Programming language: Crystal
License: MIT License
Tags: Search    
Latest version: v0.3.0

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Hermes Build Status

This is an integration of Crystal and Elasticsearch via HTTP/HTTPS protocol.


Add this to your application's shard.yml:

    github: imdrasil/hermes.cr




require "hermes"

in places where you load your configurations. For now you need to specify all configurations using dsl but in future support of yaml configuration files for different environments will be added. So this is regular configuration for playground environment:

Hermes::Config.configure do |conf|
  conf.host = "localhost"
  conf.port = 9200

Default values:

attribute value
host "localhost"
port 9200
schema "http"

Command management

For command management Hermes uses Sam. So in your sam.cr just add loading migrations and Jennifer hooks.

require "./your_configuration_folder/*"
load_dependencies "./", "hermes"
# your another tasks here


Now you can use next commands:

  • put all mappings to Elasticsearch
$ crystal sam.cr -- es:mapping:update
  • updates configurations of all indexes
$ crystal sam.cr -- es:index:update_all
  • creates all indexes
$ crystal sam.cr -- es:index:create_all
  • updates configuration of provided index
$ crystal sam.cr -- es:index:update index_name
  • creates given index
$ crystal sam.cr -- es:index:create index_name
  • destroy given index
$ crystal sam.cr -- es:index:destroy index_name
  • destroy all indexes
$ crystal sam.cr -- es:index:destroy_all


First of all specify all your indexes. Here is example of some test index:

class TestIndex < Hermes::Index
  index_name "test_index"

    mappings: {
      post: {
        properties: {
          title: {
            type:   "text",
            fields: {
              raw: {
                type: "keyword",
          likes:      {type: "integer"},
          user:       {:type => "text"},
          text:       {:type => "text"},
          tag:        {:type => "keyword"},
          created_at: {:type => "date"},

      user: {
        properties: {
          full_name: {type: "text"},
          location:  {type: "geo_point"},
          photo:     {type: "binary"},

You could use both NamedTuple and hash notation

config macros allows you specify configs for index (settings, mappings, etc.). Here regular Elasticsearch options should be used.

Also using index_name method custom index name could be stored. By default underscored class name without last "_index" part is taken.


Hermes implements some kind of Datamapper pattern so all CRUD and search logic will be inside of repository which allows to separate search and domain logic. So regular repository looks like this:

class PostRepository < Hermes::Repository(TestIndex, Post)

By default repository name is underscored class name without last "_repository" part. But it can be specified using document_type method.


This is module which includes mapping rules for fields. This allows to mix it into any class. Here is simple example:

class Post
  include Hermes::Persistent

    title: String,
    likes: {type: Int32, default: 0},
    user: String,
    text: String,
    tag: {type: String, nilable: true},
    created_at: Time | Nil,
    non_existing_field: {type: Int32 | Nil, nilable: true}

es_fields macros works almost same way as JSON.mapping except generating several extra methods:

  • #{{attribute_name}}! - for all given attributes with getters; makes not nil assertion
  • #initialize(Hash(String, Any))
  • #initialize(Hash(Symbol, Any))
  • #initialize(**)
  • #assign_es_fields(Hash) - will set all given fields
  • #assign_es_fields(**)
  • #to_hash - returns hash with all attributes (keys are strings)

Data types

All regular Crystal data types, which could be mapped from Elasticsearch data types, are supported (like Int32, String or Times, or Array(Int32)). Also supported all "special" data types:

  • binary (Hermes::Types::Binary)
  • range (Hermes::Types::Range(T))

Due to Elasticsearch documentation there are several supported data types: Int32, Int64, Float32 Float64, Time.

  • IP address (Hermes::Types::IP)
  • geometrical
    • geo_point (Hermes::Types::GeoPoint)
    • circle (Hermes::Types::Circle)
    • envelope (Hermes::Types::Envelop)
    • geometry collection (Hermes::Types::GeometryCollection)
    • line string (Hermes::Types::LineString)
    • multi line string (Hermes::Types::MultiLineString)
    • multi point (Hermes::Types::MultiPoint)
    • multi polygon (Hermes::Types::MultiPolygon)
    • point (Hermes::Types::Point)
    • polygon (Hermes::Types::Polygon)



New object can be created from Hash (with string keys), NamedTuple or new Persistent object.

PostRepository.create({"user" => "kim", "message" => "some message", "tag" => "es", "time" => Time.now })

PostRepository.create(user: "eddy", message: "some message", tag: "es", time: Time.now )

obj = Post.new({"user" => "kim", "message" => "some message", "tag" => "es", "time" => Time.now })

Due to Elasticsearch documentations, new object will be indexed in several seconds. So to do it immediatly you can manualy refresh:

# or passing true as second parameter for #save

PostRepository.save(obj, true)

Such usage could slow down everything.


Single document can be retrieved by it's id:

PostRepository.find("elastic_uid_here") # object or nil
PostRepository.find!("elastic_uid_here") # object or exception
PostRepository.multi_get(["uid1", "uid2"]) # array of found objects by their ids

Also regular Elasticsearch query dsl could be used:

    query: {
        bool: {
            must: {
                term: {user: "kim"},
            should: [
                {term: {tag: "wow"}},
                {term: {tag: "es"}},
            minimum_should_match: 1,
            boost:                1.0,

It will return SearchResponse(T) object (in this case T is a Post). It provide access to all response data and has shortcuts for search and aggregation results (entries and aggs methods).

If you need only count of matched objects:

    query: {
        bool: {
            must: {
                term: {user: "kim"},
            should: [
                {term: {tag: "wow"}},
                {term: {tag: "es"}},
            minimum_should_match: 1,
            boost:                1.0,
}) # some Int32 value

Also there is shortcut for aggregations:

PostRepository.aggregate({max_date: {max: {field: "time"}}})

It will return object of SearchResponse(T) as well as search but without entries inside.


If you want to save new version of object, use regular same:

obj.message = "another message"

Also there is method for _update Elasticsearch endpoint:

PostRepository.update("some_id", { script: {...}}) # allow specify entire request body

PostRepository.update_doc("some_id", {user: "tomas"}) # accepts "doc" part of body

PostRepository.update_by_script("some_id", {
  script: {
    inline: "ctx._source.likes += params.count",
    lang:   "painless",
    params: {count: 1},
}) # allow specify entire request body

and _update_by_query

  script: {
    inline: "ctx._source.likes += params.count",
    lang:   "painless",
    params: {count: 1},
  query: {
    term: {
      user: "kim",


To delete object by it's id use:


Also you can do it using query:

PostRepository.delete_by_query({query: {match: {message: "some message"}}})


Hermes uses one connection and is needed to be tested with multi-threading (check safety).


There are still a lot of work to do. Tasks for next versions:

  • [ ] fully cover with tests
  • [ ] add IP related logic to Hermes::Types::IP and move it to separate shard (like ruby-ip)
  • [ ] think about adding smth like connection pool
  • [ ] add Jennifer support
  • [ ] add more things below...


  1. Fork it
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create a new Pull Request

Please ask me before start any work on some feature.

Also if you want to use it in your application - ping me please, my email could be found in my profile.

To run test use regular crystal spec.


  • imdrasil Roman Kalnytskyi - creator, maintainer