The indexing buffer is used to store newly indexed documents. When it fills up, the documents in the buffer are written to a segment on disk. It is divided between all shards on the node.
The following settings are static and must be configured on every data node in the cluster:
indices.memory.index_buffer_size
10%,
meaning that 10% of the total heap allocated to a node will be used as the
indexing buffer size shared across all shards.
indices.memory.min_index_buffer_size
index_buffer_size is specified as a percentage, then this
setting can be used to specify an absolute minimum. Defaults to 48mb.
indices.memory.max_index_buffer_size
index_buffer_size is specified as a percentage, then this
setting can be used to specify an absolute maximum. Defaults to unbounded.