Use Python Scripts to Synchronize Index mappings, and an ILM policy on Alibaba Cloud Elasticsearch

Migrating data between Elasticsearch clusters requires a keen eye for details—index mappings, settings, templates, and lifecycle policies must stay consistent to avoid data loss and maintain query performance. Alibaba Cloud Elasticsearch simplifies this process, and with Python scripting, synchronization between clusters becomes a task you can handle with ease. Let's delve into how this is achieved.

Prerequisites

Two Alibaba Cloud Elasticsearch clusters are set up.
An Elastic Compute Service (ECS) instance with Python 3.6.8 or above.
Network connectivity established with IP address whitelisting.

Synchronize Index Mappings and Settings

The following example code helps to transfer index mappings and settings from a source to a destination cluster:

import requests
from requests.auth import HTTPBasicAuth

# Configuration
config = {
    'source_host': 'your-source-host:9200',
    'source_user': 'user',
    'source_password': 'password',
    'destination_host': 'your-destination-host:9200',
    'destination_user': 'user',
    'destination_password': 'password',
    'default_replicas': 1,
}

# Function to send HTTP requests
def send_http_request(method, host, endpoint, username="", password="", json_body=None):
    url = f"https://{host}{endpoint}"
    auth = HTTPBasicAuth(username, password) if username and password else None
    headers = {'Content-Type': 'application/json'} if method != 'GET' else None
    response = requests.request(method, url, auth=auth, json=json_body, headers=headers)
    response.raise_for_status()
    return response.json()

# Function to get index mappings and settings
def get_index_definitions(index):
    mapping_endpoint = f"/{index}/_mapping"
    settings_endpoint = f"/{index}/_settings"
    
    mapping_response = send_http_request('GET', config['source_host'], mapping_endpoint, config['source_user'], config['source_password'])
    settings_response = send_http_request('GET', config['source_host'], settings_endpoint, config['source_user'], config['source_password'])
    
    return { 'mappings': mapping_response[index]['mappings'], 'settings': settings_response[index]['settings']['index'] }

# Function to create index on destination cluster
def create_index_on_destination(index, body):
    create_endpoint = f"/{index}"
    send_http_request('PUT', config['destination_host'], create_endpoint, config['destination_user'], config['destination_password'], body)
    print(f"Index {index} created on destination cluster.")
    
# Main function
def main():
    indices = ['index_to_migrate'] # Replace with your indices
    for index in indices:
        body = get_index_definitions(index)
        create_index_on_destination(index, body)
        
if __name__ == '__main__':
    main()

Running the above script on the ECS instance synchronizes the index definitions to the destination cluster.

Synchronize an Index Template

Synchronize index templates with the following script:

# ... (include previous config and functions)

# Function to get index template from source
def get_template(template_name):
    endpoint = f"/_template/{template_name}"
    return send_http_request('GET', config['source_host'], endpoint, config['source_user'], config['source_password'])

# Function to create template on destination
def create_template_on_destination(template_name, body):
    endpoint = f"/_template/{template_name}"
    send_http_request('PUT', config['destination_host'], endpoint, config['destination_user'], config['destination_password'], body)
    print(f"Template {template_name} created on destination cluster.")
    
# Main function
def main():
    templates = ['template_to_migrate'] # Replace with your template names
    for template in templates:
        body = get_template(template)
        create_template_on_destination(template, body)
        
if __name__ == '__main__':
    main()

Synchronize an ILM Policy

To synchronize ILM policies, you can adjust the previous script slightly:

# ... (include previous config and functions)

# Function to get ILM policy from the source cluster
def get_ilm_policy(policy_name):
    endpoint = f"/_ilm/policy/{policy_name}"
    return send_http_request('GET', config['source_host'], endpoint, config['source_user'], config['source_password'])

# Function to create ILM policy on destination cluster
def create_ilm_policy_on_destination(policy_name, body):
    body.pop('version', None)  # Remove metadata not required for creation
    body.pop('modified_date', None)
    body.pop('modified_date_string', None)

    endpoint = f"/_ilm/policy/{policy_name}"
    send_http_request('PUT', config['destination_host'], endpoint, config['destination_user'], config['destination_password'], body)
    print(f"ILM Policy {policy_name} created on destination cluster.")

# Main function
def main():
    policies = ['policy_to_migrate']  # Replace with your ILM policy names
    for policy in policies:
        body = get_ilm_policy(policy)
        create_ilm_policy_on_destination(policy, body)

if __name__ == '__main__':
    main()

To verify the synchronization, you can execute queries on the destination Elasticsearch cluster to check the mappings (GET _cat/indices/index_name), index templates (GET _template/template_name), and ILM policies (GET _ilm/policy/policy_name).

Wrapping Up

Successfully maintaining Elasticsearch clusters is crucial, especially as your data grows and evolves. By leveraging Alibaba Cloud's powerful Elasticsearch service and Python's flexibility, you can ensure a smooth data transition between clusters while preserving the integrity and performance of your indices.
Alibaba Cloud Elasticsearch provides a robust, scalable, and fully-managed Elasticsearch service suitable for various use-cases, from search and analytics to logging and monitoring.
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This article serves as a guide for managing Elasticsearch indices through the use of Python scripting within the Alibaba Cloud environment. By following the steps laid out and utilizing the provided scripts, you can achieve a seamless synchronization process that preserves the functionality of your search and analytics workloads.

Community

Use Python Scripts to Synchronize Index mappings, and an ILM policy on Alibaba Cloud Elasticsearch

Prerequisites

Synchronize Index Mappings and Settings

Synchronize an Index Template

Synchronize an ILM Policy

Wrapping Up

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