1、mod_jk模块的总体功能
由于tomcat的HTTP处理部分都由Java所写（5.5.12版本以后出现了native库，用以提高其I/O和SSL的性能[1]），在高并发的情况下负载较高。而apache对于静态文件的处理能力比tomcat强，所以tomcat开发组开发了与apache结合使用的mod_jk模块。该协议由apache作请求代理，将HTTP协议的请求转化为AJP协议包，并传给后端的tomcat。
mod_jk和apache现在普遍使用AJP1.3协议[2]。它是一个二进制格式的协议，比字符格式的HTTP协议解析速度要快。
除了性能的提升，mod_jk另外的一个作用可以实现apache与tomcat一对多的对应，使后端tomcat负载均衡。mod_jk也提供apache与tomcat链接情况的监控。
mod_jk模块的典型工作流程是这样的：一个HTTP请求过来，mod_jk模块根据其URI选择合适的worker来进行处理。如果是lb_worker（负载均衡的worker），就再根据各种条件选择后台合适的ajp_worker（处理AJP协议的worker）。ajp_worker将HTTP协议的包，组装成AJP协议格式的包，然后选取一条空闲的链接，发送给后台的tomcat服务器。等到后台将数据发送过来时，接收并解析AJP协议，重新组装成HTTP协议，然后把结果发送给客户端。
2、mod_jk模块的框架
2.1 线程
从宏观上来讲，mod_jk由一个watchdog线程和一组worker线程(进程)组成。watchdog线程是在apache内部新创建的线程，它是一个维护线程。每隔
JkWatchdogInterval的时间（当然，所有worker线程也有一个统一的worker.maintain 时间，JkWatchdogInterval应该至少大于worker.maintain），它会扫描所有worker线程。
watchdog线程会检查每个worker线程的空闲链接、负载情况、与后端的链接情况，并使共享内存同步。worker线程是就是一些ajp13，ajp14，jni，lb或status类型的线程，负责所有实际的工作。
在mod_jk中，线程内（外）的同步均是通过线程锁（pthread_mutex_lock）来实现的。而进程之间的全局同步，是用文件记录锁（flock或fcntl）来实现。进程间的数据共享是用这样做的：进程启动时，创建一个JkShmSize大小的文件，然后mmap到内存，由于各进程mmap到内存的是相同的镜像，所以可以实现数据的共享，但是写入共享内存时，要做好互斥。
由于apache的基本处理方式（prefork和worker模式）就是一个线程/进程负责一个连接，所以mod_jk各线程中对于网络IO处理都是阻塞的。
2.2 worker对象
从具体的worker对象的角度来讲，mod_jk由ajp_worker、jni_worker、lb_worker和status_worker组成。这些对象参考了设计模式中factory的模型。每类worker都有生产workers的factory。
在mod_jk中，其中的worker主要在worker.list中列出。其中，lb_worker可以含有balance_workers，以lb_sub_worker的形式存储于lb_worker中。lb_sub_worker可以是各种类型的ajp_worker。所以真正工作的ajp_worker既可以“单干”，也可以由lb_worker来分配任务。这主要取决于URI到底映射到哪个worker上以及该worker是否在worker.list配置。
lb_worker，lb_sub_worker和ajp_worker一些配置信息都位于其结构体中，而状态信息或在运行中可变的参数则位于共享内存中的对应结构体中，当然也并不绝对，有些参数是冗余的。从正在运行的某个线程的角度上来讲，ajp_worker就是对应了一个线程。
3 从HTTP到AJP的处理流程
由于mod_jk模块是apache的处理模块，本节主要是讲述mod_jk模块从客户端到后端服务器的处理流程。中间会涉及一些apache模块的一些结构。
3.1 mod_jk模块在apache中的定义
3.1.1 mod_jk定义
/* 这是jk模块的主要定义结构体*/
module AP_MODULE_DECLARE_DATA jk_module = {
STANDARD20_MODULE_STUFF,
NULL, /* dir config creater */
NULL, /* dir merger --- default isto override */
create_jk_config, /*创建 jk模块的配置结构体*/
merge_jk_config, /* 初始化及合并 jk模块的配置结构体*/
jk_cmds, /* 所有在apahce中的命令及操作函数 */
jk_register_hooks /* 具体的操作函数处理钩子 */
};
3.1.2 mod_jk模块的主要处理函数
/* mod_jk将各处理函数挂到相应的钩子上，钩子实际上就是一些函数指针。针对某个HTTP请求，这些函数会自上而下执行。*/
static void jk_register_hooks(apr_pool_t * p)
{
/* 该函数在apache读入配置后运行，用以初始化全局互斥锁，jk日志，全局变量的初始化，以及读入 workers.properties、uriworkermap.properties文件，初始化各worker的属性，建立worker名称到worker结构体的映射，uri到worker的映射*/
ap_hook_post_config(jk_post_config,NULL, NULL, APR_HOOK_MIDDLE);
/*该函数在apache主进程fork工作子进程后做的初始化工作，主要包括初始化进程内互斥锁，开启维护线程，读入共享内存*/
ap_hook_child_init(jk_child_init, NULL, NULL, APR_HOOK_MIDDLE);
/* 将mod_jk的URI到真实URI，然后URI到worker的映射翻译过程，用以找到该URI相应的worker_name */
ap_hook_translate_name(jk_translate, NULL, NULL, APR_HOOK_MIDDLE);
#if (MODULE_MAGIC_NUMBER_MAJOR > 20010808)
/* 绑定那些alias_dir的URI到mod_jk的配置，并找到相应worker_name */
ap_hook_map_to_storage(jk_map_to_storage, NULL, NULL, APR_HOOK_MIDDLE);
/* 这是mod_jk的主要处理函数*/
ap_hook_handler(jk_handler, NULL, NULL, APR_HOOK_MIDDLE);
#endif
}
3.2 jk_handler函数
jk_handler函数是mod_jk的主要处理函数，它负责将HTTP请求从apache发到tomcat,再从tomcat接受数据，并返回给客户。
它的处理过程如下：
1. 根据前面得到的worker_name，找到相应的jk_worker（其结构体见4.4）。
2. 初始化服务结构体jk_ws_service，主要是针对HTTP服务端的一些设置及函数（服务的结构体见4.5），与AJP协议关系不大。
3. 调用jk_worker的get_endpoint函数，获取具体的jk_endpoint结构体（函数见3.3.1和3.4.1，jk_endpoint的结构体定义见4.4）。
4. 调用上述jk_endpoint的service函数。
5. 调用上述jk_endpoint的done函数，结束与tomcat的AJP连接。
6. 根据函数的结果处理各种状态。
7. 释放资源。
3.3 lb_worker的处理函数
3.3.1 lb_worker的get_endpoint
初始化lb_worker的endpoint结构体，挂上其service及done函数。
3.3.2 lb_worker的service函数
它的处理过程如下：
1. 获取共享内存中记录的worker状态。
2. 如果需要绑定sessionID，获取sessionID。
3. 调用get_most_suitable_worker函数，获取相应的lb_sub_worker(也即ajp_worker)。
4. 调用ajp_worker的get_endpoint函数。
5. 调用上述endpoint的service函数。
6. 调用上述endpoint的done函数。
7. 根据service的返回结果，更新各种记录状态。
3.3.3 get_most_suitable_worker函数
它的处理过程如下：
1. 如果需要绑定sessionID，就根据sessionID找到工作正常的最佳worker。
2. 如果找不到，则调用find_best_worker函数。其处理过程如下：
i. 又调用find_best_byvalue函数。其处理过程如下：按照Round Robin的方式在本lb_worker中找到第一个不在错误状态、也没有停止、没有disabled 、也不busy的lb_sub_worker。
ii.如果find_best_byvalue返回错误，说明本lb_worker的lb_sub_worker都处于非正常工作状态，需要调用find_failover_worker函数，通过
redirect、route、domain指令来进行查找[3]。
3.4 ajp_worker的处理函数
3.4.1 ajp_worker的get_endpoint函数
它的主要功能是：找到与后端tomcat的一个空闲连接。
3.4.2 ajp_worker的ajp_service函数
该函数主要分为 ajp_send_request和and ajp_get_reply两个函数。
它的处理过程如下：
1. 获取共享内存中的状态。
2. 分配AJP请求包、恢复包、POST包的内存。
3. 调用ajp_marshal_into_msgb函数，将HTTP请求包转化为AJP包。
4. 将当前ajp_worker的状态更新。
5. 调用ajp_send_request函数。
6. 如果发送成功，调用ajp_get_reply函数，等待并接受AJP包。
7. 如果成功，更新当前状态。
3.4.2 ajp_worker的ajp_send_request函数
它的处理过程如下：
1. 调用jk_is_socket_connected函数，检查即将发送的socket是否有效。它的检查过程是运用select函数，等1微妙，如果成功返回说明，该socket的文件描述符至少在内核中还有效。
2. 如果上一次发送超时，则调用ajp_handle_cping_cpong函数来判断后端连接是否有效。该函数主要是发出了一个AJP13_CPING_REQUEST类型的AJP包，如果tomcat收到，应返回一个AJP13_CPONG_REPLY的包。
3. 如果上述的测试都成功，调用ajp_connection_tcp_send_message，发送AJP包。
3.4.3 ajp_worker的ajp_get_reply函数
它的处理过程如下：
1. 调用jk_is_input_event，用select等待接受数据，直到socket有接受数据。
2. 调用ajp_connection_tcp_get_message，接受AJP包，并检查协议头。
3. 调用ajp_process_callback，对该AJP包进行解析处理。其处理过程如下：
i. 如果是JK_AJP13_SEND_HEADERS包，将其解包成HTTP包头。如果没有错误，就调用jk_ws_service->start_response（）函数发送HTTP回复的head。返回JK_AJP13_SEND_HEADERS。
ii.如果是JK_AJP13_SEND_BODY_CHUNK包，调用jk_ws_service->write发送HTTP回复的body。返回JK_AJP13_NO_RESPONSE。
iii.如果是JK_AJP13_GET_BODY_CHUNK包，说明还有数据要发送到tomcat，调用ajp_read_into_msg_buff，继续发送数据。返回JK_AJP13_HAS_RESPONSE。
iv.如果是JK_AJP13_END_RESPONSE包，就说明tomcat的回复已经完成。返回JK_AJP13_END_RESPONSE。
3.5jk_ws_service的一些处理函数
3.5.1 jk_ws_service 的 ws_start_response函数
该函数主要是构建HTTP回复包的头部。
3.5.2 jk_ws_service 的 ws_write函数
调用 apache的ap_rwrite函数，发送整个HTTP包。
3.5.3 jk_ws_service 的 ws_read函数
调用apache的ap_get_client_block读入全部的request body数据。
4 mod_jk的主要数据结构
4.1 lb_worker
lb_worker是负载均衡worker。主要负责调配其名下的一些lb_sub_worker 。
[plain] view plaincopyprint?
1. dist/common/jk_lb_worker.h
2. struct lb_worker
3. {
4. /* jk模块通用worker结构体。包含一些回调函数，不同的worker有不同的函数实现 */
5. jk_worker_t worker;
6. /* Shared memory worker data */
7. jk_shm_lb_worker_t *s;
8. char name[JK_SHM_STR_SIZ+1];
9. /* Sequence counter starting at 0 and increasing every time we change the config */
10. volatile unsigned int sequence;
11. jk_pool_t p;
12. jk_pool_atom_t buf[TINY_POOL_SIZE];
13. JK_CRIT_SEC cs;
14. /*其名下的workers*/
15. lb_sub_worker_t *lb_workers;
16. unsigned int num_of_workers;
17. int sticky_session;
18. int sticky_session_force;
19. int recover_wait_time;
20. int max_reply_timeouts;
21. int retries;
22. int retry_interval;
23. int lbmethod;
24. int lblock;
25. int maintain_time;
26. unsigned int max_packet_size;
27. unsigned int next_offset;
28. /* Session cookie */
29. char session_cookie[JK_SHM_STR_SIZ+1];
30. /* Session path */
31. char session_path[JK_SHM_STR_SIZ+1];
32. };
33. lb_sub_worker是由lb_worker支配的ajp_worker。当然lb_sub_worker有不同的类型。
34. 它们的实际类型存储在ajp_worker中。
35.
36. dist/common/jk_lb_worker.h
37. struct lb_sub_worker
38. {
39. /* 包含ajp_worker的回调函数及其ajp_worker结构体*/
40. jk_worker_t *worker;
41. /* Shared memory worker data */
42. jk_shm_lb_sub_worker_t *s;
43. char name[JK_SHM_STR_SIZ+1];
44. /* Sequence counter starting at 0 and increasing
45. * every time we change the config
46. */
47. volatile unsigned int sequence;
48. /* route */
49. char route[JK_SHM_STR_SIZ+1];
50. /* worker domain */
51. char domain[JK_SHM_STR_SIZ+1];
52. /* worker redirect route */
53. char redirect[JK_SHM_STR_SIZ+1];
54. /* worker distance */
55. int distance;
56. /* current activation state (config) of the worker */
57. int activation;
58. /* Current lb factor */
59. int lb_factor;
60. /* Current worker index */
61. int i;
62. /* Current lb reciprocal factor */
63. jk_uint64_t lb_mult;
64. };
65. typedef struct lb_sub_worker lb_sub_worker_t;
1. 4.2 ajp_worker
2. ajp_worker是具体工作的worker，对应后端一个tomcat应用服务。
3. dist/common/jk_ajp_common.c
4. struct ajp_worker
5. {
6. /* 包含ajp_worker的回调函数*/
7. jk_worker_t worker;
8. /* Shared memory worker data */
9. jk_shm_ajp_worker_t *s;
10. char name[JK_SHM_STR_SIZ+1];
11. /* Sequence counter starting at 0 and increasing
12. * every time we change the config
13. */
14. volatile unsigned int sequence;
15. jk_pool_t p;
16. jk_pool_atom_t buf[TINY_POOL_SIZE];
17. JK_CRIT_SEC cs;
18. struct sockaddr_in worker_inet_addr; /* Contains host and port */
19. unsigned connect_retry_attempts;
20. const char *host;
21. int port;
22. int maintain_time;
23. /*
24. * Open connections cache...
25. *
26. * 1. Critical section object to protect the cache.
27. * 2. Cache size.
28. * 3. An array of "open" endpoints.
29. */
30. unsigned int ep_cache_sz;
31. unsigned int ep_mincache_sz;
32. unsigned int ep_maxcache_sz;
33. int cache_acquire_timeout;
34. ajp_endpoint_t **ep_cache;
35. int proto; /* PROTOCOL USED AJP13/AJP14 */
36. jk_login_service_t *login;
37. /* Weak secret similar with ajp12, used in ajp13 */
38. const char *secret;
39. /*
40. * Post physical connect handler.
41. * AJP14 will set here its login handler
42. */
43. int (*logon) (ajp_endpoint_t * ae, jk_logger_t *l);
44. /*
45. * Handle Socket Timeouts
46. */
47. int socket_timeout;
48. int socket_connect_timeout;
49. int keepalive;
50. int socket_buf;
51. /*
52. * Handle Cache Timeouts
53. */
54. int cache_timeout;
55. /*
56. * Handle Connection/Reply Timeouts
57. */
58. int connect_timeout; /* connect cping/cpong delay in ms (0 means
59. disabled) */
60. int reply_timeout; /* reply timeout delay in ms (0 means disabled) */
61. int prepost_timeout; /* before sending a request cping/cpong timeout
62. delay in ms (0 means disabled) */
63. int conn_ping_interval; /* interval for sending keepalive cping packets on
64. * unused connection */
65. int ping_timeout; /* generic cping/cpong timeout. Used for keepalive
66. packets or
67. * as default for boolean valued connect and
68. prepost timeouts.
69. */
70. unsigned int ping_mode; /* Ping mode flags (which types of cpings should
71. be used) */
72. /*
73. * Recovery options
74. */
75. unsigned int recovery_opts;
76. /*
77. * Public property to enable the number of retry attempts
78. * on this worker.
79. */
80. int retries;
81. unsigned int max_packet_size; /* Maximum AJP Packet size */
82. int retry_interval; /* Number of milliseconds to sleep before
83. doing a retry */
84. /*
85. * HTTP status that will cause failover (0 means disabled)
86. */
87. unsigned int http_status_fail_num;
88. int http_status_fail[JK_MAX_HTTP_STATUS_FAILS];
89. };
90. 4.3 status_worker
91. status_worker用于产生一些状态的统计信息。
92. dist/common/jk_statuc.c
93. struct status_worker
94. {
95. jk_pool_t p;
96. jk_pool_atom_t buf[TINY_POOL_SIZE];
97. const char *name;
98. const char *css;
99. const char *ns;
100.const char *xmlns;
101.const char *doctype;
102.const char *prefix;
103.int read_only;
104.char **user_names;
105.unsigned int num_of_users;
106.int user_case_insensitive;
107.jk_uint32_t good_mask;
108.jk_uint32_t bad_mask;
109.jk_worker_t worker;
110.jk_worker_env_t *we;
111.};
112.4.4 jk_worker和 jk_endpoint
113.jk_worker是所有worker通用结构体名称, 主要包含的是一些函数指针。它是一个类
114.似java中抽象类的概念，各成员函数在从factory函数生产时初始化。
115.dist/common/jk_service.h
116.struct jk_worker
117.{
118./*
119.* A 'this' pointer which is used by the subclasses of this class to
120.* point to data/functions which are specific to a given protocol
121.* (e.g. ajp12 or ajp13 or ajp14).
122.*/
123.void *worker_private;/* 指向ajp_worker，lb_worker结构体 ...*/
124.int type;
125./*
126.* For all of the below (except destroy), the first argument is
127.* essentially a 'this' pointer.
128.*/
129./* 先于init函数调用，用于分配各类worker结构体的内存，作必要的初始化
130.* Given a worker which is in the process of being created, and a list
131.* of configuration options (or 'properties'), check to see if it the
132.* options are. This will always be called before the init() method.
133.* The init/validate distinction is a bit hazy to me.
134.* See jk_ajp13_worker.c/jk_ajp14_worker.c and jk_worker.c-
135.>wc_create_worker()
136.*/
137.int (JK_METHOD * validate) (jk_worker_t *w,
138.jk_map_t *props,
139.jk_worker_env_t *we, jk_logger_t *l);
140./*
141.* Update worker either from jk_status or reloading from workers.properties
142.*/
143.int (JK_METHOD * update) (jk_worker_t *w,
144.jk_map_t *props,
145.jk_worker_env_t *we, jk_logger_t *l);
146./*
147.* Do whatever initialization needs to be done to start this worker up.
148.* Configuration options are passed in via the props parameter.
149.*/
150.int (JK_METHOD * init) (jk_worker_t *w,
151.jk_map_t *props,
152.jk_worker_env_t *we, jk_logger_t *l);
153./*
154.* Obtain an endpoint to service a particular request. A pointer to
155.* the endpoint is stored in pend.
156.*/
157.int (JK_METHOD * get_endpoint) (jk_worker_t *w,
158.jk_endpoint_t **pend, jk_logger_t *l);
159./*
160.* Shutdown this worker. The first argument is not a 'this' pointer,
161.* but rather a pointer to 'this', so that the object can be free'd (I
162.* think -- though that doesn't seem to be happening. Hmmm).
163.*/
164.int (JK_METHOD * destroy) (jk_worker_t **w, jk_logger_t *l);
165./*
166.* Maintain this worker.
167.*/
168.int (JK_METHOD * maintain) (jk_worker_t *w, time_t now, jk_logger_t *l);
169.};
170./* jk_endpoint可以称之为通用终端服务结构体，各类worker可能有自己的endpoint结构
171.体。比如ajp_worker, 该终端是用来做具体工作的，比如发出请求，接收AJP数据等等。如
172.果是lb_worker，该终端是的作用是找出合适ajp_worker, 把任务交给它。* /
173.struct jk_endpoint
174.{
175.jk_uint64_t rd;
176.jk_uint64_t wr;
177./*
178.* Flag to pass back recoverability status from
179.* a load balancer member to the load balancer itself.
180.* Depending on the configuration and request status
181.* recovery is not allowed.
182.*/
183.int recoverable;
184./*
185.* A 'this' pointer which is used by the subclasses of this class to
186.* point to data/functions which are specific to a given protocol
187.* (e.g. ajp12 or ajp13 or ajp14).
188.*/
189.void *endpoint_private;
190./* 该函数是具体的服务函数
191.* Forward a request to the servlet engine. The request is described
192.* by the jk_ws_service_t object.
193.* is_error is either 0 meaning recoverable or set to
194.* the HTTP error code.
195.*/
196.int (JK_METHOD * service) (jk_endpoint_t *e,
197.jk_ws_service_t *s,
198.jk_logger_t *l, int *is_error);
199./*
200.* Called when this particular endpoint has finished processing a
201.* request. For some protocols (e.g. ajp12), this frees the memory
202.* associated with the endpoint. For others (e.g. ajp13/ajp14), this can
203.* return the endpoint to a cache of already opened endpoints.
204.*
205.* Note that the first argument is *not* a 'this' pointer, but is
206.* rather a pointer to a 'this' pointer. This is necessary, because
207.* we may need to free this object.
208.*/
209.int (JK_METHOD * done) (jk_endpoint_t **p, jk_logger_t *l);
210.};
211.4.5 jk_ws_service
212.该结构体是与apache相关的一些参数或函数，面向HTTP协议，与AJP协议不太相关。
213.dist/common/jk_service.h
214.struct jk_ws_service
215.{
216./*
217.* A 'this' pointer which is used by the subclasses of this class to
218.* point to data which is specific to a given web server platform
219.* (e.g. Apache or IIS).
220.*/
221.void *ws_private;
222./*
223.* Provides memory management. All data specific to this request is
224.* allocated within this pool, which can then be reclaimed at the end
225.* of the request handling cycle.
226.*
227.* Alive as long as the request is alive.
228.*/
229.jk_pool_t *pool;
230./*
231.* CGI Environment needed by servlets
232.*/
233.const char *method;
234.const char *protocol;
235.char *req_uri;
236.const char *remote_addr;
237.const char *remote_host;
238.const char *remote_user;
239.const char *auth_type;
240.const char *query_string;
241.const char *server_name;
242.unsigned server_port;
243.char *server_software;
244.jk_uint64_t content_length; /* 64 bit integer that represents the content */
245./* length should be 0 if unknown. */
246.unsigned is_chunked; /* 1 if content length is unknown (chunked rq) */
247.unsigned no_more_chunks; /* 1 if last chunk has been read */
248.jk_uint64_t content_read; /* number of bytes read */
249./*
250.* SSL information
251.*
252.* is_ssl - True if request is in ssl connection
253.* ssl_cert - If available, base64 ASN.1 encoded client certificates.
254.* ssl_cert_len - Length of ssl_cert, 0 if certificates are not available.
255.* ssl_cipher - The ssl cipher suite in use.
256.* ssl_session - The ssl session string
257.*
258.* In some servers it is impossible to extract all this information, in this
259.* case, we are passing NULL.
260.*/
261.int is_ssl;
262.char *ssl_cert;
263.unsigned ssl_cert_len;
264.char *ssl_cipher;
265.char *ssl_session;
266./*
267.* SSL extra information for Servlet 2.3 API
268.*
269.* ssl_key_size - ssl key size in use
270.*/
271.int ssl_key_size;
272./*
273.* Headers, names and values.
274.*/
275.char **headers_names; /* Names of the request headers */
276.char **headers_values; /* Values of the request headers */
277.unsigned num_headers; /* Number of request headers */
278./*
279.* Request attributes.
280.*
281.* These attributes that were extracted from the web server and are
282.* sent to Tomcat.
283.*
284.* The developer should be able to read them from the ServletRequest
285.* attributes. Tomcat is required to append org.apache.tomcat. to
286.* these attribute names.
287.*/
288.char **attributes_names; /* Names of the request attributes */
289.char **attributes_values; /* Values of the request attributes */
290.unsigned num_attributes; /* Number of request attributes */
291./*
292.* The route is in use when the adapter load balance among
293.* several workers. It is the ID of a specific target in the load balance
294.* group. We are using this variable to implement target session
295.* affinity
296.*/
297.const char *route;
298./* Temp solution for auth. For native1 it'll be sent on each request,
299.if an option is present. For native2 it'll be sent with the first
300.request. On java side, both cases will work. For tomcat3.2 or
301.a version that doesn't support secret - don't set the secret,
302.and it'll work.
303.*/
304.const char *secret;
305./*
306.* Area to get POST data for fail-over recovery in POST
307.*/
308.jk_msg_buf_t *reco_buf;
309.int reco_status;
310./*
311.* If set call flush after each write
312.*/
313.int flush_packets;
314./*
315.* If set call flush after AJP13_SEND_HEADERS.
316.*/
317.int flush_header;
318./*
319.* service extensions
320.*/
321.svc_extension_t extension;
322./*
323.* JK_TRUE if response headers have been sent back
324.*/
325.int response_started;
326./*
327.* JK_TRUE if response should not be send to the client
328.*/
329.int response_blocked;
330./*
331.* HTTP status sent from container.
332.*/
333.int http_response_status;
334./* Uri worker map. Added for virtual host support
335.*/
336.jk_uri_worker_map_t *uw_map;
337./* 下面这些回调函数实现都可以在mod_jk.c找到
338.* Callbacks into the web server. For each, the first argument is
339.* essentially a 'this' pointer. All return JK_TRUE on success
340.* and JK_FALSE on failure.
341.*/
342./*
343.* Send the response headers to the browser.
344.*/
345.int (JK_METHOD * start_response) (jk_ws_service_t *s,
346.int status,
347.const char *reason,
348.const char *const *header_names,
349.const char *const *header_values,
350.unsigned num_of_headers);
351./*
352.* Read a chunk of the request body into a buffer. Attempt to read len
353.* bytes into the buffer. Write the number of bytes actually read into
354.* actually_read.
355.*/
356.int (JK_METHOD * read) (jk_ws_service_t *s,
357.void *buffer,
358.unsigned len, unsigned *actually_read);
359./*
360.* Write a chunk of response data back to the browser.
361.*/
362.int (JK_METHOD * write) (jk_ws_service_t *s,
363.const void *buffer, unsigned len);
364./*
365.* Flush a chunk of response data back to the browser.
366.*/
367.void (JK_METHOD * flush) (jk_ws_service_t *s);
368./*
369.* Done with sending response back to the browser.
370.*/
371.void (JK_METHOD * done) (jk_ws_service_t *s);
372./*
373.* If set do not reuse socket after each full response
374.*/
375.int disable_reuse;
376./*
377.* Add more data to log facilities.
378.*/
379.void (JK_METHOD * add_log_items) (jk_ws_service_t *s,
380.const char *const *log_names,
381.const char *const *log_values,
382.unsigned num_of_items);
383./*
384.* Iterate through all vhosts
385.*/
386.void *(JK_METHOD * next_vhost) (void *d);
387./*
388.* String representation of a vhost
389.*/
390.void (JK_METHOD * vhost_to_text) (void *d, char *buf, size_t len);
391./*
392.* Get uw_map associated with a vhost
393.*/
394.jk_uri_worker_map_t *(JK_METHOD * vhost_to_uw_map) (void *d);
395.};
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1.
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1. 4.6 共享内存中一些数据结构
2. 共享内存中的数据结构基本上都是记录之用。有些参数在运行中会实时变化。
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1. dist/common/jk_shm.h
2. /** jk shm generic worker record structure */
3. struct jk_shm_worker_header
4. {
5. int id;
6. int type;
7. /* worker name */
8. char name[JK_SHM_STR_SIZ+1];
9. /* Sequence counter starting at 0 and increasing
10. * every time we change the config
11. */
12. volatile unsigned int sequence;
13. };
14. typedef struct jk_shm_worker_header jk_shm_worker_header_t;
15. /** jk shm ajp13/ajp14 worker record structure */
16. struct jk_shm_ajp_worker
17. {
18. jk_shm_worker_header_t h;
19. /* Configuration data mirrored from ajp_worker */
20. int cache_timeout;
21. int connect_timeout;
22. int reply_timeout;
23. int prepost_timeout;
24. unsigned int recovery_opts;
25. int retries;
26. int retry_interval;
27. unsigned int max_packet_size;
28. /* current error state (runtime) of the worker */
29. volatile int state;
30. /* Statistical data */
31. /* Number of currently busy channels */
32. volatile int busy;
33. /* Maximum number of busy channels
34. 该参数并非我们的maxbusy，它是该worker自程序运行以来busy的最大值 */
35. volatile int max_busy;
36. volatile time_t error_time;
37. /* Number of bytes read from remote */
38. volatile jk_uint64_t readed;
39. /* Number of bytes transferred to remote */
40. volatile jk_uint64_t transferred;
41. /* Number of times the worker was used */
42. volatile jk_uint64_t used;
43. /* Number of times the worker was used - snapshot during maintenance */
44. volatile jk_uint64_t used_snapshot;
45. /* Number of non 200 responses */
46. volatile jk_uint32_t errors;
47. /* Decayed number of reply_timeout errors */
48. volatile jk_uint32_t reply_timeouts;
49. /* Number of client errors */
50. volatile jk_uint32_t client_errors;
51. /* Last reset time */
52. volatile time_t last_reset;
53. volatile time_t last_maintain_time;
54. };
55. typedef struct jk_shm_ajp_worker jk_shm_ajp_worker_t;
56. /** jk shm lb sub worker record structure */
57. struct jk_shm_lb_sub_worker
58. {
59. jk_shm_worker_header_t h;
60. /* route */
61. char route[JK_SHM_STR_SIZ+1];
62. /* worker domain */
63. char domain[JK_SHM_STR_SIZ+1];
64. /* worker redirect route */
65. char redirect[JK_SHM_STR_SIZ+1];
66. /* Number of currently busy channels */
67. volatile int busy;
68. /* worker distance */
69. volatile int distance;
70. /* current activation state (config) of the worker */
71. volatile int activation;
72. /* current error state (runtime) of the worker */
73. volatile int state;
74. /* Current lb factor */
75. volatile int lb_factor;
76. /* 我们的参数加在这里*/
77. volatile int maxbusy;
78. /* Current lb reciprocal factor */
79. volatile jk_uint64_t lb_mult;
80. /* Current lb value */
81. volatile jk_uint64_t lb_value;
82. /* Statistical data */
83. volatile time_t error_time;
84. /* Number of times the worker was elected - snapshot during maintenance */
85. volatile jk_uint64_t elected_snapshot;
86. /* Number of non 200 responses */
87. volatile jk_uint32_t errors;
88. };
89. typedef struct jk_shm_lb_sub_worker jk_shm_lb_sub_worker_t;
90. /** jk shm lb worker record structure */
91. struct jk_shm_lb_worker
92. {
93. jk_shm_worker_header_t h;
94. /* Number of currently busy channels，该值是其名下ajp_worker的busy值之和*/
95. volatile int busy;
96. /* Maximum number of busy channels，该值是其名下ajp_worker的max_busy值之和
97. */
98. volatile int max_busy;
99. int sticky_session;
100.int sticky_session_force;
101.int recover_wait_time;
102.int max_reply_timeouts;
103.int retries;
104.int retry_interval;
105.int lbmethod;
106.int lblock;
107.unsigned int max_packet_size;
108./* Last reset time */
109.volatile time_t last_reset;
110.volatile time_t last_maintain_time;
111./* Session cookie */
112.char session_cookie[JK_SHM_STR_SIZ+1];
113./* Session path */
114.char session_path[JK_SHM_STR_SIZ+1];
115.};
116.typedef struct jk_shm_lb_worker jk_shm_lb_worker_t;
