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https://issues.apache.org/jira/browse/LOG4J2-1447?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15399495#comment-15399495
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Ralph Goers commented on LOG4J2-1447:
-------------------------------------
Lookups can be used in places where a LogEvent does not exist. Where that is
the case they must use the ThreadContext directly.
> 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 {{getContextMap() :
> 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 ContextData<String, 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(String key, V value);
> /** Returns the value for the specified key. */
> V getValue(String key);
> /** Number of key-value pairs. */
> int size();
> /** Removes all key-value pairs. */
> void clear();
> // Instead of Iterators, client code provides the consumer.
> /**
> * Performs the given action for each key-value pair in this data
> structure
> * until all entries have been processed or the action throws an
> exception.
> */
> void forEach(BiConsumer<String, ? super V> action);
> }
> /**
> * An operation that accepts two input arguments and returns no result.
> */
> interface BiConsumer<T,U> {
> /** Performs the operation given the specified arguments. */
> void accept(T t, U u);
> }
> {code}
> The LogEvent interface would have an additional method {{getContextData() :
> ContextData<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.
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