Ignoring hidden foldersedit
Previous versions of Elasticsearch would skip hidden files and directories when scanning the plugins folder. This allows broken plugin installs to remain undetected so this leniency has been removed.
Skip setting kernel parametersedit
Elasticsearch attempts to set the kernel parameter
installation. In some environments this can fail. Previous versions of
Elasticsearch accepted a flag
ES_SKIP_SET_KERNEL_PARAMTERS to skip this
writing. Starting in Elasticsearch 5.5.0, this flag has been removed and
instead the same functionality can be achieved by masking the
404s on get alias and get mapping APIsedit
Previous versions of Elasticsearch did not return a 404 in all cases when a requested alias or a requested type did not exist on the get alias or get mapping APIs, respectively. Starting in Elasticsearch 5.5.0, these APIs consistently return a 404 in any case when an alias or type is requested that does not exist.
Java API changesedit
parent_id queries have moved to parent-join module. Also the
children aggregation has been moved to the parent-join module.
The parent-join module should be loaded when using the transport client. Alternatively use the
client, which load the module automatically.