Day49 - signalfd and epoll Graceful Shutdown

Goal

Add signal handling to an epoll-based server without using signal handlers.

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Step 1 - Create signal mask

sigemptyset(&mask);
sigaddset(&mask, SIGINT);
sigaddset(&mask, SIGTERM);

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Step 2 - Block signals

sigprocmask(SIG_BLOCK, &mask, NULL);

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Step 3 - Create signalfd

fd = signalfd(-1, &mask, SFD_NONBLOCK | SFD_CLOEXEC);

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Step 4 - Add to epoll

Wrap as epoll_item:

item.type = EPOLL_ITEM_SIGNAL;
add_epoll_item(epfd, &item, EPOLLIN);

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Step 5 - Handle event

read(signal_fd, &siginfo, sizeof(siginfo));

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Step 6 - Shutdown

if (signal == SIGINT || SIGTERM)
    exit loop;

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Step 7 - Cleanup

Release all resources after exiting event loop.

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Testing

Ctrl+C

./server

Press:

Ctrl+C

Expected:

[SIGNAL] received signal=2
[INFO] Graceful shutdown requested

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kill

kill -TERM <pid>

Expected:

signal=15

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Result

• No signal handler required
• All logic handled inside epoll loop
• Clean shutdown achieved