Most Docker-based solutions (including platform-managed stacks) are continuously developed, delivering new product versions and fixes. Thus, it is recommended to regularly update your templates to their latest tags, i.e., releases.
Such an operation is called redeploy and allows you to update your Docker-based container to a new tag (version) without affecting the application inside. In general, the process is following:
- A new container based on the redeployment target template is created internally. System files from this container will be used to update the original one.
- A list of paths to the preserved data (custom user data and some of the system-related files) is gathered in the initial container.
- The initial container is stopped. Not preserved data is erased and replaced with files of the desired new tag (from the internal container copy).
Note: The changes to the redeployed container are applied on the snapshot first, only merging in case all the configurations were successful. In other words, the platform creates a return point, discarding changes and returning to the initial state in case of failure.
Tip: Redeployment of a single node leads to a temporary service downtime. However, if operating with multiple (horizontally scaled) instances, the update can be performed on containers sequentially to minimize downtime.
In such a way, you are able to update your Docker-based container to a new tag (version) without affecting the application inside.
Update Container via Dashboard
The most straightforward and user-friendly way to redeploy a template tag is to use the platform dashboard. Alternatively, you can easily automate redeployment processes via API. The instructions below will walk you through the required steps:
Note: When working with the MySQL, MariaDB, or Percona databases, downgrading (i.e., redeploying to the lower version) is not supported. In case the operation is necessary, we recommend creating a backup and restoring a database after redeployment (or in a separate container altogether).
1. The dedicated redeployment dialog frame can be accessed in two ways:
- select the Redeploy Container(s) button next to the required node or layer (for updating all the comprised containers at once)
- click the pencil icon next to the layer tag version in the topology wizard (when Changing Environment Topology of the existing environment)
2. As a result, the Redeploy containers frame will be opened, where you can select a new Tag for your container(s).
Also, you can adjust some additional options:
- Keep volumes data – if enabled, data in the volumes will be protected from erasing and will remain available after redeploy
- for horizontally scaled containers, you can choose between two deployment options:
- Simultaneous deployment – redeploys all nodes at once, which is comparatively quicker but causes a brief downtime of your application
- Sequential deployment with delay – redeploys instances one-by-one with a specified delay between operations. This option ensures that there is always a running node to process incoming requests (i.e., minimum downtime)
- Temporarily remove node(s) from DNS – if enabled, a node will be excluded from the DNS tables (internal and external) during the sequential redeploy operation
After all the configurations are set, click the Redeploy button and confirm the action in a pop-up.
3. Once the update is completed, you’ll see the corresponding notification in the top right corner of the dashboard.
Click the Show Logs button to open the appropriate tab with information on the updated container – Node ID, old and new tags, and operation duration.
Now, you know how to redeploy a container via the platform dashboard.
