Block until all messages that have already been sent to this LogHandler have been processed.
Declared in <folly/logging/LogHandler.h>
virtual
void
flush() = 0;For LogHandlers that perform asynchronous processing of log messages, this ensures that messages already sent to this handler have finished being processed.
Other threads may still call handleMessage() while flush() is running. handleMessage() calls that did not complete before the flush() call started will not necessarily be processed by the flush call.