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performance optimisation for Log4j2LoggerBackend - get log4j context direct from the logger, and reduce allocations in the common path #418

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performance optimisation for Log4j2LoggerBackend - get log4j context direct from the logger, and reduce allocations in the common path #418

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29 changes: 18 additions & 11 deletions log4j2/src/main/java/com/google/common/flogger/backend/log4j2/Log4j2LogEventUtil.java
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Original file line number Diff line number Diff line change
Expand Up @@ -37,6 +37,7 @@
import java.util.stream.Collectors;
import java.util.stream.StreamSupport;
import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.core.Logger;
import org.apache.logging.log4j.core.LoggerContext;
import org.apache.logging.log4j.core.config.Configuration;
import org.apache.logging.log4j.core.config.DefaultConfiguration;
Expand All @@ -59,7 +60,7 @@ final class Log4j2LogEventUtil {

private Log4j2LogEventUtil() {}

static LogEvent toLog4jLogEvent(String loggerName, LogData logData) {
static LogEvent toLog4jLogEvent(Logger logger, LogData logData) {
MetadataProcessor metadata =
MetadataProcessor.forScopeAndLogSite(Platform.getInjectedMetadata(), logData.getMetadata());

Expand All @@ -78,7 +79,7 @@ static LogEvent toLog4jLogEvent(String loggerName, LogData logData) {
* which can perhaps be installed as default if nothing else is present. Then, we would not rely
* on Log4j2 internals.
*/
LoggerContext ctx = LoggerContext.getContext(false);
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@JerryShea JerryShea Aug 10, 2025 •
edited
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this can be very expensive

LoggerContext ctx = logger.getContext();
Configuration config = ctx.getConfiguration();
String message;
if (config instanceof DefaultConfiguration) {
Expand All @@ -89,14 +90,14 @@ static LogEvent toLog4jLogEvent(String loggerName, LogData logData) {
}

Throwable thrown = metadata.getSingleValue(LogContext.Key.LOG_CAUSE);
return toLog4jLogEvent(loggerName, logData, message, toLog4jLevel(logData.getLevel()), thrown);
return toLog4jLogEvent(logger.getName(), logData, message, toLog4jLevel(logData.getLevel()), thrown);
}

static LogEvent toLog4jLogEvent(String loggerName, RuntimeException error, LogData badData) {
static LogEvent toLog4jLogEvent(Logger logger, RuntimeException error, LogData badData) {
String message = formatBadLogData(error, badData);
// Re-target this log message as a warning (or above) since it indicates a real bug.
Level level = badData.getLevel().intValue() < WARNING.intValue() ? WARNING : badData.getLevel();
return toLog4jLogEvent(loggerName, badData, message, toLog4jLevel(level), error);
return toLog4jLogEvent(logger.getName(), badData, message, toLog4jLevel(level), error);
}

private static LogEvent toLog4jLogEvent(
Expand Down Expand Up @@ -246,13 +247,19 @@ private static StringMap createContextMap(LogData logData) {
MetadataProcessor metadataProcessor =
MetadataProcessor.forScopeAndLogSite(Platform.getInjectedMetadata(), logData.getMetadata());

StringMap contextData = ContextDataFactory.createContextData(metadataProcessor.keyCount());
metadataProcessor.process(
HANDLER,
(key, value) ->
contextData.putValue(key, ValueQueue.maybeWrap(value, contextData.getValue(key))));
final StringMap contextData;
// don't allocate for the common case of no keys
if (metadataProcessor.keyCount() > 0) {
contextData = ContextDataFactory.createContextData(metadataProcessor.keyCount());
metadataProcessor.process(
HANDLER,
(key, value) ->
contextData.putValue(key, ValueQueue.maybeWrap(value, contextData.getValue(key))));

contextData.freeze();
contextData.freeze();
} else {
contextData = ContextDataFactory.emptyFrozenContextData();
}

return contextData;
}
Expand Down
4 changes: 2 additions & 2 deletions log4j2/src/main/java/com/google/common/flogger/backend/log4j2/Log4j2LoggerBackend.java
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Expand Up @@ -55,11 +55,11 @@ public boolean isLoggable(java.util.logging.Level level) {
public void log(LogData logData) {
// The caller is responsible to call isLoggable() before calling this method to ensure that only
// messages above the given threshold are logged.
logger.get().log(toLog4jLogEvent(logger.getName(), logData));
logger.get().log(toLog4jLogEvent(logger, logData));
}

@Override
public void handleError(RuntimeException error, LogData badData) {
logger.get().log(toLog4jLogEvent(logger.getName(), error, badData));
logger.get().log(toLog4jLogEvent(logger, error, badData));
}
}