Hermes

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

Installation

Add this to your application's shard.yml:

dependencies:
  hermes:
    github: imdrasil/hermes.cr

Usage

Configuration

Put

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
end

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
Sam.help

Commands

Now you can use next commands:

$ crystal sam.cr -- es:mapping:update
$ crystal sam.cr -- es:index:update_all
$ crystal sam.cr -- es:index:create_all
$ crystal sam.cr -- es:index:update index_name
$ crystal sam.cr -- es:index:create index_name
$ crystal sam.cr -- es:index:destroy index_name
$ crystal sam.cr -- es:index:destroy_all

Index

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

class TestIndex < Hermes::Index
  index_name "test_index"

  config({
    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"},
        },
      },
    },
  })
end
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.

Repository

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)
end

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

Persistent

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

  es_fields(
    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}
  )
end

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

Data types

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

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

CRUD

Create

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 })
PostRepository.save(obj)

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

TestIndex.refresh
# or passing true as second parameter for #save

PostRepository.save(obj, true)

Such usage could slow down everything.

Read

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
PostRepository.all

Also regular Elasticsearch query dsl could be used:

PostRepository.search({
    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:

PostRepository.count({
    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.

Update

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

obj.message = "another message"
PostRepository.save(obj)

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

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

Delete

To delete object by it's id use: 

PostRepository.delete(obj._id)

Also you can do it using query:

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

Restrictions

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

Development

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

Contributing

  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.

Contributors