The DNS Health Check Settings on the ArvanCloud Panel
The A record responsibility is to assign the domain name to an IP address (the IP address of the central server that hosts your website). Sometimes, it is needed to hold several servers for one domain to improve accessibility. For example, a service/website which must be accessible 24/7. In such a case, you should use several servers as your website hosts (one IP for each server), and as a result, you should allocate some different IP addresses for one A record. That is how you can troubleshoot the lack of accessibility problems.
One method to check the accessibility of every server to respond to the users' requests is to employ the DNS Health Check. The Health Check property enables you to transfer an HTTP/HTTPS request to a specific URL (e.g. the website Home Page) on a specified port, via a particular protocol, and at a definite time.
If you receive the status code 200 for one A record from the allocated IPs, it signifies that the server is now able to respond to the users' requests. Yet, every other answer indicates two points:
- The server is not accessible,
- The system has removed the server IP address from the list of allocated IPs.
The DNS Health Check General Settings on the ArvanCloud User's Panel
You can customize the general settings of the DNS Health Check on the ArvanCloud User's Panel, in the Health Check section. For this purpose, you ought to first click on the activation button of the Health Check Settings.
In the Fewest Number of Allowed Answers, you can determine the number of requests transferred to the allocated IPs for one record. In the Fewest Number of Error Answers, you can plan that if an IP does not respond to a definite number of the transferred requests, the system should remove it from the list of IPs. Moreover, in the Rest Time section, you can manage the time needed to send the requests.
For example, if you enter the following values:
- 3 in the Number of Allowed Answers field,
- 3 in the Number of Error Answers field,
- And 10 in the Rest Time field (default values).
It signifies that the system will transfer three requests per 10 seconds to the allocated IPs.
However, if you do not receive any response for all your three requests, then the system will remove the IP from the list of IPs.
The DNS Health Check Settings on the Records Management
Open the ArvanCloud user's panel, go to the Record Management section on the Cloud DNS, and then click on the Edit icon head-on the related A record.
In the open window, first, enter the added IPs for the record in the Value section. If you click on the + icon, a new field in which you can type your new IP and allocate more ones will be open.
Hint: Be careful that you should enter the origin server addresses that host your website, not the ArvanCloud edge server addresses.
In the Answer Type section, you can configure the output display format when you implement the nslookup or dig command. For example, if you select the Single mode for the Answer Type, the commands only request the first IP allocated to the record and display the response that returns from that one. Nevertheless, provided that you select the Multiple modes, the commands will request every IP allocated to the record and display all their responses in the output.
In the Load Distribution section, you can configure how to distribute the transferred requests among the servers - either round-robin or based on their weight. Round-robin load distribution means to send a request for allocated IPs in turn. On the other hand, according to the weight mode, the process of sending requests to the IPs occurs based on their assigned weight.
If you select the Automatic option in the Geographical Location section, it will transfer the request to the nearest allocated IP address according to the user's geographical location and IP. Furthermore, in the case that you select the Manual option, you can allocate an IP for responding to the requests transferred from a specific geographical area (for example, Germany).
In the TTL section, you can manage the time during which a record is cached in the Recursive Resolver.
In the Health Check Settings, you should, first, activate the status. Then, define the protocol for sending the request (HTTP/HTTPS) in the Protocol section. In the Port section, enter the port number via which the request should be sent. For example, if your website Home Page address is www.example.com/home.html, you should only type the path "home.html" in the address section.
Observing the Output Reports of the DNS Health Check
You can observe the output reports of the DNS Health Check on the Cloud DNS product >> the Reports section >> the Health Check status.