Remko Popma created LOG4J2-1447:
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Summary: Garbage-free data structure for LogEvent's context map
data
Key: LOG4J2-1447
URL: https://issues.apache.org/jira/browse/LOG4J2-1447
Project: Log4j 2
Issue Type: Improvement
Components: Core
Affects Versions: 2.6.1
Reporter: Remko Popma
Assignee: Remko Popma
Fix For: 2.7
With each logging call, context map data is copied from the {{ThreadContext}}
map into the {{LogEvent}}.
The LogEvent interface exposes this data via the {{getContextData() :
Map<String, String>}} method, and this is implementated by storing the data in
a Map<String, String>. The JDK Map is not an easy data structure to make
garbage-free. It would also be nice to have the ability in LogEvent to carry
data of any type.
One idea is to introduce a small interface that is general enough to be
map-like but can be implemented in a garbage-free manner.
LogEvent implementations would have an instance of this interface instead of
the current {{java.util.Map<String, String> contextMap}} attribute.
The interface could look something like this:
{code}
interface CustomData<K, V> {
/** Called to implement {@link LogEvent#getContextMap()}. */
Map<String, String> asMap();
/** Put key-value pair into the table.
Remove key if value is null. */
void put(K key, V value);
/** Returns the value for the specified key. */
V getValue(K key);
/** Number of key-value pairs. */
int size();
/** Removes all key-value pairs. */
void clear();
// Instead of Iterators, use an index-based approach.
/** Returns the index of the specified key. */
int indexOfKey(K key);
/** Returns the i-th key. */
K getKeyAt(int i);
/** Returns the value for the i-th key. */
V getValueAt(int i);
}
{code}
The LogEvent interface would have an additional method {{getCustomData() :
CustomData<K, V>}} that gives downstream components direct access to the new
data structure.
Existing downstream components would still be able to call
{{logEvent.getContextMap()}} to get a {{Map<String, String>}} view of the
context map data and this would work as expected (although it may not be
garbage-free).
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