Elasticsearch实战：常见错误及详细解决方案

1.read_only_allow_delete":“true”

当我们在向某个索引添加一条数据的时候，可能（极少情况）会碰到下面的报错：

{"error": {"root_cause": [{"type": "cluster_block_exception","reason": "blocked by: [FORBIDDEN/12/index read-only / allow delete (api)];"}],"type": "cluster_block_exception","reason": "blocked by: [FORBIDDEN/12/index read-only / allow delete (api)];"},"status": 403
}

上述报错是说索引现在的状态是只读模式（read-only），如果查看该索引此时的状态：

GET z1/_settings
#结果如下
{"z1" : {"settings" : {"index" : {"number_of_shards" : "5","blocks" : {"read_only_allow_delete" : "true"},"provided_name" : "z1","creation_date" : "1556204559161","number_of_replicas" : "1","uuid" : "3PEevS9xSm-r3tw54p0o9w","version" : {"created" : "6050499"}}}}
}

可以看到"read_only_allow_delete" : "true"，说明此时无法插入数据，当然，我们也可以模拟出来这个错误：

PUT z1
{"mappings": {"doc": {"properties": {"title": {"type":"text"}}}},"settings": {"index.blocks.read_only_allow_delete": true}
}PUT z1/doc/1
{"title": "es真难学"
}

现在我们如果执行插入数据，就会报开始的错误。那么怎么解决呢？

清理磁盘，使占用率低于 85%。
手动调整该项，具体参考官网

这里介绍一种，我们将该字段重新设置为：

PUT z1/_settings
{"index.blocks.read_only_allow_delete": null
}

现在再查看该索引就正常了，也可以正常的插入数据和查询了。

2. illegal_argument_exception

有时候，在聚合中，我们会发现如下报错：

{"error": {"root_cause": [{"type": "illegal_argument_exception","reason": "Fielddata is disabled on text fields by default. Set fielddata=true on [age] in order to load fielddata in memory by uninverting the inverted index. Note that this can however use significant memory. Alternatively use a keyword field instead."}],"type": "search_phase_execution_exception","reason": "all shards failed","phase": "query","grouped": true,"failed_shards": [{"shard": 0,"index": "z2","node": "NRwiP9PLRFCTJA7w3H9eqA","reason": {"type": "illegal_argument_exception","reason": "Fielddata is disabled on text fields by default. Set fielddata=true on [age] in order to load fielddata in memory by uninverting the inverted index. Note that this can however use significant memory. Alternatively use a keyword field instead."}}],"caused_by": {"type": "illegal_argument_exception","reason": "Fielddata is disabled on text fields by default. Set fielddata=true on [age] in order to load fielddata in memory by uninverting the inverted index. Note that this can however use significant memory. Alternatively use a keyword field instead.","caused_by": {"type": "illegal_argument_exception","reason": "Fielddata is disabled on text fields by default. Set fielddata=true on [age] in order to load fielddata in memory by uninverting the inverted index. Note that this can however use significant memory. Alternatively use a keyword field instead."}}},"status": 400
}

这是怎么回事呢？是因为，聚合查询时，指定字段不能是text类型。比如下列示例：

PUT z2/doc/1
{"age":"18"
}
PUT z2/doc/2
{"age":20
}GET z2/doc/_search
{"query": {"match_all": {}},"aggs": {"my_sum": {"sum": {"field": "age"}}}
}

当我们向elasticsearch中，添加一条数据时（此时，如果索引存在则直接新增或者更新文档，不存在则先创建索引），首先检查该age字段的映射类型。如上示例中，我们添加第一篇文档时（z1索引不存在），elasticsearch会自动的创建索引，然后为age字段创建映射关系（es 就猜此时age字段的值是什么类型，如果发现是text类型，那么存储该字段的映射类型就是text），此时age字段的值是text类型，所以，第二条插入数据，age的值也是text类型，而不是我们看到的long类型。我们可以查看一下该索引的mappings信息：

GET z2/_mapping
#mapping信息如下
{"z2" : {"mappings" : {"doc" : {"properties" : {"age" : {"type" : "text","fields" : {"keyword" : {"type" : "keyword","ignore_above" : 256}}}}}}}
}

上述返回结果发现，age类型是text。而该类型又不支持聚合，所以，就会报错了。解决办法就是：

如果选择动态创建一篇文档，映射关系取决于你添加的第一条文档的各字段都对应什么类型。而不是我们看到的那样，第一次是text，第二次不加引号，就是long类型了不是这样的。
如果嫌弃上面的解决办法麻烦，那就选择手动创建映射关系。首先指定好各字段对应什么类型。后续才不至于出错。

3.Result window is too large

很多时候，我们在查询文档时，一次查询结果很可能会有很多，而 elasticsearch 一次返回多少条结果，由size参数决定：

GET e2/doc/_search
{"size": 100000,"query": {"match_all": {}}
}

而默认是最多范围一万条，那么当我们的请求超过一万条时（比如有十万条），就会报：

Result window is too large, from + size must be less than or equal to: [10000] but was [100000]. See the scroll api for a more efficient way to request large data sets. This limit can be set by changing the [index.max_result_window] index level setting.

意思是一次请求返回的结果太大，可以另行参考 scroll API或者设置index.max_result_window参数手动调整size的最大默认值：

#kibana中设置
PUT e2/_settings
{"index": {"max_result_window": "100000"}
}
#Python中设置
from elasticsearch import Elasticsearch
es = Elasticsearch()
es.indices.put_settings(index='e2', body={"index": {"max_result_window": 100000}})

如上例，我们手动调整索引e2的size参数最大默认值到十万，这时，一次查询结果只要不超过 10 万就都会一次返回。注意，这个设置对于索引es的size参数是永久生效的。