If two processes try installing the same library at the same time, it can become corrupted or the process may fail - to avoid this we have a synchronization mechanism in place.

However due to JVM limitations, the FileLockManager can only synchronize distinct JVMs. To aid this, we created a ThreadSafeFileLockManager which, when shared within a single JVM, is able to synchronize threads within a single JVM and within distinct JVMs at the same time.

Our scenario however is more complicated - the Language Server and Runtime do run on the same JVM, but due to Classpath Separation, they cannot that easily share an instance of ThreadSafeFileLockManager.

This task consists of creating a LockManager conforming wrapper which will allow to synchronize installation operations happening on both sides - in the Language Server as well as the Runtime.

To achieve that, we need to create a wrapper for LockManager that will live in the runtime, which will use Truffle's serverTransport and MessageEndpoint reuse the RuntimeServerInstrument and its connection to communicate with a ThreadSafeLockManager instance running in the language-server.

It would be best to implement this before #1772.

Value

• Libraries can be safely installed both in the Language Server and the Runtime.

Specification

• Create a simple protocol for the lock manager.
• Implement a LockManager which will use the MessageEndpoint to send lock requests and handle responses. It should ensure that it will be used from a single thread or should otherwise be thread-safe.
• Use the serverTransport functionality to bind the MessageEndpoint to a service which will pass the aforementioned requests to the language server's instance of ThreadSafeLockManager.
• Make it possible to send requests using RuntimeServerConnector in both directions.
• Redirect lock requests to the LockManagerService which wraps an underlying ThreadSafeLockManager.
• Create a ConnectedLockManager that connects to an Endpoint and passes the lock requests to the Language Server using the runtime connector mechanism.
• When creating the context, if running in Language Server mode, connect to the LS's lock manager using the mechanism created above; in text mode create a local ThreadSafeFileLockManager.

Acceptance Criteria & Test Cases

• The above specification has been completed.
• Test the ConnectedLockManager by connecting it to the LockManagerService.
• Manually test the language server with the IDE to make sure that nothing is broken.