What causes "get session ID: %s" in juicedata/juicefs?

Check metadata engine connectivity and health (auth, network, read-only state) and retry the mount

get session ID: %s

Error message

get session ID: %s

What it means

During NewSession, baseMeta must allocate a session ID by incrementing the `nextSession` counter in the metadata engine; if incrCounter fails, this error wraps the cause. Without a session ID the client cannot register itself, so startup fails.

Source

Thrown at pkg/meta/base.go:796

	ctx := m.sessCtx
	go m.refresh(ctx)

	if err := m.en.cacheACLs(ctx); err != nil {
		return err
	}

	if m.conf.ReadOnly {
		logger.Infof("Create read-only session OK with version: %s", version.Version())
		return nil
	}

	if record {
		// use the original sid if it's not 0
		action := "Update"
		if m.sid == 0 {
			v, err := m.en.incrCounter("nextSession", 1)
			if err != nil {
				return fmt.Errorf("get session ID: %s", err)
			}
			m.sid = uint64(v)
			m.conf.Sid = m.sid
			action = "Create"
		}
		if err := m.en.doNewSession(m.newSessionInfo(), action == "Update"); err != nil {
			return fmt.Errorf("create session: %s", err)
		}
		logger.Infof("%s session %d OK with version: %s", action, m.sid, version.Version())
	}

	m.loadQuotas()

	m.sessWG.Add(3)
	go m.flushStats(ctx)
	go m.flushDirStat(ctx)
	go m.flushQuotas(ctx)
	m.startDeleteSliceTasks() // start MaxDeletes tasks

View on GitHub (pinned to c9a67b23e8)

Solutions

Check metadata engine connectivity and health (auth, network, read-only state) and retry the mount
Verify the client has write permission on the metadata engine (counter must be incremented)
Inspect engine logs for the underlying incrCounter error and fix the backend

Example fix

# before: replica rejects writes
juicefs mount redis://replica:6379 /jfs
# after: point at primary
juicefs mount redis://primary:6379 /jfs

Defensive patterns

Strategy: retry

Validate before calling

// preflight: ensure the metadata engine accepts writes
// e.g. redis-cli -h host PING and confirm role:master (not read-only replica)

Try / catch

if err := meta.NewSession(); err != nil { if strings.Contains(err.Error(), "get session ID") { time.Sleep(backoff); retry(meta.NewSession) } }

Prevention

Point clients at the primary, not a read-only replica
Monitor metadata backend health before mounts
Use connection retries/keepalives in orchestration

When it happens

Trigger: Metadata engine unreachable or erroring when incrementing nextSession (network partition, Redis READONLY replica, SQL connection failure); corrupted counter value that cannot be incremented.

Common situations: Redis in read-only mode or out of memory; MySQL/PostgreSQL connection issues at mount time; transient network blips during mount in Kubernetes environments.

Related errors

AI-assisted analysis of juicedata/juicefs@c9a67b23e8 (2026-09-06). Data as JSON: /api/errors/22c53f3b7d94dd86. Report an issue: GitHub.