Add Prometheus metric for Docker image disk usage

metrics.py

@@ -16,6 +16,11 @@ class Metrics(enum.Enum):
         prometheus_client.Gauge,
         ["repo"],
     )
+    DOCKER_IMAGE_DISK_USAGE_BYTES = (
+        "docker_image_disk_usage_bytes",
+        "Total disk usage of all Docker images in bytes",
+        prometheus_client.Gauge,
+    )
 
     def __init__(self, title, description, prometheus_type, labels=()):
         # we use the above default value for labels because it matches what's used

server.py

@@ -14,8 +14,6 @@
 import requests
 import time
 from metrics import MetricsHandler
-
-
 from prometheus_client import generate_latest
 
 
@@ -131,7 +129,21 @@ def push_update_success_as_discord_embed(
         )
     except Exception:
         logger.exception("push_update_success_as_discord_embed had a bad time")
-
+def get_docker_images_disk_usage_bytes():
+    """
+    Returns the total disk usage of all Docker images in bytes.
+    """
+    try:
+        cmd = [
+            "sh", "-c",
+             'docker images --format "{{.Size}}" | awk \'/GB/ {gsub("GB", ""); sum+=($1*1024*1024*1024)} /MB/ {gsub("MB", ""); sum+=($1*1024*1024)} /kB/ {gsub("kB", ""); sum+=($1*1024)} END {print int(sum)}\''
+        ]
+        result = subprocess.run(cmd, capture_output=True, text=True, check=True)
+        output = result.stdout.strip()
+        return int(output)
+    except Exception:
+        logging.exception("Error getting Docker image disk usage:")
+        return None
 
 def update_repo(repo_config: RepoToWatch) -> RepoUpdateResult:
     MetricsHandler.last_push_timestamp.labels(repo=repo_config.name).set(time.time())
@@ -212,6 +224,9 @@ async def github_webhook(request: Request):
 
 @app.get("/metrics")
 def get_metrics():
+    usage = get_docker_images_disk_usage_bytes()
+    if usage is not None:
+        docker_image_disk_usage_bytes.set(usage)
     return Response(
         media_type="text/plain",
         content=generate_latest(),