Adding an Image Retention Policy

Scenario

You can add a retention policy to an image in SWR to automatically delete any unused image tags. The policy takes effect immediately after you set it. There are two types of policies:

• Number of days: keeping only image tags that have been pushed to SWR within a certain number of days.
• Number of tags: keeping only a certain number of the most recent image tags.

You can configure filters for your retention policy to prevent certain image tags from being affected by the retention policy.

Notes and Constraints

Only one retention rule can be added to an image. If you want to add a new retention policy, you must delete the existing policy.

Procedure

1. Log in to the SWR console.
2. In the navigation pane on the left, choose My Images, and click the desired image to enter its details page.
3. On the Retention tab page, click Add Retention Policy. Configure the policy based on Table 1 and click OK.
   Figure 1 Adding a retention policy
   

   Table 1 Parameters for adding an image retention policy

   Parameter	Description
   Policy Type	There are two types of retention policies: Number of days: keeping only image tags that have been pushed to SWR within a certain number of days. Number of tags: keeping only a certain number of the most recent image tags.
   Count Limit (Number of days)	When you set Policy Type to Number of days, the value of Count Limit indicates the maximum number of the most recent image tags to be retained. The value should be an integer ranging from 1 to 365.
   Count Limit (Number of tags)	When you set Policy Type to Number of tags, the value of Count Limit indicates the maximum number of the most recent image tags to be retained. The value should be an integer ranging from 1 to 1,000.
   Tag Filter	Enter image tags that you do not want this retention policy to apply to.
   Regular Expression Filter	Enter a regular expression. Image tags meeting this regular expression will not be affected by this retention policy.

   After the retention policy is added, SWR immediately applies the policy and displays deleted image tags (if any) in the Retention Logs area.

   Figure 2 Checking the retention policy and logs
   

Example 1: Set Policy Type to Number of Days

The update time of Nginx v1 image and Nginx v2 image is shown in the following figure.

Figure 3 Image tags

1. Add a retention policy.

   Set Policy Type to Number of days, and Count Limit to 3.

   Figure 4 Adding a retention policy
   
2. Check whether the retention policy has taken effect.

   Check Retention Logs. Nginx v1 image has been stored for more than three days (the current time is 2021/09/01 16:00:00). Therefore, it is automatically removed.

   Check Image Tag. Only Nginx v2 image is left.

   Figure 5 Image tag v2
   

   The retention policy has taken effect.

Example 2: Set Policy Type to Number of Tags, and Specify Regular Expression Filter

Click Image Tags tab page. Nginx v1 image, Nginx v2 image, Nginx v1.0.0 image and Nginx v2.0.0 image are shown in Image tags.

Figure 6 Nginx image tags

1. Add a retention policy.

   Set Policy Type to Number of tags, Count Limit to 1, and Regular Expression Filter to ^v2.*.

   Figure 7 Adding a retention policy
   
2. Check whether the retention policy has taken effect.

   Before the retention policy takes effect, Nginx v2 image and Nginx v2.0.0 image are filtered for matching the regular expression. Only one of Nginx v1 image and Nginx v1.0.0 image will be stored. Nginx v1 image will be removed because it is older.

   Check Retention Logs and Image Tag. If Nginx v1 image is removed, the retention policy has taken effect.

   Figure 8 Image tags
   

   The following regular expressions are for your reference:

   • ^[0-9]*$: filters out tags consisting of numbers.
   • ^.{2,5}$: filters out tags with a length ranging from 2 to 5 characters.
   • ^[a-z]+$: filters out tags consisting of lowercase letters.
   • ^[A-Za-z0-9]+$: filters out tags consisting of letters and numbers.
   

   If there is an OR (|) operator in a regular expression, enclose the OR part in parentheses, or the regular expression will be parsed incorrectly and all tags of the image will be removed.

   For example, if you only want to retain tags containing a or s, the regular should be (.*a.*|.*s.*).