AppenderAWSCloudWatchLog
                        Log to AWS CloudWatch Logs
AppenderDbi             Log to databases via DBI
AppenderDigest          Abstract class for digests (multi-log message
                        notifications)
AppenderDynatrace       Log to Dynatrace via HTTP
AppenderElasticSearch   Log to ElasticSearch
AppenderGmail           Send emails via the Gmail REST API
AppenderMail            Abstract class for email Appenders
AppenderPool            Log to databases via pool
AppenderPushbullet      Send push-notifications via RPushbullet
AppenderSendmail        Send emails via sendmailR
AppenderSyslog          Log to the POSIX system log
LayoutDbi               Format log events for output to databases
LayoutElasticSearch     Format log events for output to ElasticSearch
Serializer              Serializers
as_unix_epoch_ms        Convert POSIXct to Unix Epoch milliseconds
select_dbi_layout       Automatically select appropriate layout for
                        logging to a database
transform_event_dynatrace
                        A json layout for Dynatrace ingestion
transform_event_elasticsearch
                        A json layout for Elasticsearch ingestion
unpack_json_cols        Unserialize data frame columns that contain
                        JSON
