src/main/connection.c

   1 /*
   2  *   This program is free software; you can redistribute it and/or modify
   3  *   it under the terms of the GNU General Public License as published by
   4  *   the Free Software Foundation; either version 2 of the License, or
   5  *   (at your option) any later version.
   6  *
   7  *   This program is distributed in the hope that it will be useful,
   8  *   but WITHOUT ANY WARRANTY; without even the implied warranty of
   9  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  10  *   GNU General Public License for more details.
  11  *
  12  *   You should have received a copy of the GNU General Public License
  13  *   along with this program; if not, write to the Free Software
  14  *   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
  15  */
  16
  17 /**
  18  * @file connection.c
  19  * @brief Handle pools of connections (threads, sockets, etc.)
  20  * @note This API must be used by all modules in the public distribution that
  21  * maintain pools of connections.
  22  *
  23  * @copyright 2012  The FreeRADIUS server project
  24  * @copyright 2012  Alan DeKok <aland@deployingradius.com>
  25  */
  26 RCSID("$Id$")
  27
  28 #include <freeradius-devel/radiusd.h>
  29 #include <freeradius-devel/rad_assert.h>
  30
  31 typedef struct fr_connection fr_connection_t;
  32
  33 static int fr_connection_pool_check(fr_connection_pool_t *pool);
  34
  35 extern bool check_config;
  36
  37 #ifndef NDEBUG
  38 #ifdef HAVE_PTHREAD_H
  39 /* #define PTHREAD_DEBUG (1) */
  40 #endif
  41 #endif
  42
  43 /** An individual connection within the connection pool
  44  *
  45  * Defines connection counters, timestamps, and holds a pointer to the
  46  * connection handle itself.
  47  *
  48  * @see fr_connection_pool_t
  49  */
  50 struct fr_connection {
  51         fr_connection_t *prev;          //!< Previous connection in list.
  52         fr_connection_t *next;          //!< Next connection in list.
  53
  54         time_t          created;        //!< Time connection was created.
  55         time_t          last_used;      //!< Last time the connection was
  56                                         //!< reserved.
  57
  58         uint32_t        num_uses;       //!< Number of times the connection
  59                                         //!< has been reserved.
  60         uint64_t        number;         //!< Unique ID assigned when the
  61                                         //!< connection is created, these will
  62                                         //!< monotonically increase over the
  63                                         //!< lifetime of the connection pool.
  64         void            *connection;    //!< Pointer to whatever the module
  65                                         //!< uses for a connection handle.
  66         bool            in_use;         //!< Whether the connection is currently
  67                                         //!< reserved.
  68 #ifdef PTHREAD_DEBUG
  69         pthread_t       pthread_id;     //!< When 'in_use == true'
  70 #endif
  71 };
  72
  73 /** A connection pool
  74  *
  75  * Defines the configuration of the connection pool, all the counters and
  76  * timestamps related to the connection pool, the mutex that stops multiple
  77  * threads leaving the pool in an inconsistent state, and the callbacks
  78  * required to open, close and check the status of connections within the pool.
  79  *
  80  * @see fr_connection
  81  */
  82 struct fr_connection_pool_t {
  83         uint32_t        start;          //!< Number of initial connections
  84         uint32_t        min;            //!< Minimum number of concurrent
  85                                         //!< connections to keep open.
  86         uint32_t        max;            //!< Maximum number of concurrent
  87                                         //!< connections to allow.
  88         uint32_t        spare;          //!< Number of spare connections to try
  89         uint32_t        retry_delay;    //!< seconds to delay re-open
  90                                         //!< after a failed open.
  91         uint32_t        cleanup_interval; //!< Initial timer for how
  92                                           //!< often we sweep the pool
  93                                           //!< for free connections.
  94                                           //!< (0 is infinite).
  95         int             delay_interval;  //!< When we next do a
  96                                         //!< cleanup.  Initialized to
  97                                         //!< cleanup_interval, and increase
  98                                         //!< from there based on the delay.
  99         int             next_delay;     //!< The next delay time.
 100                                         //!< cleanup.  Initialized to
 101                                         //!< cleanup_interval, and decays
 102                                         //!< from there.
 103         uint64_t        max_uses;       //!< Maximum number of times a
 104                                         //!< connection can be used before being
 105                                         //!< closed.
 106         uint32_t        lifetime;       //!< How long a connection can be open
 107                                         //!< before being closed (irrespective
 108                                         //!< of whether it's idle or not).
 109         uint32_t        idle_timeout;   //!< How long a connection can be idle
 110                                         //!< before being closed.
 111
 112         bool            trigger;        //!< If true execute connection triggers
 113                                         //!< associated with the connection
 114                                         //!< pool.
 115
 116         bool            spread;         //!< If true requests will be spread
 117                                         //!< across all connections, instead of
 118                                         //!< re-using the most recently used
 119                                         //!< connections first.
 120
 121         time_t          last_checked;   //!< Last time we pruned the connection
 122                                         //!< pool.
 123         time_t          last_spawned;   //!< Last time we spawned a connection.
 124         time_t          last_failed;    //!< Last time we tried to spawn a
 125                                         //!< a connection but failed.
 126         time_t          last_throttled; //!< Last time we refused to spawn a
 127                                         //!< connection because the last
 128                                         //!< connection failed, or we were
 129                                         //!< already spawning a connection.
 130         time_t          last_at_max;    //!< Last time we hit the maximum number
 131                                         //!< of allowed connections.
 132
 133         uint64_t        count;          //!< Number of connections spawned over
 134                                         //!< the lifetime of the pool.
 135         uint32_t        num;            //!< Number of connections in the pool.
 136         int             active;         //!< Number of currently reserved
 137                                         //!< connections.
 138
 139         fr_connection_t *head;          //!< Start of the connection list.
 140         fr_connection_t *tail;          //!< End of the connection list.
 141
 142         bool            spawning;       //!< Whether we are currently attempting
 143                                         //!< to spawn a new connection.
 144
 145 #ifdef HAVE_PTHREAD_H
 146         pthread_mutex_t mutex;          //!< Mutex used to keep consistent state
 147                                         //!< when making modifications in
 148                                         //!< threaded mode.
 149 #endif
 150
 151         CONF_SECTION    *cs;            //!< Configuration section holding
 152                                         //!< the section of parsed config file
 153                                         //!< that relates to this pool.
 154         void            *ctx;           //!< Pointer to context data that will
 155                                         //!< be passed to callbacks.
 156
 157         char            *log_prefix;    //!< Log prefix to prepend to all log
 158                                         //!< messages created by the connection
 159                                         //!< pool code.
 160
 161         fr_connection_create_t  create; //!< Function used to create new
 162                                         //!< connections.
 163         fr_connection_alive_t   alive;  //!< Function used to check status
 164                                         //!< of connections.
 165         fr_connection_delete_t  delete; //!< Function used to close existing
 166                                         //!< connections.
 167 };
 168
 169 #define LOG_PREFIX "rlm_%s (%s)"
 170 #ifndef HAVE_PTHREAD_H
 171 #define pthread_mutex_lock(_x)
 172 #define pthread_mutex_unlock(_x)
 173 #endif
 174
 175 static const CONF_PARSER connection_config[] = {
 176         { "start", FR_CONF_OFFSET(PW_TYPE_INTEGER, fr_connection_pool_t, start), "5" },
 177         { "min", FR_CONF_OFFSET(PW_TYPE_INTEGER, fr_connection_pool_t, min), "5" },
 178         { "max", FR_CONF_OFFSET(PW_TYPE_INTEGER, fr_connection_pool_t, max), "10" },
 179         { "spare", FR_CONF_OFFSET(PW_TYPE_INTEGER, fr_connection_pool_t, spare), "3" },
 180         { "uses", FR_CONF_OFFSET(PW_TYPE_INTEGER64, fr_connection_pool_t, max_uses), "0" },
 181         { "lifetime", FR_CONF_OFFSET(PW_TYPE_INTEGER, fr_connection_pool_t, lifetime), "0" },
 182         { "cleanup_delay", FR_CONF_OFFSET(PW_TYPE_INTEGER, fr_connection_pool_t, cleanup_interval), NULL},
 183         { "cleanup_interval", FR_CONF_OFFSET(PW_TYPE_INTEGER, fr_connection_pool_t, cleanup_interval), "30" },
 184         { "idle_timeout", FR_CONF_OFFSET(PW_TYPE_INTEGER, fr_connection_pool_t, idle_timeout), "60" },
 185         { "retry_delay", FR_CONF_OFFSET(PW_TYPE_INTEGER, fr_connection_pool_t, retry_delay), "1" },
 186         { "spread", FR_CONF_OFFSET(PW_TYPE_BOOLEAN, fr_connection_pool_t, spread), "no" },
 187         { NULL, -1, 0, NULL, NULL }
 188 };
 189
 190 /** Removes a connection from the connection list
 191  *
 192  * @note Must be called with the mutex held.
 193  *
 194  * @param[in,out] pool to modify.
 195  * @param[in] this Connection to delete.
 196  */
 197 static void fr_connection_unlink(fr_connection_pool_t *pool,
 198                                  fr_connection_t *this)
 199 {
 200         if (this->prev) {
 201                 rad_assert(pool->head != this);
 202                 this->prev->next = this->next;
 203         } else {
 204                 rad_assert(pool->head == this);
 205                 pool->head = this->next;
 206         }
 207         if (this->next) {
 208                 rad_assert(pool->tail != this);
 209                 this->next->prev = this->prev;
 210         } else {
 211                 rad_assert(pool->tail == this);
 212                 pool->tail = this->prev;
 213         }
 214
 215         this->prev = this->next = NULL;
 216 }
 217
 218 /** Adds a connection to the head of the connection list
 219  *
 220  * @note Must be called with the mutex held.
 221  *
 222  * @param[in,out] pool to modify.
 223  * @param[in] this Connection to add.
 224  */
 225 static void fr_connection_link_head(fr_connection_pool_t *pool,
 226                                     fr_connection_t *this)
 227 {
 228         rad_assert(pool != NULL);
 229         rad_assert(this != NULL);
 230         rad_assert(pool->head != this);
 231         rad_assert(pool->tail != this);
 232
 233         if (pool->head) {
 234                 pool->head->prev = this;
 235         }
 236
 237         this->next = pool->head;
 238         this->prev = NULL;
 239         pool->head = this;
 240         if (!pool->tail) {
 241                 rad_assert(this->next == NULL);
 242                 pool->tail = this;
 243         } else {
 244                 rad_assert(this->next != NULL);
 245         }
 246 }
 247
 248 /** Adds a connection to the tail of the connection list
 249  *
 250  * @note Must be called with the mutex held.
 251  *
 252  * @param[in,out] pool to modify.
 253  * @param[in] this Connection to add.
 254  */
 255 static void fr_connection_link_tail(fr_connection_pool_t *pool,
 256                                     fr_connection_t *this)
 257 {
 258         rad_assert(pool != NULL);
 259         rad_assert(this != NULL);
 260         rad_assert(pool->head != this);
 261         rad_assert(pool->tail != this);
 262
 263         if (pool->tail) {
 264                 pool->tail->next = this;
 265         }
 266         this->prev = pool->tail;
 267         this->next = NULL;
 268         pool->tail = this;
 269         if (!pool->head) {
 270                 rad_assert(this->prev == NULL);
 271                 pool->head = this;
 272         } else {
 273                 rad_assert(this->prev != NULL);
 274         }
 275 }
 276
 277
 278 /** Spawns a new connection
 279  *
 280  * Spawns a new connection using the create callback, and returns it for
 281  * adding to the connection list.
 282  *
 283  * @note Will call the 'open' trigger.
 284  * @note Must be called with the mutex free.
 285  *
 286  * @param[in] pool to modify.
 287  * @param[in] now Current time.
 288  * @param[in] in_use whether the new connection should be "in_use" or not
 289  * @return the new connection struct or NULL on error.
 290  */
 291 static fr_connection_t *fr_connection_spawn(fr_connection_pool_t *pool,
 292                                             time_t now, bool in_use)
 293 {
 294         fr_connection_t *this;
 295         void *conn;
 296
 297         rad_assert(pool != NULL);
 298
 299         /*
 300          *      Prevent all threads from blocking if the resource
 301          *      were managing connections for appears to be unavailable.
 302          */
 303         if ((pool->num == 0) && pool->spawning) {
 304                 return NULL;
 305         }
 306
 307         pthread_mutex_lock(&pool->mutex);
 308         rad_assert(pool->num <= pool->max);
 309
 310         /*
 311          *      Don't spawn multiple connections at the same time.
 312          */
 313         if (pool->spawning) {
 314                 pthread_mutex_unlock(&pool->mutex);
 315
 316                 ERROR("%s: Cannot open new connection, "
 317                       "connection spawning already in "
 318                       "progress", pool->log_prefix);
 319                 return NULL;
 320         }
 321
 322         /*
 323          *      If the last attempt failed, wait a bit before
 324          *      retrying.
 325          */
 326         if (pool->last_failed && ((pool->last_failed + pool->retry_delay) > now)) {
 327                 bool complain = false;
 328
 329                 if (pool->last_throttled != now) {
 330                         complain = true;
 331
 332                         pool->last_throttled = now;
 333                 }
 334
 335                 pthread_mutex_unlock(&pool->mutex);
 336
 337                 if (!RATE_LIMIT_ENABLED || complain) {
 338                         ERROR("%s: Last connection attempt failed, waiting %d seconds before retrying",
 339                               pool->log_prefix, pool->retry_delay);
 340                 }
 341
 342                 return NULL;
 343         }
 344
 345         pool->spawning = true;
 346
 347         /*
 348          *      Unlock the mutex while we try to open a new
 349          *      connection.  If there are issues with the back-end,
 350          *      opening a new connection may take a LONG time.  In
 351          *      that case, we want the other connections to continue
 352          *      to be used.
 353          */
 354         pthread_mutex_unlock(&pool->mutex);
 355
 356         INFO("%s: Opening additional connection (%" PRIu64 ")", pool->log_prefix, pool->count);
 357
 358         /*
 359          *      This may take a long time, which prevents other
 360          *      threads from releasing connections.  We don't care
 361          *      about other threads opening new connections, as we
 362          *      already have no free connections.
 363          */
 364         conn = pool->create(pool->ctx);
 365         if (!conn) {
 366                 ERROR("%s: Opening connection failed (%" PRIu64 ")", pool->log_prefix, pool->count);
 367
 368                 pool->last_failed = now;
 369                 pool->spawning = false; /* atomic, so no lock is needed */
 370                 return NULL;
 371         }
 372
 373         /*
 374          *      And lock the mutex again while we link the new
 375          *      connection back into the pool.
 376          */
 377         pthread_mutex_lock(&pool->mutex);
 378
 379         this = talloc_zero(pool, fr_connection_t);
 380         if (!this) {
 381                 pthread_mutex_unlock(&pool->mutex);
 382                 return NULL;
 383         }
 384
 385         this->created = now;
 386         this->connection = conn;
 387         this->in_use = in_use;
 388
 389         this->number = pool->count++;
 390         this->last_used = now;
 391         fr_connection_link_head(pool, this);
 392         pool->num++;
 393         pool->spawning = false;
 394         pool->last_spawned = time(NULL);
 395         pool->delay_interval = pool->cleanup_interval;
 396         pool->next_delay = pool->cleanup_interval;
 397         pool->last_failed = 0;
 398
 399         pthread_mutex_unlock(&pool->mutex);
 400
 401         if (pool->trigger) exec_trigger(NULL, pool->cs, "open", true);
 402
 403         return this;
 404 }
 405
 406 /** Close an existing connection.
 407  *
 408  * Removes the connection from the list, calls the delete callback to close
 409  * the connection, then frees memory allocated to the connection.
 410  *
 411  * @note Will call the 'close' trigger.
 412  * @note Must be called with the mutex held.
 413  *
 414  * @param[in,out] pool to modify.
 415  * @param[in,out] this Connection to delete.
 416
 417  */
 418 static void fr_connection_close(fr_connection_pool_t *pool,
 419                                 fr_connection_t *this)
 420 {
 421         /*
 422          *      If it's in use, release it.
 423          */
 424         if (this->in_use) {
 425 #ifdef PTHREAD_DEBUG
 426                 pthread_t pthread_id = pthread_self();
 427                 rad_assert(pthread_equal(this->pthread_id, pthread_id) != 0);
 428 #endif
 429                 this->in_use = false;
 430
 431                 rad_assert(pool->active > 0);
 432                 pool->active--;
 433         }
 434
 435         if (pool->trigger) exec_trigger(NULL, pool->cs, "close", true);
 436
 437         fr_connection_unlink(pool, this);
 438         pool->delete(pool->ctx, this->connection);
 439         rad_assert(pool->num > 0);
 440         pool->num--;
 441         talloc_free(this);
 442 }
 443
 444 /** Find a connection handle in the connection list
 445  *
 446  * Walks over the list of connections searching for a specified connection
 447  * handle and returns the first connection that contains that pointer.
 448  *
 449  * @note Will lock mutex and only release mutex if connection handle
 450  * is not found, so will usually return will mutex held.
 451  * @note Must be called with the mutex free.
 452  *
 453  * @param[in] pool to search in.
 454  * @param[in] conn handle to search for.
 455  * @return the connection containing the specified handle, or NULL if non is
 456  * found.
 457  */
 458 static fr_connection_t *fr_connection_find(fr_connection_pool_t *pool, void *conn)
 459 {
 460         fr_connection_t *this;
 461
 462         if (!pool || !conn) return NULL;
 463
 464         pthread_mutex_lock(&pool->mutex);
 465
 466         /*
 467          *      FIXME: This loop could be avoided if we passed a 'void
 468          *      **connection' instead.  We could use "offsetof" in
 469          *      order to find top of the parent structure.
 470          */
 471         for (this = pool->head; this != NULL; this = this->next) {
 472                 if (this->connection == conn) {
 473 #ifdef PTHREAD_DEBUG
 474                         pthread_t pthread_id;
 475
 476                         pthread_id = pthread_self();
 477                         rad_assert(pthread_equal(this->pthread_id, pthread_id) != 0);
 478 #endif
 479
 480                         rad_assert(this->in_use == true);
 481                         return this;
 482                 }
 483         }
 484
 485         pthread_mutex_unlock(&pool->mutex);
 486         return NULL;
 487 }
 488
 489 /** Delete a connection from the connection pool.
 490  *
 491  * Resolves the connection handle to a connection, then (if found)
 492  * closes, unlinks and frees that connection.
 493  *
 494  * @note Must be called with the mutex free.
 495  *
 496  * @param[in,out] pool Connection pool to modify.
 497  * @param[in] conn to delete.
 498  * @return 0 if the connection could not be found, else 1.
 499  */
 500 int fr_connection_del(fr_connection_pool_t *pool, void *conn)
 501 {
 502         fr_connection_t *this;
 503
 504         this = fr_connection_find(pool, conn);
 505         if (!this) return 0;
 506
 507         INFO("%s: Deleting connection (%" PRIu64 ")", pool->log_prefix, this->number);
 508
 509         fr_connection_close(pool, this);
 510         fr_connection_pool_check(pool);
 511         return 1;
 512 }
 513
 514 /** Delete a connection pool
 515  *
 516  * Closes, unlinks and frees all connections in the connection pool, then frees
 517  * all memory used by the connection pool.
 518  *
 519  * @note Will call the 'stop' trigger.
 520  * @note Must be called with the mutex free.
 521  *
 522  * @param[in,out] pool to delete.
 523  */
 524 void fr_connection_pool_delete(fr_connection_pool_t *pool)
 525 {
 526         fr_connection_t *this, *next;
 527
 528         if (!pool) return;
 529
 530         DEBUG("%s: Removing connection pool", pool->log_prefix);
 531
 532         pthread_mutex_lock(&pool->mutex);
 533
 534         for (this = pool->head; this != NULL; this = next) {
 535                 next = this->next;
 536
 537                 INFO("%s: Closing connection (%" PRIu64 ")", pool->log_prefix, this->number);
 538
 539                 fr_connection_close(pool, this);
 540         }
 541
 542         if (pool->trigger) exec_trigger(NULL, pool->cs, "stop", true);
 543
 544         rad_assert(pool->head == NULL);
 545         rad_assert(pool->tail == NULL);
 546         rad_assert(pool->num == 0);
 547
 548         talloc_free(pool);
 549 }
 550
 551 /** Create a new connection pool
 552  *
 553  * Allocates structures used by the connection pool, initialises the various
 554  * configuration options and counters, and sets the callback functions.
 555  *
 556  * Will also spawn the number of connections specified by the 'start'
 557  * configuration options.
 558  *
 559  * @note Will call the 'start' trigger.
 560  *
 561  * @param[in] parent configuration section containing a 'pool' subsection.
 562  * @param[in] ctx pointer to pass to callbacks.
 563  * @param[in] c Callback to create new connections.
 564  * @param[in] a Callback to check the status of connections.
 565  * @param[in] d Callback to delete connections.
 566  * @param[in] prefix to prepend to all log message, if NULL will create prefix
 567  *      from parent conf section names.
 568  * @return A new connection pool or NULL on error.
 569  */
 570 fr_connection_pool_t *fr_connection_pool_init(CONF_SECTION *parent,
 571                                               void *ctx,
 572                                               fr_connection_create_t c,
 573                                               fr_connection_alive_t a,
 574                                               fr_connection_delete_t d,
 575                                               char const *prefix)
 576 {
 577         uint32_t i;
 578         fr_connection_pool_t *pool;
 579         fr_connection_t *this;
 580         CONF_SECTION *modules;
 581         CONF_SECTION *cs;
 582         char const *cs_name1, *cs_name2;
 583         time_t now = time(NULL);
 584
 585         if (!parent || !ctx || !c || !d) return NULL;
 586
 587         cs = cf_section_sub_find(parent, "pool");
 588         if (!cs) cs = cf_section_sub_find(parent, "limit");
 589
 590         /*
 591          *      Pool is allocated in the NULL context as
 592          *      threads are likely to allocate memory
 593          *      beneath the pool.
 594          */
 595         pool = talloc_zero(NULL, fr_connection_pool_t);
 596         if (!pool) return NULL;
 597
 598         /*
 599          *      Ensure the pool is freed at the same time
 600          *      as its parent.
 601          */
 602         if (fr_link_talloc_ctx_free(cs ? cs : parent, pool) < 0) {
 603                 talloc_free(pool);
 604                 return NULL;
 605         }
 606
 607         pool->cs = cs;
 608         pool->ctx = ctx;
 609         pool->create = c;
 610         pool->alive = a;
 611         pool->delete = d;
 612
 613         pool->head = pool->tail = NULL;
 614
 615 #ifdef HAVE_PTHREAD_H
 616         pthread_mutex_init(&pool->mutex, NULL);
 617 #endif
 618
 619         if (!prefix) {
 620                 modules = cf_item_parent(cf_sectiontoitem(parent));
 621                 if (modules) {
 622                         cs_name1 = cf_section_name1(modules);
 623                         if (cs_name1 && (strcmp(cs_name1, "modules") == 0)) {
 624                                 cs_name1 = cf_section_name1(parent);
 625                                 cs_name2 = cf_section_name2(parent);
 626                                 if (!cs_name2) {
 627                                         cs_name2 = cs_name1;
 628                                 }
 629
 630                                 pool->log_prefix = talloc_typed_asprintf(pool, LOG_PREFIX, cs_name1,
 631                                                                    cs_name2);
 632                         }
 633                 } else {                /* not a module configuration */
 634                         cs_name1 = cf_section_name1(parent);
 635
 636                         pool->log_prefix = talloc_typed_strdup(pool, cs_name1);
 637                 }
 638         } else {
 639                 pool->log_prefix = talloc_typed_strdup(pool, prefix);
 640         }
 641
 642         DEBUG("%s: Initialising connection pool", pool->log_prefix);
 643
 644         if (cs) {
 645                 if (cf_section_parse(cs, pool, connection_config) < 0) {
 646                         goto error;
 647                 }
 648
 649                 if (cf_section_sub_find(cs, "trigger")) pool->trigger = true;
 650         } else {
 651                 pool->start = 5;
 652                 pool->min = 5;
 653                 pool->max = 10;
 654                 pool->spare = 3;
 655                 pool->cleanup_interval = 30;
 656                 pool->idle_timeout = 60;
 657         }
 658
 659         /*
 660          *      Some simple limits
 661          */
 662         if (pool->max == 0) {
 663                 cf_log_err_cs(cs, "Cannot set 'max' to zero");
 664                 goto error;
 665         }
 666         if (pool->min > pool->max) {
 667                 cf_log_err_cs(cs, "Cannot set 'min' to more than 'max'");
 668                 goto error;
 669         }
 670
 671         if (pool->max > 1024) pool->max = 1024;
 672         if (pool->start > pool->max) pool->start = pool->max;
 673         if (pool->spare > (pool->max - pool->min)) {
 674                 pool->spare = pool->max - pool->min;
 675         }
 676         if ((pool->lifetime > 0) && (pool->idle_timeout > pool->lifetime)) {
 677                 pool->idle_timeout = 0;
 678         }
 679
 680         if ((pool->idle_timeout > 0) && (pool->cleanup_interval > pool->idle_timeout)) {
 681                 pool->cleanup_interval = pool->idle_timeout;
 682         }
 683
 684         /*
 685          *      Don't open any connections.  Instead, force the limits
 686          *      to only 1 connection.
 687          *
 688          */
 689         if (check_config) {
 690                 pool->start = pool->min = pool->max = 1;
 691                 return pool;
 692         }
 693
 694         /*
 695          *      Create all of the connections, unless the admin says
 696          *      not to.
 697          */
 698         for (i = 0; i < pool->start; i++) {
 699                 this = fr_connection_spawn(pool, now, false);
 700                 if (!this) {
 701                 error:
 702                         fr_connection_pool_delete(pool);
 703                         return NULL;
 704                 }
 705         }
 706
 707         if (pool->trigger) exec_trigger(NULL, pool->cs, "start", true);
 708
 709         return pool;
 710 }
 711
 712
 713 /** Check whether a connection needs to be removed from the pool
 714  *
 715  * Will verify that the connection is within idle_timeout, max_uses, and
 716  * lifetime values. If it is not, the connection will be closed.
 717  *
 718  * @note Will only close connections not in use.
 719  * @note Must be called with the mutex held.
 720  *
 721  * @param[in,out] pool to modify.
 722  * @param[in,out] this Connection to manage.
 723  * @param[in] now Current time.
 724  * @return 0 if the connection was closed, otherwise 1.
 725  */
 726 static int fr_connection_manage(fr_connection_pool_t *pool,
 727                                 fr_connection_t *this,
 728                                 time_t now)
 729 {
 730         rad_assert(pool != NULL);
 731         rad_assert(this != NULL);
 732
 733         /*
 734          *      Don't terminated in-use connections
 735          */
 736         if (this->in_use) return 1;
 737
 738         if ((pool->max_uses > 0) &&
 739             (this->num_uses >= pool->max_uses)) {
 740                 DEBUG("%s: Closing expired connection (%" PRIu64 "): Hit max_uses limit", pool->log_prefix,
 741                       this->number);
 742         do_delete:
 743                 if (pool->num <= pool->min) {
 744                         RATE_LIMIT(WARN("%s: You probably need to lower \"min\"", pool->log_prefix));
 745                 }
 746                 fr_connection_close(pool, this);
 747                 return 0;
 748         }
 749
 750         if ((pool->lifetime > 0) &&
 751             ((this->created + pool->lifetime) < now)) {
 752                 DEBUG("%s: Closing expired connection (%" PRIu64 ")", pool->log_prefix, this->number);
 753                 goto do_delete;
 754         }
 755
 756         if ((pool->idle_timeout > 0) &&
 757             ((this->last_used + pool->idle_timeout) < now)) {
 758                 INFO("%s: Closing connection (%" PRIu64 "): Hit idle_timeout, was idle for %u seconds",
 759                      pool->log_prefix, this->number, (int) (now - this->last_used));
 760                 goto do_delete;
 761         }
 762
 763         return 1;
 764 }
 765
 766
 767 /** Check whether any connections needs to be removed from the pool
 768  *
 769  * Maintains the number of connections in the pool as per the configuration
 770  * parameters for the connection pool.
 771  *
 772  * @note Will only run checks the first time it's called in a given second,
 773  * to throttle connection spawning/closing.
 774  * @note Will only close connections not in use.
 775  * @note Must be called with the mutex held, will release mutex before
 776  * returning.
 777  *
 778  * @param[in,out] pool to manage.
 779  * @return 1
 780  */
 781 static int fr_connection_pool_check(fr_connection_pool_t *pool)
 782 {
 783         uint32_t spawn, idle, extra;
 784         time_t now = time(NULL);
 785         fr_connection_t *this, *next;
 786
 787         if (pool->last_checked == now) {
 788                 pthread_mutex_unlock(&pool->mutex);
 789                 return 1;
 790         }
 791
 792         /*
 793          *      Some idle connections are OK, if they're within the
 794          *      configured "spare" range.  Any extra connections
 795          *      outside of that range can be closed.
 796          */
 797         idle = pool->num - pool->active;
 798         if (idle <= pool->spare) {
 799                 extra = 0;
 800         } else {
 801                 extra = idle - pool->spare;
 802         }
 803
 804         /*
 805          *      The other end can close connections.  If so, we'll
 806          *      have fewer than "min".  When that happens, open more
 807          *      connections to enforce "min".
 808          */
 809         if (pool->num <= pool->min) {
 810                 if (pool->spawning) {
 811                         spawn = 0;
 812                 } else {
 813                         spawn = pool->min - pool->num;
 814                 }
 815                 extra = 0;
 816
 817         } else if (pool->num >= pool->max) {
 818                 /*
 819                  *      Ensure we don't spawn more connections.  If
 820                  *      there are extra idle connections, we can
 821                  *      delete all of them.
 822                  */
 823                 spawn = 0;
 824                 /* leave extra alone from above */
 825
 826         } else if (idle <= pool->spare) {
 827                 /*
 828                  *      Not enough spare connections.  Spawn a few.
 829                  *      But cap the pool size at "max"
 830                  */
 831                 spawn = pool->spare - idle;
 832                 extra = 0;
 833
 834                 if ((pool->num + spawn) > pool->max) {
 835                         spawn = pool->max - pool->num;
 836                 }
 837
 838         } else if ((pool->min + extra) >= pool->num) {
 839                 /*
 840                  *      If closing the extra connections would take us
 841                  *      below "min", then don't do that.  Cap the
 842                  *      spare connections at the ones which will take
 843                  *      us exactly to "min".
 844                  */
 845                 spawn = 0;
 846                 extra = pool->num - pool->min;
 847
 848         } else {
 849                 /*
 850                  *      Closing the "extra" connections won't take us
 851                  *      below "min".  It's therefore safe to close
 852                  *      them all.
 853                  */
 854                 spawn = 0;
 855                 /* leave extra alone from above */
 856         }
 857
 858         if (spawn) {
 859                 pthread_mutex_unlock(&pool->mutex);
 860                 fr_connection_spawn(pool, now, false); /* ignore return code */
 861                 pthread_mutex_lock(&pool->mutex);
 862         }
 863
 864         /*
 865          *      We haven't spawned connections in a while, and there
 866          *      are too many spare ones.  Close the one which has been
 867          *      unused for the longest.
 868          */
 869         if (extra && (now >= (pool->last_spawned + pool->delay_interval))) {
 870                 fr_connection_t *found;
 871
 872                 found = NULL;
 873                 for (this = pool->tail; this != NULL; this = this->prev) {
 874                         if (this->in_use) continue;
 875
 876                         if (!found ||
 877                            (this->last_used < found->last_used)) {
 878                                 found = this;
 879                         }
 880                 }
 881
 882                 rad_assert(found != NULL);
 883
 884                 INFO("%s: Closing connection (%" PRIu64 "), from %d unused connections", pool->log_prefix,
 885                      found->number, extra);
 886                 fr_connection_close(pool, found);
 887
 888                 /*
 889                  *      Decrease the delay for the next time we clean
 890                  *      up.
 891                  */
 892                 pool->next_delay >>= 1;
 893                 if (pool->next_delay == 0) pool->next_delay = 1;
 894                 pool->delay_interval += pool->next_delay;
 895         }
 896
 897         /*
 898          *      Pass over all of the connections in the pool, limiting
 899          *      lifetime, idle time, max requests, etc.
 900          */
 901         for (this = pool->head; this != NULL; this = next) {
 902                 next = this->next;
 903                 fr_connection_manage(pool, this, now);
 904         }
 905
 906         pool->last_checked = now;
 907         pthread_mutex_unlock(&pool->mutex);
 908
 909         return 1;
 910 }
 911
 912 /** Get a connection from the connection pool
 913  *
 914  * @param[in,out] pool to reserve the connection from.
 915  * @param[in] spawn whether to spawn a new connection
 916  * @return a pointer to the connection handle, or NULL on error.
 917  */
 918 static void *fr_connection_get_internal(fr_connection_pool_t *pool, int spawn)
 919 {
 920         time_t now;
 921         fr_connection_t *this, *next;
 922
 923         if (!pool) return NULL;
 924
 925         pthread_mutex_lock(&pool->mutex);
 926
 927         now = time(NULL);
 928         for (this = pool->head; this != NULL; this = next) {
 929                 next = this->next;
 930
 931                 if (!this->in_use) goto do_return;
 932         }
 933
 934         if (pool->num == pool->max) {
 935                 bool complain = false;
 936
 937                 /*
 938                  *      Rate-limit complaints.
 939                  */
 940                 if (pool->last_at_max != now) {
 941                         complain = true;
 942                         pool->last_at_max = now;
 943                 }
 944
 945                 pthread_mutex_unlock(&pool->mutex);
 946
 947                 if (!RATE_LIMIT_ENABLED || complain) {
 948                         ERROR("%s: No connections available and at max connection limit", pool->log_prefix);
 949                 }
 950
 951                 return NULL;
 952         }
 953
 954         pthread_mutex_unlock(&pool->mutex);
 955
 956         if (!spawn) return NULL;
 957
 958         this = fr_connection_spawn(pool, now, true); /* MY connection! */
 959         if (!this) return NULL;
 960         pthread_mutex_lock(&pool->mutex);
 961
 962 do_return:
 963         pool->active++;
 964         this->num_uses++;
 965         this->last_used = now;
 966         this->in_use = true;
 967
 968 #ifdef PTHREAD_DEBUG
 969         this->pthread_id = pthread_self();
 970 #endif
 971         pthread_mutex_unlock(&pool->mutex);
 972
 973         DEBUG("%s: Reserved connection (%" PRIu64 ")", pool->log_prefix, this->number);
 974
 975         return this->connection;
 976 }
 977
 978
 979 /** Reserve a connection in the connection pool
 980  *
 981  * Will attempt to find an unused connection in the connection pool, if one is
 982  * found, will mark it as in in use increment the number of active connections
 983  * and return the connection handle.
 984  *
 985  * If no free connections are found will attempt to spawn a new one, conditional
 986  * on a connection spawning not already being in progress, and not being at the
 987  * 'max' connection limit.
 988  *
 989  * @note fr_connection_release must be called once the caller has finished
 990  * using the connection.
 991  *
 992  * @see fr_connection_release
 993  * @param[in,out] pool to reserve the connection from.
 994  * @return a pointer to the connection handle, or NULL on error.
 995  */
 996 void *fr_connection_get(fr_connection_pool_t *pool)
 997 {
 998         return fr_connection_get_internal(pool, true);
 999 }
1000
1001 /** Get the number of connections currently in the pool
1002  *
1003  * @param pool to count connections for.
1004  * @return the number of connections in the pool
1005  */
1006 int fr_connection_get_num(fr_connection_pool_t *pool)
1007 {
1008         return pool->num;
1009 }
1010
1011 /** Release a connection
1012  *
1013  * Will mark a connection as unused and decrement the number of active
1014  * connections.
1015  *
1016  * @see fr_connection_get
1017  * @param[in,out] pool to release the connection in.
1018  * @param[in,out] conn to release.
1019  */
1020 void fr_connection_release(fr_connection_pool_t *pool, void *conn)
1021 {
1022         fr_connection_t *this;
1023
1024         this = fr_connection_find(pool, conn);
1025         if (!this) return;
1026
1027         this->in_use = false;
1028
1029         /*
1030          *      Determines whether the last used connection gets
1031          *      re-used first.
1032          */
1033         if (pool->spread) {
1034                 /*
1035                  *      Put it at the tail of the list, so
1036                  *      that it will get re-used last.
1037                  */
1038                 if (this != pool->tail) {
1039                         fr_connection_unlink(pool, this);
1040                         fr_connection_link_tail(pool, this);
1041                 }
1042         } else {
1043                 /*
1044                  *      Put it at the head of the list, so
1045                  *      that it will get re-used quickly.
1046                  */
1047                 if (this != pool->head) {
1048                         fr_connection_unlink(pool, this);
1049                         fr_connection_link_head(pool, this);
1050                 }
1051         }
1052
1053         rad_assert(pool->active > 0);
1054         pool->active--;
1055
1056         DEBUG("%s: Released connection (%" PRIu64 ")", pool->log_prefix, this->number);
1057
1058         /*
1059          *      We mirror the "spawn on get" functionality by having
1060          *      "delete on release".  If there are too many spare
1061          *      connections, go manage the pool && clean some up.
1062          */
1063         fr_connection_pool_check(pool);
1064 }
1065
1066 /** Reconnect a suspected inviable connection
1067  *
1068  * This should be called by the module if it suspects that a connection is
1069  * not viable (e.g. the server has closed it).
1070  *
1071  * Will attempt to create a new connection handle using the create callback,
1072  * and if this is successful the new handle will be assigned to the existing
1073  * pool connection.
1074  *
1075  * If this is not successful, the connection will be removed from the pool.
1076  *
1077  * When implementing a module that uses the connection pool API, it is advisable
1078  * to pass a pointer to the pointer to the handle (void **conn)
1079  * to all functions which may call reconnect. This is so that if a new handle
1080  * is created and returned, the handle pointer can be updated up the callstack,
1081  * and a function higher up the stack doesn't attempt to use a now invalid
1082  * connection handle.
1083  *
1084  * @warning After calling reconnect the caller *MUST NOT* attempt to use
1085  * the old handle in any other operations, as its memory will have been freed.
1086  *
1087  * @see fr_connection_get
1088  * @param[in,out] pool to reconnect the connection in.
1089  * @param[in,out] conn to reconnect.
1090  * @return new connection handle if successful else NULL.
1091  */
1092 void *fr_connection_reconnect(fr_connection_pool_t *pool, void *conn)
1093 {
1094         void *new_conn;
1095         fr_connection_t *this;
1096         uint64_t conn_number;
1097
1098         if (!pool || !conn) return NULL;
1099
1100         this = fr_connection_find(pool, conn);
1101         if (!this) return NULL;
1102
1103         /*
1104          *      The pool is now locked.
1105          */
1106         conn_number = this->number;
1107
1108         DEBUG("%s: Reconnecting (%" PRIu64 ")", pool->log_prefix, conn_number);
1109
1110         new_conn = pool->create(pool->ctx);
1111         if (!new_conn) {
1112                 /*
1113                  *      We can't create a new connection, so close
1114                  *      this one.
1115                  */
1116                 fr_connection_close(pool, this);
1117
1118                 /*
1119                  *      Maybe there's a connection which is unused and
1120                  *      available.  If so, return it.
1121                  */
1122                 pthread_mutex_unlock(&pool->mutex);
1123                 new_conn = fr_connection_get_internal(pool, false);
1124                 if (new_conn) return new_conn;
1125
1126                 RATE_LIMIT(ERROR("%s: Failed to reconnect (%" PRIu64 "), no free connections are available", pool->log_prefix,
1127                                  conn_number));
1128                 return NULL;
1129         }
1130
1131         if (pool->trigger) exec_trigger(NULL, pool->cs, "close", true);
1132         pool->delete(pool->ctx, conn);
1133         this->connection = new_conn;
1134         pthread_mutex_unlock(&pool->mutex);
1135         return new_conn;
1136 }