Related to #9049.
By default, the default value for `timestamp` is `now` which means the date the document was processed by the indexing chain.
You can now reject documents which not provide a `timestamp` value by setting `ignore_missing` to false (default to `true`):
```js
{
"tweet" : {
"_timestamp" : {
"enabled" : true,
"ignore_missing" : false
}
}
}
```
When you update the cluster to 1.5 or master, this index created with 1.4 we automatically migrate an index created with 1.4 to the 1.5 syntax.
Let say you have defined this in elasticsearch 1.4.x:
```js
DELETE test
PUT test
{
"settings": {
"number_of_shards": 1,
"number_of_replicas": 0
}
}
PUT test/type/_mapping
{
"type" : {
"_timestamp" : {
"enabled" : true,
"default" : null
}
}
}
```
After migration, the mapping become:
```js
{
"test": {
"mappings": {
"type": {
"_timestamp": {
"enabled": true,
"store": false,
"ignore_missing": false
},
"properties": {}
}
}
}
}
```
Closes#8882.
fb10346953