# How to Connect # Connecting with Node.js This guide walks you through the process of connecting a Node.js application to a Hydra database using the `pg` package. You’ll learn how to set up the environment, configure the connection, and run a simple SQL query. ### **Variables** To connect to a Hydra database, the following parameters are required. You can find these details in the **Elestio service overview page** of your Hydra service.
**Variable** **Description** **Purpose**
`USER` Hydra (PostgreSQL) username Identifies the database user with access privileges
`PASSWORD` Hydra password Authenticates the user against the Hydra database
`HOST` Hostname of the Hydra instance Specifies the server address of the database
`PORT` Port for Hydra (usually 5432) Specifies the network port for connections
`DATABASE` Name of the Hydra database Specifies which database to access
These values can usually be found in the Elestio service overview details as shown in the image below, make sure to take a copy of these details and add it to the code moving ahead. [![Screenshot 2025-05-07 at 2.09.07 PM.jpg](https://docs.elest.io/uploads/images/gallery/2025-05/scaled-1680-/screenshot-2025-05-07-at-2-09-07-pm.jpg)](https://docs.elest.io/uploads/images/gallery/2025-05/screenshot-2025-05-07-at-2-09-07-pm.jpg) ### **Prerequisites** - **Install Node.js and NPM** - Check if Node.js is installed: ``` node -v npm -v ``` - - If not, download and install it from [https://nodejs.org](https://nodejs.org). - **Install the pg Package** - Hydra is PostgreSQL-compatible, so use the pg package: ``` npm install pg --save ``` ### **Code** Once all prerequisites are set up, create a new file named `hydra.js` and add the following code. ```javascript const { Client } = require("pg"); // Database connection configuration const config = { host: "HOST", user: "USER", password: "PASSWORD", database: "DATABASE", port: PORT, ssl: { rejectUnauthorized: false, // Only if Hydra requires SSL (check Elestio settings) }, }; // Create a new client instance const client = new Client(config); // Connect to the Hydra database client.connect((err) => { if (err) { console.error("Connection failed:", err.stack); return; } console.log("Connected to Hydra"); // Run a test query client.query("SELECT version()", (err, res) => { if (err) { console.error("Query failed:", err.stack); } else { console.log("Hydra/PostgreSQL Version:", res.rows[0].version); } // Close the connection client.end((err) => { if (err) console.error("Error closing connection:", err.stack); }); }); }); ``` To execute the script, open the terminal or command prompt and navigate to the directory where `hydra.js`. Once in the correct directory, run the script with the command ``` node hydra.js ``` If successful, you’ll see: ``` Connected to Hydra Hydra/PostgreSQL Version: PostgreSQL 14.13 (Debian 14.13-1.pgdg120+1) on x86_64-pc-linux-gnu, compiled by gcc (Debian 12.2.0-14) 12.2.0, 64-bit ``` # Connecting with Python This guide explains how to connect a Python application to a Hydra database using the `psycopg2-binary` package. It covers environment setup, configuration, and execution of a simple query to test connectivity. ### **Variables** To connect to a Hydra database, you only need **one environment variable** — the connection URI.
**Variable** **Description** **Purpose**
`HYDRA_URI` Full Hydra (PostgreSQL-compatible) connection string from the Elestio service overview Provides all credentials and connection details in a single URI
A typical URI format looks like: ``` postgresql://:@:/ ``` You can find the details needed in the URI from the **Elestio service overview** details. Copy and replace the variables carefully in the URI example provided above. [![image.png](https://docs.elest.io/uploads/images/gallery/2025-05/scaled-1680-/kHqimage.png)](https://docs.elest.io/uploads/images/gallery/2025-05/kHqimage.png) ### **Prerequisites** **Install Python** Check if Python is installed: ``` python --version ``` If not installed, download it from [https://python.org](https://python.org). **Install** `psycopg2-binary` Install the PostgreSQL driver for Python: ``` pip install psycopg2-binary ``` ### **Code** Once all prerequisites are set up, create a new file named `hydra.py` and add the following code and replace the `HYDRA_URI` with actual link or in environment setup as you wish: ```python import psycopg2 import os def get_db_version(): try: # Use the Hydra URI from environment variable connection_uri = os.getenv('HYDRA_URI', 'POSTGRESQL_URI') db_connection = psycopg2.connect(connection_uri) db_cursor = db_connection.cursor() db_cursor.execute('SELECT VERSION()') db_version = db_cursor.fetchone()[0] return db_version except Exception as e: print(f"Database connection error: {e}") return None finally: if 'db_cursor' in locals(): db_cursor.close() if 'db_connection' in locals(): db_connection.close() def display_version(): version = get_db_version() if version: print(f"Connected to Hydra: {version}") if __name__ == "__main__": display_version() ``` > 🔐 **Tip:** Save your URI in an .env file or set it in your terminal session like this: ```bash export HYDRA_URI=postgresql://user:password@host:port/database ``` To execute the script, open the terminal or command prompt and navigate to the directory where `hydra.py`. Once in the correct directory, run the script with the command ```bash python hydra.py ``` If the connection is successful, you’ll see: ``` Connected to Hydra: PostgreSQL 14.13 (Debian 14.13-1.pgdg120+1) on x86_64-pc-linux-gnu, compiled by gcc (Debian 12.2.0-14) 12.2.0, 64-bit ``` # Connecting with PHP This guide explains how to connect a PHP application to a Hydra database using the **PDO extension**. It covers setting up prerequisites, configuring the connection URI, and running a test SQL query. ### **Variables** To connect to a Hydra database, you only need **one environment variable** — the connection URI.
**Variable** **Description** **Purpose**
`HYDRA_URI` Full Hydra connection string from Elestio Encodes all connection info in one URI
A typical URI looks like this: ``` postgresql://:@:/ ``` You can find the details needed in the URI from the **Elestio service overview** details. Copy and replace the variables carefully in the URI example provided above. [![image.png](https://docs.elest.io/uploads/images/gallery/2025-05/scaled-1680-/eTcimage.png)](https://docs.elest.io/uploads/images/gallery/2025-05/eTcimage.png) ### **Prerequisites** **Install PHP** Check if PHP is installed: ``` php -v ``` If not, download and install PHP from: [https://www.php.net/downloads.php](https://www.php.net/downloads.php) ### **Code** Once all prerequisites are set up, create a new file named `hydra.php` and add the following code and replace the `HYDRA_URI` with actual link or in environment setup as you wish: ```php query("SELECT VERSION()")->fetchColumn(); echo "Connected to Hydra: " . $version . PHP_EOL; } catch (PDOException $e) { echo "Connection failed: " . $e->getMessage() . PHP_EOL; } ``` To execute the script, open the terminal or command prompt and navigate to the directory where `hydra.php`. Once in the correct directory, run the script with the command ```bash export HYDRA_URI=postgresql://user:password@host:port/database ``` Navigate to the directory containing `hydra.php` and run: ``` php hydra.php ``` If successful, you’ll see output like: ``` Connected to Hydra: PostgreSQL 14.13 (Debian 14.13-1.pgdg120+1) on x86_64-pc-linux-gnu, compiled by gcc (Debian 12.2.0-14) 12.2.0, 64-bit ``` # Connecting with Go This guide walks you through setting up a Go application to connect to a Hydra database, using the PostgreSQL-compatible `lib/pq` driver, and running a basic query to verify the connection. ### **Variables** To connect to a Hydra database, you only need **one environment variable** — the connection URI. This URI contains all the necessary information like username, password, host, port, and database name.
**Variable** **Description** **Purpose**
`HYDRA_URI` Full Hydra (PostgreSQL-compatible) connection string from the Elestio service overview Provides all credentials and connection details in a single URI
A typical URI format looks like: ```bash postgresql://:@:/ ``` You can find the details needed in the URI from the **Elestio service overview** details. Copy and replace the variables carefully in the URI example provided above. [![image.png](https://docs.elest.io/uploads/images/gallery/2025-05/scaled-1680-/kHqimage.png)](https://docs.elest.io/uploads/images/gallery/2025-05/kHqimage.png) ### **Prerequisites** - **Install Go** - Check if Go is installed: ``` go version ``` - - If not, download and install Go: [https://go.dev/dl/](https://go.dev/dl/) - **Install pq Driver** ``` go get github.com/lib/pq ``` ### **Code** Once all prerequisites are set up, create a new file named `main.go` and add the following code, and replace the `HYDRA_URI` with actual link or in environment setup as you wish: ```go package main import ( "database/sql" "fmt" "log" "os" _ "github.com/lib/pq" ) func getDBConnection(connStr string) (*sql.DB, error) { db, err := sql.Open("postgres", connStr) if err != nil { return nil, fmt.Errorf("failed to open database connection: %v", err) } if err := db.Ping(); err != nil { return nil, fmt.Errorf("failed to ping database: %v", err) } return db, nil } func main() { // Get the Hydra connection string from environment variable connStr := os.Getenv("HYDRA_URI") if connStr == "" { log.Fatal("HYDRA_URI environment variable not set") } db, err := getDBConnection(connStr) if err != nil { log.Fatal(err) } defer db.Close() query := "SELECT current_database(), current_user, version()" row := db.QueryRow(query) var dbName, user, version string if err := row.Scan(&dbName, &user, &version); err != nil { log.Fatal("Failed to scan row:", err) } fmt.Printf("Connected to Hydra\nDatabase: %s\nUser: %s\nVersion: %s\n", dbName, user, version) } ``` Set your Hydra URI as an environment variable: ```bash export HYDRA_URI=postgresql://user:password@host:port/database ``` To execute the script, open the terminal or command prompt and navigate to the directory where `main.go`. Once in the correct directory, run the script with the command ```bash go run main.go ``` If successful, you’ll see output like: ```bash Connected to Hydra Database: elestio User: postgres Version: PostgreSQL 14.13 (Debian 14.13-1.pgdg120+1) on x86_64-pc-linux-gnu, compiled by gcc (Debian 12.2.0-14) 12.2.0, 64-bit ``` # Connecting with Java This guide shows how to connect your Java app to a **Hydra database** using the [PostgreSQL JDBC driver](https://jdbc.postgresql.org/), parse command-line arguments, and run a basic query. ### **Variables** To connect to a Hydra database, the following parameters are required. You can find these details in the **Elestio service overview page** of your Hydra service.
**Variable** **Description** **Purpose**
`USER` Hydra (PostgreSQL) username Identifies the database user with access privileges
`PASSWORD` Hydra password Authenticates the user against the Hydra database
`HOST` Hostname of the Hydra instance Specifies the server address of the database
`PORT` Port for Hydra (usually 5432) Specifies the network port for connections
`DATABASE` Name of the Hydra database Specifies which database to access
These values can usually be found in the Elestio service overview details as shown in the image below, make sure to take a copy of these details and add it to the code moving ahead. [![Screenshot 2025-05-07 at 2.09.07 PM.jpg](https://docs.elest.io/uploads/images/gallery/2025-05/scaled-1680-/screenshot-2025-05-07-at-2-09-07-pm.jpg)](https://docs.elest.io/uploads/images/gallery/2025-05/screenshot-2025-05-07-at-2-09-07-pm.jpg) ### **Prerequisites** ##### **Install Java & JDBC driver** Check if Java is installed by running: ```bash java -version ``` If not installed, install it first and then download and install **JDBC** driver from [https://jdbc.postgresql.org/download/](https://jdbc.postgresql.org/download/) or if you have Maven installed, run the following command with updated version of the driver: ```bash mvn org.apache.maven.plugins:maven-dependency-plugin:2.8:get \ -Dartifact=org.postgresql:postgresql:42.7.5:jar \ -Ddest=postgresql-42.7.5.jar ``` ## **Code** Once all prerequisites are set up, create a new file named `HydraPg.java` and add the following code: ```java import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; import java.util.HashMap; import java.util.Map; public class HydraPg { static class Config { String host, port, database, username, password; Config(String host, String port, String database, String username, String password) { this.host = host; this.port = port; this.database = database; this.username = username; this.password = password; } String getJdbcUrl() { return String.format("jdbc:postgresql://%s:%s/%s?sslmode=require", host, port, database); } boolean isComplete() { return host != null && port != null && database != null && username != null && password != null; } } static Map parseArgs(String[] args) { Map map = new HashMap<>(); for (int i = 0; i < args.length - 1; i += 2) { map.put(args[i], args[i + 1]); } return map; } public static void main(String[] args) { try { Class.forName("org.postgresql.Driver"); Map argMap = parseArgs(args); Config cfg = new Config( argMap.get("-host"), argMap.get("-port"), argMap.get("-database"), argMap.get("-username"), argMap.get("-password") ); if (!cfg.isComplete()) { System.err.println("Missing required arguments. Example usage:"); System.err.println("java -cp postgresql-42.7.5.jar:. HydraPg -host -port -database -username -password "); return; } try (Connection conn = DriverManager.getConnection(cfg.getJdbcUrl(), cfg.username, cfg.password)) { System.out.println("Connected to Hydra database successfully."); Statement stmt = conn.createStatement(); ResultSet rs = stmt.executeQuery("SELECT current_database(), current_user, version()"); while (rs.next()) { System.out.println("Database: " + rs.getString(1)); System.out.println("User: " + rs.getString(2)); System.out.println("Version: " + rs.getString(3)); } rs.close(); stmt.close(); } } catch (ClassNotFoundException e) { System.err.println("PostgreSQL JDBC driver not found."); e.printStackTrace(); } catch (SQLException e) { System.err.println("Connection or query error:"); e.printStackTrace(); } } } ``` To execute the script, open the terminal or command prompt and navigate to the directory where `HydraPg.java`. Once in the correct directory, run the script with the command (Update the variables with actual values acquired from previous steps). ```bash javac HydraPg.java ``` ``` java -cp postgresql-42.7.5.jar:. HydraPg -host HOST -port PORT -database DATABASE -username USERNAME -password PASSWORD ``` If the connection is successful, the terminal will display output similar to: ```bash Connected to Hydra database successfully. Database: elestio User: postgres Version: PostgreSQL 14.13 (Debian 14.13-1.pgdg120+1) on x86_64-pc-linux-gnu, compiled by gcc (Debian 12.2.0-14) 12.2.0, 64-bit ``` # Connecting with psql This guide explains how to connect to a **Hydra** database using the **`psql`** command-line tool. It walks through the necessary setup, connection process, and execution of a simple SQL query. ### **Variables** To connect to a Hydra database, you only need **one environment variable** — the connection URI.
**Variable** **Description** **Purpose**
`HYDRA_URI` Full Hydra connection string from Elestio Encodes all connection info in one URI
A typical URI looks like this: ```bash postgresql://:@:/ ``` You can find the details needed in the URI from the **Elestio service overview** details. Copy and replace the variables carefully in the URI example provided above. [![image.png](https://docs.elest.io/uploads/images/gallery/2025-05/scaled-1680-/eTcimage.png)](https://docs.elest.io/uploads/images/gallery/2025-05/eTcimage.png) ### **Prerequisites** While following this tutorial, you will need to have **`psql`** already installed; if not head over to [https://www.postgresql.org/download/](https://www.postgresql.org/download/) and download it first. ### **Connecting to Hydra** Open your terminal and run the following command to connect to your Hydra database using the full connection URI: ``` psql HYDRA_URI ``` If the connection is successful, you’ll see output similar to this. Here it will show you the database you tried to connect to, which in this case is Elestio: ```bash psql (17.4, server 14.13 (Debian 14.13-1.pgdg120+1)) SSL connection (protocol: TLSv1.3, cipher: TLS_AES_256_GCM_SHA384, compression: off, ALPN: none) Type "help" for help. elestio=# ```
To ensure you're connected correctly, run this command inside the `psql` prompt: ```postgresql SELECT version(); ``` You should receive output like the following: ```postgresql version --------------------------------------------------------------------------------------------------------------------- PostgreSQL 16.8 (Debian 16.8-1.pgdg120+1) on x86_64-pc-linux-gnu, compiled by gcc (Debian 12.2.0-14) 12.2.0, 64-bit (1 row) ```
# Connecting with pgAdmin **pgAdmin** is a widely used graphical interface for Hydra that allows you to manage, connect to, and run queries on your databases with ease. ### **Variables** To connect using `pgAdmin`, you'll need the following connection parameters. When you deploy a Hydra service on Elestio, you also get a pgAdmin dashboard configured for you to use with these variables. These details are available in the **Elestio service overview page**:
VariableDescriptionPurpose
`USER`pgAdmin usernameIdentifies the pgAdmin user with access permission.
`PASSWORD`pgAdmin passwordAuthentication key for the `USER`.
You can find these values in your Elestio project dashboard under **Admin** section. [![Screenshot 2025-05-07 at 10.08.35 PM.jpg](https://docs.elest.io/uploads/images/gallery/2025-05/scaled-1680-/screenshot-2025-05-07-at-10-08-35-pm.jpg)](https://docs.elest.io/uploads/images/gallery/2025-05/screenshot-2025-05-07-at-10-08-35-pm.jpg) ### **Prerequisites** Make sure the **Hydra** service is correctly deployed on Elestio and you are able to access the Admin section like the one in the image above. ### **Setting Up the Connection** 1. Launch **pgAdmin** from the Admin UI URL and log in with the credentials acquired in the steps before. ![Screenshot 2025-04-01 at 3.51.28 PM.jpg](https://docs.elest.io/uploads/images/gallery/2025-04/scaled-1680-/screenshot-2025-04-01-at-3-51-28-pm.jpg) 2. Click on **"Create"** and select **"Server…"** from the dropdown, or find **Add New Server** from the quick links![Screenshot 2025-04-01 at 3.55.59 PM.jpg](https://docs.elest.io/uploads/images/gallery/2025-04/scaled-1680-/screenshot-2025-04-01-at-3-55-59-pm.jpg) 3. In the **General** tab: - Enter a name for your connection (e.g., `Trial pgAdmin Connection`).![image.png](https://docs.elest.io/uploads/images/gallery/2025-04/scaled-1680-/image.png) 4. Go to the **Connection** tab and enter the following details: - **Host name/address**: `HOSTNAME` - **Port**: `PORT` - **Maintenance database**: `DATABASE` - **Username**: `USERNAME` - **Password**: `PASSWORD` ![image.png](https://docs.elest.io/uploads/images/gallery/2025-04/scaled-1680-/6v6image.png)