6588 add couchdb check - add pending updates

docs/20_Checks/check_couchdb.md

@@ -18,7 +18,7 @@ Check couchdb status.
 ______________________________________________________________________
 
 CHECK_COUCHDB
-v0.3
+v0.4
 
 (c) Institute for Medical Education - University of Bern
 Licence: GNU GPL 3
@@ -41,6 +41,7 @@ OPTIONS:
     MODE is one of
       up           show general couchdb status
       replication  show last replication status
+      pending      show count of pending updates for nodes, dbs and users
 
 EXAMPLE:
 check_couchdb -m up
@@ -80,10 +81,10 @@ It switches to critical if one of the seeds is not "ok".
 `check_couchdb -m up` returns
 
 ```txt
-OK: Couchdb status (value in /_up is 'ok')
-Reponse: 
+OK: Couchdb :: health status (value 'status' in /_up is 'ok')
+Reponse of /_up: 
 {
-  "status": "ok",                                   <<< checked value
+  "status": "ok",
   "seeds": {
     "couchdb@192.168.25.172": {
       "timestamp": "2023-08-28T07:27:54.938619Z",
@@ -97,8 +98,46 @@ Reponse:
     "couchdb@192.168.25.61": {}
   }
 }
+
  ```
 
+### pending
+
+From url ``/up`` it fetches from seeds -> [node] -> pending_updates the values for
+
+* _nodes
+* _dbs
+* _users
+
+and summarizes its values.
+
+It switches to warning if one of the values is > 0.
+
+This check sends performance data.
+
+``check_couchdb -m pending`` returns
+
+```txt
+OK: Couchdb :: pending updates: 0 (values below 'pending_updates' in /_up)
+Reponse: of /_up
+{
+  "status": "ok",
+  "seeds": {
+    "couchdb@192.168.25.172": {
+      "timestamp": "2023-08-28T07:27:54.938619Z",
+      "last_replication_status": "ok",
+      "pending_updates": {
+        "_nodes": 0,
+        "_dbs": 0,
+        "_users": 0
+      }
+    },
+    "couchdb@192.168.25.61": {}
+  }
+}
+ |nodes=0;; dbs=0;; users=0;; 
+```
+
 ### replication
 
 From url ``/up`` it fetches seeds -> [node] -> last_replication_status.
@@ -107,14 +146,14 @@ It switches to critical if one of the seeds is not "ok".
 ``check_couchdb -m replication`` returns
 
 ```txt
-OK: Couchdb replication
-Reponse: 
+OK: Couchdb :: replication (values 'last_replication_status' in /_up are 'ok')
+Reponse: of /_up
 {
   "status": "ok",
   "seeds": {
     "couchdb@192.168.25.172": {
       "timestamp": "2023-08-28T07:27:54.938619Z",
-      "last_replication_status": "ok",              <<< checked value
+      "last_replication_status": "ok",
       "pending_updates": {
         "_nodes": 0,
         "_dbs": 0,