Elasticsearch _reindex API not copying documents - elasticsearch

Question

I'm trying to upgrade an old 1.5 elastic index to 6.0, according to docs (https://www.elastic.co/guide/en/elasticsearch/reference/6.0/reindex-upgrade.html)
I can create a new index in 6.0 and then use reindex from remote using reindex from remote (https://www.elastic.co/guide/en/elasticsearch/reference/6.0/reindex-upgrade-remote.html)
Both of these instances are running inside docker containers I just wanted to test this in local before actually doing it in production
I can see there are documents indexed in my old index.
curl -XGET 'http://localhost:9200/old_index/_search?pretty'
{
"took" : 8,
"timed_out" : false,
"_shards" : {
"total" : 5,
"successful" : 5,
"failed" : 0
},
"hits" : {
"total" : 1,
"max_score" : 1.0,
"hits" : [ {
"_index" : "old_index",
"_type" : "item",
"_id" : "92",
"_score" : 1.0,
"_source":{"user_id":3,"slug":"asdfaisjeilej","name":"lake.jpgasdad","item_type":"image","created_at":"2018-01-23T18:11:30Z","deleted_at":null,"content_length":1252171}
}]}
}
After creating a new index (new_index) in my elasticsearch 6.0 instance, with a slightly diff mapping (change string types to text), I then proceed to reindex from remote using the following command. (note than my other instance is running in port 9400)
curl -XPOST 'localhost:9400/_reindex?pretty' -H 'Content-Type: application/json' -d'
{
"source": {
"remote": {
"host": "http://localhost:9200"
},
"index": "old_index"
},
"dest": {
"index": "new_index"
}
}
I get the following response
{
"took" : 136,
"timed_out" : false,
"total" : 0,
"updated" : 0,
"created" : 0,
"deleted" : 0,
"batches" : 0,
"version_conflicts" : 0,
"noops" : 0,
"retries" : {
"bulk" : 0,
"search" : 0
},
"throttled_millis" : 0,
"requests_per_second" : -1.0,
"throttled_until_millis" : 0,
"failures" : [ ]
}
So basically, documents from old_index are not being copied to new_index, and I have no idea why this is happening. Is there a step I'm missing, I'm following elasticsearch docs exactly as they read apparently.

Answer 1

As I mentioned, I also had the same issue while migrating from Elasticsearch-2 to Elasticsearch-6 after I tested the remote-reindexing in staging environment without dockers.
My workaround was to create an instance of the old version (not on docker), load it from backup and reindex from it to elasticsearch 6 instance that not running on docker.
If you still want to run elasticsearch 6 on docker you can always mount the data to your container.
Hope you find it helpful.