After upgrade from ES 1.0.2 to ES 2.3.4, cluster state is red

Elastic Stack Elasticsearch
1

I have 4 indices built using ES 1.0.2, after upgrading to 2.3.4, below is the cluster state

{
"cluster_name": "59f92c3bcfadac7eaf599dad8eace0b3",
"status": "red",
"timed_out": false,
"number_of_nodes": 1,
"number_of_data_nodes": 1,
"active_primary_shards": 0,
"active_shards": 0,
"relocating_shards": 0,
"initializing_shards": 0,
"unassigned_shards": 4,
"delayed_unassigned_shards": 0,
"number_of_pending_tasks": 0,
"number_of_in_flight_fetch": 0,
"task_max_waiting_in_queue_millis": 0,
"active_shards_percent_as_number": 0
}

Is there a way to overcome this?

2

Only one mode is expected? Use GET /_cat/indices?v to see which indices are red. GET /_cat/shards?v will list all shards. You most likely have primary shards unassigned.

https://www.elastic.co/guide/en/elasticsearch/reference/current/cat.html

3

I guess you have errors in logs.

Did you upgrade directly from 1.0.2 to 2.3.4?
You did not run the migration plugin?
You did not follow the upgrade documentation and the breaking changes doc?

https://www.elastic.co/guide/en/elasticsearch/reference/current/breaking-changes.html