[float]
[[reserved-fields]] 
==== Reserved fields in {ls} events 

Some fields in {ls} events are reserved, or are required to adhere to a certain
shape. Using these fields can cause runtime exceptions when the event API or
plugins encounter incompatible values.

[cols="<,<",options="header",]
|=======================================================================
| | 
| <<metadata,`@metadata`>> |A key/value map. 

Ruby-based Plugin API: value is an 
https://javadoc.io/static/org.jruby/jruby-core/9.2.5.0/org/jruby/RubyHash.html[org.jruby.RubyHash]. 

Java-based Plugin API: value is an 
https://github.com/elastic/logstash/blob/master/logstash-core/src/main/java/org/logstash/ConvertedMap.java[org.logstash.ConvertedMap].
 
In serialized form (such as JSON): a key/value map where the keys must be
strings and the values are not constrained to a particular type.

| `@timestamp` |An object holding representation of a specific moment in time.

Ruby-based Plugin API: value is an
https://javadoc.io/static/org.jruby/jruby-core/9.2.5.0/org/jruby/RubyTime.html[org.jruby.RubyTime].

Java-based Plugin API: value is a
https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/time/Instant.html[java.time.Instant].

In serialized form (such as JSON) or when setting with Event#set: an
ISO8601-compliant String value is acceptable.

| `@version` |A string, holding an integer value.
| `tags` |An array of distinct strings
|=======================================================================