Add periodic callhome functionality (#14918)

* Add periodic callhome functionality

Periodically (every 24hrs by default), fetch callhome information and
upload it to SUBNET.

New config keys under the `callhome` subsystem:

enable - Set to `on` for enabling callhome. Default `off`
frequency - Interval between callhome cycles. Default `24h`

* Improvements based on review comments

- Update `enableCallhome` safely
- Rename pctx to ctx
- Block during execution of callhome
- Store parsed proxy URL in global subnet config
- Store callhome URL(s) in constants
- Use existing global transport
- Pass auth token to subnetPostReq
- Use `config.EnableOn` instead of `"on"`

* Use atomic package instead of lock

* Use uber atomic package

* Use `Cancel` instead of `cancel`

Co-authored-by: Harshavardhana <harsha@minio.io>

Co-authored-by: Harshavardhana <harsha@minio.io>
Co-authored-by: Aditya Manthramurthy <donatello@users.noreply.github.com>

cmd/callhome.go

@@ -0,0 +1,136 @@
+// Copyright (c) 2015-2022 MinIO, Inc.
+//
+// This file is part of MinIO Object Storage stack
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package cmd
+
+import (
+	"context"
+	"fmt"
+	"math/rand"
+	"time"
+
+	"github.com/minio/madmin-go"
+	"github.com/minio/minio/internal/logger"
+	uatomic "go.uber.org/atomic"
+)
+
+const (
+	// callhomeSchemaVersion1 is callhome schema version 1
+	callhomeSchemaVersion1 = "1"
+
+	// callhomeSchemaVersion is current callhome schema version.
+	callhomeSchemaVersion = callhomeSchemaVersion1
+
+	// callhomeCycleDefault is the default interval between two callhome cycles (24hrs)
+	callhomeCycleDefault = 24 * time.Hour
+)
+
+// CallhomeInfo - Contains callhome information
+type CallhomeInfo struct {
+	SchemaVersion string             `json:"schema_version"`
+	AdminInfo     madmin.InfoMessage `json:"admin_info"`
+}
+
+var (
+	enableCallhome            = uatomic.NewBool(false)
+	callhomeLeaderLockTimeout = newDynamicTimeout(30*time.Second, 10*time.Second)
+	callhomeFreq              = uatomic.NewDuration(callhomeCycleDefault)
+)
+
+func updateCallhomeParams(ctx context.Context, objAPI ObjectLayer) {
+	alreadyEnabled := enableCallhome.Load()
+	enableCallhome.Store(globalCallhomeConfig.Enable)
+	callhomeFreq.Store(globalCallhomeConfig.Frequency)
+
+	// If callhome was disabled earlier and has now been enabled,
+	// initialize the callhome process again.
+	if !alreadyEnabled && enableCallhome.Load() {
+		initCallhome(ctx, objAPI)
+	}
+}
+
+// initCallhome will start the callhome task in the background.
+func initCallhome(ctx context.Context, objAPI ObjectLayer) {
+	go func() {
+		r := rand.New(rand.NewSource(time.Now().UnixNano()))
+		// Leader node (that successfully acquires the lock inside runCallhome)
+		// will keep performing the callhome. If the leader goes down for some reason,
+		// the lock will be released and another node will acquire it and take over
+		// because of this loop.
+		for {
+			runCallhome(ctx, objAPI)
+			if !enableCallhome.Load() {
+				return
+			}
+
+			// callhome running on a different node.
+			// sleep for some time and try again.
+			duration := time.Duration(r.Float64() * float64(callhomeFreq.Load()))
+			if duration < time.Second {
+				// Make sure to sleep atleast a second to avoid high CPU ticks.
+				duration = time.Second
+			}
+			time.Sleep(duration)
+
+			if !enableCallhome.Load() {
+				return
+			}
+		}
+	}()
+}
+
+func runCallhome(ctx context.Context, objAPI ObjectLayer) {
+	// Make sure only 1 callhome is running on the cluster.
+	locker := objAPI.NewNSLock(minioMetaBucket, "callhome/runCallhome.lock")
+	lkctx, err := locker.GetLock(ctx, callhomeLeaderLockTimeout)
+	if err != nil {
+		return
+	}
+
+	ctx = lkctx.Context()
+	defer locker.Unlock(lkctx.Cancel)
+
+	callhomeTimer := time.NewTimer(callhomeFreq.Load())
+	defer callhomeTimer.Stop()
+
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case <-callhomeTimer.C:
+			if !enableCallhome.Load() {
+				// Stop the processing as callhome got disabled
+				return
+			}
+			performCallhome(ctx)
+
+			// Reset the timer for next cycle.
+			callhomeTimer.Reset(callhomeFreq.Load())
+		}
+	}
+}
+
+func performCallhome(ctx context.Context) {
+	err := sendCallhomeInfo(
+		CallhomeInfo{
+			SchemaVersion: callhomeSchemaVersion,
+			AdminInfo:     getServerInfo(ctx, nil),
+		})
+	if err != nil {
+		logger.LogIf(ctx, fmt.Errorf("Unable to perform callhome: %w", err))
+	}
+}