#graceful-restart
Posts
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Digging into nginx's Source 6: Master and Workers — Processes, Signals and Zero-Downtime Reload
We follow src/os/unix/ngx_process_cycle.c to see how one nginx -s reload wakes the master's sigsuspend() loop, starts new workers with the new config, and lets the old workers finish what they were doing before they leave. Why the signal handler only sets a flag, the socketpair channel between master and workers, the respawn, just_spawn and exiting bits in the ngx_processes[] table, how a worker killed with kill -9 comes back, and the USR2 binary upgrade — all checked with strace, debug logs and ps.
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Digging into Apache httpd's Source 5: main() and Startup — Why the Config Is Read Twice, and Restarts
What happens inside main() when you start httpd, followed through all 914 lines of server/main.c. Why the config file is read twice, how one apachectl graceful makes main()'s loop go round once more, and where a server started as root drops to User — checked against the source and against real log output.