node: Announce capacity via the attributes

It is done automatically (as a sum of existing space on every file system
available on the configured shards) but can be overwritten if `Capacity`
attribute is provided via the application configuration.
Closes #602.

Signed-off-by: Pavel Karpy <carpawell@nspcc.ru>

CHANGELOG.md

@@ -10,7 +10,7 @@ Changelog for NeoFS Node
 - Stored payload metric per container (#2116)
 - Stored payload metric per shard (#2023)
 - Histogram metrics for RPC and engine operations (#2351) 
-- SN's version is announced via the attributes automatically but can be overwritten explicitly (#2455)
+- SN's version and capacity is announced via the attributes automatically but can be overwritten explicitly (#2455, #602)
 
 ### Fixed
 - `neo-go` RPC connection loss handling (#1337)

cmd/neofs-node/config.go

@@ -9,6 +9,7 @@ import (
 	"os"
 	"os/signal"
 	"path/filepath"
+	"strconv"
 	"strings"
 	"sync"
 	atomicstd "sync/atomic"
@@ -532,16 +533,17 @@ var persistateSideChainLastBlockKey = []byte("side_chain_last_processed_block")
 func initCfg(appCfg *config.Config) *cfg {
 	c := &cfg{}
 
-	// attaching version to the node's attributes; do not
-	// move it anywhere below reading the other attributes
-	// since a user should be able to overwrite it.
-	writeAppVersion(c)
-
 	err := c.readConfig(appCfg)
 	if err != nil {
 		panic(fmt.Errorf("config reading: %w", err))
 	}
 
+	// filling system attributes; do not move it anywhere
+	// below applying the other attributes since a user
+	// should be able to overwrite it.
+	err = writeSystemAttributes(c)
+	fatalOnErr(err)
+
 	key := nodeconfig.Key(appCfg)
 
 	var netAddr network.AddressGroup
@@ -969,8 +971,35 @@ func (c *cfg) configWatcher(ctx context.Context) {
 	}
 }
 
-// writeAppVersion writes app version as defined at compilation
-// step to the node's attributes.
-func writeAppVersion(c *cfg) {
+// writeSystemAttributes writes app version as defined at compilation
+// step to the node's attributes and an aggregated disk capacity
+// according to the all space on the all configured disks.
+func writeSystemAttributes(c *cfg) error {
+	// `Version` attribute
+
 	c.cfgNodeInfo.localInfo.SetAttribute("Version", misc.Version)
+
+	// `Capacity` attribute
+
+	var paths []string
+	for _, sh := range c.applicationConfiguration.EngineCfg.shards {
+		for _, storage := range sh.subStorages {
+			path := storage.path
+			paths = append(paths, path)
+
+			err := util.MkdirAllX(path, storage.perm)
+			if err != nil {
+				return fmt.Errorf("can not create (ensure it exists) dir by '%s' path: %w", path, err)
+			}
+		}
+	}
+
+	total, err := totalBytes(paths)
+	if err != nil {
+		return fmt.Errorf("calculating capacity on every shard: %w", err)
+	}
+
+	c.cfgNodeInfo.localInfo.SetAttribute("Capacity", strconv.FormatUint(total/(1<<30), 10))
+
+	return nil
 }

cmd/neofs-node/fs_unix.go

@@ -0,0 +1,31 @@
+//go:build !windows
+
+package main
+
+import (
+	"fmt"
+
+	"golang.org/x/sys/unix"
+)
+
+func totalBytes(paths []string) (uint64, error) {
+	var stat unix.Statfs_t
+	var total uint64 // bytes
+	fsIDMap := make(map[unix.Fsid]struct{})
+
+	for _, path := range paths {
+		err := unix.Statfs(path, &stat)
+		if err != nil {
+			return 0, fmt.Errorf("get FS stat by '%s' path: %w", path, err)
+		}
+
+		if _, handled := fsIDMap[stat.Fsid]; handled {
+			continue
+		}
+
+		total += stat.Blocks * uint64(stat.Bsize)
+		fsIDMap[stat.Fsid] = struct{}{}
+	}
+
+	return total, nil
+}

cmd/neofs-node/fs_windows.go

@@ -0,0 +1,37 @@
+//go:build windows
+
+package main
+
+import (
+	"fmt"
+	"path/filepath"
+
+	"golang.org/x/sys/windows"
+)
+
+func totalBytes(paths []string) (uint64, error) {
+	var total uint64 // bytes
+	mDisks := make(map[string]struct{}, len(paths))
+
+	for _, path := range paths {
+		var availB uint64
+		var totalB uint64
+		var freeTotalB uint64
+		var pathP = windows.StringToUTF16Ptr(path)
+
+		err := windows.GetDiskFreeSpaceEx(pathP, &availB, &totalB, &freeTotalB)
+		if err != nil {
+			return 0, fmt.Errorf("get disk stat by '%s' path: %w", path, err)
+		}
+
+		disk := filepath.VolumeName(path)
+		if _, handled := mDisks[disk]; handled {
+			continue
+		}
+
+		total += totalB
+		mDisks[disk] = struct{}{}
+	}
+
+	return total, nil
+}

go.mod

@@ -32,6 +32,7 @@ require (
 	go.etcd.io/bbolt v1.3.7
 	go.uber.org/atomic v1.10.0
 	go.uber.org/zap v1.24.0
+	golang.org/x/sys v0.8.0
 	golang.org/x/term v0.5.0
 	google.golang.org/grpc v1.51.0
 	google.golang.org/protobuf v1.28.1
@@ -97,7 +98,6 @@ require (
 	golang.org/x/mod v0.6.0 // indirect
 	golang.org/x/net v0.7.0 // indirect
 	golang.org/x/sync v0.1.0 // indirect
-	golang.org/x/sys v0.8.0 // indirect
 	golang.org/x/text v0.7.0 // indirect
 	golang.org/x/time v0.1.0 // indirect
 	golang.org/x/tools v0.2.0 // indirect