Elastic Search dynamic script 详解

问题描述

最近工程中会使用到ElasticSearch(以下统称ES),就是将一些统计结果(点击量:click_count,曝光量:impr_count,点击曝光比:ctr=click_count/impr_count)写入到ES,会用到ES的dynamic script去实时修改ctr。然后就遇到了too many dynamic script rejected的问题。

问题解决过程

1. 获取EsClient的源码

public static synchronized TransportClient getInstance() throws UnknownHostException {
        if(transportClient == null){
            String clusterName = DataSourceUtils.getProperteValue("es.cluster", "es");
            String host = DataSourceUtils.getProperteValue("es.host","localhost");
            Integer port = Integer.parseInt(DataSourceUtils.getProperteValue("es.port","9300"));
            Settings settings = Settings.builder()
                    .put("cluster.name", clusterName)
                    .put("client.transport.sniff", true)
                    .build();
            transportClient = new PreBuiltTransportClient(settings).addTransportAddress(new InetSocketTransportAddress(InetAddress.getByName(host), port));
        }
        return transportClient;
    }

2. 贴上有问题的源码(dynamic script update ctr)

TransportClient esClient = EsClient.getInstance();
UpdateRequest updateRequest = new UpdateRequest("notes2", "note", "2");
String script = String.format("ctx._source.click_count=%d;ctx._source.impr_count=%d;ctx._source.ctr=(double)ctx._source.click_count/ctx._source.impr_count", 15, 120);
updateRequest.script(new Script(script));
updateRequest.retryOnConflict(3);
esClient.update(updateRequest).get();

用以上code去update ctr, 然后发现log中出现了too many dynamic script rejected,导致ctr更新失败。

3. 寻找原因

在ES官网上查找Script相关的文档说明,在Script Parameters栏目发现以下参数

lang

Specifies the language the script is written in. Defaults to painless.
指定编写脚本的语言,默认为painless。

source, id

Specifies the source of the script. An inline script is specified source. A stored script is specified id and is retrieved from the cluster state.
指定脚本的来源。inline类型的脚本是指定source。stored类型的脚本是指定source的id,通过id从ES集群上检索对应的source。

params

Specifies any named parameters that are passed into the script as variables.
指定作为变量传递到脚本的任何参数。

然后在这个下面的一段话,很重要，就是解决我们问题的关键信息

The first time Elasticsearch sees a new script, it compiles it and stores the compiled version in a cache. Compilation can be a heavy process.

If you need to pass variables into the script, you should pass them in as named params instead of hard-coding values into the script itself. For example, if you want to be able to multiply a field value by different multipliers, don’t hard-code the multiplier into the script:

"source": "doc['my_field'] * 2"

Instead, pass it in as a named parameter:

"source": "doc['my_field'] * multiplier",
"params": {
"multiplier": 2
}

通过以上code我们可以得知 对于dynamic script我们应该使用params参数来传递参数,而不是把参数拼接在script中,这样就不需要ES就会在第一次的时候把script编译后保存在缓存中,而不是每次都会去编译。

方法一 使用inline type script

TransportClient esClient = EsClient.getInstance();
UpdateRequest updateRequest = new UpdateRequest("notes2", "note", "2");
Map params = new HashMap() {
    {
        put("click_count", 120);
        put("impr_count", 5);
    }
};

String code = "ctx._source.click_count=params.click_count;ctx._source.impr_count=params.impr_count;ctx._source.ctr=(double)ctx._source.click_count/ctx._source.impr_count*100";
Script script = new Script(ScriptType.INLINE, "painless", code, params);
updateRequest.script(script);
esClient.update(updateRequest).get();

方法二 使用stored type script

TransportClient esClient = EsClient.getInstance();
UpdateRequest updateRequest = new UpdateRequest("notes2", "note", "2");
Map params = new HashMap() {
    {
        put("click_count", 120);
        put("impr_count", 5);
    }
};

//String code = "ctx._source.read_time=params.read_time;ctx._source.read_num=params.read_num;ctx._source.avg_read_time=(double)ctx._source.read_time/ctx._source.read_num";
Script script = new Script(ScriptType.STORED, "painless", "ctr_calc", params);
updateRequest.script(script);
esClient.update(updateRequest).get();

使用方法二stored script的时候 需要在kibana里面将script存储到ES集群里面

方法如下

POST _scripts/ctr_calc
{
  "script": {
    "lang": "painless",
    "source": "ctx._source.click_count=params.click_count;ctx._source.impr_count=params.impr_count;ctx._source.ctr=(double)ctx._source.click_count/ctx._source.impr_count*100"
  }
}

4. 测试

通过以上两种方法,都可以解决too many dynamic script rejected的问题。

参考

TommyYang's Blog