How to fix RemoteTransportException: Failed to deserialize response from in Elasticsearch

# Check version on all nodes
curl -X GET "localhost:9200/_cat/nodes?v&h=name,version,jdk"

# Or use the nodes API for detailed info
curl -X GET "localhost:9200/_nodes?filter_path=nodes.*.version,nodes.*.jvm"

# Example output showing version mismatch (PROBLEM):
name         version  jdk
node-1       7.10.0   1.8.0_51
node-2       7.11.0   1.8.0_51  # Different ES version!
node-3       7.10.0   1.8.0_144 # Different JDK version!

# Correct output (all versions match):
name         version  jdk
node-1       7.17.0   11.0.2
node-2       7.17.0   11.0.2
node-3       7.17.0   11.0.2

# For Node.js
npm list @elastic/elasticsearch

# For Python
pip show elasticsearch

# For Java
# Check pom.xml or build.gradle
grep "org.elasticsearch.client" pom.xml

# Check Java version on each node
java -version

# Example of problematic mismatch:
# Node 1: java version "1.8.0_51"
# Node 2: java version "1.8.0_144"  # Different minor version

# Update to same Java version on all nodes
# For Ubuntu/Debian
sudo apt update
sudo apt install openjdk-11-jdk

# For RHEL/CentOS
sudo yum install java-11-openjdk

# Verify versions match
for node in node1 node2 node3; do
  ssh $node "java -version 2>&1 | head -n 1"
done

# Set JAVA_HOME consistently
export JAVA_HOME=/usr/lib/jvm/java-11-openjdk-amd64
export PATH=$JAVA_HOME/bin:$PATH

# Update elasticsearch.yml or jvm.options if needed
# Ensure Elasticsearch uses the correct Java installation

# Step 1: Disable shard allocation
curl -X PUT "localhost:9200/_cluster/settings" -H 'Content-Type: application/json' -d'
{
  "persistent": {
    "cluster.routing.allocation.enable": "primaries"
  }
}'

# Step 2: Stop non-essential indexing and flush
curl -X POST "localhost:9200/_flush/synced"

# Step 3: Upgrade one node at a time
# On the node to upgrade:
sudo systemctl stop elasticsearch

# Update Elasticsearch package
sudo apt upgrade elasticsearch  # or yum, rpm, etc.

# Start the upgraded node
sudo systemctl start elasticsearch

# Step 4: Wait for node to rejoin cluster
curl -X GET "localhost:9200/_cat/nodes?v"

# Step 5: Re-enable shard allocation
curl -X PUT "localhost:9200/_cluster/settings" -H 'Content-Type: application/json' -d'
{
  "persistent": {
    "cluster.routing.allocation.enable": "all"
  }
}'

# Step 6: Wait for cluster to stabilize
curl -X GET "localhost:9200/_cluster/health?wait_for_status=green&timeout=50s"

# Step 7: Repeat for each remaining node

// Node.js client - Check version compatibility
// package.json
{
  "dependencies": {
    "@elastic/elasticsearch": "^8.12.0"  // Must match ES 8.x
  }
}

// Update client library
npm install @elastic/[email protected]

// Verify connection with new client
const { Client } = require('@elastic/elasticsearch');
const client = new Client({
  node: 'http://localhost:9200',
  requestTimeout: 60000
});

async function testConnection() {
  try {
    const info = await client.info();
    console.log('Connected to Elasticsearch version:', info.version.number);
  } catch (error) {
    console.error('Connection failed:', error);
  }
}

# Python client - Update to match server
# requirements.txt
elasticsearch==8.12.0  # Match major version with server

# Install updated client
pip install elasticsearch==8.12.0

# Test connection
from elasticsearch import Elasticsearch

es = Elasticsearch(['http://localhost:9200'])
info = es.info()
print(f"Connected to Elasticsearch {info['version']['number']}")

<!-- Java client - Maven -->
<dependency>
  <groupId>org.elasticsearch.client</groupId>
  <artifactId>elasticsearch-rest-high-level-client</artifactId>
  <version>7.17.0</version>  <!-- Match server version -->
</dependency>

# Check network connectivity between nodes
ping node2.example.com

# Test transport port connectivity
nc -zv node2.example.com 9300

# Monitor packet loss and latency
mtr node2.example.com

# Check for network errors in system logs
journalctl -u elasticsearch -n 100 | grep -i "network|transport|connection"

# Review Elasticsearch transport logs
# Set transport logging to debug in elasticsearch.yml
logger.org.elasticsearch.transport: DEBUG

# Or dynamically via API
curl -X PUT "localhost:9200/_cluster/settings" -H 'Content-Type: application/json' -d'
{
  "transient": {
    "logger.org.elasticsearch.transport": "DEBUG",
    "logger.org.elasticsearch.transport.netty4": "TRACE"
  }
}'

# Check for TCP retransmissions (indicates network issues)
netstat -s | grep -i retrans

# Verify MTU settings match across nodes
ip link show | grep mtu

# Test large packet transmission
ping -M do -s 1472 node2.example.com

# List installed plugins on each node
bin/elasticsearch-plugin list

# Example output
analysis-icu
discovery-ec2
repository-s3

# Check plugin compatibility with Elasticsearch version
# Plugins compiled for ES 7.10 won't work with ES 7.17

# Remove incompatible plugin
sudo bin/elasticsearch-plugin remove plugin-name

# Restart Elasticsearch
sudo systemctl restart elasticsearch

# Install compatible version of plugin
sudo bin/elasticsearch-plugin install plugin-name

# Verify cluster health after plugin changes
curl -X GET "localhost:9200/_cluster/health?pretty"

# Check for plugin-related errors in logs
tail -f /var/log/elasticsearch/elasticsearch.log | grep -i plugin

# Graceful restart of a single node
# Step 1: Disable shard allocation
curl -X PUT "localhost:9200/_cluster/settings" -H 'Content-Type: application/json' -d'
{
  "transient": {
    "cluster.routing.allocation.enable": "primaries"
  }
}'

# Step 2: Stop the node
sudo systemctl stop elasticsearch

# Step 3: Verify services stopped
ps aux | grep elasticsearch

# Step 4: Start the node
sudo systemctl start elasticsearch

# Step 5: Wait for node to join cluster
watch -n 2 'curl -s "localhost:9200/_cat/nodes?v"'

# Step 6: Re-enable shard allocation
curl -X PUT "localhost:9200/_cluster/settings" -H 'Content-Type: application/json' -d'
{
  "transient": {
    "cluster.routing.allocation.enable": "all"
  }
}'

# Monitor cluster recovery
curl -X GET "localhost:9200/_cat/recovery?v&active_only=true"

# Check for continued deserialization errors
tail -f /var/log/elasticsearch/elasticsearch.log | grep -i "deserialize|serialization"

# Verify cluster is healthy
curl -X GET "localhost:9200/_cluster/health?pretty"