app/vmctl: set default value for --vm-native-step-interval flag (#4327)

* app/vmctl: set default value for `--vm-native-step-interval` flag

* app/vmctl: update CHANGELOG.md

* app/vmctl: update CHANGELOG.md, fix docs

* app/vmctl: fix typo

* app/vmctl: fix typo

app/vmctl/README.md

@@ -736,6 +736,7 @@ See `./vmctl vm-native --help` for details and full list of flags.
 Migration in `vm-native` mode takes two steps:
 1. Explore the list of the metrics to migrate via `api/v1/label/__name__/values` API;
 2. Migrate explored metrics one-by-one.
+
 ```
 ./vmctl vm-native \
     --vm-native-src-addr=http://127.0.0.1:8481/select/0/prometheus \ # migrate from

app/vmctl/flags.go

@@ -362,6 +362,7 @@ var (
 		&cli.StringFlag{
 			Name:  vmNativeStepInterval,
 			Usage: fmt.Sprintf("Split export data into chunks. Requires setting --%s. Valid values are '%s','%s','%s','%s'.", vmNativeFilterTimeStart, stepper.StepMonth, stepper.StepDay, stepper.StepHour, stepper.StepMinute),
+			Value: stepper.StepMonth,
 		},
 		&cli.BoolFlag{
 			Name:  vmNativeDisableHTTPKeepAlive,

app/vmctl/stepper/split_test.go

@@ -121,6 +121,55 @@ func Test_splitDateRange(t *testing.T) {
 			},
 			wantErr: false,
 		},
+		{
+			name: "month chunking with one day time range",
+			args: args{
+				start:       "2022-01-03T11:11:11Z",
+				end:         "2022-01-04T12:12:12Z",
+				granularity: StepMonth,
+			},
+			want: []testTimeRange{
+				{
+					"2022-01-03T11:11:11Z",
+					"2022-01-04T12:12:12Z",
+				},
+			},
+			wantErr: false,
+		},
+		{
+			name: "month chunking with same day time range",
+			args: args{
+				start:       "2022-01-03T11:11:11Z",
+				end:         "2022-01-03T12:12:12Z",
+				granularity: StepMonth,
+			},
+			want: []testTimeRange{
+				{
+					"2022-01-03T11:11:11Z",
+					"2022-01-03T12:12:12Z",
+				},
+			},
+			wantErr: false,
+		},
+		{
+			name: "month chunking with one month and two days range",
+			args: args{
+				start:       "2022-01-03T11:11:11Z",
+				end:         "2022-02-03T00:00:00Z",
+				granularity: StepMonth,
+			},
+			want: []testTimeRange{
+				{
+					"2022-01-03T11:11:11Z",
+					"2022-01-31T23:59:59.999999999Z",
+				},
+				{
+					"2022-02-01T00:00:00Z",
+					"2022-02-03T00:00:00Z",
+				},
+			},
+			wantErr: false,
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {

docs/CHANGELOG.md

@@ -62,6 +62,7 @@ The following tip changes can be tested by building VictoriaMetrics components f
 * FEATURE: [vmbackupmanager](https://docs.victoriametrics.com/vmbackupmanager.html): add `created_at` field to the output of `/api/v1/backups` API and `vmbackupmanager backup list` command. See this [doc](https://docs.victoriametrics.com/vmbackupmanager.html#api-methods) for data format details.
 * FEATURE: [vmbackupmanager](https://docs.victoriametrics.com/vmbackupmanager.html): add commands for locking/unlocking backups against deletion by retention policy. See this [doc](https://docs.victoriametrics.com/vmbackupmanager.html#api-methods) for data format details.
 * FEATURE: [vmctl](https://docs.victoriametrics.com/vmctl.html): add support for [different time formats](https://docs.victoriametrics.com/Single-server-VictoriaMetrics.html#timestamp-formats) for `--vm-native-filter-time-start` and `--vm-native-filter-time-end` command-line flags. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/4091).
+* FEATURE: [vmctl](https://docs.victoriametrics.com/vmctl.html): set default value for `--vm-native-step-interval` command-line flag to `month`. This enables [time-based chunking](https://docs.victoriametrics.com/vmctl.html#using-time-based-chunking-of-migration) of data based on monthly step value when using native migration mode. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/4309).
 
 * BUGFIX: reduce the probability of sudden increase in the number of small parts on systems with small number of CPU cores.
 * BUGFIX: reduce the possibility of increased CPU usage when data with timestamps older than one hour is ingested into VictoriaMetrics. This reduces spikes for the graph `sum(rate(vm_slow_per_day_index_inserts_total))`. See [this pull request](https://github.com/VictoriaMetrics/VictoriaMetrics/pull/4258).

docs/vmctl.md

@@ -740,6 +740,7 @@ See `./vmctl vm-native --help` for details and full list of flags.
 Migration in `vm-native` mode takes two steps:
 1. Explore the list of the metrics to migrate via `api/v1/label/__name__/values` API;
 2. Migrate explored metrics one-by-one.
+
 ```
 ./vmctl vm-native \
     --vm-native-src-addr=http://127.0.0.1:8481/select/0/prometheus \ # migrate from