Any way to circumvent the problem of unsupported filesystem watchers?

[tiagorvmartins]

I have an application that I am trying to run inside gramine sgx and apparently it relies on filesystem watchers, which I believe it's not supported according to the docs:

Monitoring filesystem events (inotify, fanotify)

Gramine does not currently implement inotify and fanotify APIs. 
Gramine could implement them in the future, if need arises.

I can see the log debug line:
(libos_parser.c:1641:warn_unsupported_syscall) [P1:T7:geth] warning: Unsupported system call inotify_init1

And then further on:
ERROR[09-13|15:45:13.356] Failed to start filesystem watcher err="function not implemented"

Maybe there is another solution to my problem,
I have been thinking about this solution:

I could use Temporary in-memory-only files using the type tmpfs filesystem mount.
However I need to be able to stop the process and restart it from the place where it stopped.
For this, I would need to be able to mount a few files to the container such that it continues processing from the same point.

And if I am correct, using tmpfs I wouldn't be able to extract this files and saved them outside of the container to use them again -
"tmpfs do not support mmap and each process has its own, non-shared tmpfs (i.e., processes don’t see each other’s files)"

Context:

• its a binary (geth) that when ran it creates a geth.ipc domain socket "file" and I believe this is the one responsible for triggering the filesystem watcher errors, but not entirely sure.

Thank you, let me know if you need any more information.

[dimakuv]

I could use Temporary in-memory-only files using the type tmpfs filesystem mount.

Sounds like a wrong solution for your use case. Temporary files (tmpfs) are ephemeral -- they only live as long as the SGX enclave lives. As soon as the SGX enclave is terminated (i.e. the Gramine process is terminated), these temporary files are lost forever.

Maybe there is another solution to my problem

Typically applications have some configuration knobs to disable fancy Linux features. I would assume that Geth has some knob/config to not use filesystem watchers?

Otherwise, if Geth insists on using filesystem watchers, you have bad luck, and you'll have to wait until Gramine implements this feature...

[tiagorvmartins]

Thank you for the prompt answer @dimakuv
Let's assume I could maintain the state of my application with normal fs mounts default chroot, and isolate the only file that depends on filesystem watchers to use tmpfs - I believe that could work?

More on this question, lets say the file structure is this:

• /app/
• /app/state-data/ - mounted using fs.mount type chroot
• /app/watcher/ - mounted using tmpfs

One last question:
Assuming that the above would be feasible, can I feed into gramine-sgx the watcher file from host and mark it inside gramine as tmpfs - (I believe not, but just wanted to confirm).

I guess, this file would need to be part of the image itself then and marked as tmpfs, correct?
Thank you

[dimakuv]

Assuming that the above would be feasible, can I feed into gramine-sgx the watcher file from host and mark it inside gramine as tmpfs - (I believe not, but just wanted to confirm).

That's not possible. Files marked in Gramine as tmpfs are completely unrelated to the host files. They are purely in-Gramine-enclave representations, not backed by real files on the host.