Need help?

Our experts have had an average response time of 11.7 minutes in August 2021 to fix urgent issues.

We will keep your servers stable, secure, and fast at all times for one fixed price.

Amazon Redshift Connection Error – How to Troubleshoot the Errors

by | Aug 7, 2021

Amazon Redshift Connection Error will prevent us from connecting to the Amazon Redshift cluster.

Here, at Bobcares, we assist our customers with several AWS queries as part of our AWS Support Services.

Today, let us see how we can fix this error.


Amazon Redshift Connection Error

In this article, let us see how our Support Techs troubleshoot the connections errors in Amazon Redshift.


Recently resized or restored from a snapshot

Suppose we resize or restore the Amazon Redshift cluster from a snapshot. Then we need to check the cluster’s subnet.

The cluster must launch in the same subnet from before the snapshot resize or restore.

On the other hand, if we didn’t resize or restore we need to verify the network configurations.

It must be the same for both the old and new subnets.


Resides in a public subnet

Suppose we try to connect to an Amazon Redshift cluster in a public subnet, we need to check:

  • If the Amazon Redshift cluster is set to “Publicly Accessible.”
  • If we have an internet gateway attached to the route table.

We can use telnet to test connectivity to the Amazon Redshift cluster:

telnet <cluster endpoint> <cluster port>


Resides in a private subnet

If the Amazon Redshift cluster resides in a private subnet, we need to:

  • Attach the NAT Gateway to the public subnet’s route table.
  • Make sure that your cluster isn’t set to “Publicly Accessible”.

In order to confirm that the  client can reach the private IP address of the Amazon Redshift cluster’s leader node, we use the dig command:

dig <cluster endpoint>

To test the connection to the Amazon Redshift cluster, we use the telnet command:

telnet <cluster endpoint><cluster port>


Telnet is unsuccessful or the cluster remains inaccessible

However, if the telnet indicates “unsuccessful”, we verify that the following conditions are true:

  • The Amazon Redshift port (default 5439) of type TCP is allowed in the Security Group’s inbound rule.
  • The CIDR range or IP we connect to the Amazon Redshift cluster from is added in the Security Group’s ingress rule.

On the other hand, if it indicates “successful” but the cluster remains inaccessible from the client, we need to check the network’s firewall.

In this case, the firewall might be blocking the Amazon Redshift port.


Invalid operation connection error

Generally, if the Amazon Redshift cluster requires to enable SSL for any connection, we may receive the following error:

Error: [Amazon](500310) Invalid operation: no pg_hba.conf entry for host "", user "username", database "dbname", SSL off;

We need to confirm whether the require_ssl parameter is set to “true”.

1. To do so, we open the Amazon Redshift console.

2. Then we select the Config tab.

3. Here, we modify the parameter group that associates with the Amazon Redshift cluster.

4. If necessary, we verify the SSL configuration using the AWS Command Line Interface (AWS CLI):


Once done, if the configuration is set to “true”, our Support Techs recommend updating the require_ssl parameter back to “false”.


Fatal connection error

In case we have too many open connections in the Amazon Redshift cluster we receive the error:

Error: FATAL: connection limit [500]/[2000] exceeded for user

In order to find the number of open connections our Support Techs recommend the steps below:

1. Initially, we open the Amazon CloudWatch console.

2. Then we look for the DatabaseConnections metric in the Amazon CloudWatch Logs entries.

3. Here, we use the STL_CONNECTION_LOG table to check the open connections:

select recordtime, username, dbname, remotehost, remoteport
from stl_connection_log
where event = 'initiating session'
and pid not in
(select pid from stl_connection_log
where event = 'disconnecting session')
order by 1 desc;

4. After that, we use the STV_SESSIONS table to view information about the active user sessions for Amazon Redshift:

select * from stv_sessions;

Suppose we have a large number of open connections. In such a case, we use the PG_TERMINATE_BACKEND command to shut down any idle sessions.


Connection refused error

If the Amazon Redshift cluster fails to establish a connection, it is likely to show the error:

Error: amazon 500150 error setting/closing connection: operation timed out/ connection refused.

This indicates a permissions issue with accessing the Amazon Redshift cluster.

To resolve this, we do the following:

  • For cluster in an Amazon VPC, we add the client CIDR/IP address to the VPC security group.
  • For clusters outside of a VPC, we add the client CIDR/IP address to the cluster security group.

[Stuck with any of the above errors? We are here to assist you]



In short, we saw how our Support Techs go about Amazon Redshift Connection Error.


Never again lose customers to poor server speed! Let us help you.

Our server experts will monitor & maintain your server 24/7 so that it remains lightning fast and secure.


var google_conversion_label = "owonCMyG5nEQ0aD71QM";


Submit a Comment

Your email address will not be published. Required fields are marked *

Privacy Preference Center


Necessary cookies help make a website usable by enabling basic functions like page navigation and access to secure areas of the website. The website cannot function properly without these cookies.

PHPSESSID - Preserves user session state across page requests.

gdpr[consent_types] - Used to store user consents.

gdpr[allowed_cookies] - Used to store user allowed cookies.

PHPSESSID, gdpr[consent_types], gdpr[allowed_cookies]


Statistic cookies help website owners to understand how visitors interact with websites by collecting and reporting information anonymously.

_ga - Preserves user session state across page requests.

_gat - Used by Google Analytics to throttle request rate

_gid - Registers a unique ID that is used to generate statistical data on how you use the website.

smartlookCookie - Used to collect user device and location information of the site visitors to improve the websites User Experience.

_ga, _gat, _gid
_ga, _gat, _gid


Marketing cookies are used to track visitors across websites. The intention is to display ads that are relevant and engaging for the individual user and thereby more valuable for publishers and third party advertisers.

IDE - Used by Google DoubleClick to register and report the website user's actions after viewing or clicking one of the advertiser's ads with the purpose of measuring the efficacy of an ad and to present targeted ads to the user.

test_cookie - Used to check if the user's browser supports cookies.

1P_JAR - Google cookie. These cookies are used to collect website statistics and track conversion rates.

NID - Registers a unique ID that identifies a returning user's device. The ID is used for serving ads that are most relevant to the user.

DV - Google ad personalisation

IDE, test_cookie, 1P_JAR, NID, DV, NID
IDE, test_cookie


These are essential site cookies, used by the google reCAPTCHA. These cookies use an unique identifier to verify if a visitor is human or a bot.