Before you begin reading this guide, we recommend you run Elasticsearch Error Check-Up which can resolve issues that cause many errors.
This guide will help you check for common problems that cause the log ” Actual Exception ” to appear. It’s important to understand the issues related to the log, so to get started, read the general overview on common issues and tips related to the Elasticsearch concepts: replication.
Advanced users might want to skip right to the common problems section in each concept or try running the Check-Up which analyses ES to pinpoint the cause of many errors and provides suitable actionable recommendations how to resolve them (free tool that requires no installation).
Overview
Replication refers to storing a redundant copy of the data. Starting from version 7.x, Elasticsearch creates one primary shard with a replication factor set to 1. Replicas never get assigned to the same node on which primary shards are assigned, which means you should have at least two nodes in the cluster to assign the replicas. If a primary shard goes down, the replica automatically acts as a primary shard.
What it is used for
Replicas are used to provide high availability and failover. A higher number of replicas is also helpful for faster searches.
Examples
Update replica count
PUT /api-logs/_settings?pretty
{
"index" : {
"number_of_replicas" : 2
}
}Common problems
Log Context
Log “actual Exception” classname is TransportReplicationAction.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :
Releasables.close(indexShardReference);
try {
channel.sendResponse(t);
} catch (IOException responseException) {
logger.warn("failed to send error message back to client for action [{}]"; responseException; transportReplicaAction);
logger.warn("actual Exception"; t);
}
}
}
private void doFinish() {
