support multiple instance with the same writekey

[RanjitCS]

Is your feature request related to a problem? Please describe.
We have a scenario where multiple JVMs (essentially replicas of each other) are configured to use the same analytics-kotlin.properties file and share the same events directory. Under high load, we’ve observed that the file-index property fluctuates unexpectedly (e.g., jumping from 1–100, then back to 50, etc.).

Upon investigation, we noticed that the StorageImpl class uses semaphores for synchronization; however, this mechanism does not provide protection against concurrent file access by multiple processes. Some events also seem to be dropped/skipped over due to this.We would like to ensure that the read/write operations are always in sync

Describe the solution you'd like
Would it be possible to change to a file locking mechanism instead of semaphore? Or some other solution to protect multiple processes accessing same file/folder?

Describe alternatives you've considered
We are considering a few alternatives.

1. Separate files/folders per JVM: The simplest approach is to assign unique files or directories for each JVM instance. However, this introduces new challenges: if a JVM crashes or is stopped unexpectedly, the location of its files/folders can be lost, requiring a separate helper process to recover or transfer batch files to the new instance’s directory. The new instance that comes up would not be able to use the same files/folders as before as we would need to have a unique identifier for each JVM and there is a chance that we could lose events.

2. Custom StorageImpl with FileLocks: As a last resort, we’re contemplating building our own version of StorageImpl that implements robust file locking internally.

[wenxi-zeng]

hi @RanjitCS, these are some good observations. and you're right, this SDK does not support multiple instance with the same writekey, because that would lead multiple processes writing to the same file. your point 1 is the exact challenges we are working on to get true multiple instances support. this is on our load map. we haven't got chance into it because of other priorities. I will get back to you once this is supported.

in the meanwhile please implement a custom storage like you mentioned in point 2. file locks will lead to performance degrade. so we'll try other alternatives that introduce less impact.

[RanjitCS]

Thanks for your review and recommendation!