doc: warn against awaiting replies in module hooks - #65590
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Awaiting a reply from the registering thread inside a resolve or load hook deadlocks: resolution is synchronous from that thread's perspective, so it is blocked in the request and cannot answer. Fixes: nodejs#63085 Signed-off-by: Paul Bouchon <mail@bitpshr.net>
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Fixes: #63085
module.register()documents that hooks can send messages back to the registering thread, and the example does exactly that. What is not documented is that a hook cannot wait for a reply. Resolution and loading are synchronous from the perspective of the thread that triggered them, so that thread is blocked until the hook settles and can never answer in the meantime. Awaiting a reply inside aresolveorloadhook deadlocks both threads.This adds a short paragraph after the messaging example saying so. The issue reporter hit this and it is not obvious from the surrounding text, which reads as though the channel is bidirectional in the usual way.