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1.Nginx Internals Joshua Zhu 09/19/2009
2. Agenda Source code layout Key concepts and infrastructure The event-driven architecture HTTP request handling Mail proxying process Nginx module development Misc. topics
3. Source Code Layout Files $ find . -name "*\.[hc]" -print | wc –l 234 $ ls src core event http mail misc os Lines of code $ find . -name "*\.[hc]" -print | xargs wc -l | tail -n1 110953 total
4. Code Organization core/ The backbone and infrastructure event/ The event-driven engine and modules http/ The HTTP server and modules mail/ The Mail proxy server and modules misc/ C++ compatibility test and the Google perftools module os/ OS dependent implementation files
5. Nginx Architecture Non-blocking Event driven Single threaded[*] One master process and several worker processes Resource efficient Highly modular
6.The Big Picture
7. Agenda Source code layout Key concepts and infrastructure The event-driven architecture HTTP request handling Mail proxying process Nginx module development Misc. topics
8. Memory Pool Avoid memory fragmentation Avoid memory leak Allocation and deallocation can be very fast Lifetime and pool size Cycle Connection Request
9. Memory Pool (cont’d) ngx_pool_t Small blocks Large blocks Free chain list Cleanup handler list API ngx_palloc memory aligned ngx_pnalloc ngx_pcalloc
10.Memory Pool Example (1 Chunk)
11.Memory Pool Example (2 Chunks)
12. Buffer Management Buffer Pointers memory start/pos/last/end file file_pos/file_last/file Flags last_buf last_in_chain flush in_file memory …
13. Buffer Management (cont’d) Buffer chain Singly-linked list of buffers Output chain Context in/free/busy chains Output filter Chain writer Writer context
14. String Utilities ngx_str_t data len sizeof() - 1 Memory related String formatting String comparison String search Base64 encoding/decoding URI escaping/unescaping UTF-8 decoding String-to-number conversion
15. Data Structures Abstract data types Array List Queue Hash table Red black tree Radix tree Characteristic Set object values after added keep interfaces clean Chunked memory (part) efficient
16. Logging Error log Level Debug Access log Multiple logs Log format variables Per location Rotation
17. Configuration File Directive name type set conf offset post Parsing ngx_conf_parse Values init merge
18. Configuration File (cont’d) Block events http server upstream location if Variables Buildins Other types http_ sent_http_ upstream_http_ cookie_ arg_
19. Agenda Source code layout Key concepts and infrastructure The event-driven architecture HTTP request handling Mail proxying process Nginx module development Misc. topics
20. Master and Workers Master Monitor workers, respawn when a worker dies Handle signals and notify workers exit reconfiguration update log rotation … Worker Process client requests handle connections Get cmd from master
21.Master Process Cycle
22.Worker Process Cycle
23.Inter-process Communication Signals Channel socketpair command Shared memory Connection counter Stat Atomic & spinlock Mutex
24. Event ngx_event_t Read Write Timeout Callbacks Handlers ngx_event_accept ngx_process_events_and_timers ngx_handle_read_event ngx_handle_write_event Posted events Posted accept events queue Posted events queue
25. Time Cache The overhead of gettimeofday() Time cache variables ngx_cached_time ngx_current_msec Time strings ngx_cached_err_log_time ngx_cached_http_time ngx_cached_http_log_time Timer resolution Interval timer setitimer()
26.Events and Timers Processing
27. Timer Management Actions Add a timer Delete a timer Get the minimum timer Red black tree[*] O(log n) complexity
28. Accept Mutex Thundering herd Serialize accept() Lock/unlock Listening sockets Delay
29. I/O Multiplexing kqueue/epoll NGX_USE_CLEAR_EVENT (edge triggered) select/poll/dev/poll NGX_USE_LEVEL_EVENT (level triggered) … Advanced I/O sendfile() writev() direct I/O mmap() AIO TCP/IP options TCP_CORK/TCP_NODELAY/TCP_DEFER_ACCEPT
