Converting DSL Query to NEST (elasticsearch)

Question

My DSL query that I have in Kibana is :

GET elastic-search-app-log*/_search
{
  "_source": ["@timestamp", "level", "messageTemplate", "message"],  
  "query": {
    "match": {
      "_id" : "x5pcgHkBlRaz9flxW1uw"
    }
  }
}

Which will return the following in the CLI:

{
  "took" : 19,
  "timed_out" : false,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : {
      "value" : 1,
      "relation" : "eq"
    },
    "max_score" : 1.0,
    "hits" : [
      {
        "_index" : "elastic-search-app-logs-development-2021-05",
        "_type" : "_doc",
        "_id" : "x5pcgHkBlRaz9flxW1uw",
        "_score" : 1.0,
        "_source" : {
          "@timestamp" : "2021-05-18T11:43:25.6155311-05:00",
          "level" : "Error",
          "message" : "Something bad happened",
          "messageTemplate" : "Something bad happened"
        }
      }
    ]
  }
}

This is what I attempted to do, but it gives me an error when I build it:

        [HttpGet("{_id}")]
        public async Task<EsSource> Get(String _id) 
        {
            var response = await _elasticClient.Search<EsSource>(s => s
                .Source(src => src.Includes(i => i
                                  .Fields(f => f.TimeStamp,
                                          f => f.Level,
                                          f => f.MessageTemplate,
                                          f => f.Message)))
                .Index("elastic-search-app-logs*")
                .Query(q => q
                    .Match(m => m.Field("_id").Query(_id))));

            return response?.Documents?.FirstOrDefault();
        }

My EsSource Model class:

public class EsSource
{
    public String TimeStamp { get; set; }
    public String Level { get; set; }
    public String MessageTemplate { get; set; }
    public String Message { get; set; }
}

Error in VS19 says:

ESController.cs(39,28,47,61): error CS1061: 'ISearchResponse<EsSource>' does not contain a definition for 'GetAwaiter' and no accessible extension method 'GetAwaiter' accepting a first argument of type 'ISearchResponse<EsSource>' could be found (are you missing a using directive or an assembly reference?)

Am I not translating the DSL query to NEST correctly? I am extremely new to this and would love all the help I can get.

Rob · Accepted Answer · 2021-05-20 08:58:57Z

1

You need to change Search method to SearchAsync as return type from Search is ISearchResponse<EsSource> and it doesn't contain GetAwaiter so you can't await on it.

[HttpGet("{_id}")]
public async Task<EsSource> Get(String _id) 
{
    var response = await _elasticClient.SearchAsync<EsSource>(s => s
        .Source(src => src.Includes(i => i
                          .Fields(f => f.TimeStamp,
                                  f => f.Level,
                                  f => f.MessageTemplate,
                                  f => f.Message)))
        .Index("elastic-search-app-logs*")
        .Query(q => q
            .Match(m => m.Field("_id").Query(_id))));

    return response?.Documents?.FirstOrDefault();
}

answered May 20, 2021 at 8:58

Rob

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4 Comments

NoviceCoder Over a year ago

Thank you! That made it work, did not realize I was using Search and not SearchAsync. On another note, do you know how home when I enter the _id that is shown in the original post and execute it on swagger, timeStamp is displaying null but everything else is displaying? Is there something causing it to be null even though timeStamp in the CLI is actually showing a value? Let me know if I need to better clarify this

Rob Over a year ago

That's because you are working with response.Documents and your type doesn't have Id prop. You can add it to your type or you can use response.Hits which contains matched documents and meta data for it.

NoviceCoder Over a year ago

I attempted to use response.hits cannot implicitly convert type System.Collections.Gneric.IReadOnlyCollection<Nest.IHit<ESPractice.Models.EsSource>> to ESPractice.Models.EsSource and it recommended a cast so I did that and still gave me an error. I then tried return response?.Hits.Select(h => h.Source) and tried return?.Hits?.FirstOrDefault() instead of the return?.Documents?.FirstOrDefault() and still gave me an error. Not sure why it is doing that

Rob Over a year ago

Think it should be return?.Hits?.FirstOrDefault()?.Source instead of return?.Hits?.FirstOrDefault().

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