From 7cff8fbb5a9c7f08a3e822a323b6a24316238ebd Mon Sep 17 00:00:00 2001 From: Joshua Tauberer Date: Mon, 14 Jul 2008 12:02:32 +0000 Subject: [PATCH] 2008-07-14 Joshua Tauberer * src/mod_mono.c: Always acquire a lock at the start of processing a request. The active requests counter function now assumes the lock is already aquired. Also added a accepting_requests flag to the dashboard so that xsp configurations can be paused. Now when restarting mod-mono-server from the control panel, the configuration is set to not accepting requests (503s returned) until after the restart. This fixed a problem that when requests came in during a restart, mod-mono-server would never successfully come back but it would keep getting forked. The flag can also be turned on and off through the control panel. svn path=/trunk/mod_mono/; revision=107874 --- ChangeLog | 13 ++++ src/mod_mono.c | 159 ++++++++++++++++++++++++++++++++++++------------- 2 files changed, 130 insertions(+), 42 deletions(-) diff --git a/ChangeLog b/ChangeLog index 61ee6fa..722f872 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,16 @@ +2008-07-14 Joshua Tauberer + + * src/mod_mono.c: Always acquire a lock at the start of processing + a request. The active requests counter function now assumes the + lock is already aquired. Also added a accepting_requests flag + to the dashboard so that xsp configurations can be paused. Now + when restarting mod-mono-server from the control panel, the + configuration is set to not accepting requests (503s returned) + until after the restart. This fixed a problem that when requests + came in during a restart, mod-mono-server would never successfully + come back but it would keep getting forked. The flag can also + be turned on and off through the control panel. + 2008-07-14 Marek Habersack * src/mod_mono.c (write_string_to_buffer, send_initial_data): use diff --git a/src/mod_mono.c b/src/mod_mono.c index 8288fcc..0802941 100644 --- a/src/mod_mono.c +++ b/src/mod_mono.c @@ -65,6 +65,7 @@ typedef struct { char restart_issued; int active_requests; int waiting_requests; + int accepting_requests; } dashboard_data; #define INITIAL_DATA_MAX_ALLOCA_SIZE 8192 @@ -466,6 +467,7 @@ ensure_dashboard_initialized (module_cfg *config, xsp_data *xsp, apr_pool_t *p) xsp->dashboard->restart_issued = 0; xsp->dashboard->active_requests = 0; xsp->dashboard->waiting_requests = 0; + xsp->dashboard->accepting_requests = 1; } } } @@ -1996,6 +1998,13 @@ static int increment_active_requests (xsp_data *conf) { #ifndef APACHE13 + /* This function tries to increment the counters that limit + * the number of simultaenous requests being processed. It + * assumes that the mutex is held when the function is called + * and returns with the mutex still held, although it may + * unlock and lock the mutex itself. + */ + apr_status_t rv; int max_active_requests = atoi(conf->max_active_requests); @@ -2004,21 +2013,20 @@ increment_active_requests (xsp_data *conf) /* Limit the number of concurrent requests. If no * limiting is in effect (or can't be done because * there is no dashboard), return the OK status. - * Same test as in the decrement function. */ - if (max_active_requests == 0 || !conf->dashboard_mutex || !conf->dashboard) + * Same test as in the decrement function and the + * control panel. */ + if (!conf->dashboard_mutex || !conf->dashboard) return 1; - rv = apr_global_mutex_lock (conf->dashboard_mutex); - /* Drop the request on failure to lock the dashboard because - * we don't want to decrement the counter later since we couldn't - * increment it here. */ - if (rv != APR_SUCCESS) - return 0; - // From here on, rv holds onto whether we still have // the lock acquired, just in case some error ocurrs // acquiring it during the loop. - if (conf->dashboard->active_requests >= max_active_requests) { + rv = APR_SUCCESS; + + /* If any limiting is in effect, and if there are the maximum + * allowed concurrent requests, then we have to hold the request + * for a bit of time. */ + if (max_active_requests > 0 && conf->dashboard->active_requests >= max_active_requests) { /* We need to wait until the active requests * go below the maximum. */ @@ -2028,7 +2036,6 @@ increment_active_requests (xsp_data *conf) * is max_active_req+max_waiting_req. */ if (conf->dashboard->waiting_requests >= max_waiting_requests) { - apr_global_mutex_unlock (conf->dashboard_mutex); ap_log_error (APLOG_MARK, APLOG_ERR, STATUS_AND_SERVER, "Maximum number of concurrent mod_mono requests to %s reached (%d active, %d waiting). Request dropped.", conf->dashboard_lock_file, max_active_requests, max_waiting_requests); @@ -2063,7 +2070,6 @@ increment_active_requests (xsp_data *conf) // many requests are going, stop processing the // request. if (rv == APR_SUCCESS && conf->dashboard->active_requests >= max_active_requests) { - apr_global_mutex_unlock (conf->dashboard_mutex); ap_log_error (APLOG_MARK, APLOG_ERR, STATUS_AND_SERVER, "Maximum number (%d) of concurrent mod_mono requests to %s reached. Droping request.", max_active_requests, conf->dashboard_lock_file); @@ -2078,7 +2084,6 @@ increment_active_requests (xsp_data *conf) return 0; conf->dashboard->active_requests++; - apr_global_mutex_unlock (conf->dashboard_mutex); return 1; #else @@ -2092,11 +2097,9 @@ decrement_active_requests (xsp_data *conf) #ifndef APACHE13 apr_status_t rv; - int max_active_requests = atoi(conf->max_active_requests); - /* Check if limiting is in effect. Same test as in the - * increment function. */ - if (max_active_requests == 0 || !conf->dashboard_mutex || !conf->dashboard) + * increment function and the control panel. */ + if (!conf->dashboard_mutex || !conf->dashboard) return; rv = apr_global_mutex_lock (conf->dashboard_mutex); @@ -2194,12 +2197,23 @@ mono_execute_request (request_rec *r, char auto_app) } else conf->dashboard_mutex_initialized_in_child = 1; } + + if (conf->dashboard_mutex && conf->dashboard) { + if (apr_global_mutex_lock (conf->dashboard_mutex) == APR_SUCCESS) { + int ok = conf->dashboard->accepting_requests; + if (ok) + ok = increment_active_requests (conf); + + apr_global_mutex_unlock (conf->dashboard_mutex); + + if (!ok) + return HTTP_SERVICE_UNAVAILABLE; + } + } #endif rv = -1; /* avoid a warning about uninitialized value */ - if (!increment_active_requests (conf)) - return HTTP_SERVICE_UNAVAILABLE; - + while (connect_attempts--) { rv = setup_socket (&sock, conf, r->pool); DEBUG_PRINT (2, "After setup_socket"); @@ -2603,6 +2617,31 @@ terminate_xsp (void *data) return terminate_xsp2(data, NULL, 0, 0); } +static void +set_accepting_requests (void *data, char *alias, int accepting_requests) +{ + server_rec *server; + module_cfg *config; + xsp_data *xsp; + int i; + + server = (server_rec *) data; + config = ap_get_module_config (server->module_config, &mono_module); + + for (i = 0; i < config->nservers; i++) { + xsp = &config->servers [i]; + + /* If alias isn't null, skip XSPs that don't have that alias. */ + if (alias != NULL && strcmp(xsp->alias, alias)) + continue; + +#ifndef APACHE13 + if (xsp->dashboard) + xsp->dashboard->accepting_requests = accepting_requests; +#endif + } +} + static int mono_control_panel_handler (request_rec *r) { @@ -2630,43 +2669,63 @@ mono_control_panel_handler (request_rec *r) uri = &r->parsed_uri; if (!uri->query || !strcmp (uri->query, "")) { /* No query string -> Emit links for configuration commands. */ - request_send_response_string (r, "
    \n"); + request_send_response_string (r, "
      \n"); + request_send_response_string (r, "
    • All Backends
      \n
      • \n"); for (i = 0; i < config->nservers; i++) { xsp = &config->servers [i]; if (xsp->run_xsp && !strcasecmp (xsp->run_xsp, "false")) continue; - buffer = apr_psprintf (r->pool, "
    • %s: " - "Restart Server", xsp->alias, xsp->alias); + buffer = apr_psprintf (r->pool, "
    • %s
        \n", xsp->alias); + request_send_response_string(r, buffer); + + buffer = apr_psprintf (r->pool, "
      • Restart Server
        • \n", xsp->alias); request_send_response_string(r, buffer); #ifndef APACHE13 ensure_dashboard_initialized (config, xsp, pconf); - if (xsp->dashboard_mutex) { - rv = apr_global_mutex_lock (xsp->dashboard_mutex); - if (rv == APR_SUCCESS) { - if (xsp->restart_mode == AUTORESTART_MODE_REQUESTS) { - buffer = apr_psprintf (r->pool, " [%d requests served; limit: %d]", - xsp->dashboard->handled_requests, xsp->restart_requests); - request_send_response_string(r, buffer); - } else if (xsp->restart_mode == AUTORESTART_MODE_TIME) { - buffer = apr_psprintf (r->pool, " [%ds time running; limit: %ds]", - (int)(time(NULL) - xsp->dashboard->start_time), (int)xsp->restart_time); - request_send_response_string(r, buffer); - } - - rv = apr_global_mutex_unlock (xsp->dashboard_mutex); - if (rv != APR_SUCCESS) - ap_log_error (APLOG_MARK, APLOG_ALERT, STATCODE_AND_SERVER (rv), - "Failed to release %s lock after mono-ctrl output, the process may deadlock!", - xsp->dashboard_lock_file); + if (xsp->dashboard_mutex && xsp->dashboard + && apr_global_mutex_lock (xsp->dashboard_mutex) == APR_SUCCESS) { + + if (xsp->dashboard->accepting_requests) + buffer = apr_psprintf (r->pool, "
      • Stop Accepting Requests
        • \n", xsp->alias); + else + buffer = apr_psprintf (r->pool, "
      • Resume Accepting Requests
        • \n", xsp->alias); + request_send_response_string(r, buffer); + + if (xsp->restart_mode == AUTORESTART_MODE_REQUESTS) { + buffer = apr_psprintf (r->pool, "
      • %d requests served; limit: %d
        • \n", + xsp->dashboard->handled_requests, xsp->restart_requests); + request_send_response_string(r, buffer); + } else if (xsp->restart_mode == AUTORESTART_MODE_TIME) { + buffer = apr_psprintf (r->pool, "
      • %ds time running; limit: %ds
        • \n", + (int)(time(NULL) - xsp->dashboard->start_time), (int)xsp->restart_time); + request_send_response_string(r, buffer); } + + buffer = apr_psprintf (r->pool, "
      • %d requests currently being processed; limit: %s
        • \n", + xsp->dashboard->active_requests, xsp->max_active_requests); + request_send_response_string(r, buffer); + + buffer = apr_psprintf (r->pool, "
      • %d requests currently waiting to be processed; limit: %s
        • \n", + xsp->dashboard->waiting_requests, xsp->max_waiting_requests); + request_send_response_string(r, buffer); + + + rv = apr_global_mutex_unlock (xsp->dashboard_mutex); + if (rv != APR_SUCCESS) + ap_log_error (APLOG_MARK, APLOG_ALERT, STATCODE_AND_SERVER (rv), + "Failed to release %s lock after mono-ctrl output, the process may deadlock!", + xsp->dashboard_lock_file); } #endif - request_send_response_string(r, "\n"); + request_send_response_string(r, "
      • \n"); } request_send_response_string (r, "
    \n"); @@ -2676,9 +2735,25 @@ mono_control_panel_handler (request_rec *r) char *alias = uri->query + 8; /* +8 == .Substring(8) */ if (!strcmp (alias, "ALL")) alias = NULL; + set_accepting_requests (r->server, alias, 0); terminate_xsp2 (r->server, alias, 1, 0); start_xsp (config, 1, alias); + set_accepting_requests (r->server, alias, 1); request_send_response_string (r, "
    mod-mono-server processes restarted.

    \n"); + } else if (uri->query && !strncmp (uri->query, "pause=", 6)) { + /* Stop accepting requests for this server */ + char *alias = uri->query + 6; /* +6 == .Substring(6) */ + if (!strcmp (alias, "ALL")) + alias = NULL; + set_accepting_requests (r->server, alias, 0); + request_send_response_string (r, "
    no longer accepting requests

    \n"); + } else if (uri->query && !strncmp (uri->query, "resume=", 7)) { + /* Resume accepting requests for this server */ + char *alias = uri->query + 7; /* +7 == .Substring(7) */ + if (!strcmp (alias, "ALL")) + alias = NULL; + set_accepting_requests (r->server, alias, 1); + request_send_response_string (r, "
    resumed accepting requests

    \n"); } else { /* Invalid command. */ request_send_response_string (r, "
    Invalid query string command.
    \n");