search（4）- elastic4s-ElasticDsl
- 2020 年 4 月 16 日
- 笔记
- elasticsearch, scala, 编程语言
上次分析了一下elastic4s的运算框架。本来计划接着开始实质的函数调用示范，不过看过了Elastic4s的所有使用说明文档后感觉还是走的快了一点。主要原因是elasticsearch在7.0后有了很多重点调整改变，elastic4s虽然一直在源代码方面紧跟ES的变化，但使用文件却一直未能更新，所以从说明文档中学习elastic4s的使用方法是不可能的，必须从源码中摸索。花了些时间过了一次elastic4s的源码，感觉这个工具库以后还是挺有用的：一是通过编程方式产生json请求比较灵活，而且可以通过compiler来保证json语句的正确性。二是对搜索结果的处理方面：由于返回的搜索结果是一堆又长又乱的复杂json，不敢想象自己要如何正确的解析这些json, 然后才能调用到正确的结果，但elastic4s提供了一套很完善的response类，使用起来可能会很方便。实际上elastic4s的编程模式和scala语言运用还是值得学习的。既然这样，我想可能用elastic4s做一套完整的示范，包括：索引创建、索引维护、搜索、聚合统计等，对了解和掌握elastic4s可能大有帮助。在这之前，我们还是再回顾一下elastic4s的运算原理：elastic4s的功能其实很简单：通过dsl语句组合产生json请求，然后发送给ES-rest终端, 对返回的json结果进行处理，筛选出目标答案。
上篇我们讨论过elastic4s的基本运算框架：
client.execute(
createIndex("company")
.shards(2).replicas(3)
)
...
val bookschema = putMapping("books")
.as(
KeywordField("isbn"),
textField("title"),
doubleField("price")
)
client.execute(
bookschema
)
...
val futAccts = client.execute(
search("bank").termQuery("city" -> "dante")
)
futAccts.onComplete{
case Success(esresp) =>
esresp.result.hits.hits.foreach(h =>println(h.sourceAsMap))
case Failure(err) => println(s"search error: ${err.getMessage}")
}
实际上execute(T)的T代表elastic4s支持的所有ES操作类型。这种方法实现有赖于scala的typeclass模式。我们先看看execute函数定义：
// Executes the given request type T, and returns an effect of Response[U]
// where U is particular to the request type.
// For example a search request will return a Response[SearchResponse].
def execute[T, U, F[_]](t: T)(implicit
executor: Executor[F],
functor: Functor[F],
handler: Handler[T, U],
manifest: Manifest[U]): F[Response[U]] = {
val request = handler.build(t)
val f = executor.exec(client, request)
functor.map(f) { resp =>
handler.responseHandler.handle(resp) match {
case Right(u) => RequestSuccess(resp.statusCode, resp.entity.map(_.content), resp.headers, u)
case Left(error) => RequestFailure(resp.statusCode, resp.entity.map(_.content), resp.headers, error)
}
}
}
上篇提过Handler[T,U]是个typeclass, 代表对不同类型T的json构建方法。elastic4s提供了这个T类型的操作方法，如下：
trait ElasticDsl
extends ElasticApi
with Logging
with ElasticImplicits
with BulkHandlers
with CatHandlers
with CountHandlers
with ClusterHandlers
with DeleteHandlers
with ExistsHandlers
with ExplainHandlers
with GetHandlers
with IndexHandlers
with IndexAdminHandlers
with IndexAliasHandlers
with IndexStatsHandlers
with IndexTemplateHandlers
with LocksHandlers
with MappingHandlers
with NodesHandlers
with ReindexHandlers
with RoleAdminHandlers
with RoleHandlers
with RolloverHandlers
with SearchHandlers
with SearchTemplateHandlers
with SearchScrollHandlers
with SettingsHandlers
with SnapshotHandlers
with UpdateHandlers
with TaskHandlers
with TermVectorHandlers
with UserAdminHandlers
with UserHandlers
with ValidateHandlers {
implicit class RichRequest[T](t: T) {
def request(implicit handler: Handler[T, _]): ElasticRequest = handler.build(t)
def show(implicit handler: Handler[T, _]): String = Show[ElasticRequest].show(handler.build(t))
}
}
object ElasticDsl extends ElasticDsl
所有的操作api在这里：
trait ElasticApi
extends AliasesApi
with ElasticImplicits
with AggregationApi
with AnalyzerApi
with BulkApi
with CatsApi
with CreateIndexApi
with ClearRolesCacheApi
with ClusterApi
with CollapseApi
with CountApi
with CreateRoleApi
with CreateUserApi
with DeleteApi
with DeleteIndexApi
with DeleteRoleApi
with DeleteUserApi
with DynamicTemplateApi
with ExistsApi
with ExplainApi
with ForceMergeApi
with GetApi
with HighlightApi
with IndexApi
with IndexAdminApi
with IndexRecoveryApi
with IndexTemplateApi
with LocksApi
with MappingApi
with NodesApi
with NormalizerApi
with QueryApi
with PipelineAggregationApi
with ReindexApi
with RoleApi
with ScriptApi
with ScoreApi
with ScrollApi
with SearchApi
with SearchTemplateApi
with SettingsApi
with SnapshotApi
with SortApi
with SuggestionApi
with TaskApi
with TermVectorApi
with TokenizerApi
with TokenFilterApi
with TypesApi
with UpdateApi
with UserAdminApi
with UserApi
with ValidateApi {
implicit class RichFuture[T](future: Future[T]) {
def await(implicit duration: Duration = 60.seconds): T = Await.result(future, duration)
}
}
object ElasticApi extends ElasticApi
通过 import ElasticDsl._ ，所有类型的api,handler操作方法都有了。下面是例子里的api方法：
trait CreateIndexApi {
def createIndex(name: String): CreateIndexRequest = CreateIndexRequest(name)
...
}
trait MappingApi {
...
def putMapping(indexes: Indexes): PutMappingRequest = PutMappingRequest(IndexesAndType(indexes))
}
trait SearchApi {
def search(index: String): SearchRequest = search(Indexes(index))
...
}
CreateIndexRequest, PutMappingRequest,SearchRequest这几个类型都提供了handler隐式实例：
trait IndexAdminHandlers {
...
implicit object CreateIndexHandler extends Handler[CreateIndexRequest, CreateIndexResponse] {
override def responseHandler: ResponseHandler[CreateIndexResponse] = new ResponseHandler[CreateIndexResponse] {
override def handle(response: HttpResponse): Either[ElasticError, CreateIndexResponse] =
response.statusCode match {
case 200 | 201 => Right(ResponseHandler.fromResponse[CreateIndexResponse](response))
case 400 | 500 => Left(ElasticError.parse(response))
case _ => sys.error(response.toString)
}
}
override def build(request: CreateIndexRequest): ElasticRequest = {
val endpoint = "/" + URLEncoder.encode(request.name, "UTF-8")
val params = scala.collection.mutable.Map.empty[String, Any]
request.waitForActiveShards.foreach(params.put("wait_for_active_shards", _))
request.includeTypeName.foreach(params.put("include_type_name", _))
val body = CreateIndexContentBuilder(request).string()
val entity = HttpEntity(body, "application/json")
ElasticRequest("PUT", endpoint, params.toMap, entity)
}
}
}
...
trait MappingHandlers {
...
implicit object PutMappingHandler extends Handler[PutMappingRequest, PutMappingResponse] {
override def build(request: PutMappingRequest): ElasticRequest = {
val endpoint = s"/${request.indexesAndType.indexes.mkString(",")}/_mapping${request.indexesAndType.`type`.map("/" + _).getOrElse("")}"
val params = scala.collection.mutable.Map.empty[String, Any]
request.updateAllTypes.foreach(params.put("update_all_types", _))
request.ignoreUnavailable.foreach(params.put("ignore_unavailable", _))
request.allowNoIndices.foreach(params.put("allow_no_indices", _))
request.expandWildcards.foreach(params.put("expand_wildcards", _))
request.includeTypeName.foreach(params.put("include_type_name", _))
val body = PutMappingBuilderFn(request).string()
val entity = HttpEntity(body, "application/json")
ElasticRequest("PUT", endpoint, params.toMap, entity)
}
}
}
...
trait SearchHandlers {
...
implicit object SearchHandler extends Handler[SearchRequest, SearchResponse] {
override def build(request: SearchRequest): ElasticRequest = {
val endpoint =
if (request.indexes.values.isEmpty)
"/_all/_search"
else
"/" + request.indexes.values
.map(URLEncoder.encode(_, "UTF-8"))
.mkString(",") + "/_search"
val params = scala.collection.mutable.Map.empty[String, String]
request.requestCache.map(_.toString).foreach(params.put("request_cache", _))
request.searchType
.filter(_ != SearchType.DEFAULT)
.map(SearchTypeHttpParameters.convert)
.foreach(params.put("search_type", _))
request.routing.map(_.toString).foreach(params.put("routing", _))
request.pref.foreach(params.put("preference", _))
request.keepAlive.foreach(params.put("scroll", _))
request.allowPartialSearchResults.map(_.toString).foreach(params.put("allow_partial_search_results", _))
request.batchedReduceSize.map(_.toString).foreach(params.put("batched_reduce_size", _))
request.indicesOptions.foreach { opts =>
IndicesOptionsParams(opts).foreach { case (key, value) => params.put(key, value) }
}
request.typedKeys.map(_.toString).foreach(params.put("typed_keys", _))
val body = request.source.getOrElse(SearchBodyBuilderFn(request).string())
ElasticRequest("POST", endpoint, params.toMap, HttpEntity(body, "application/json"))
}
}
}
