feat: add tool to analyze deferred queue

chatmaild/pyproject.toml

@@ -24,6 +24,7 @@ chatmail-metadata = "chatmaild.metadata:main"
 chatmail-expire = "chatmaild.expire:daily_expire_main"
 chatmail-quota-expire = "chatmaild.expire:quota_expire_main"
 chatmail-fsreport = "chatmaild.fsreport:main"
+chatmail-deferred = "chatmaild.deferred:main"
 lastlogin = "chatmaild.lastlogin:main"
 turnserver = "chatmaild.turnserver:main"
 

chatmaild/src/chatmaild/deferred.py

@@ -0,0 +1,39 @@
+"""
+Analyze deferred mails and print most common failing destinations.
+
+Example:
+
+    python -m chatmaild.deferred
+"""
+
+import json
+import subprocess
+from collections import Counter, defaultdict
+
+
+def main():
+    p = subprocess.Popen(["postqueue", "-j"], text=True, stdout=subprocess.PIPE)
+    domain_reasons = defaultdict(Counter)
+    domain_total = Counter()
+
+    for line in p.stdout:
+        item = json.loads(line)
+        if item["queue_name"] != "deferred":
+            continue
+
+        for recipient in item["recipients"]:
+            _, domain = recipient["address"].rsplit("@", 1)
+            reason = recipient["delay_reason"].removeprefix(
+                "host 127.0.0.1[127.0.0.1] said: "
+            )
+            domain_total[domain] += 1
+            domain_reasons[domain][reason] += 1
+
+    for domain, total in reversed(domain_total.most_common()):
+        print(f"{domain} ({total} recipients)")
+        for reason, count in domain_reasons[domain].most_common():
+            print(f"  {count}: {reason}")
+
+
+if __name__ == "__main__":
+    main()