Briefly, this error occurs when there is a mismatch in the Elasticsearch versions across different nodes in a cluster. This could be due to an incomplete upgrade or a new node with a different version joining the cluster. To resolve this issue, ensure all nodes in the cluster are running the same version of Elasticsearch. This can be done by upgrading all nodes to the latest version or downgrading any nodes that are running a newer version. Always remember to backup your data before performing any upgrade or downgrade operations.
This guide will help you check for common problems that cause the log ” Unknown license version found; please upgrade all nodes to the latest elasticsearch release ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: plugin, license, version, upgrade.
Overview
A version corresponds to the Elasticsearch built-in tracking system that tracks the changes in each document’s update. When a document is indexed for the first time, it is assigned a version 1 using _version key. When the same document gets a subsequent update, the _version is incremented by 1 with every index, update or delete API call.
What it is used for
A version is used to handle the concurrency issues in Elasticsearch which come into play during simultaneous accessing of an index by multiple users. Elasticsearch handles this issue with an optimistic locking concept using the _version parameter to avoid letting multiple users edit the same document at the same time and protects users from generating incorrect data.
Notes
You cannot see the history of the document using _version. That means Elasticsearch does not use _version to keep a track of original changes that had been performed on the document. For example, if a document has been updated 10 times, it’s _version would be marked by Elasticsearch as 11, but you cannot go back and see what version 5 of the document looked like. This has to be implemented independently.
Common problems
If optimistic locking is not implemented while making updates to a document, Elasticsearch may return a conflict error with the 409 status code, which means that multiple users are trying to update the same version of the document at the same time.
POST /ratings/123?version=50
{
"name": "Joker",
"rating": 50
}Log Context
Log “Unknown license version found; please upgrade all nodes to the latest elasticsearch release” class name is License.java. We extracted the following from Elasticsearch source code for those seeking an in-depth context :
} public static License readLicense(StreamInput in) throws IOException {
int version = in.readVInt(); // Version for future extensibility
if (version > VERSION_CURRENT) {
throw new ElasticsearchException("Unknown license version found; please upgrade all nodes to the latest elasticsearch release");
}
Builder builder = builder();
builder.version(version);
builder.uid(in.readString());
builder.type(in.readString());
