Table of Contents

1. Challenge

   Troubleshoot HAProxy Service Issues

   HAProxy Troubleshooting Using systemctl.

   The first thing we might want to check is the status of our haproxy service itself. If it's not running, it's not working. Our haproxy service is managed by systemctl.

   Check the status of the haproxy service using systemctl. Ensure that the service is enabled and active. If it is not, fix it.

   HAProxy Troubleshooting Using journalctl.

   Both haproxy and systemd log to the systemd journal, so the next place we might want to check is there.

   Check the systemd journal using journalctl for HAProxy errors. Address any issues you might find that prevent HAProxy from starting.

2. Challenge

   Troubleshoot HAProxy Configuration Issues

   Checking the HAProxy Configuration File.

   Sometimes we have one or more errors in our configuration file that prevent the haproxy service from starting. We can use the haproxy command to validate our configuration file.

   Validate the /etc/haproxy/haproxy.cfg file using the haproxy command. Address any issues you find that would prevent HAProxy from working properly.

3. Challenge

   Troubleshooting HAProxy Issues Using the stats Interface

   Using the stats Socket for Troubleshooting.

   We might want to try using the stats socket directly to glean information about our environment. Let's give it a try! Add some formatting to the stats socket output using cut and column, and a looping mechanism using watch. Use CTRL-C to exit. Address any issues you find.

   Using the stats Web Interface for Troubleshooting.

   If we want an easy-to-read interface to HAProxy's stats facility, we can use the HAProxy stats web interface. Let's open a web browser and connect to port 8050 on the public IP of our HAProxy server. Address any issues you find.

4. Challenge

   Troubleshoot HAProxy Using Log Information

   HAProxy Troubleshooting Using HAProxy Logs and halog.

   We can leverage the detailed and precise HAProxy logs for troubleshooting. When combined with the halog command, we can generate meaningful statistics that can help pinpoint issues.

   Try extracting some data from the /var/log/haproxy-combined-traffic.log file using halog:

   • Pull data on per-server HTTP statistics.
   • List URLs with 404 errors.
   • List URLs by the number of errors generated.
   • Try some of your own! See what evidence you can find!

   Examining HAProxy Logs Using grep.

   We can use our old friend grep to hand-examine our HAProxy logs. We can use grep to look for pattern matches in the log files.

   Try the following:

   • Look for elements with a DOWN status.
   • Find all the 404 error log entries.