Don't close StringReaders because of (1) batching, (2) resources are not

allocated, and (3) they'll be GC'd away.

See #3127 where closing
StringReaders too soon can cause problems.

Author: garydgregory

log4j-core/src/main/java/org/apache/logging/log4j/core/appender/db/jdbc/JdbcDatabaseManager.java

@@ -17,6 +17,7 @@
 package org.apache.logging.log4j.core.appender.db.jdbc;
 
 import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
+import java.io.Reader;
 import java.io.Serializable;
 import java.io.StringReader;
 import java.sql.Clob;
@@ -945,7 +946,10 @@ private Object truncate(final String nameKey, Object value) {
 
     @Override
     protected void writeInternal(final LogEvent event, final Serializable serializable) {
-        StringReader reader = null;
+        // Don't close StringReaders because of (1) batching, (2) resources are not allocated, and (3) they'll be GC'd
+        // away.
+        // See https://github.com/apache/logging-log4j2/issues/3127 where closing StringReaders too soon can cause
+        // problems.
         try {
             if (!this.isRunning() || isClosed(this.connection) || isClosed(this.statement)) {
                 throw new AppenderLoggingException(
@@ -990,7 +994,7 @@ protected void writeInternal(final LogEvent event, final Serializable serializab
                 if (column.isEventTimestamp()) {
                     this.statement.setTimestamp(j++, new Timestamp(event.getTimeMillis()));
                 } else if (column.isClob()) {
-                    reader = new StringReader(column.getLayout().toSerializable(event));
+                    final Reader reader = new StringReader(column.getLayout().toSerializable(event));
                     if (column.isUnicode()) {
                         this.statement.setNClob(j++, reader);
                     } else {
@@ -1040,7 +1044,6 @@ protected void writeInternal(final LogEvent event, final Serializable serializab
             } catch (final SQLException e) {
                 // Ignore
             }
-            Closer.closeSilently(reader);
         }
     }
 

src/changelog/.2.x.x/3127_JDBC_appender_IOException_stream_closed.xml

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<entry xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+       xmlns="https://logging.apache.org/xml/ns"
+       xsi:schemaLocation="https://logging.apache.org/xml/ns https://logging.apache.org/xml/ns/log4j-changelog-0.xsd"
+       type="changed">
+  <issue id="3127" link="https://github.com/apache/logging-log4j2/issues/3127"/>
+  <description format="asciidoc">Don't close StringReaders because of batching.</description>
+</entry>