header_filter_by_lua的说明：

1. header_filter_by_lua

2.  

3. syntax: header_filter_by_lua <lua-script-str>

4.  

5. context: http, server, location, location if

6.  

7. phase: output-header-filter

8.  

9. WARNING Since the v0.9.17 release, use of this directive is discouraged; use the new header_filter_by_lua_block directive instead.

10.  

11. Uses Lua code specified in <lua-script-str> to define an output header filter.

12.  

13. Note that the following API functions are currently disabled within this context:

14.  

15. Output API functions (e.g., ngx.say and ngx.send_headers)

16. Control API functions (e.g., ngx.redirect and ngx.exec)

17. Subrequest API functions (e.g., ngx.location.capture and ngx.location.capture_multi)

18. Cosocket API functions (e.g., ngx.socket.tcp and ngx.req.socket).

19. Here is an example of overriding a response header (or adding one if absent) in our Lua header filter:

20.  

21. location / {

22. proxy_pass http://mybackend;

23. header_filter_by_lua 'ngx.header.Foo = "blah"';

24. }

25. This directive was first introduced in the v0.2.1rc20 release.

官网：https://github.com/openresty/lua-nginx-module#header_filter_by_lua

作用：

a)新增自定义的HTTP头

b)重新设置upstream返回的HTTP头，也就是起到覆盖作用

使用示范源码：nginx.conf

1. worker_processes 1;

2. error_log logs/error.log;

3. events {

4. worker_connections 1024;

5. }

6.  

7. http {

8.  

9. log_format main '$msec $status $request $request_time '

10. '$http_referer $remote_addr [ $time_local ] '

11. '$upstream_response_time $host $bytes_sent '

12. '$request_length $upstream_addr';

13.  

14. access_log logs/access.log main buffer=32k flush=1s;

15.  

16. upstream remote_world {

17. server 127.0.0.1:8080;

18. }

19.  

20. server {

21. listen 80;

22.  

23. location /exec {

24. content_by_lua '

25. local cjson = require "cjson"

26. local headers = {

27. ["Etag"] = "663b92165e216225df78fbbd47c9c5ba",

28. ["Last-Modified"] = "Fri, 12 May 2016 18:53:33 GMT",

29. }

30. ngx.var.my_headers = cjson.encode(headers)

31. ngx.var.my_upstream = "remote_world"

32. ngx.var.my_uri = "/world"

33. ngx.exec("/upstream")

34. ';

35. }

36.  

37. location /upstream {

38. internal;

39.  

40. set $my_headers $my_headers;

41. set $my_upstream $my_upstream;

42. set $my_uri $my_uri;

43. proxy_pass http://$my_upstream$my_uri;

44.  

45. header_filter_by_lua '

46. local cjson = require "cjson"

47. headers = cjson.decode(ngx.var.my_headers)

48. for k, v in pairs(headers) do

49. ngx.header[k] = v

50. end

51. ';

52. }

53. }

54.  
55.  

56. server {

57. listen 8080;

58.  

59. location /world {

60. echo "hello world";

61. }

62. }

63. }

运行：openresty -p `pwd` -c conf/nginx.conf

运行结果：

原文出自：http://blog.csdn.net/daiyudong2020/article/details/53149242