Make journals work with elasticsearch 2.x

[msievers]

Running the specs with elasticsearch 2.1.2 reveals an error in spec/chewy/index/actions_spec#413

rspec ./spec/chewy/index/actions_spec.rb:409 # Chewy::Index::Actions.reset! journaling should not eq 0

Digging into this with pry reveals the following error while executing import

{:create=>
  {{"type"=>"mapper_parsing_exception",
    "reason"=>"failed to parse [created_at]",
    "caused_by"=>{"type"=>"illegal_argument_exception", "reason"=>"Invalid format: \"1474461120\" is malformed at \"20\""}}=>
    ["AVdMuzzyVa0tBwCq2J07"]}}

The problem arises because

• the mapping stats, that created_at is a date with the format basic_date_time
  • see lib/chewy/journal.rb#L10
• but is given as epoch
  • see lib/chewy/journal.rb#L30

This is ok for elasticsearch < 2, because

• The date type will also accept a long number representing UTC milliseconds since the epoch, regardless of the format it can handle.
  • see https://www.elastic.co/guide/en/elasticsearch/reference/1.4/mapping-core-types.html#date

For elasticsearch > 2 it isn't ok, because the given epoch does not match the specified format.

My solution for this is to drop the format specification and let the mapping simply state that created_at is a date

• should be ok for elasticsearch < 2, which will recognize the given epoch as before
• should be ok for elasticsearch >= 2, because if no format is given it defaults to "strict_date_optional_time||epoch_millis"
  • see https://www.elastic.co/guide/en/elasticsearch/reference/current/date.html

[pyromaniac]

Thanks!