update wiki pages

Single-server-VictoriaMetrics.md

@@ -1175,7 +1175,9 @@ VictoriaMetrics also exposes currently running queries with their execution time
   has at least 20% of free space comparing to disk size. The remaining amount of free space
   can be [monitored](#monitoring) via `vm_free_disk_space_bytes` metric. The total size of data
   stored on the disk can be monitored via sum of `vm_data_size_bytes` metrics.
-  See also `vm_merge_need_free_disk_space` metrics, which are set to 1 if background merge cannot be initiated due to free disk space shortage.
+  See also `vm_merge_need_free_disk_space` metrics, which are set to values higher than 0
+  if background merge cannot be initiated due to free disk space shortage. The value shows the number of per-month partitions,
+  which would start background merge if they had more free disk space.
 
 * If VictoriaMetrics doesn't work because of certain parts are corrupted due to disk errors,
   then just remove directories with broken parts. This will recover VictoriaMetrics at the cost

vmalert.md

@@ -168,6 +168,8 @@ The shortlist of configuration flags is the following:
     	Optional basic auth username for -datasource.url
   -datasource.lookback duration
         Lookback defines how far to look into past when evaluating queries. For example, if datasource.lookback=5m then param "time" with value now()-5m will be added to every query.
+  -datasource.maxIdleConnections int
+        Defines the number of idle (keep-alive connections) to configured datasource.Consider to set this value equal to the value: groups_total * group.concurrency. Too low value may result into high number of sockets in TIME_WAIT state. (default 100)
   -datasource.tlsCAFile string
     	Optional path to TLS CA file to use for verifying connections to -datasource.url. By default system CA is used
   -datasource.tlsCertFile string