Sematext's Logs Management App looks for the following fields in logs and gives them a special treatment:
host is a single-valued field and should contain the ID (typically a hostname) of the device or server sending logs.
source is a single-valued field and should contain the ID or descriptor of where the data is coming from. For example, this could be a file name or even a full path to a filename, or the name of the application or process.
facility is a single-valued field used by syslog to indicate the facility level. Logsene stores the keyword values of these levels (such as user or auth).
severity is a single-valued field and should contain the log level, such as error or info.
syslog-tag is a single-valued field used by syslog to indicate the name and the PID of the application generating the event (for example, httpd: )
tags is a multi-valued array field that can contain zero or more tags. Tags can contain multiple tokens separated by space.
message is a string field that can contain any sort of text (usually the original log line or some other free text)
@timestamp is a date field, on which log retention is based. If it's not present, Logsene will add a timestamp upon event receipt
All of these fields are optional, but their use is strongly encouraged. If found in logs with low-enough cardinality, all distinct values of these fields will be loaded and shown in the UI as filters and thus allowing one to very quickly narrow down the search.