Self-Hosting a Vector Database: OpenSearch on Oracle ARM with Coolify

If you are building AI applications, RAG (Retrieval-Augmented Generation) pipelines, or just need a powerful search engine, you need a Vector Database. While services like Pinecone are great, they get expensive.

In this guide, I’ll walk you through self-hosting OpenSearch (the open-source fork of Elasticsearch) on an Oracle Cloud ARM server using Coolify. We will set up both the Database Node (for storing vectors) and the Dashboard (for visualizing data).

What is OpenSearch?

OpenSearch is a distributed search and analytics suite. It is a community-driven fork of Elasticsearch and Kibana.

• OpenSearch (The Database): Stores data, indexes it, and performs queries. Most importantly, it includes the k-NN (k-Nearest Neighbors) plugin out of the box, turning it into a powerful Vector Database for AI embeddings.

• OpenSearch Dashboards (The UI): A web interface to visualize data, manage indices, and run queries via a console.

Prerequisites

• Server: Oracle Cloud ARM (Ampere) instance (Aarch64 architecture).

• OS: Ubuntu.

• Manager: Coolify installed.

• RAM: At least 4GB (Oracle Free Tier offers 24GB, which is perfect).

Step 1: Prepare the Server (Critical!)

Before touching Docker, you must increase the Virtual Memory map count on your Linux host. Elasticsearch/OpenSearch uses memory mapping (mmap) extensively. If you skip this, the container will crash immediately.

SSH into your server and run:

# Set the limit
sudo sysctl -w vm.max_map_count=262144

# Make it permanent (persists after reboot)
echo "vm.max_map_count=262144" | sudo tee -a /etc/sysctl.conf

Note: You can verify this by running sysctl vm.max_map_count. If it returns 262144 or higher, you are safe.

Step 2: Create the Resource in Coolify

• Open Coolify.

• Navigate to your Project -> Environment.

• Click + New Resource -> Docker Compose.

• Paste the following configuration.

The Docker Compose Configuration

This file is optimized for ARM processors and includes specific fixes to prevent SSL handshake errors and disable unnecessary multi-tenancy popups.

services:
  opensearch-node:
    image: opensearchproject/opensearch:latest
    container_name: opensearch-node
    environment:
      - cluster.name=opensearch-cluster
      - node.name=opensearch-node
      - discovery.type=single-node
      - bootstrap.memory_lock=true
      # Oracle ARM usually has 24GB RAM. We allocate 2GB heap here.
      - "OPENSEARCH_JAVA_OPTS=-Xms2g -Xmx2g"
      - OPENSEARCH_INITIAL_ADMIN_PASSWORD=${OPENSEARCH_INITIAL_ADMIN_PASSWORD}
      # DISABLE HTTP CLIENT AUTH (Fixes 504/SSL errors from Dashboard)
      - plugins.security.ssl.http.clientauth_mode=NONE
    ulimits:
      memlock:
        soft: -1
        hard: -1
      nofile:
        soft: 65536
        hard: 65536
    volumes:
      - opensearch-data:/usr/share/opensearch/data
    networks:
      - opensearch-net
    restart: always

  opensearch-dashboards:
    image: opensearchproject/opensearch-dashboards:latest
    container_name: opensearch-dashboards
    depends_on:
      - opensearch-node
    environment:
      - 'OPENSEARCH_HOSTS=["https://opensearch-node:9200"]'
      # DISABLE MULTI-TENANCY (Removes the "Select Tenant" popup)
      - OPENSEARCH_SECURITY_MULTITENANCY_ENABLED=false
      # Stop Dashboard from complaining about self-signed certs
      - OPENSEARCH_SSL_VERIFICATIONMODE=none
    networks:
      - opensearch-net
    restart: always

volumes:
  opensearch-data:

networks:
  opensearch-net:

Step 3: Environment Variables

Before deploying, you must set the admin password. OpenSearch enforces strict password complexity rules.

• In Coolify, go to the Environment Variables tab for this resource.

• Add the key used in the compose file:

Key: OPENSEARCH_INITIAL_ADMIN_PASSWORD

• Value: StrongPass123! (Must include: Uppercase, Lowercase, Number, Special Character).

• Save.

Step 4: Deploy and Configure Domain

• Click Deploy.

• Once the deployment is “Healthy,” go to the opensearch-dashboards service settings (click the gear icon next to it).

• Domains: Set your public URL (e.g., https://search.yourdomain.com).

• Port Exposes: Set to 5601.

• Save and Restart the dashboard service.

Step 5: Verify Installation

• Go to your dashboard URL.

• Log in with admin and your password.

• Because we disabled Multi-Tenancy, you should go straight to the Home screen.

• Click the “Hamburger Menu” (top left) -> Management -> Dev Tools.

• Run this command to create a test Vector Index:

PUT /my-vector-index
{
  "settings": {
    "index": {
      "knn": true,
      "knn.algo_param.ef_search": 100
    }
  },
  "mappings": {
    "properties": {
      "my_vector_field": {
        "type": "knn_vector",
        "dimension": 1536,
        "method": {
          "name": "hnsw",
          "engine": "lucene"
        }
      }
    }
  }
}

If you see "acknowledged": true, your Vector Database is ready!

Pro Tip: Connecting Other Apps in Coolify

One of the best features of Coolify is the internal network. If you have a Node.js, Python, or Go app running in the same Coolify environment, do not use the public domain to connect to the database. Connect internally for zero latency and better security.

• Go to your OpenSearch resource in Coolify.

• Enable “Connect To Predefined Network”.

• Do the same for your Application resource.

• Use these connection details in your App’s .env file:

• Host: opensearch-node

• Port: 9200

• Protocol: http (Use HTTP internally; SSL is handled at the edge)

• Auth: Basic Auth (admin / password)

Example Connection String:

http://admin:YourStrongPass@opensearch-node:9200

Summary of “Gotchas” Fixed

If you try to install this blindly, you usually hit these errors. This guide solved them:

• Exit Code 78: Solved by sysctl vm.max_map_count.

• 504 Gateway Timeout: Solved by setting plugins.security.ssl.http.clientauth_mode=NONE.

• Tenant Popups: Solved by OPENSEARCH_SECURITY_MULTITENANCY_ENABLED=false.

• SSL Handshake Failures: Solved by removing Transport layer auth requirements in the YAML.