B4J Library [server] jElasticsearch - Search and Text Analytics

Erel

Administrator
Staff member
Licensed User
The battle between a directory:



And search:



Has been won long ago.

Providing a search feature is important for good user experience.
Unfortunately it is not a simple task.
Elasticsearch is a search framework built over Lucene. Lucene is an open source project for text search. (Note that the forum search and similar threads features are also powered by Lucene.)

Elasticsearch simplifies many tasks required to build a search engine and adds many features over Lucene.
Elasticsearch is quite similar to MongoDB. It is also a document store. However the use cases and focus are different. Elasticsearch stores the data in a Lucene index and offers powerful text features.

jElasticsearch is a wrapper for the REST client provided by Elasticsearch.
It is expected to be used from a server solution.

The attached example implements a simple search engine that builds an index from B4X libraries files and allows searching them.



Note that it uses the new Background Worker feature of jServer library: https://www.b4x.com/android/forum/threads/73269/#content
It depends on jServer v2.70+.

The worker checks for updates every 10 minutes.

Building a good search engine is not simple. It requires learning the main search concepts and the many available options.
I recommend starting with the guide: https://www.elastic.co/guide/en/elasticsearch/guide/current/index.html
And reference: https://www.elastic.co/guide/en/elasticsearch/reference/current/index.html

Elasticsearch can be downloaded here: https://www.elastic.co/downloads/elasticsearch
You need to start Elasticsearch.bat and then run the example.

jElasticsearch depends on several additional jars:
www.b4x.com/b4j/files/jElasticsearch_additional.zip

Copy them to the additional libraries folder.

V1.10 - Fixes compatibility with ES6.0. Note that you need to download jElasticsearch_additional as well.
 

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Last edited:

hibrid0

Active Member
Licensed User
Hi, I have a server with 3 tb of documents.
I want to make a tool on b4j to search.
Maybe this will work for search on local disk?
 

Hugo Abrego Nava

New Member
Licensed User
Hi, I just installed the ElasticSearch product and works fine in my equipment, so I installed this ElasticSearch library and the client works well for the GET and a simple PerformRawRequest, but when I try to use ".Search" I get this error:
org.elasticsearch.client.ResponseException: GET http://127.0.0.1:9200/products/default/_search: HTTP/1.1 406 Not Acceptable
{"error":"Content-Type header [text/plain; charset=UTF-8] is not supported","status":406}

This my test code:
B4X:
Sub AppStart (Args() As String)
    Private esclient As ESClient
    Private tr As TextReader
    Private query As String
    Private qmap  As Map
    Private jparse As JSONParser
    esclient.Initialize("", Array("127.0.0.1:9200"))
    Log(esclient.PerformRawRequest( "GET", "_cluster/health", Null, "").ResponseAsMap)
    Log(esclient.PerformRawRequest( "GET", "products/default/_search?q=name:prod1", Null, "").ResponseAsMap)
    Log(esclient.Get("products","default","1"))
   
    tr.Initialize(File.OpenInput(File.DirApp,"query.txt"))
    query=tr.ReadAll
    Log(query)
    jparse.Initialize(query)
    qmap=jparse.NextObject
    Log(qmap)
    Log(esclient.Search("products","default",qmap).ResponseAsMap)
    esclient.Close
End Sub
And this the Log:
B4X:
(MyMap) {number_of_pending_tasks=0, cluster_name=elasticsearch, active_shards=6, active_primary_shards=6, unassigned_shards=6, delayed_unassigned_shards=0, timed_out=false, relocating_shards=0, initializing_shards=0, task_max_waiting_in_queue_millis=0, number_of_data_nodes=1, number_of_in_flight_fetch=0, active_shards_percent_as_number=50.0, status=yellow, number_of_nodes=1}
(MyMap) {_shards={total=5, failed=0, successful=5, skipped=0}, hits={hits=[{_index=products, _type=default, _source={quantity=1, name=prod1}, _id=1, _score=0.2876821}], total=1, max_score=0.2876821}, took=18, timed_out=false}
(MyMap) {quantity=1, name=prod1}
{"query":
  {"match":
    {"name": "prod1"}
  }
}
(MyMap) {query={match={name=prod1}}}
org.elasticsearch.client.ResponseException: GET http://127.0.0.1:9200/products/default/_search: HTTP/1.1 406 Not Acceptable
{"error":"Content-Type header [text/plain; charset=UTF-8] is not supported","status":406}
    at org.elasticsearch.client.RestClient$1.completed(RestClient.java:311)
    at org.elasticsearch.client.RestClient$1.completed(RestClient.java:300)
    at org.apache.http.concurrent.BasicFuture.completed(BasicFuture.java:119)
    at org.apache.http.impl.nio.client.DefaultClientExchangeHandlerImpl.responseCompleted(DefaultClientExchangeHandlerImpl.java:177)
    at org.apache.http.nio.protocol.HttpAsyncRequestExecutor.processResponse(HttpAsyncRequestExecutor.java:436)
    at org.apache.http.nio.protocol.HttpAsyncRequestExecutor.inputReady(HttpAsyncRequestExecutor.java:326)
    at org.apache.http.impl.nio.DefaultNHttpClientConnection.consumeInput(DefaultNHttpClientConnection.java:265)
    at org.apache.http.impl.nio.client.InternalIODispatch.onInputReady(InternalIODispatch.java:81)
    at org.apache.http.impl.nio.client.InternalIODispatch.onInputReady(InternalIODispatch.java:39)
    at org.apache.http.impl.nio.reactor.AbstractIODispatch.inputReady(AbstractIODispatch.java:114)
    at org.apache.http.impl.nio.reactor.BaseIOReactor.readable(BaseIOReactor.java:162)
    at org.apache.http.impl.nio.reactor.AbstractIOReactor.processEvent(AbstractIOReactor.java:337)
    at org.apache.http.impl.nio.reactor.AbstractIOReactor.processEvents(AbstractIOReactor.java:315)
    at org.apache.http.impl.nio.reactor.AbstractIOReactor.execute(AbstractIOReactor.java:276)
    at org.apache.http.impl.nio.reactor.BaseIOReactor.execute(BaseIOReactor.java:104)
    at org.apache.http.impl.nio.reactor.AbstractMultiworkerIOReactor$Worker.run(AbstractMultiworkerIOReactor.java:588)
    at java.lang.Thread.run(Thread.java:748)
Can you help me to fix this error?
 

Hugo Abrego Nava

New Member
Licensed User
Hello, I have changed the existing jar with the attachment rest-5.0.1.jar, but it doesn't work. I get the same error.
And yes, I am running ES v6.0
Do I need to downgrade the version?
 

Hugo Abrego Nava

New Member
Licensed User
I try to connect ES to the internet but it was not possible, it does not start when I set a different IP from the localhost in my VPS.
 

Hugo Abrego Nava

New Member
Licensed User
Hi Erel, I finally managed to boot ES6 using my IP, it is an undocumented trick, in the .YML file when the network is configured the IP must be in brackets. So if you still need it, I can send my IP by mail.
 
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