Tangential flow when the system encounters a failure, or when doing anything to control the inlet flow (such as gradation release), the inlet of a means of controlling the flow rate. Under such a multi-room environment, a computer room problems, or a chassis problem, or some server downtime or application crash, and need to be cut traffic. Cut large-scale application flow is an important means of operation and maintenance.
To understand the principles cut traffic, first know what the Domain Name System do? Domain name system is to use domain names into IP addresses (but could not be resolved to the IP port corresponding). When you apply for a domain name, make sure you need to assign VIP : If required, the domain name will be resolved to the VIP , and then through the load balancer to distribute the service requests to the server business. If not, the domain name will be resolved directly to the server when the server goes down, your staff will need to delete the domain name from the DNS server. Domain name change took effect by setting the TTL to control the resolution records in DNS cache time on the cache. Typically DNS cache is in a TTL update analytical record of the cycle, but there are also non-compliance with the protocol specification cause some users to resolve record has not been updated in the public Internet. This happens need to contact the carrier to help clear the cache.
Common means cutting traffic are:
- DNS handover: applications due consideration of disaster recovery in different rooms of the same system is deployed, and the domain name different room to provide both differential, in this case, upstream of the system and further by adjusting the flow rate switched domain. If the application used in the system is deployed in a different room with a domain name, the domain name corresponding to adjust only VIP or IP to switch traffic.
- Switching VIP diversion: by modifying the VIP Reality under the IP switching flow address.
- LVS / HAProxy : General by LVS / HAProxy to the failure of Nginx node cut away, Award flow evenly on the machine running, and ensure the normal.
- Cut the amount of application layer: a maximum of insider trading systems, usually by modifying the unified configuration, to control the direction of flow, this approach is the need to focus on testing. After checking the modified configuration file, the system according to whether traffic is expected to switch to the corresponding cluster, and the data is correct.
Note that: Before cutting the flow of cold assurance cluster (cluster no longer flow) return the necessary verification. Try to ensure a relatively smooth tangential flow, to prevent excessive impact on the instantaneous flow line system. After cutting the flow is complete, the system is necessary to return verification.