问题

java client长时间没有连接es后，再次调用访问接口，报错连接超时

环境

以下方法实测在spring-data-elasticsearch 4.2.10和spring-data-elasticsearch 3.2.12.RELEASE环境下有效

解决

1、因为问题的原因是长时间没有连接导致的，最直接、常见的解决方案就是定期的去调用连接es，以此保证连接不会中断，这样的操作我们称之为保活策略

2、在RestClientBuilder的回调函数中提供了一个setKeepAliveStrategy方法，可以用来设置保活策略

RestClientBuilder builder = RestClient.builder(httpPostArr)
                // 异步httpclient配置
                .setHttpClientConfigCallback(httpClientBuilder -> {
                    // httpclient保活策略
                    httpClientBuilder.setKeepAliveStrategy(((response, context) -> Duration.ofMinutes(5).toMillis()));
                    return httpClientBuilder;
});

3、完整代码：在ElasticRestClientConfig配置类中声明设置保活策略

@Configuration
@EnableElasticsearchRepositories(basePackages = "com.example.estest")
public class ElasticRestClientConfig extends AbstractElasticsearchConfiguration {

    @Value("${spring.elasticsearch.rest.uris}")
    private String url;
    @Value("${spring.elasticsearch.rest.username}")
    private String username;
    @Value("${spring.elasticsearch.rest.password}")
    private String password;

    @Override
    @Bean
    public RestHighLevelClient elasticsearchClient() {
        url = url.replace("http://","");
        String[] urlArr = url.split(",");
        HttpHost[] httpPostArr = new HttpHost[urlArr.length];
        for (int i = 0; i < urlArr.length; i++) {
            HttpHost httpHost = new HttpHost(urlArr[i].split(":")[0].trim(),
                    Integer.parseInt(urlArr[i].split(":")[1].trim()), "http");
            httpPostArr[i] = httpHost;
        }
        final CredentialsProvider credentialsProvider = new BasicCredentialsProvider();
        credentialsProvider.setCredentials(AuthScope.ANY,new UsernamePasswordCredentials(username,password));
        RestClientBuilder builder = RestClient.builder(httpPostArr)
                // 异步httpclient配置
                .setHttpClientConfigCallback(httpClientBuilder -> {
                    // 账号密码登录
                    httpClientBuilder.setDefaultCredentialsProvider(credentialsProvider);
                    // httpclient连接数配置
                    httpClientBuilder.setMaxConnTotal(30);
                    httpClientBuilder.setMaxConnPerRoute(10);
                    // httpclient保活策略
                    httpClientBuilder.setKeepAliveStrategy(((response, context) -> Duration.ofMinutes(5).toMillis()));
                    return httpClientBuilder;
                });
        return new RestHighLevelClient(builder);
    }
}

4、再次启动项目则不会出现连接超时报错