main.py: Add filter to clean image with tag match

Inspired by https://github.com/awslabs/ecr-cleanup-lambda/pull/17/files

Add parameter to allow only deleting images where the tag contains a
specific string

Specify a regex to match tags. If no tags on the image match, the image
will be skipped/ignored.

Allow us to only clean a specifig type/tag of images

README.md

@@ -68,14 +68,19 @@ Deletes the images that are not used by running tasks and which are older than t
 
 `python main.py –dryrun False –imagestokeep 20 –region us-west-2 -ignoretagsregex release|archive -repositories foo bar`
 
+Deletes the images that are not used by running tasks and which are older than the last 20 versions (in foo and bar repositories), in Oregon only, select only images with tag begening by `^re` but ignore image tags that contains `release` or `review`:
+
+`python main.py –dryrun False –imagestokeep 20 –region us-west-2 -ignoretagsregex release|review -filtertagsregex ^re -repositories foo bar`
+
 Environment variables can be used instead of arguments:
 
 ```
 export REGION=us-west-2
 export DRYRUN=False
 export IMAGES_TO_KEEP=20
 export REPOSITORIES_FILTER='foo bar'
-export IGNORE_TAGS_REGEX='release|archive'
+export IGNORE_TAGS_REGEX='release|review'
+export FILTER_TAGS_REGEX='^re'
 
 python main.py
 ```

main.py

@@ -24,6 +24,7 @@
 DRYRUN = None
 IMAGES_TO_KEEP = None
 IGNORE_TAGS_REGEX = None
+FILTER_TAGS_REGEX = None
 REPOSITORIES_FILTER = None
 
 def handler(event, context):
@@ -38,10 +39,18 @@ def handler(event, context):
         discover_delete_images(REGION)
 
 def ignore_tags_image(image,running_sha):
+    skip = False
+    if (FILTER_TAGS_REGEX != ""):
+        skip = True
+
     for tag in image['imageTags']:
-        if "latest" in tag or re.compile(IGNORE_TAGS_REGEX).search(tag) is not None or (running_sha and image['imageDigest'] in running_sha):
+        if ( "latest" in tag
+                or re.compile(IGNORE_TAGS_REGEX).search(tag) is not None
+                or (running_sha and image['imageDigest'] in running_sha)):
             return True
-    return False
+        if (re.compile(FILTER_TAGS_REGEX).search(tag) is not None):
+            skip=False
+    return skip
 
 
 def discover_delete_images(regionname):
@@ -122,7 +131,6 @@ def discover_delete_images(regionname):
 
         image_count = 0
         for image in tagged_images:
-            print(image['imageDigest'])
             if ignore_tags_image(image,running_sha):
                 continue
             if image_count >= int(IMAGES_TO_KEEP):
@@ -199,6 +207,7 @@ def delete_images(ecr_client, deletesha, deletetag, id, name):
     parser.add_argument('-repositories', help='Filter for repositories names discovery separated by space', default=os.environ.get('REPOSITORIES_FILTER', "").split(),
                          nargs='+', action='store', dest='repositories_filter')
     parser.add_argument('-ignoretagsregex', help='Regex of tag names to ignore', default=os.environ.get('IGNORE_TAGS_REGEX', ""), action='store', dest='ignoretagsregex')
+    parser.add_argument('-filtertagsregex', help='Regex filter of tag names to limit on images with matching tag', default=os.environ.get('FILTER_TAGS_REGEX', ""), action='store', dest='filtertagsregex')
 
     args = parser.parse_args()
 
@@ -210,6 +219,7 @@ def delete_images(ecr_client, deletesha, deletetag, id, name):
 
     IMAGES_TO_KEEP = args.imagestokeep
     IGNORE_TAGS_REGEX = args.ignoretagsregex
+    FILTER_TAGS_REGEX = args.filtertagsregex
     REPOSITORIES_FILTER = args.repositories_filter
 
     handler(request, None)