How do you debug your Nest queries?

问题:

I'm new to Nest, and I very likely am not creating my query like I think I am. My question is more along the lines of teach a man to fish rather than give me a fish. However, I'll use my current problem as an example.

I have several documents in ElasticSearch of the type Series. I'll stub it out below without the attributes and public modifiers with just the information pertinent to the query:

class Series
{
    string Id {get; set;}
    DateTime StartDate {get; set;}
    DateTime EndDate {get; set;}
    HashSet<Role> ReleasableTo {get; set;}
}

These are all fine and dandy. I can Get() a Series object no problem. The problem I'm running into is trying to figure out how Nest is formatting my query. My immediate goal is to find the most recent Series that is releasable to Role.Visitor. I set up the Nest query like this:

ISearchResponse<Series> response = client
    .Search<Series>(r => 
         r.Filter(f => 
             f.Term<Role>(t=>t.ReleasableTo.First(), Role.Visitor))
    .SortDescending(ser => ser.EndDate).Size(1));

In my mind, this should be producing a query that filters the Series so it only considers the ones that are ReleasableTo my Role.Visitor, reverse sorts by end date, and limits the results to one returned. That would be exactly what I want. In the multiple thousands of records I have for Series, about 90% fit this profile. Unfortunately the query returns 0 results. There is no error, just no results. What I don't know is if I'm using the API incorrectly, if Nest is producing a query structure that doesn't make sense, or I simply don't know ElasticSearch well enough. When I remove the Filter clause I get a result, but I'm not guaranteed everyone is allowed to see it.

How do I view the JSON that Nest produces and sends to ElasticSearch?

回答1:

You can get the values of search request URL and JSON request body as under:

var requestURL = response.RequestInformation.RequestUrl;
var jsonBody = Encoding.UTF8.GetString(response.RequestInformation.Request);

You can find other useful properties in RequestInformation for debugging.

回答2:

NEST is Baroque of .NET APIs. For 2.1+ on call level:

IElasticClient client = new ElasticClient();
var searchDescriptor = new SearchDescriptor<Series>();
var query = Query<Series>.Term(...);
var pretty = query.ToPrettyString(query);
var json = client.ToRawRequest(searchDescriptor.Query(descriptor => query));

On configuration level:

    var settings = new ConnectionSettings()
                     .PrettyJson().DisableDirectStreaming()
                     .OnRequestCompleted(details=> Debug.WriteLine(Encoding.UTF8.GetString(details.RequestBodyInBytes)));

On response level look into CallDetails.RequestBodyInBytes.

Used extensions:

    /// <summary>
    /// Converts search to raw JSON request for debugging.
    /// </summary>
    /// <typeparam name="T">The type.</typeparam>
    /// <param name="self">The self.</param>
    /// <param name="searchDescriptor">The search descriptor.</param>
    /// <returns>The string.</returns>
    public static string ToRawRequest<T>(this IElasticClient self, SearchDescriptor<T> searchDescriptor) where T : class
    {
        using (var output = new MemoryStream())
        {
            self.Serializer.Serialize(searchDescriptor, output);
            output.Position = 0;
            var rawQuery = new StreamReader(output).ReadToEnd();
            return rawQuery;
        }
    }

    /// <summary>
    /// Prints query into string.
    /// </summary>
    /// <param name="self">The self.</param>
    /// <returns>The value.</returns>
    public static string ToPrettyString(this QueryContainer self)
    {
        using (var settings = new ConnectionSettings())
        {
            var visitor = new DslPrettyPrintVisitor(settings);
            self.Accept(visitor);
            return visitor.PrettyPrint.Replace(Environment.NewLine, string.Empty);
        }                                                                         
    }

回答3:

I like to take it a step further than bsarkar suggests and eliminate the need for a roundtrip altogether:

var client = new ElasticClient();

var seriesSearch = new SearchDescriptor<Series>();
seriesSearch.Filter(f => f
    .Term<Role>(t => t.ReleasableTo.First(), Role.Visitor))
    .SortDescending(ser => ser.EndDate)
    .Size(1));

string searchJson = Encoding.UTF8.GetString(client.Serializer.Serialize(seriesSearch));

Note that your ElasticClient doesn't need any connection properties, so you have no dependency on an ES node.

回答4:

Really easily. If this is my code that searches:

var results = client.Search<SearchItem>(s => s.AllIndices()
    .Query(q =>
            q.Term(p => p.LastName, searchItem.LastName)
            && q.Term(p => p.FirstName, searchItem.FirstName)
            && q.Term(p => p.ApplicationCode, searchItem.ApplicationCode)
            )
    .Size(1000)
    );
var list = results.Documents.ToList();

I then set a breakpoint on the line above. Then, in Visual Studio Immediate Window, I enter this:

?results.ConnectionStatus

and it gives me this:

{StatusCode: 200, 
    Method: POST, 
    Url: http://localhost:9200/_all/searchitem/_search, 
    Request: {
  "size": 1000,
  "query": {
    "bool": {
      "must": [
        {
          "term": {
            "lastName": {
              "value": "carr"
            }
          }
        },
        {
          "term": {
            "firstName": {
              "value": "adrian"
            }
          }
        }
      ]
    }
  }
}

Hope this helps.

回答5:

Using the latest elastic search 5+, I was able to get mine (thanks to Adrian Carr's method) with the following:

var jsonOutput = System.Text.Encoding.UTF8.GetString(
    response.ApiCall.RequestBodyInBytes
)

Which gave me the following output:

{
   "from":0,
   "size":0,
   "query":{
      "bool":{
      ...
      }
   }
}

回答6:

You can use EnableTrace or ConnectionStatusHandler. More details here.

回答7:

Tested in Nest 6.2.0

You can now just do:

#if DEBUG
  connectionSettings.EnableDebugMode(details =>
  {
    Logger.Debug($"ES Request: {Encoding.UTF8.GetString(details.RequestBodyInBytes ?? new byte[0])}");
    Logger.Verbose($"ES Response: {Encoding.UTF8.GetString(details.ResponseBodyInBytes ?? new byte[0])}");
  });
#endif

The call EnableDebugMode will automatically call DisableDirectStreaming, PrettyJson, and then OnRequestCompleted, passing in the function you gave it.

NOTE: There may be a bug somewhere in their response stuff. The response seems to be lacking some closing brackets for some reason.