解决Elasticsearch索引只读（read-only）

原因为：es 的设置默认是 85% 和 90 %，95%

当为85%时：Elasticsearch不会将碎片分配给磁盘使用率超过85%的节点（ cluster.routing.allocation.disk.watermark.low）

当为90%时：Elasticsearch尝试重新分配给磁盘低于使用率90%的节点（cluster.routing.allocation.disk.watermark.high）

当为85%时：Elasticsearch执行只读模块（cluster.routing.allocation.disk.watermark.flood_stage）

1、扩大磁盘或者删除部分历史索引

2、重置改只读索引快

某一个索引重置只读模块
PUT /twitter/_settings
{
  "index.blocks.read_only_allow_delete": null
}
所有索引重置只读模块

PUT /_all/_settings { "index.blocks.read_only_allow_delete": null }

PUT /_cluster/settings
{
  "persistent" : {
    "cluster.blocks.read_only" : false } }

修改默认设置

可以修改为具体的磁盘空间值，也可以修改为百分之多少
临时修改
PUT _cluster/settings
{
  "transient": {
    "cluster.routing.allocation.disk.watermark.low": "100gb",
    "cluster.routing.allocation.disk.watermark.high": "50gb",
    "cluster.routing.allocation.disk.watermark.flood_stage": "10gb",
    "cluster.info.update.interval": "1m"
  }
}
永久修改
PUT _cluster/settings
{
  "persistent": { "cluster.routing.allocation.disk.watermark.low": "100gb", "cluster.routing.allocation.disk.watermark.high": "50gb", "cluster.routing.allocation.disk.watermark.flood_stage": "10gb", "cluster.info.update.interval": "1m" } }

转载自：https://www.elastic.co/guide/en/elasticsearch/reference/6.8/disk-allocator.html