Configure Presto Admin Password and Restore Web UI Access - E-MapReduce

Before accessing the Presto web UI or submitting Presto jobs, set the administrator password for your Presto cluster. This topic explains how to configure the password in the E-MapReduce (EMR) console.

Prerequisites

Before you begin, ensure that you have:

An EMR on ACK cluster with Presto deployed
Access to the EMR console
htpasswd installed on your local machine (see Install htpasswd)

How it works

The Presto cluster stores credentials in a password.db file. Each line follows the format username:hashed_password, where the password must be hashed using bcrypt. A valid entry looks like:

admin:$2y$10$BqTb8hScP5DfcpmHo5PeyugxHz5Ky/qf3wrpD7SNm8sWuA3VlGqsa

The htpasswd utility from Apache HTTP Server generates bcrypt-compatible hashes. The flags used in the generation command are:

Flag	Purpose
`-B`	Use bcrypt hashing algorithm
`-C 10`	Set bcrypt cost to 10
`-n`	Print output to stdout instead of writing to a file

Because -n prints to stdout, you must copy the output and paste it into the configuration manually.

Install htpasswd

Install htpasswd based on your operating system:

OS	Command
macOS	Run the `htpasswd` command directly (pre-installed with macOS)
CentOS	`yum install httpd`
Ubuntu	`apt-get install apache2-utils`

Commands and package names may vary depending on your system version and configuration. Adjust as needed.

Configure the administrator password

Step 1: Open the password.db tab

Log on to the EMR console. In the left-side navigation pane, click EMR on ACK.
On the EMR on ACK page, find the target cluster and click Configure in the Actions column.
On the Configure tab, move the pointer over the icon and select password.db.

Step 2: Generate and save the password

On your local machine, run the following command to generate a bcrypt password hash:
```
htpasswd -nBC 10 admin
```
Enter your chosen password when prompted. The command prints a hash similar to:
```
admin:$2y$10$BqTb8hScP5DfcpmHo5PeyugxHz5Ky/qf3wrpD7SNm8sWuA3VlGqsa
```
On the password.db tab in the EMR console, replace the value of admin with the hash output from the previous step.
Click Save.
In the dialog box that appears, configure the Execution Reason parameter and click Save.

Step 3: Restart Presto

Click the Service Details tab.
In the Components section, find TrinoCoordinator and click Restart in the Actions column.
In the dialog box that appears, configure the Execution Reason parameter and click OK.
In the Confirm message, click OK.

Verify the configuration

After Presto restarts, you can use the new password to access the web UI of Presto and submit Presto jobs:

Open the Presto web UI in your browser.
Log in with the username admin and your new password.
Try logging in with an incorrect password and confirm that access is denied.