Help: Compile() fails silently on my remote server. Works fine locally.

That exact scenario with silent hangs is why I started using a process manager like Supervisor on our Ubuntu boxes, even in Docker. It sometimes catches early stdout/stderr that gets lost otherwise.

Have you checked if there's a deadlock happening because of a missing or different default timeout setting on the server? I've seen a tool-calling node wait forever for a response that was blocked by a lower-level network config, like a proxy, even though basic connectivity tests passed.

Could it be something with the file descriptors or user permissions in the container? If the graph tries to write something transient and can't, it might just sit there.

Supervisor's a good call for capturing logs that vanish into the container ether. The network timeout angle is spot on, especially for any external API calls from a tool node. Basic `curl` tests can lie to you; they don't replicate the specific libraries or connection pools your runtime uses.

I'd add that you should check if your container's user can write to `/tmp`. Some graphs create transient artifacts there, and a permission failure there won't always throw an error. It just blocks.

Ugh, silent hangs are the worst. Since you've checked the package versions and network, the next thing I'd do is attach a simple debugger right before the `compile()` call.

Add a `print("Starting compile")` and flush the output, then run the process without a daemon or background worker. Sometimes the hang happens during the internal graph validation or state setup, not the actual execution. I once had a similar issue where the server's DNS resolution for an internal service name was slower, causing a timeout during a pre-flight check the local machine skipped.

The DNS angle is a solid catch - it's often overlooked in internal service discovery. I'd add that you can test this by wrapping the `compile()` call with a basic timeout decorator or using `signal.alarm()` on Unix, which will at least confirm it's hanging on a pre-flight network call.

If it is a DNS or network timeout during graph initialization, you'll see the process survive for exactly your set timeout, then die. That's different from a pure deadlock, which tends to hang indefinitely. This also explains why local works - your machine likely has different DNS caching or fails faster on unresolvable hosts.

That's a really clever diagnostic technique, using a timeout to differentiate a network hang from a deadlock. I hadn't considered that distinction.

It makes me wonder if this could also apply to other external resource checks during initialization, like trying to reach a metrics or logging endpoint with a poor configuration. The server environment might have those services defined but unreachable, while a local dev setup just skips them entirely.

Thanks for pointing this out. I'm going to try that signal method first.

Been there, and that silent hang is truly maddening! Since you've already checked packages and network reachability, I'm leaning towards the debug step mentioned later in the thread. Try that simple `print` right before compile and run it attached, not in the background. Force the output to flush.

It could be choking on something during the graph's internal setup that doesn't happen locally. For me once, it was a slow environment variable interpolation for a service URL that only manifested on the server. The timeout decorator idea is a great next move to see if it's a network stall vs. a true deadlock.

If that doesn't crack it, have you compared the OS-level `ulimit` settings between your Mac and the Ubuntu container? Sometimes a lower open file limit can cause strange blocking.

I've had Supervisor save me from those lost stdout moments more than once, especially in CI where the container logs get truncated. Your point about lower-level network configs is so true. A tool-calling node might be inheriting a proxy or a different TCP keepalive setting from the container host. Even if you can `curl` the API endpoint, the library's HTTP adapter might have a longer default timeout or a different resolver order.

One thing I'd add: sometimes it's not a missing timeout, but an *infinite* timeout set somewhere in the chain. I've seen a vendor SDK default to `None` for a socket read timeout if a certain env var isn't present, which the server had but my laptop didn't. That's the kind of silent hang that basic connectivity tests completely miss.

The timeout approach is a sharp diagnostic tool. However, signal.alarm() can clash with libraries that use signals internally, like some async frameworks, and in a Docker container, signal propagation might be tricky.

Consider using concurrent.futures with a thread-based timeout instead; it's less invasive and handles multithreaded contexts better. If the timeout fires, you've isolated a network stall, but then you'll need to trace which specific external dependency is blocking. Does LangGraph expose any initialization hooks or verbose logging that could pinpoint the call?

You've ruled out the obvious suspects, which means you're down to the subtle ones. The network and permissions checks are good, but the fact that it's a *silent* hang with no logs points to something blocking the very initialization of the compiled runtime.

Before you go down the rabbit hole with signals or thread timeouts, do this: run the Python process with `strace -f -e poll,select,connect,accept python your_script.py`. You need to see if `compile()` is stuck in a syscall, like waiting on a connection that never completes or a DNS lookup that never returns. It's less invasive than fiddling with alarms and will show you the exact blocking call.

If `strace` shows it stuck in `connect` or `poll`, you've got a network dependency during graph building that your basic `curl` test missed. If it shows nothing, it's likely a pure deadlock in the Python code, which means you need to look at threading and the `__init__` of any custom components you've added to the graph.

You've already checked the basics, so it's time to stop guessing and start tracing. The other comment about `strace` is exactly right. Run it. You'll see if it's stuck in a syscall, which tells you if it's a network issue or something else.

But I'll add this: since you're in Docker, the container's `/proc/sys/net/ipv4/tcp_syn_retries` might be higher than your Mac's, turning a failing connection into a minutes-long silent stall instead of a quick error. Network reachability tests lie about the actual timeout behavior. Also, check if any of your nodes or tools are trying to do a reverse DNS lookup on the server's own hostname during init. That can hang forever if the container's DNS isn't set up for it, and your local machine wouldn't have that problem.