replication controller
after Replication Controller is a core element of Kubernetes, and application hosting to Kubernetes, need to ensure that the application can continue to run, Replication Controller is the assurance of key, key functions are as follows:
1. Make sure that the number of pod: it will ensure that there is Kubernetes Pod in a specified number of runs. If less than the specified number of pod, Replication Controller creates a new, otherwise it will be deleted to ensure that the number of excess Pod unchanged.
2. Make sure the pod Health: When the pod unhealthy, run error or inability to provide services, Replication Controller also kill unhealthy pod, re-create new ones.
3. elastically stretchable: during peak or off-peak time, you can improve resource utilization by adjusting the number of pod Replication Controller dynamic. At the same time, configure the monitoring functions (Hroizontal Pod Autoscaler), will automatically obtain the overall timing of the associated resource Replication Controller pod from usage monitoring platform, so that the automatic retractable.
4. Scroll upgrade: a rolling upgrade is a smooth upgrade path, through the gradual replacement of the strategy to ensure the stability of the whole system, you can discover and solve problems when initializing the upgrade, to avoid problems expanding.
Deployment
Deployment is also a core Kubernetes's main responsibility is to ensure that the same number of pod and health, 90% of the Replication Controller functions exactly the same, can be seen as a new generation of Replication Controller. However, it has the new feature outside Replication Controller:
1.Replication all the Controller functions: Deployment Replication Controller inherits all of the functions described above.
2. events and status View: You can view detailed upgrade Deployment of the progress and status.
3. Rollback: Upgrade pod when mirroring or identify problems associated parameters can be used rollback rolled back to the stable release or the specified version.
4. Record Version: Deployment of each operation, can be preserved, given subsequent rollback may be used.
5. Pause and boot: For each upgrade, you can pause at any time and start.
6. A variety of upgrade options: Recreate: Deletes all existing pod, re-create new; RollingUpdate: rolling upgrade, and gradually replace the strategy, while at the same time rolling upgrade to support more additional parameters, such as setting the maximum number of unavailable pod The minimum update interval, and so on.