git.zarb.org Git - sdbl4j/blob - src/java/org/gc/sdbl4j/DBConnectionPool.java

   1 /*
   2  *
   3  * Copyright (C) 2010 Guillaume Cottenceau and MNC S.A.
   4  *
   5  * This file is part of sdbl4j, and is licensed under the Apache 2.0 license.
   6  *
   7  */
   8
   9 package org.gc.sdbl4j;
  10
  11 import java.util.ArrayList;
  12 import java.util.Collections;
  13 import java.util.ConcurrentModificationException;
  14 import java.util.HashMap;
  15 import java.util.HashSet;
  16 import java.util.LinkedList;
  17 import java.util.List;
  18 import java.util.Map;
  19 import java.util.Set;
  20 import java.util.concurrent.ConcurrentHashMap;
  21 import java.util.concurrent.ConcurrentMap;
  22 import java.sql.Connection;
  23 import java.sql.SQLException;
  24
  25 import org.apache.log4j.Logger;
  26
  27 /**
  28  * There are subtle interleaved synchronizations happening here.
  29  * Use a traffic load generator with low preOpenedConnections for all modifications in here!
  30  */
  31 public class DBConnectionPool {
  32
  33     private static Logger log = Logger.getLogger( DBConnectionPool.class );
  34
  35     private static class BusyConnection {
  36         public Connection conn;
  37         public String backtrace;
  38         public long tsTotal;
  39         public long tsLatest;
  40         public BusyConnection( Connection conn ) {
  41             this.conn = conn;
  42             backtrace = DBUtils.backtrace( 3 );
  43             tsTotal = tsLatest = System.currentTimeMillis();
  44         }
  45         public void updateRequester() {
  46             backtrace = DBUtils.backtrace( 2 );
  47             tsLatest = System.currentTimeMillis();
  48         }
  49         public String toString() {
  50             List<String> us = new ArrayList<String>();
  51             boolean users_list_ok = false;
  52             int attempts = 0;
  53             while ( ! users_list_ok ) {
  54                 try {
  55                     Set<Thread> users = supplementary_thread_busy_connection_users.get( conn );
  56                     if ( users != null ) {
  57                         for ( Thread u : users ) {
  58                             us.add( u.getName() );
  59                         }
  60                     }
  61                     users_list_ok = true;
  62                 } catch ( ConcurrentModificationException cme ) {
  63                     // There are subtle interleaved synchronizations happening here.
  64                     // Use a traffic load generator with low preOpenedConnections for all modifications in here!
  65                     attempts++;
  66                     if ( attempts > 3 ) {
  67                         log.error( "3 attempts, abandon" );
  68                         break;
  69                     }
  70                     us.clear();
  71                 }
  72             }
  73             return "{" + conn + ",oldnessTotal=" + ( System.currentTimeMillis() - tsTotal )
  74                    + ",oldnessLatest=" + ( System.currentTimeMillis() - tsLatest )
  75                    + ",supplementaryThreadUsers=" + DBUtils.join( ";", us ) + ",requester=\n" + backtrace + "}";
  76         }
  77     }
  78
  79     private static Map<String, ConnectionParameters> dbParameters = null;
  80     private static Map<String, LinkedList<Connection>> available_connections;
  81     private static Map<String, ConcurrentMap<Object, BusyConnection>> busy_connections;
  82     private static Map<Connection, Set<Thread>> supplementary_thread_busy_connection_users;
  83
  84     /**
  85      * List of threads that are created in external libraries in that require a db connection.
  86      * All connections from those threads MUST be manually released after use.
  87      * */
  88     private static Set<String> supported_external_threads;
  89
  90     public static void init( Map<String, ConnectionParameters> parameters ) {
  91         dbParameters = parameters;
  92         available_connections = new HashMap<String, LinkedList<Connection>>();
  93         busy_connections = new HashMap<String, ConcurrentMap<Object, BusyConnection>>();
  94         for ( Map.Entry<String, ConnectionParameters> db : parameters.entrySet() ) {
  95             log.info( "Initializing: " + db.getValue() );
  96             if ( db.getValue().getPreOpenedConnections() > db.getValue().getMaxConnections() ) {
  97                 log.error( db.getKey() + ": pre opened connections > max connections, this is stupid!" );
  98             }
  99             if ( db.getValue().getAlertLevel() < db.getValue().getPreOpenedConnections() ) {
 100                 log.error( db.getKey() + ": alert level < pre opened connections, this is stupid!" );
 101             }
 102             LinkedList<Connection> connections = new LinkedList<Connection>();
 103             available_connections.put( db.getKey(), connections );
 104             for ( int i = 0; i < db.getValue().getPreOpenedConnections(); i++ ) {
 105                 connections.add( db.getValue().createConnection() );
 106             }
 107             busy_connections.put( db.getKey(), new ConcurrentHashMap<Object, BusyConnection>() );
 108             if ( db.getValue().getMaxConnections() < 1 ) {
 109                 log.error( db.getKey() + ": max connections cannot be < 1" );
 110             }
 111         }
 112         supplementary_thread_busy_connection_users = new HashMap<Connection, Set<Thread>>();
 113         supported_external_threads = new HashSet<String>();
 114     }
 115
 116     /**
 117      * Add an external thread name that requires a DB connection.<br/>
 118      * All connections from this thread MUST be manually released after use.
 119      * @param threadName
 120      */
 121     public static void addSupportedExternalThread( String threadName ) {
 122         if ( threadName.equals( "" ) ) {
 123             return;
 124         }
 125         supported_external_threads.add( threadName );
 126     }
 127
 128     /** Check if the given thread name is a supported thread creating from an external library. */
 129     public static boolean isSupportedExternalThread( String threadName ) {
 130         for ( String name : supported_external_threads ) {
 131             if ( threadName.startsWith( name ) ) {
 132                 return true;
 133             }
 134         }
 135         return false;
 136     }
 137
 138     public static Map<String, ConnectionParameters> getParameters() {
 139         return dbParameters;
 140     }
 141
 142     public static List<String> listBusyConnections() {
 143         List<String> retval = new ArrayList<String>();
 144         List<String> kinds = new ArrayList<String>( dbParameters.keySet() );
 145         Collections.sort( kinds );
 146         for ( String dbkind : kinds ) {
 147             int count = 0;
 148             List<String> kind = new ArrayList<String>();
 149             for ( Map.Entry<Object, BusyConnection> busy : busy_connections.get( dbkind ).entrySet() ) {
 150                 if ( busy.getKey() instanceof Thread ) {
 151                     // e.g. used by a request processing thread
 152                     kind.add( ( (Thread) busy.getKey() ).getName() + busy.getValue() );
 153                 } else {
 154                     // e.g. used by supplementary thread(s)
 155                     kind.add( ( (ThreadGroup) busy.getKey() ).getName() + busy.getValue() );
 156                 }
 157                 count++;
 158             }
 159             if ( count == 0 ) {
 160                 retval.add( dbkind + ": 0" );
 161             } else {
 162                 retval.add( dbkind + ": " + count + " (" + DBUtils.join( ", ", kind ) + ")" );
 163             }
 164         }
 165         return retval;
 166     }
 167
 168     /**
 169      * Get a database connection to use. Normally never called directly, only by auto-generated database access
 170      * code.
 171      *
 172      * - in case the calling Thread is a request processing Thread:
 173      *
 174      *   This connection will be associated to the calling Thread and reserved for it (one connection dedicated to
 175      *   one processing thread model).
 176      *
 177      * - in case the calling Thread is a supplementary Thread(1)
 178      *
 179      *   This connection can be reserved or shared with other supplementary Threads depending on configuration
 180      *   (<code>connectionGroup</code> for asynchronous events, dedicated instance properties for other threads).
 181      *
 182      * (1) a supplementary Thread, e.g. not a request processing Thread
 183      */
 184     public static Connection getConnection( String dbkind ) {
 185         // for request processing threads, we have one connection per thread; for supplementary threads, we
 186         // have one connection per thread group; to optimize request processing, we first try to look if we
 187         // have a busy thread associated with this thread, even if it's possibly not a request processing thread
 188         ConcurrentMap<Object, BusyConnection> connections = busy_connections.get( dbkind );
 189         if ( connections == null ) {
 190             log.error( "DB kind '" + dbkind + "' doesn't exist" );
 191             return null;
 192         }
 193         BusyConnection conn = connections.get( Thread.currentThread() );  // ConcurrentMap
 194         if ( conn != null ) {
 195             if ( log.isTraceEnabled() ) {
 196                 log.trace( dbkind + ": use busy connection - " + conn );
 197             }
 198             conn.updateRequester();
 199             return conn.conn;
 200         }
 201
 202         // supplementary threads are recognized by using a specific parent's thread group
 203         if ( Thread.currentThread().getThreadGroup().getParent() == SupplementaryThreadHelper.parentThreadGroup ) {
 204             return getConnectionForSupplementaryThread( dbkind );
 205
 206         } else {
 207             // sanity
 208             if ( ! Thread.currentThread().getName().startsWith( "http" )
 209                  && ! Thread.currentThread().getName().startsWith( "pool" )
 210                  && ! Thread.currentThread().getName().equals( "main" )
 211                  && ! Thread.currentThread().getName().equals( "startStop" ) ) {
 212                 if ( isSupportedExternalThread( Thread.currentThread().getName() ) ) {
 213                     log.debug( "Thread identified as being externally created (external library): the DB " +
 214                                "connections allocated to non-request processing threads MUST be " +
 215                                "manually released after use" );
 216                 } else {
 217                     log.error( "Thread identified as request processing thread (parent of thread group is not "
 218                                + "SupplementaryThreadHelper.parentThreadGroup), but name doesn't start with http or pool or main or startStop!"
 219                                + " (thread name: " + Thread.currentThread().getName() + ")" );
 220                 }
 221             }
 222             return findOrCreateAvailableConnection( dbkind, Thread.currentThread() );
 223         }
 224
 225     }
 226
 227     public static void supplementaryThreadReleaseConnections() {
 228         if ( dbParameters == null ) {
 229             log.trace( "Do nothing (hook for combining old style and new style DB accesses in acme)" );
 230             return;
 231         }
 232         log.trace( "Enter for group " + Thread.currentThread().getThreadGroup().getName() + ", thread "
 233                    + Thread.currentThread().getName() );
 234         for ( String dbkind : dbParameters.keySet() ) {
 235             // There are subtle interleaved synchronizations happening here.
 236             // Use a traffic load generator with low preOpenedConnections for all modifications in here!
 237             synchronized( Thread.currentThread().getThreadGroup() ) {
 238                 BusyConnection conn = busy_connections.get( dbkind ).get( Thread.currentThread().getThreadGroup() );
 239                 if ( conn != null ) {
 240                     // at least one of the threads in this thread group use this connection, either that thread,
 241                     // others, or that thread and others; first, check if that thread is really using it:
 242                     // There are subtle interleaved synchronizations happening here.
 243                     // Use a traffic load generator with low preOpenedConnections for all modifications in here!
 244                     synchronized( supplementary_thread_busy_connection_users ) {
 245                         Set<Thread> users = supplementary_thread_busy_connection_users.get( conn.conn );
 246                         if ( log.isTraceEnabled() ) {
 247                             List<String> us = new ArrayList<String>();
 248                             for ( Thread u : users ) {
 249                                 us.add( u.getName() );
 250                             }
 251                         }
 252                         if ( users.remove( Thread.currentThread() ) ) {
 253                             // this thread was using this connection. now let's see if no other threads are.
 254                             if ( users.size() == 0 ) {
 255                                 if ( log.isTraceEnabled() ) {
 256                                     log.trace( "Group " + Thread.currentThread().getThreadGroup().getName()
 257                                                + ", thread " + Thread.currentThread().getName()
 258                                                + ", release connection " + conn + " on no more users" );
 259                                 }
 260                                 releaseConnection( dbkind, Thread.currentThread().getThreadGroup() );
 261                                 supplementary_thread_busy_connection_users.remove( conn.conn );
 262                             }
 263                         }
 264                     }
 265                 }
 266             }
 267         }
 268     }
 269
 270     private static void releaseConnection( String dbkind, Object key ) {
 271         LinkedList<Connection> available = available_connections.get( dbkind );
 272         Map<Object, BusyConnection> busy = busy_connections.get( dbkind );
 273         ConnectionParameters dbParams = dbParameters.get( dbkind );
 274
 275         BusyConnection conn = busy.get( key );  // ConcurrentMap
 276         if ( conn == null ) {
 277             return;
 278         }
 279
 280         if ( available == null ) {
 281             log.error( "No available connections for " + key + " - already closed?" );
 282             return;
 283         }
 284
 285         // There are subtle interleaved synchronizations happening here.
 286         // Use a traffic load generator with low preOpenedConnections for all modifications in here!
 287         synchronized( available ) {
 288             BusyConnection conn2 = busy.remove( key );
 289             // sanity
 290             if ( conn2 == null || ! conn.conn.equals( conn2.conn ) ) {
 291                 log.error( "Internal error, removed connection " + conn2 + " not equals to getted connection "
 292                            + conn );
 293                 return;
 294             }
 295
 296             if ( busy.size() + available.size() >= dbParams.getPreOpenedConnections() ) {
 297                 if ( log.isTraceEnabled() ) {
 298                     log.trace( "closing connection for " + dbkind + " - " + conn + " - "
 299                                + " busy:" + busy.size() + " available:" + available.size() + " busies:\n"
 300                                + DBUtils.join( "\n", listBusyConnections() ) );
 301                 } else if ( log.isDebugEnabled() ) {
 302                     log.debug( "closing connection for " + dbkind + " - " + conn + " - "
 303                                + " busy:" + busy.size() + " available:" + available.size() );
 304                 }
 305                 try {
 306                     conn.conn.close();
 307                 } catch ( SQLException se ) {
 308                     log.warn( "error closing connection for dbkind=" + dbkind + ": " + se );
 309                 }
 310
 311             } else {
 312                 available.addFirst( conn.conn );
 313             }
 314
 315             available.notify();
 316         }
 317     }
 318
 319     /** Close all of the database connections. */
 320     public static void closeConnections() {
 321         log.info( "START - closing connections" );
 322         if ( available_connections.size() == 0 ) {
 323             log.error( "No available connections - already closed?" );
 324             return;
 325         }
 326         for ( String dbkind : dbParameters.keySet() ) {
 327             // There are subtle interleaved synchronizations happening here.
 328             // Use a traffic load generator with low preOpenedConnections for all modifications in here!
 329             synchronized( available_connections.get( dbkind ) ) {
 330                 for ( Connection conn : available_connections.get( dbkind ) ) {
 331                     try {
 332                         conn.close();
 333                     } catch ( SQLException se ) {
 334                         log.warn( "error closing connection for dbkind=" + dbkind + ": " + se );
 335                     }
 336                 }
 337                 for ( Map.Entry<Object, BusyConnection> busy : busy_connections.get( dbkind ).entrySet() ) {
 338                     log.warn( "Still busy connection (leak?): "
 339                               + ( ( busy.getKey() instanceof Thread ) ? ( (Thread) busy.getKey() ).getName()
 340                                                                       : ( (ThreadGroup) busy.getKey() ).getName() )
 341                               + " - " + busy.getValue() );
 342                 }
 343             }
 344         }
 345         available_connections.clear();
 346         log.info( "END - closing connections" );
 347     }
 348
 349     private static Connection getConnectionForSupplementaryThread( String dbkind ) {
 350
 351         ThreadGroup group = Thread.currentThread().getThreadGroup();
 352
 353         // synchronize on group, because more than one thread may be requesting a connection at the same time,
 354         // and we want no race condition to potentially populate busy_connections in that situation
 355         // There are subtle interleaved synchronizations happening here.
 356         // Use a traffic load generator with low preOpenedConnections for all modifications in here!
 357         synchronized( group ) {
 358             // re-run the check for existing busy connections, on the proper key now
 359             BusyConnection conn = busy_connections.get( dbkind ).get( group );
 360             if ( conn != null ) {
 361                 if ( log.isTraceEnabled() ) {
 362                     log.trace( dbkind + ": use busy connection for " + group.getName() + " - " + conn );
 363                 }
 364                 // remember this thread is also using this connection
 365                 // There are subtle interleaved synchronizations happening here.
 366                 // Use a traffic load generator with low preOpenedConnections for all modifications in here!
 367                 synchronized( supplementary_thread_busy_connection_users ) {
 368                     supplementary_thread_busy_connection_users.get( conn.conn ).add( Thread.currentThread() );
 369                 }
 370                 conn.updateRequester();
 371                 return conn.conn;
 372             }
 373
 374             Connection c = findOrCreateAvailableConnection( dbkind, group );
 375             // that thread is the first user of this connection
 376             Set<Thread> users = new HashSet<Thread>();
 377             users.add( Thread.currentThread() );
 378             // There are subtle interleaved synchronizations happening here.
 379             // Use a traffic load generator with low preOpenedConnections for all modifications in here!
 380             synchronized( supplementary_thread_busy_connection_users ) {
 381                 Set<Thread> previous_users = supplementary_thread_busy_connection_users.put( c, users );
 382                 // sanity
 383                 if ( previous_users != null ) {
 384                     List<String> us = new ArrayList<String>();
 385                     for ( Thread u : previous_users ) {
 386                         us.add( u.getName() );
 387                     }
 388                     log.error( "Internal error (previous users should be empty): previous users: "
 389                                + previous_users );
 390                 }
 391             }
 392             return c;
 393         }
 394     }
 395
 396     /**
 397      * Find a currently available connection, or create a new one if none is available and we have
 398      * not yet reached the maximum.
 399      */
 400     private static Connection findOrCreateAvailableConnection( String dbkind, Object busyKey ) {
 401
 402         // find an available connection
 403         LinkedList<Connection> available = available_connections.get( dbkind );
 404         Map<Object, BusyConnection> busy = busy_connections.get( dbkind );
 405         ConnectionParameters dbParams = dbParameters.get( dbkind );
 406         // There are subtle interleaved synchronizations happening here.
 407         // Use a traffic load generator with low preOpenedConnections for all modifications in here!
 408         synchronized( available ) {
 409             Connection conn = available.poll();
 410             if ( conn == null ) {
 411                 if ( busy.size() < dbParams.getMaxConnections() ) {
 412                     conn = dbParams.createConnection();
 413                     if ( conn == null ) {
 414                         throw new RuntimeException( "Connection creation not available" );
 415                     }
 416                     log.debug( "created connection " + conn + ", since busy size is " + busy.size() );
 417                 }
 418             } else {
 419                 try {
 420                     long time_before = System.currentTimeMillis();
 421                     conn.createStatement().executeQuery( "SELECT 1" );
 422                     if ( log.isDebugEnabled() ) {
 423                         log.debug( ( System.currentTimeMillis() - time_before ) + " ms for: SELECT 1 [connection validation]" );
 424                     }
 425                 } catch ( SQLException se ) {
 426                     log.error( "Validation error for idle connection for " + dbkind + ": " + se
 427                                + ", will replace connection with a newly created one" );
 428                     try {
 429                         conn.close();
 430                     } catch ( SQLException se2 ) {}
 431                     conn = dbParams.createConnection();
 432                     if ( conn == null ) {
 433                         throw new RuntimeException( "Connection creation not available" );
 434                     }
 435                 }
 436                 if ( log.isTraceEnabled() ) {
 437                     if ( busyKey instanceof ThreadGroup ) {
 438                         log.trace( dbkind + ": use available connection for "
 439                                    + ( (ThreadGroup) busyKey ).getName() + " - " + conn );
 440                     } else {
 441                         log.trace( dbkind + ": use available connection - " + conn );
 442                     }
 443                 }
 444             }
 445             if ( conn != null ) {
 446                 busy.put( busyKey, new BusyConnection( conn ) );
 447                 if ( busy.size() + available.size() >= dbParams.getAlertLevel() ) {
 448                     log.warn( "Many connections for dbkind=" + dbkind + ": busy=" + busy.size()
 449                               + " max=" + dbParams.getMaxConnections() + ": "
 450                               + DBUtils.join( ", ", listBusyConnections() ) );
 451                 }
 452                 return conn;
 453
 454             } else {
 455                 // TODO: switch to log.warn when we are reasonably confident with
 456                 log.error( "No available connections for dbkind=" + dbkind + ": busy=" + busy.size()
 457                           + " max=" + dbParams.getMaxConnections() + " busies=["
 458                           + DBUtils.join( ", ", listBusyConnections() ) + "], waiting...\n"
 459                           + DBUtils.backtrace() );
 460                 try {
 461                     available.wait();
 462                 } catch ( InterruptedException ex ) {}
 463                 log.error( "Wait over" );
 464                 return findOrCreateAvailableConnection( dbkind, busyKey );
 465             }
 466         }
 467     }
 468
 469     public static void releaseConnectionsForProcessingThread() {
 470         for ( String dbkind : dbParameters.keySet() ) {
 471             releaseConnection( dbkind, Thread.currentThread() );
 472         }
 473     }
 474
 475 }