ElasticSearch fix 406 Not Acceptable: error

I'm trying to index a document with ElasticSearch PHP client (version 8.8), and I'm getting an error when trying to execute the create document request:

406 Not Acceptable: {"error":"Content-Type header [application/vnd.elasticsearch+json; compatible-with=8] is not supported","status":406}

The weird thing is that the client allowed me to create an index, but when I tried to index a document, I got an error...😕

My configuration is:

• ElasticSearch PHP client: version 8.8
• ElasticSearch server: version 7.10

The issue

To better understand the issue, I'll use curl to reproduce it.

Here is what the ElasticSearch PHP clients send to the server:

curl --location 'http://localhost:9200/products_1/_doc/1' \
--header 'Content-Type: application/vnd.elasticsearch+json; compatible-with=8' \
--data '{
   "title": "hello" 
}'

Notice anything weird? Yes, the Content-Type header is a bit unusual.

Content-Type: application/vnd.elasticsearch+json; compatible-with=8

This tells the ElasticSearch server: I expect a response of a type application/vnd.elasticsearch+json and compatible-with=8 which is ElasticSearch version 8.

The ElasticSearch server responds: 

Content-Type header [application/vnd.elasticsearch+json; compatible-with=8] is not supported

which means I cannot return this content type because I'm not supporting it.

If I change the Content-Type to application/json the request is accepted

curl --location 'http://localhost:9200/products_1/_doc/1' \
--header 'Content-Type: application/json' \
--data '{
   "title": "hello" 
}'

responds

{
  "_index": "products_1",
  "_type": "_doc",
  "_id": "1",
  "_version": 4,
  "result": "updated",
  "_shards": {
    "total": 2,
    "successful": 1,
    "failed": 0
  },
  "_seq_no": 3,
  "_primary_term": 1
}

How to fix this?

As a general rule of thumb, the client's major version should match the server's major version.

There are three options:

1. Update the client to match the server version
2. Update the server version to match the client
3. Configure your client and change the request Content-Type.

In my case, option 3 is out of the question; the PHP ElasticSearch client doesn't support custom Content-Type, or I cannot find how to do it.

Note that a Python client has that configuration, so check your client supports custom Content-Type.