ElasticSearch与mysql数据库实时同步的问题

我知道有一个工具叫ElasticSearch-jdbc，也看了官方文档，根据官方文档写了个测试（命令见最下），但是不能实时同步，它会隔差不多1分钟左右再更新。不知道是什么地方出问题了。还请路过大神不吝赐教！
命令：
{
"type" : "jdbc",
"jdbc" : {
"url" : "jdbc:mysql://xxx.xxx.xxx.xxx:3306/world",
"user" : "root",
"password" : "xxxxxx",
"schedule":"*/5 * * * * ?",
"locale" : "en_US",
"sql" : [
{
"statement":"select \"world\" as _index, \"city\" as _type, ID as _id, Name as \"Name\", CountryCode as \"CountryCode\", District as \"District\", Population as \"Population\" from city where \"mytimestamp\" > ?",
"parameter": [ "$metrics.lastexecutionstart" ]
},
{
"statement" : "delete from city where \"_job\" = ?",
"parameter" : [ "$job" ]
}
],
"statefile":"statefile.json",
"elasticsearch" : {
"cluster" : "my_cluster_name1",
"host" : "localhost",
"port" : 9300
},
"index" : "world",
"type" : "city",
"index_settings" : {
"index" : {
"number_of_shards" : 1
}
}
}
}