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  1. GeoTools
  2. GEOT-4506

JDBCDataStore initialization not thread-safe

    Details

    • Type: Bug
    • Status: Closed
    • Priority: Medium
    • Resolution: Fixed
    • Affects Version/s: 8.0
    • Fix Version/s: 13.5, 14.2, 15-M0
    • Component/s: jdbc
    • Labels:
      None

      Description

      the initialization of the JDBCDataStore is done lazily:

      > getClassToSqlTypeMappings()

      Unknown macro: { // (1) classToSqlTypeMappings = >(); dialect.registerClassToSqlMappings(classToSqlTypeMappings); // (2) }

      classToSqlTypeMappings;
      }

      I am currently using several threads that share one JDBCDataStore and if this store is new, the threaded access causes - depending on thread timing - some unwanted behavior: While the first thread is registering several classes by its dialect (2), another thread takes the incomplete Map<Class<?>, Integer> (because it is not null (1)) and continues. For access operations like a simple Map.get(), the concurrency issue has no deep impact. But there are other lines of code e.g. in JDBCDataStore itself which will fail with an exception:

      <?> clazz) {
      mapping = getClassToSqlTypeMappings().get(clazz);

      ) {
      class which matches best
      List<Map.Entry< ArrayList();
      // (3)
      (e.getKey().isAssignableFrom(clazz) )

      Unknown macro: { matches.add(e); }

      }

      The iteration of the map in line (3) leads to a ConcurrentModificationException when another thread is registering classes for the sql mapping in this time:

      Caused by: java.io.IOException
      at org.geotools.jdbc.JDBCFeatureSource.getReaderInternal(JDBCFeatureSource.java:611)
      at org.geotools.jdbc.JDBCFeatureStore.getReaderInternal(JDBCFeatureStore.java:225)
      at org.geotools.data.store.ContentFeatureSource.getReader(ContentFeatureSource.java:562)
      at org.geotools.data.store.ContentDataStore.getFeatureReader(ContentDataStore.java:417)
      ... 7 more
      Caused by: java.util.ConcurrentModificationException
      at java.util.HashMap$HashIterator.nextEntry(HashMap.java:793)
      at java.util.HashMap$EntryIterator.next(HashMap.java:834)
      at java.util.HashMap$EntryIterator.next(HashMap.java:832)
      at org.geotools.jdbc.JDBCDataStore.getMapping(JDBCDataStore.java:611)
      at org.geotools.jdbc.PreparedStatementSQLDialect.setValue(PreparedStatementSQLDialect.java:108)
      at org.geotools.jdbc.JDBCDataStore.setPreparedFilterValues(JDBCDataStore.java:3176)
      at org.geotools.jdbc.JDBCDataStore.setPreparedFilterValues(JDBCDataStore.java:3153)
      at org.geotools.jdbc.JDBCDataStore.selectJoinSQLPS(JDBCDataStore.java:3139)
      at org.geotools.jdbc.JDBCFeatureSource.getReaderInternal(JDBCFeatureSource.java:588)
      ... 10 more

      So I modified the code in this way:

      /**

      • Synchronizer access on
        Unknown macro: {@link #classToSqlTypeMappings}

        */
        ();
        //...
        > getClassToSqlTypeMappings() {
        Map<> mapping = classToSqlTypeMappings;
        ) {
        (classToSqlTypeMappingsLock)

        Unknown macro: { mapping = classToSqlTypeMappings; )
        Unknown macro: { classToSqlTypeMappings = >(); dialect.registerClassToSqlMappings(classToSqlTypeMappings); }
        }

        }
        classToSqlTypeMappings;
        }

      The same lazy initialization is done on other members of JDBCDataStore, so I would suggest a modification for all these lines of code.

      Comment by Andrea Aime:
      <blockquote>Hum, that's double checked locking, in order to make it work I believe you'll also have to mark classToSqlTypeMappings as volatile</blockquote>

      <hr />

      Full messages from mailing list archive: http://sourceforge.net/mailarchive/message.php?msg_id=30528488 - 2nd

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            • Assignee:
              Unassigned
              Reporter:
              harrison.grundy codehaus (Inactive)
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              • Created:
                Updated:
                Resolved: