Error parsing date formatted using RFC3339 with 1 digit subsecond

[rucciva]

Describe the feature:

Elasticsearch version (bin/elasticsearch --version): 7.0.0 (docker)

Plugins installed: []

JVM version (java -version): openjdk version "12" 2019-03-19

OS version (uname -a if on a Unix-like system): 4.15.0-29-generic #31-Ubuntu SMP Tue Jul 17 15:39:52 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

Description of the problem including expected versus actual behavior:

Exception when indexing document with certain date value

"Caused byjava.lang.IllegalArgumentExceptionfailed to parse date field [2019-04-26T07:43:02.6Z] with format [strict_date_optional_time||epoch_millis]

Steps to reproduce:

Please include a minimal but complete recreation of the problem, including
(e.g.) index creation, mappings, settings, query etc. The easier you make for
us to reproduce it, the more likely that somebody will take the time to look at it.

1. PUT /test/_doc/1
   {
     "date" : "2015-01-01T12:10:30Z"
   }
   

2. PUT /test/_doc/1
   {
     "date" : "2015-01-01T12:10:30.2Z"
   }
   

Provide logs (if relevant):

{
  "error": {
    "root_cause": [
      {
        "type": "mapper_parsing_exception",
        "reason": "failed to parse field [date] of type [date] in document with id '1'"
      }
    ],
    "type": "mapper_parsing_exception",
    "reason": "failed to parse field [date] of type [date] in document with id '1'",
    "caused_by": {
      "type": "illegal_argument_exception",
      "reason": "failed to parse date field [2015-01-01T12:10:30.2Z] with format [strict_date_optional_time||epoch_millis]",
      "caused_by": {
        "type": "date_time_parse_exception",
        "reason": "Failed to parse with all enclosed parsers"
      }
    }
  },
  "status": 400
}

[elasticmachine]

Pinging @elastic/es-search

[jtibshirani]

From my testing, the second date is accepted on 6.7, but not 7.0. This is likely related to the Joda -> Java time migration, so I'll add relabel this in hopes that @elastic/es-core-infra can have a look.