Improve --started filter

- add example to help
- change behaviour if CMS does not supply the start time info for nodes

README.md

@@ -73,7 +73,6 @@ ydbops restart --storage \
 ```
 
 ## How to create a new version
-### In Github
 1. Define new semver version number (e.g. 1.1.0)
 2. Update CHANGELOG.md with proper information about new version. Add the following to the beginning of the file, before previous entries:
 ```

pkg/rolling/options.go

@@ -184,7 +184,10 @@ after that would be considered a regular cluster failure`)
 		fmt.Sprintf("How often to query CMS while waiting for new permissions %v", DefaultCMSQueryIntervalSeconds))
 
 	fs.StringVar(&startedUnparsedFlag, "started", "",
-		fmt.Sprintf("Apply filter by node started time. Format: [<>%%Y-%%m-%%dT%%H:%%M:%%SZ], e.g. >2024-03-13T17:20:06Z"))
+		fmt.Sprintf(`Apply filter by node started time.
+Format: "<>%%Y-%%m-%%dT%%H:%%M:%%SZ", quotes are necessary, otherwise shell treats '<' or '>' as stream redirection.
+For example, --started ">2024-03-13T17:20:06Z" means all nodes started LATER than 2024 March 13, 17:20:06 UTC.
+If you reverse the sign (--started ">2024-03-13T17:20:06Z"), you will select nodes with LARGER uptimes.`))
 
 	fs.StringVar(&versionUnparsedFlag, "version", "",
 		`Apply filter by node version.

pkg/rolling/restarters/primitives.go

@@ -82,6 +82,14 @@ func SatisfiesStartingTime(node *Ydb_Maintenance.Node, startedTime *options.Star
 
 	nodeStartTime := node.GetStartTime().AsTime()
 
+	if nodeStartTime.IsZero() {
+		zap.S().Warnf(
+			"Node %s did not have startTime specified by CMS (possibly an old YDB version). Avoid using --started filter on current YDB cluster",
+			node.Host,
+		)
+		return false
+	}
+
 	if startedTime.Direction == '<' {
 		return startedTime.Timestamp.After(nodeStartTime)
 	}
@@ -139,6 +147,14 @@ func ExcludeByCommonFields(nodes []*Ydb_Maintenance.Node, spec FilterNodeParams)
 		}
 
 		if spec.Version != nil {
+			if node.Version == "" {
+				zap.S().Warnf(
+					"Node %s did not have version field specified by CMS (possibly an old YDB version). Avoid using --version filter on current YDB cluster",
+					node.Host,
+				)
+				continue
+			}
+
 			satisfiesVersion, err := spec.Version.Satisfies(node.Version)
 			if err != nil {
 				unknownVersions[node.Version] = append(unknownVersions[node.Version], node.Host)