3 @brief Spawn and manage a collection of child process to service requests.
5 Spawn a collection of child processes, replacing them as needed. Forward requests to them
6 and let the children do the work.
8 Each child processes some maximum number of requests before it terminates itself. When a
9 child dies, either deliberately or otherwise, we can spawn another one to replace it,
10 keeping the number of children within a predefined range.
12 Use a doubly-linked circular list to keep track of the children to whom we have forwarded
13 a request, and who are still working on them. Use a separate linear linked list to keep
14 track of children that are currently idle. Move them back and forth as needed.
16 For each child, set up two pipes:
17 - One for the parent to send requests to the child.
18 - One for the child to notify the parent that it is available for another request.
20 The message sent to the child represents an XML stanza as received from Jabber.
22 When the child finishes processing the request, it writes the string "available" back
23 to the parent. Then the parent knows that it can send that child another request.
28 #include <sys/types.h>
34 #include <sys/select.h>
37 #include "opensrf/utils.h"
38 #include "opensrf/log.h"
39 #include "opensrf/transport_client.h"
40 #include "opensrf/osrf_stack.h"
41 #include "opensrf/osrf_settings.h"
42 #include "opensrf/osrf_application.h"
44 #define READ_BUFSIZE 1024
45 #define ABS_MAX_CHILDREN 256
48 int max_requests; /**< How many requests a child processes before terminating. */
49 int min_children; /**< Minimum number of children to maintain. */
50 int max_children; /**< Maximum number of children to maintain. */
51 int fd; /**< Unused. */
52 int data_to_child; /**< Unused. */
53 int data_to_parent; /**< Unused. */
54 int current_num_children; /**< How many children are currently on the list. */
55 int keepalive; /**< Keepalive time for stateful sessions. */
56 char* appname; /**< Name of the application. */
57 /** Points to a circular linked list of children. */
58 struct prefork_child_struct* first_child;
59 /** List of of child processes that aren't doing anything at the moment and are
60 therefore available to service a new request. */
61 struct prefork_child_struct* idle_list;
62 /** List of allocated but unused prefork_children, available for reuse. Each one is just
63 raw memory, apart from the "next" pointer used to stitch them together. In particular,
64 there is no child process for them, and the file descriptors are not open. */
65 struct prefork_child_struct* free_list;
66 transport_client* connection; /**< Connection to Jabber. */
69 struct prefork_child_struct {
70 pid_t pid; /**< Process ID of the child. */
71 int read_data_fd; /**< Child uses to read request. */
72 int write_data_fd; /**< Parent uses to write request. */
73 int read_status_fd; /**< Parent reads to see if child is available. */
74 int write_status_fd; /**< Child uses to notify parent when it's available again. */
75 int max_requests; /**< How many requests a child can process before terminating. */
76 const char* appname; /**< Name of the application. */
77 int keepalive; /**< Keepalive time for stateful sessions. */
78 struct prefork_child_struct* next; /**< Linkage pointer for linked list. */
79 struct prefork_child_struct* prev; /**< Linkage pointer for linked list. */
82 typedef struct prefork_child_struct prefork_child;
84 /** Boolean. Set to true by a signal handler when it traps SIGCHLD. */
85 static volatile sig_atomic_t child_dead;
87 static int prefork_simple_init( prefork_simple* prefork, transport_client* client,
88 int max_requests, int min_children, int max_children );
89 static prefork_child* launch_child( prefork_simple* forker );
90 static void prefork_launch_children( prefork_simple* forker );
91 static void prefork_run( prefork_simple* forker );
92 static void add_prefork_child( prefork_simple* forker, prefork_child* child );
94 static void del_prefork_child( prefork_simple* forker, pid_t pid );
95 static void check_children( prefork_simple* forker, int forever );
96 static int prefork_child_process_request( prefork_child*, char* data );
97 static int prefork_child_init_hook( prefork_child* );
98 static prefork_child* prefork_child_init( prefork_simple* forker,
99 int read_data_fd, int write_data_fd,
100 int read_status_fd, int write_status_fd );
102 /* listens on the 'data_to_child' fd and wait for incoming data */
103 static void prefork_child_wait( prefork_child* child );
104 static void prefork_clear( prefork_simple* );
105 static void prefork_child_free( prefork_simple* forker, prefork_child* );
106 static void osrf_prefork_register_routers( const char* appname );
107 static void osrf_prefork_child_exit( prefork_child* );
109 static void sigchld_handler( int sig );
112 @brief Spawn and manage a collection of drone processes for servicing requests.
113 @param appname Name of the application.
114 @return 0 if successful, or -1 if error.
116 int osrf_prefork_run( const char* appname ) {
119 osrfLogError( OSRF_LOG_MARK, "osrf_prefork_run requires an appname to run!");
123 set_proc_title( "OpenSRF Listener [%s]", appname );
130 // Get configuration settings
131 osrfLogInfo( OSRF_LOG_MARK, "Loading config in osrf_forker for app %s", appname );
133 char* max_req = osrf_settings_host_value( "/apps/%s/unix_config/max_requests", appname );
134 char* min_children = osrf_settings_host_value( "/apps/%s/unix_config/min_children", appname );
135 char* max_children = osrf_settings_host_value( "/apps/%s/unix_config/max_children", appname );
136 char* keepalive = osrf_settings_host_value( "/apps/%s/keepalive", appname );
139 osrfLogWarning( OSRF_LOG_MARK, "Keepalive is not defined, assuming %d", kalive );
141 kalive = atoi( keepalive );
144 osrfLogWarning( OSRF_LOG_MARK, "Max requests not defined, assuming %d", maxr );
146 maxr = atoi( max_req );
149 osrfLogWarning( OSRF_LOG_MARK, "Min children not defined, assuming %d", minc );
151 minc = atoi( min_children );
154 osrfLogWarning( OSRF_LOG_MARK, "Max children not defined, assuming %d", maxc );
156 maxc = atoi( max_children );
160 free( min_children );
161 free( max_children );
162 /* --------------------------------------------------- */
164 char* resc = va_list_to_string( "%s_listener", appname );
166 // Make sure that we haven't already booted
167 if( !osrfSystemBootstrapClientResc( NULL, NULL, resc )) {
168 osrfLogError( OSRF_LOG_MARK, "Unable to bootstrap client for osrf_prefork_run()" );
175 prefork_simple forker;
177 if( prefork_simple_init( &forker, osrfSystemGetTransportClient(), maxr, minc, maxc )) {
178 osrfLogError( OSRF_LOG_MARK,
179 "osrf_prefork_run() failed to create prefork_simple object" );
183 // Finish initializing the prefork_simple.
184 forker.appname = strdup( appname );
185 forker.keepalive = kalive;
187 // Spawn the children; put them in the idle list.
188 prefork_launch_children( &forker );
190 // Tell the router that you're open for business.
191 osrf_prefork_register_routers( appname );
193 // Sit back and let the requests roll in
194 osrfLogInfo( OSRF_LOG_MARK, "Launching osrf_forker for app %s", appname );
195 prefork_run( &forker );
197 osrfLogWarning( OSRF_LOG_MARK, "prefork_run() returned - how??" );
198 prefork_clear( &forker );
203 @brief Register the application with a specified router.
204 @param appname Name of the application.
205 @param routerName Name of the router.
206 @param routerDomain Domain of the router.
208 Tell the router that you're open for business so that it can route requests to you.
210 Called only by the parent process.
212 static void osrf_prefork_send_router_registration(
213 const char* appname, const char* routerName, const char* routerDomain ) {
214 // Get a pointer to the global transport_client
215 transport_client* client = osrfSystemGetTransportClient();
217 // Construct the Jabber address of the router
218 char* jid = va_list_to_string( "%s@%s/router", routerName, routerDomain );
219 osrfLogInfo( OSRF_LOG_MARK, "%s registering with router %s", appname, jid );
221 // Create the registration message, and send it
222 transport_message* msg = message_init( "registering", NULL, NULL, jid, NULL );
223 message_set_router_info( msg, NULL, NULL, appname, "register", 0 );
224 client_send_message( client, msg );
232 @brief Register with a router, or not, according to some config settings.
233 @param appname Name of the application
234 @param RouterChunk A representation of part of the config file.
236 Parse a "complex" router configuration chunk.
238 Examine the services listed for a given router (normally in opensrf_core.xml). If
239 there is an entry for this service, or if there are @em no services listed, then
240 register with this router. Otherwise don't.
242 Called only by the parent process.
244 static void osrf_prefork_parse_router_chunk( const char* appname, const jsonObject* routerChunk ) {
246 const char* routerName = jsonObjectGetString( jsonObjectGetKeyConst( routerChunk, "name" ));
247 const char* domain = jsonObjectGetString( jsonObjectGetKeyConst( routerChunk, "domain" ));
248 const jsonObject* services = jsonObjectGetKeyConst( routerChunk, "services" );
249 osrfLogDebug( OSRF_LOG_MARK, "found router config with domain %s and name %s",
250 routerName, domain );
252 if( services && services->type == JSON_HASH ) {
253 osrfLogDebug( OSRF_LOG_MARK, "investigating router information..." );
254 const jsonObject* service_obj = jsonObjectGetKeyConst( services, "service" );
256 ; // do nothing (shouldn't happen)
257 else if( JSON_ARRAY == service_obj->type ) {
258 // There are multiple services listed. Register with this router
259 // if and only if this service is on the list.
261 for( j = 0; j < service_obj->size; j++ ) {
262 const char* service = jsonObjectGetString( jsonObjectGetIndex( service_obj, j ));
263 if( service && !strcmp( appname, service ))
264 osrf_prefork_send_router_registration( appname, routerName, domain );
267 else if( JSON_STRING == service_obj->type ) {
268 // There's only one service listed. Register with this router
269 // if and only if this service is the one listed.
270 if( !strcmp( appname, jsonObjectGetString( service_obj )) )
271 osrf_prefork_send_router_registration( appname, routerName, domain );
274 // This router is not restricted to any set of services,
275 // so go ahead and register with it.
276 osrf_prefork_send_router_registration( appname, routerName, domain );
281 @brief Register the application with one or more routers, according to the configuration.
282 @param appname Name of the application.
284 Called only by the parent process.
286 static void osrf_prefork_register_routers( const char* appname ) {
288 jsonObject* routerInfo = osrfConfigGetValueObject( NULL, "/routers/router" );
291 for( i = 0; i < routerInfo->size; i++ ) {
292 const jsonObject* routerChunk = jsonObjectGetIndex( routerInfo, i );
294 if( routerChunk->type == JSON_STRING ) {
295 /* this accomodates simple router configs */
296 char* routerName = osrfConfigGetValue( NULL, "/router_name" );
297 char* domain = osrfConfigGetValue( NULL, "/routers/router" );
298 osrfLogDebug( OSRF_LOG_MARK, "found simple router settings with router name %s",
300 osrf_prefork_send_router_registration( appname, routerName, domain );
305 osrf_prefork_parse_router_chunk( appname, routerChunk );
309 jsonObjectFree( routerInfo );
313 @brief Initialize a child process.
314 @param child Pointer to the prefork_child representing the new child process.
315 @return Zero if successful, or -1 if not.
317 Called only by child processes. Actions:
318 - Connect to one or more cache servers
319 - Reconfigure logger, if necessary
320 - Discard parent's Jabber connection and open a new one
321 - Dynamically call an application-specific initialization routine
322 - Change the command line as reported by ps
324 static int prefork_child_init_hook( prefork_child* child ) {
326 if( !child ) return -1;
327 osrfLogDebug( OSRF_LOG_MARK, "Child init hook for child %d", child->pid );
329 // Connect to cache server(s).
330 osrfSystemInitCache();
331 char* resc = va_list_to_string( "%s_drone", child->appname );
333 // If we're a source-client, tell the logger now that we're a new process.
334 char* isclient = osrfConfigGetValue( NULL, "/client" );
335 if( isclient && !strcasecmp( isclient,"true" ))
336 osrfLogSetIsClient( 1 );
339 // Remove traces of our parent's socket connection so we can have our own.
340 osrfSystemIgnoreTransportClient();
343 if( !osrfSystemBootstrapClientResc( NULL, NULL, resc )) {
344 osrfLogError( OSRF_LOG_MARK, "Unable to bootstrap client for osrf_prefork_run()" );
351 // Dynamically call the application-specific initialization function
352 // from a previously loaded shared library.
353 if( ! osrfAppRunChildInit( child->appname )) {
354 osrfLogDebug( OSRF_LOG_MARK, "Prefork child_init succeeded\n" );
356 osrfLogError( OSRF_LOG_MARK, "Prefork child_init failed\n" );
360 // Change the command line as reported by ps
361 set_proc_title( "OpenSRF Drone [%s]", child->appname );
366 @brief Respond to a client request forwarded by the parent.
367 @param child Pointer to the state of the child process.
368 @param data Pointer to the raw XMPP message received from the parent.
369 @return 0 on success; non-zero means that the child process should clean itself up
370 and terminate immediately, presumably due to a fatal error condition.
372 Called only by a child process.
374 static int prefork_child_process_request( prefork_child* child, char* data ) {
375 if( !child ) return 0;
377 transport_client* client = osrfSystemGetTransportClient();
379 // Make sure that we're still connected to Jabber; reconnect if necessary.
380 if( !client_connected( client )) {
381 osrfSystemIgnoreTransportClient();
382 osrfLogWarning( OSRF_LOG_MARK, "Reconnecting child to opensrf after disconnect..." );
383 if( !osrf_system_bootstrap_client( NULL, NULL )) {
384 osrfLogError( OSRF_LOG_MARK,
385 "Unable to bootstrap client in prefork_child_process_request()" );
387 osrf_prefork_child_exit( child );
391 // Construct the message from the xml.
392 transport_message* msg = new_message_from_xml( data );
394 // Respond to the transport message. This is where method calls are buried.
395 osrfAppSession* session = osrf_stack_transport_handler( msg, child->appname );
399 int rc = session->panic;
402 osrfLogWarning( OSRF_LOG_MARK,
403 "Drone for session %s terminating immediately", session->session_id );
404 osrfAppSessionFree( session );
408 if( session->stateless && session->state != OSRF_SESSION_CONNECTED ) {
409 // We're no longer connected to the client, which presumably means that
410 // we're done with this request. Bail out.
411 osrfAppSessionFree( session );
415 // If we get this far, then the client has opened an application connection so that it
416 // can send multiple requests directly to the same server drone, bypassing the router
417 // and the listener. For example, it may need to do a database transaction, requiring
418 // multiple method calls within the same database session.
420 // Hence we go into a loop, responding to successive requests from the same client, until
421 // either the client disconnects or an error occurs.
423 osrfLogDebug( OSRF_LOG_MARK, "Entering keepalive loop for session %s", session->session_id );
424 int keepalive = child->keepalive;
432 // Respond to any input messages. This is where the method calls are buried.
433 osrfLogDebug( OSRF_LOG_MARK,
434 "osrf_prefork calling queue_wait [%d] in keepalive loop", keepalive );
435 start = time( NULL );
436 retval = osrf_app_session_queue_wait( session, keepalive, &recvd );
439 osrfLogDebug( OSRF_LOG_MARK, "Data received == %d", recvd );
441 // Now we check a number of possible reasons to exit the loop.
443 // If the method call decided to terminate immediately,
444 // note that for future reference.
448 // If an error occurred when we tried to service the request, exit the loop.
450 osrfLogError( OSRF_LOG_MARK, "queue-wait returned non-success %d", retval );
454 // If the client disconnected, exit the loop.
455 if( session->state != OSRF_SESSION_CONNECTED )
458 // If we timed out while waiting for a request, exit the loop.
459 if( !recvd && (end - start) >= keepalive ) {
460 osrfLogInfo( OSRF_LOG_MARK,
461 "No request was received in %d seconds, exiting stateful session", keepalive );
462 osrfAppSessionStatus(
466 0, "Disconnected on timeout" );
471 // If the child process has decided to terminate immediately, exit the loop.
476 osrfLogDebug( OSRF_LOG_MARK, "Exiting keepalive loop for session %s", session->session_id );
477 osrfAppSessionFree( session );
482 @brief Partially initialize a prefork_simple provided by the caller.
483 @param prefork Pointer to a a raw prefork_simple to be initialized.
484 @param client Pointer to a transport_client (connection to Jabber).
485 @param max_requests The maximum number of requests that a child process may service
487 @param min_children Minimum number of child processes to maintain.
488 @param max_children Maximum number of child processes to maintain.
489 @return 0 if successful, or 1 if not (due to invalid parameters).
491 static int prefork_simple_init( prefork_simple* prefork, transport_client* client,
492 int max_requests, int min_children, int max_children ) {
494 if( min_children > max_children ) {
495 osrfLogError( OSRF_LOG_MARK, "min_children (%d) is greater "
496 "than max_children (%d)", min_children, max_children );
500 if( max_children > ABS_MAX_CHILDREN ) {
501 osrfLogError( OSRF_LOG_MARK, "max_children (%d) is greater than ABS_MAX_CHILDREN (%d)",
502 max_children, ABS_MAX_CHILDREN );
506 osrfLogInfo( OSRF_LOG_MARK, "Prefork launching child with max_request=%d,"
507 "min_children=%d, max_children=%d", max_requests, min_children, max_children );
509 /* flesh out the struct */
510 prefork->max_requests = max_requests;
511 prefork->min_children = min_children;
512 prefork->max_children = max_children;
514 prefork->data_to_child = 0;
515 prefork->data_to_parent = 0;
516 prefork->current_num_children = 0;
517 prefork->keepalive = 0;
518 prefork->appname = NULL;
519 prefork->first_child = NULL;
520 prefork->idle_list = NULL;
521 prefork->free_list = NULL;
522 prefork->connection = client;
528 @brief Spawn a new child process and put it in the idle list.
529 @param forker Pointer to the prefork_simple that will own the process.
530 @return Pointer to the new prefork_child, or not at all.
532 Spawn a new child process. Create a prefork_child for it and put it in the idle list.
534 After forking, the parent returns a pointer to the new prefork_child. The child
535 services its quota of requests and then terminates without returning.
537 static prefork_child* launch_child( prefork_simple* forker ) {
543 // Set up the data and status pipes
544 if( pipe( data_fd ) < 0 ) { /* build the data pipe*/
545 osrfLogError( OSRF_LOG_MARK, "Pipe making error" );
549 if( pipe( status_fd ) < 0 ) {/* build the status pipe */
550 osrfLogError( OSRF_LOG_MARK, "Pipe making error" );
556 osrfLogInternal( OSRF_LOG_MARK, "Pipes: %d %d %d %d",
557 data_fd[0], data_fd[1], status_fd[0], status_fd[1] );
559 // Create and initialize a prefork_child for the new process
560 prefork_child* child = prefork_child_init( forker, data_fd[0],
561 data_fd[1], status_fd[0], status_fd[1] );
563 if( (pid=fork()) < 0 ) {
564 osrfLogError( OSRF_LOG_MARK, "Forking Error" );
565 prefork_child_free( forker, child );
569 // Add the new child to the head of the idle list
570 child->next = forker->idle_list;
571 forker->idle_list = child;
573 if( pid > 0 ) { /* parent */
575 signal( SIGCHLD, sigchld_handler );
576 ( forker->current_num_children )++;
579 osrfLogDebug( OSRF_LOG_MARK, "Parent launched %d", pid );
580 /* *no* child pipe FD's can be closed or the parent will re-use fd's that
581 the children are currently using */
587 osrfLogInternal( OSRF_LOG_MARK,
588 "I am new child with read_data_fd = %d and write_status_fd = %d",
589 child->read_data_fd, child->write_status_fd );
591 child->pid = getpid();
592 close( child->write_data_fd );
593 close( child->read_status_fd );
596 if( prefork_child_init_hook( child ) == -1 ) {
597 osrfLogError( OSRF_LOG_MARK,
598 "Forker child going away because we could not connect to OpenSRF..." );
599 osrf_prefork_child_exit( child );
602 prefork_child_wait( child ); // Should exit without returning
603 osrf_prefork_child_exit( child ); // Just to be sure
604 return NULL; // Unreachable, but it keeps the compiler happy
609 @brief Terminate a child process.
610 @param child Pointer to the prefork_child representing the child process (not used).
612 Called only by child processes. Dynamically call an application-specific shutdown
613 function from a previously loaded shared library; then exit.
615 static void osrf_prefork_child_exit( prefork_child* child ) {
616 osrfAppRunExitCode();
621 @brief Launch all the child processes, putting them in the idle list.
622 @param forker Pointer to the prefork_simple that will own the children.
624 Called only by the parent process (in order to become a parent).
626 static void prefork_launch_children( prefork_simple* forker ) {
627 if( !forker ) return;
629 while( c++ < forker->min_children )
630 launch_child( forker );
634 @brief Signal handler for SIGCHLD: note that a child process has terminated.
635 @param sig The value of the trapped signal; always SIGCHLD.
637 Set a boolean to be checked later.
639 static void sigchld_handler( int sig ) {
640 signal( SIGCHLD, sigchld_handler );
645 @brief Replenish the collection of child processes, after one has terminated.
646 @param forker Pointer to the prefork_simple that manages the child processes.
648 The parent calls this function when it notices (via a signal handler) that
649 a child process has died.
651 Wait on the dead children so that they won't be zombies. Spawn new ones as needed
652 to maintain at least a minimum number.
654 void reap_children( prefork_simple* forker ) {
658 // Reset our boolean so that we can detect any further terminations.
661 // Bury the children so that they won't be zombies. WNOHANG means that waitpid() returns
662 // immediately if there are no waitable children, instead of waiting for more to die.
663 // Ignore the return code of the child. We don't do an autopsy.
664 while( (child_pid = waitpid( -1, NULL, WNOHANG )) > 0 ) {
665 --forker->current_num_children;
666 del_prefork_child( forker, child_pid );
669 // Spawn more children as needed.
670 while( forker->current_num_children < forker->min_children )
671 launch_child( forker );
675 @brief Read transport_messages and dispatch them to child processes for servicing.
676 @param forker Pointer to the prefork_simple that manages the child processes.
678 This is the main loop of the parent process, and once entered, does not exit.
680 For each usable transport_message received: look for an idle child to service it. If
681 no idle children are available, either spawn a new one or, if we've already spawned the
682 maximum number of children, wait for one to become available. Once a child is available
683 by whatever means, write an XML version of the input message, to a pipe designated for
686 static void prefork_run( prefork_simple* forker ) {
688 if( NULL == forker->idle_list )
689 return; // No available children, and we haven't even started yet
691 transport_message* cur_msg = NULL;
695 if( forker->first_child == NULL && forker->idle_list == NULL ) {/* no more children */
696 osrfLogWarning( OSRF_LOG_MARK, "No more children..." );
700 // Wait indefinitely for an input message
701 osrfLogDebug( OSRF_LOG_MARK, "Forker going into wait for data..." );
702 cur_msg = client_recv( forker->connection, -1 );
704 if( cur_msg == NULL )
705 continue; // Error? Interrupted by a signal? Try again...
707 message_prepare_xml( cur_msg );
708 const char* msg_data = cur_msg->msg_xml;
709 if( ! msg_data || ! *msg_data ) {
710 osrfLogWarning( OSRF_LOG_MARK, "Received % message from %s, thread %",
711 (msg_data ? "empty" : "NULL"), cur_msg->sender, cur_msg->thread );
712 message_free( cur_msg );
713 continue; // Message not usable; go on to the next one.
716 int honored = 0; /* will be set to true when we service the request */
722 check_children( forker, 0 );
725 osrfLogDebug( OSRF_LOG_MARK, "Server received inbound data" );
727 prefork_child* cur_child = NULL;
729 // Look for an available child in the idle list. Since the idle list operates
730 // as a stack, the child we get is the one that was most recently active, or
731 // most recently spawned. That means it's the one most likely still to be in
732 // physical memory, and the one least likely to have to be swapped in.
733 while( forker->idle_list ) {
735 osrfLogInfo( OSRF_LOG_MARK, "Looking for idle child" );
736 // Grab the prefork_child at the head of the idle list
737 cur_child = forker->idle_list;
738 forker->idle_list = cur_child->next;
739 cur_child->next = NULL;
741 osrfLogInternal( OSRF_LOG_MARK,
742 "Searching for available child. cur_child->pid = %d", cur_child->pid );
743 osrfLogInternal( OSRF_LOG_MARK, "Current num children %d",
744 forker->current_num_children );
746 osrfLogDebug( OSRF_LOG_MARK, "forker sending data to %d", cur_child->pid );
747 osrfLogInternal( OSRF_LOG_MARK, "Writing to child fd %d",
748 cur_child->write_data_fd );
750 int written = write( cur_child->write_data_fd, msg_data, strlen( msg_data ) + 1 );
752 // This child appears to be dead or unusable. Discard it.
753 osrfLogWarning( OSRF_LOG_MARK, "Write returned error %d: %s",
754 errno, strerror( errno ));
755 kill( cur_child->pid, SIGKILL );
756 del_prefork_child( forker, cur_child->pid );
760 add_prefork_child( forker, cur_child ); // Add it to active list
765 /* if none available, add a new child if we can */
767 osrfLogDebug( OSRF_LOG_MARK, "Not enough children, attempting to add..." );
769 if( forker->current_num_children < forker->max_children ) {
770 osrfLogDebug( OSRF_LOG_MARK, "Launching new child with current_num = %d",
771 forker->current_num_children );
773 launch_child( forker ); // Put a new child into the idle list
774 if( forker->idle_list ) {
776 // Take the new child from the idle list
777 prefork_child* new_child = forker->idle_list;
778 forker->idle_list = new_child->next;
779 new_child->next = NULL;
781 osrfLogDebug( OSRF_LOG_MARK, "Writing to new child fd %d : pid %d",
782 new_child->write_data_fd, new_child->pid );
785 new_child->write_data_fd, msg_data, strlen( msg_data ) + 1 );
787 // This child appears to be dead or unusable. Discard it.
788 osrfLogWarning( OSRF_LOG_MARK, "Write returned error %d: %s",
789 errno, strerror( errno ));
790 kill( cur_child->pid, SIGKILL );
791 del_prefork_child( forker, cur_child->pid );
793 add_prefork_child( forker, new_child );
802 osrfLogWarning( OSRF_LOG_MARK, "No children available, waiting..." );
803 check_children( forker, 1 );
804 // Tell the loop not to call check_children again, since we're calling it now
809 reap_children( forker );
811 } // end while( ! honored )
813 message_free( cur_msg );
815 } /* end top level listen loop */
819 /* XXX Add a flag which tells select() to wait forever on children
820 in the best case, this will be faster than calling usleep(x), and
821 in the worst case it won't be slower and will do less logging...
824 @brief See if any children have become available.
825 @param forker Pointer to the prefork_simple that owns the children.
826 @param forever Boolean: true if we should wait indefinitely.
828 Call select() for all the children in the active list. Read each active file
829 descriptor and move the corresponding child to the idle list.
831 If @a forever is true, wait indefinitely for input. Otherwise return immediately if
832 there are no active file descriptors.
834 static void check_children( prefork_simple* forker, int forever ) {
837 reap_children( forker );
839 if( NULL == forker->first_child ) {
840 // If forever is true, then we're here because we've run out of idle
841 // processes, so there should be some active ones around.
842 // If forever is false, then the children may all be idle, and that's okay.
844 osrfLogError( OSRF_LOG_MARK, "No active child processes to check" );
850 FD_ZERO( &read_set );
854 // Prepare to select() on pipes from all the active children
855 prefork_child* cur_child = forker->first_child;
857 if( cur_child->read_status_fd > max_fd )
858 max_fd = cur_child->read_status_fd;
859 FD_SET( cur_child->read_status_fd, &read_set );
860 cur_child = cur_child->next;
861 } while( cur_child != forker->first_child );
863 FD_CLR( 0, &read_set ); /* just to be sure */
866 osrfLogWarning( OSRF_LOG_MARK,
867 "We have no children available - waiting for one to show up..." );
869 if( (select_ret=select( max_fd + 1, &read_set, NULL, NULL, NULL )) == -1 ) {
870 osrfLogWarning( OSRF_LOG_MARK, "Select returned error %d on check_children: %s",
871 errno, strerror( errno ));
873 osrfLogInfo( OSRF_LOG_MARK,
874 "select() completed after waiting on children to become available" );
882 if( (select_ret=select( max_fd + 1, &read_set, NULL, NULL, &tv )) == -1 ) {
883 osrfLogWarning( OSRF_LOG_MARK, "Select returned error %d on check_children: %s",
884 errno, strerror( errno ));
888 if( select_ret == 0 )
891 // Check each child in the active list.
892 // If it has responded, move it to the idle list.
893 cur_child = forker->first_child;
894 prefork_child* next_child = NULL;
897 next_child = cur_child->next;
898 if( FD_ISSET( cur_child->read_status_fd, &read_set )) {
899 osrfLogDebug( OSRF_LOG_MARK,
900 "Server received status from a child %d", cur_child->pid );
904 /* now suck off the data */
906 if( (n=read( cur_child->read_status_fd, buf, sizeof( buf ) - 1 )) < 0 ) {
907 osrfLogWarning( OSRF_LOG_MARK,
908 "Read error after select in child status read with errno %d: %s",
909 errno, strerror( errno ));
913 osrfLogDebug( OSRF_LOG_MARK, "Read %d bytes from status buffer: %s", n, buf );
916 // Remove the child from the active list
917 if( forker->first_child == cur_child ) {
918 if( cur_child->next == cur_child )
919 forker->first_child = NULL; // only child in the active list
921 forker->first_child = cur_child->next;
923 cur_child->next->prev = cur_child->prev;
924 cur_child->prev->next = cur_child->next;
926 // Add it to the idle list
927 cur_child->prev = NULL;
928 cur_child->next = forker->idle_list;
929 forker->idle_list = cur_child;
931 cur_child = next_child;
932 } while( forker->first_child && forker->first_child != next_child );
936 @brief Service up a set maximum number of requests; then shut down.
937 @param child Pointer to the prefork_child representing the child process.
939 Called only by child process.
941 Enter a loop, for up to max_requests iterations. On each iteration:
942 - Wait indefinitely for a request from the parent.
943 - Service the request.
944 - Increment a counter. If the limit hasn't been reached, notify the parent that you
945 are available for another request.
947 After exiting the loop, shut down and terminate the process.
949 static void prefork_child_wait( prefork_child* child ) {
952 growing_buffer* gbuf = buffer_init( READ_BUFSIZE );
953 char buf[READ_BUFSIZE];
955 for( i = 0; i < child->max_requests; i++ ) {
958 int gotdata = 0; // boolean; set to true if we get data
959 clr_fl( child->read_data_fd, O_NONBLOCK );
961 // Read a request from the parent, via a pipe, into a growing_buffer.
962 while( (n = read( child->read_data_fd, buf, READ_BUFSIZE-1 )) > 0 ) {
964 osrfLogDebug( OSRF_LOG_MARK, "Prefork child read %d bytes of data", n );
966 set_fl( child->read_data_fd, O_NONBLOCK );
969 buffer_add_n( gbuf, buf, n );
972 if( errno == EAGAIN )
975 if( errno == EPIPE ) {
976 osrfLogDebug( OSRF_LOG_MARK, "C child attempted read on broken pipe, exiting..." );
980 int terminate_now = 0; // Boolean
983 osrfLogWarning( OSRF_LOG_MARK,
984 "Prefork child read returned error with errno %d", errno );
987 } else if( gotdata ) {
988 // Process the request
989 osrfLogDebug( OSRF_LOG_MARK, "Prefork child got a request.. processing.." );
990 terminate_now = prefork_child_process_request( child, gbuf->buf );
991 buffer_reset( gbuf );
994 if( terminate_now ) {
995 // We're terminating prematurely -- presumably due to a fatal error condition.
996 osrfLogWarning( OSRF_LOG_MARK, "Prefork child terminating abruptly" );
1000 if( i < child->max_requests - 1 ) {
1001 // Report back to the parent for another request.
1003 ssize_t len = write(
1004 child->write_status_fd, "available" /*less than 64 bytes*/, msg_len );
1005 if( len != msg_len ) {
1006 osrfLogError( OSRF_LOG_MARK,
1007 "Drone terminating: unable to notify listener of availability: %s",
1009 buffer_free( gbuf );
1010 osrf_prefork_child_exit( child );
1015 buffer_free( gbuf );
1017 osrfLogDebug( OSRF_LOG_MARK, "Child with max-requests=%d, num-served=%d exiting...[%ld]",
1018 child->max_requests, i, (long) getpid());
1020 osrf_prefork_child_exit( child );
1024 @brief Add a prefork_child to the end of the active list.
1025 @param forker Pointer to the prefork_simple that owns the list.
1026 @param child Pointer to the prefork_child to be added.
1028 static void add_prefork_child( prefork_simple* forker, prefork_child* child ) {
1030 if( forker->first_child == NULL ) {
1031 // Simplest case: list is initially empty.
1032 forker->first_child = child;
1033 child->next = child;
1034 child->prev = child;
1036 // Find the last node in the circular list.
1037 prefork_child* last_child = forker->first_child->prev;
1039 // Insert the new child between the last and first children.
1040 last_child->next = child;
1041 child->prev = last_child;
1042 child->next = forker->first_child;
1043 forker->first_child->prev = child;
1048 @brief Delete and destroy a dead child from our list.
1049 @param forker Pointer to the prefork_simple that owns the dead child.
1050 @param pid Process ID of the dead child.
1052 Look for the dead child first in the list of active children. If you don't find it
1053 there, look in the list of idle children. If you find it, remove it from whichever
1054 list it's on, and destroy it.
1056 static void del_prefork_child( prefork_simple* forker, pid_t pid ) {
1058 osrfLogDebug( OSRF_LOG_MARK, "Deleting Child: %d", pid );
1060 prefork_child* cur_child = NULL;
1062 // Look first in the active list
1063 if( forker->first_child ) {
1064 cur_child = forker->first_child; /* current pointer */
1065 while( cur_child->pid != pid && cur_child->next != forker->first_child )
1066 cur_child = cur_child->next;
1068 if( cur_child->pid == pid ) {
1069 // We found the right node. Remove it from the list.
1070 if( cur_child->next == cur_child )
1071 forker->first_child = NULL; // only child in the list
1073 if( forker->first_child == cur_child )
1074 forker->first_child = cur_child->next; // Reseat forker->first_child
1076 // Stitch the adjacent nodes together
1077 cur_child->prev->next = cur_child->next;
1078 cur_child->next->prev = cur_child->prev;
1081 cur_child = NULL; // Didn't find it in the active list
1085 // Maybe it's in the idle list. This can happen if, for example,
1086 // a child is killed by a signal while it's between requests.
1088 prefork_child* prev = NULL;
1089 cur_child = forker->idle_list;
1090 while( cur_child && cur_child->pid != pid ) {
1092 cur_child = cur_child->next;
1096 // Detach from the list
1098 prev->next = cur_child->next;
1100 forker->idle_list = cur_child->next;
1101 } // else we can't find it
1104 // If we found the node, destroy it.
1106 prefork_child_free( forker, cur_child );
1110 @brief Create and initialize a prefork_child.
1111 @param forker Pointer to the prefork_simple that will own the prefork_child.
1112 @param read_data_fd Used by child to read request from parent.
1113 @param write_data_fd Used by parent to write request to child.
1114 @param read_status_fd Used by parent to read status from child.
1115 @param write_status_fd Used by child to write status to parent.
1116 @return Pointer to the newly created prefork_child.
1118 The calling code is responsible for freeing the prefork_child by calling
1119 prefork_child_free().
1121 static prefork_child* prefork_child_init( prefork_simple* forker,
1122 int read_data_fd, int write_data_fd,
1123 int read_status_fd, int write_status_fd ) {
1125 // Allocate a prefork_child -- from the free list if possible, or from
1126 // the heap if necessary. The free list is a non-circular, singly-linked list.
1127 prefork_child* child;
1128 if( forker->free_list ) {
1129 child = forker->free_list;
1130 forker->free_list = child->next;
1132 child = safe_malloc( sizeof( prefork_child ));
1135 child->read_data_fd = read_data_fd;
1136 child->write_data_fd = write_data_fd;
1137 child->read_status_fd = read_status_fd;
1138 child->write_status_fd = write_status_fd;
1139 child->max_requests = forker->max_requests;
1140 child->appname = forker->appname; // We don't make a separate copy
1141 child->keepalive = forker->keepalive;
1149 @brief Terminate all child processes and clear out a prefork_simple.
1150 @param prefork Pointer to the prefork_simple to be cleared out.
1152 We do not deallocate the prefork_simple itself, just its contents.
1154 static void prefork_clear( prefork_simple* prefork ) {
1156 // Kill all the active children, and move their prefork_child nodes to the free list.
1157 while( prefork->first_child ) {
1158 kill( prefork->first_child->pid, SIGKILL );
1159 del_prefork_child( prefork, prefork->first_child->pid );
1162 // Kill all the idle prefork children, close their file
1163 // descriptors, and move them to the free list.
1164 prefork_child* child = prefork->idle_list;
1165 prefork->idle_list = NULL;
1167 prefork_child* temp = child->next;
1168 kill( child->pid, SIGKILL );
1169 prefork_child_free( prefork, child );
1172 //prefork->current_num_children = 0;
1174 // Physically free the free list of prefork_children.
1175 child = prefork->free_list;
1176 prefork->free_list = NULL;
1178 prefork_child* temp = child->next;
1183 // Close the Jabber connection
1184 client_free( prefork->connection );
1185 prefork->connection = NULL;
1187 // After giving the child processes a second to terminate, wait on them so that they
1188 // don't become zombies. We don't wait indefinitely, so it's possible that some
1189 // children will survive a bit longer.
1191 while( (waitpid( -1, NULL, WNOHANG )) > 0 ) {
1192 --prefork->current_num_children;
1195 free( prefork->appname );
1196 prefork->appname = NULL;
1200 @brief Destroy and deallocate a prefork_child.
1201 @param forker Pointer to the prefork_simple that owns the prefork_child.
1202 @param child Pointer to the prefork_child to be destroyed.
1204 static void prefork_child_free( prefork_simple* forker, prefork_child* child ) {
1205 close( child->read_data_fd );
1206 close( child->write_data_fd );
1207 close( child->read_status_fd );
1208 close( child->write_status_fd );
1210 // Stick the prefork_child in a free list for potential reuse. This is a
1211 // non-circular, singly linked list.
1213 child->next = forker->free_list;
1214 forker->free_list = child;