HCP System Management Help
The effects of failing over and failing back an active/active link differ depending on whether DNS failover was enabled for the system that became unavailable. In all cases, however, when the link fails over, replication on that link stops. When the link fails back, normal replication restarts.
Failover with an active/active link
With an active/active link, failover can occur in either direction between the two systems involved in the link. While the link is failed over, the replicated HCP tenants and namespaces and default-namespace directories remain read-write on both systems. However, because failover normally occurs when one system is unavailable, to avoid wasting resources, neither system tries to read or repair objects from the other system.
With DNS failover enabled, when an active/active link fails over from one of the HCP systems involved in the link (system A) to the other system involved in the link (system B), system B broadcasts a new configuration to the DNS. This new configuration causes client requests targeted to system A by domain name to be redirected to system B when the request is for an HCP namespace or default-namespace directory that’s included in the failed-over link.
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Note: System B can service redirected namespace access requests only if the applicable namespace is configured to allow service by remote systems. |
If a client request targeted to system A is for an HCP namespace or default-namespace directory that is not included in the failed-over link, the request is not redirected to system B. Client requests that target system A by IP address are also not redirected to system B.
Client requests that use a domain name to target the Tenant Management Console for a replicated HCP tenant on system A are redirected to system B, but system B cannot process such requests. Instead, system B returns a 403 error code.
While the link is failed over, system A does not broadcast any configuration information to the DNS.
With DNS failover disabled, failing over an active/active link stops replication on the link but does not cause any other changes. Clients can still access system A by domain name (if system A is available).
For more information on DNS failover, see Managing DNS failover.
Failback with an active/active link
Failing back an active/active link entails a single action, fail back. When an active/active link fails back:
•Replication immediately restarts in both directions on the link.
•With DNS failover enabled, each HCP system involved in the link broadcasts its own configuration to the DNS. From that point on, client requests that target either system by domain name are directed to the specified system.
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