relastic

Tool for reindexing ElasticSearch documents after mapping changes.

Usage

Command line usage

$ java -jar relastic-0.3.0-standalone.jar --host HOST \
                                          --port PORT \
                                          --from-index twitter_v1 \
                                          --to-index twitter_v2 \
                                          --alias twitter_read \
                                          --new-alias twitter_write \
                                          --mappings document-mappings.json \
                                          --settings document-settings.json

Executing this will:

1. create a new index twitter_v2 with mappings and settings from specified files
2. add twitter_write alias to twitter_v2 immediately
3. copies all documents from twitter_v1 to twitter_v2
4. add twitter_read alias to twitter_v2 and remove it from twitter_v1 after all documents have been copied

You can omit --from-index, --alias, --new-alias, --mappings and --settings.

--host and --port default to localhost and 9300 (tranport client is used, not HTTP)

NOTE: After reindexing has started, any new documents written to from-index won't be copied to the new index. To make sure all documents are copied, use to-index as the index with all ElasticSearch write operations.

Clojure usage

Include

[yleisradio/relastic "0.3.0"]

to your project.clj. Then:

(require '[relastic.core :as relastic])
(relastic/update-mappings conn :from-index "twitter_v1"
                               :to-index "twitter_v2"
                               :alias "twitter_read"
                               :new-alias "twitter_write"
                               :mappings {:tweet {:properties {:user {:type "string"
                                                                      :index "not_analyzed"}}}}
                               :settings {:index {:refresh_interval "20s"}})

conn should be a ElasticSearch TransportClient (use clojurewerkz.elastisch.native/connect to receive one)

Otherwise, same options apply as when used from command line.

Migrating documents

If you want to modify documents before they are indexed to :to-index, you can do so by passing an optional :migration-fn function. This is useful in scenarios where you've removed a field from your schema and also want it removed from the documents, or when you've added a field and want to fill in a default value.

(defn- migrate-document [{:keys [_type] :as doc}]
  (if (= _type "tweet")
    (assoc-in doc [:_source :author] "anonymous")
    doc))

(relastic/update-mappings conn :from-index "twitter_v1"
                               :to-index "twitter_v2"
                               :mappings new-mappings
                               :settings new-settings
                               :migration-fn migrate-document)

The example above would add :author "anonymous" field to all tweet documents, but leave other document types unmodified.

The :migration-fn takes only one argument, the elasticsearch document. The available fields are the same that would be available through ElasticSearch's REST API. For migration purposes, the most important fields here are:

• :_type - original document type
• :_source - original document as map

The return value should be a map with the same fields that were in the original document. Usually you'll only want to alter the :_source field, but if you want, you can also rename the type to something else. This would cause the documents to appear under different type name in the new index.

You should not reconstruct the document map by yourself. Instead, use assoc-in, update-in or something similar to only do the necessary modifications.

At the moment, it's not possible to specify :migration-fn from command line.

License

Copyright © 2015 Yleisradio Oy

Distributed under the Eclipse Public License either version 1.0 or (at your option) any later version.