Golang DB.Txn方法代碼示例

func (p *planner) releaseLeases(db client.DB) {
	if p.leases != nil {
		for _, lease := range p.leases {
			if err := p.leaseMgr.Release(lease); err != nil {
				log.Warning(err)
			}
		}
		p.leases = nil
	}

	// TODO(pmattis): This is a hack. Remove when schema change operations work
	// properly.
	if p.modifiedSchemas != nil {
		for _, d := range p.modifiedSchemas {
			var lease *LeaseState
			err := db.Txn(func(txn *client.Txn) error {
				var err error
				lease, err = p.leaseMgr.Acquire(txn, d.id, d.version)
				return err
			})
			if err != nil {
				log.Warning(err)
				continue
			}
			if err := p.leaseMgr.Release(lease); err != nil {
				log.Warning(err)
			}
		}
		p.modifiedSchemas = nil
	}
}

// purgeOldLeases refreshes the leases on a table. Unused leases older than
// minVersion will be released.
// If deleted is set, minVersion is ignored; no lease is acquired and all
// existing unused leases are released. The table is further marked for
// deletion, which will cause existing in-use leases to be eagerly released once
// they're not in use any more.
// If t has no active leases, nothing is done.
func (t *tableState) purgeOldLeases(
	db *client.DB, deleted bool, minVersion sqlbase.DescriptorVersion, store LeaseStore,
) error {
	t.mu.Lock()
	empty := len(t.active.data) == 0
	t.mu.Unlock()
	if empty {
		// We don't currently have a lease on this table, so no need to refresh
		// anything.
		return nil
	}

	// Acquire and release a lease on the table at a version >= minVersion.
	var lease *LeaseState
	err := db.Txn(func(txn *client.Txn) error {
		var err error
		if !deleted {
			lease, err = t.acquire(txn, minVersion, store)
			if err == errTableDeleted {
				deleted = true
			}
		}
		if err == nil || deleted {
			t.mu.Lock()
			defer t.mu.Unlock()
			var toRelease []*LeaseState
			if deleted {
				t.deleted = true
				// If the table has been deleted, all leases are stale.
				toRelease = append([]*LeaseState(nil), t.active.data...)
			} else {
				// Otherwise, all but the lease we just took are stale.
				toRelease = append([]*LeaseState(nil), t.active.data[:len(t.active.data)-1]...)
			}
			if err := t.releaseLeasesIfNotActive(toRelease, store); err != nil {
				return err
			}
			return nil
		}
		return err
	})
	if err != nil {
		return err
	}
	if lease == nil {
		return nil
	}
	return t.release(lease, store)
}

func (hv *historyVerifier) runCmds(cmds []*cmd, historyIdx int, db *client.DB, t *testing.T) (string, map[string]int64, error) {
	var strs []string
	env := map[string]int64{}
	err := db.Txn(func(txn *client.Txn) error {
		for _, c := range cmds {
			c.historyIdx = historyIdx
			c.env = env
			c.init(nil)
			fmtStr, err := c.execute(txn, t)
			if err != nil {
				return err
			}
			strs = append(strs, fmt.Sprintf(fmtStr, 0, 0))
		}
		return nil
	})
	return strings.Join(strs, " "), env, err
}

// startTestWriter creates a writer which initiates a sequence of
// transactions, each which writes up to 10 times to random keys with
// random values. If not nil, txnChannel is written to non-blockingly
// every time a new transaction starts.
func startTestWriter(db *client.DB, i int64, valBytes int32, wg *sync.WaitGroup, retries *int32,
	txnChannel chan struct{}, done <-chan struct{}, t *testing.T) {
	src := rand.New(rand.NewSource(i))
	defer func() {
		if wg != nil {
			wg.Done()
		}
	}()

	for j := 0; ; j++ {
		select {
		case <-done:
			return
		default:
			first := true
			err := db.Txn(func(txn *client.Txn) error {
				if first && txnChannel != nil {
					select {
					case txnChannel <- struct{}{}:
					default:
					}
				} else if !first && retries != nil {
					atomic.AddInt32(retries, 1)
				}
				first = false
				for j := 0; j <= int(src.Int31n(10)); j++ {
					key := randutil.RandBytes(src, 10)
					val := randutil.RandBytes(src, int(src.Int31n(valBytes)))
					if err := txn.Put(key, val); err != nil {
						log.Infof("experienced an error in routine %d: %s", i, err)
						return err
					}
				}
				return nil
			})
			if err != nil {
				t.Error(err)
			} else {
				time.Sleep(1 * time.Millisecond)
			}
		}
	}
}

func (hv *historyVerifier) runTxn(txnIdx int, priority int32,
	isolation roachpb.IsolationType, cmds []*cmd, db *client.DB, t *testing.T) error {
	var retry int
	txnName := fmt.Sprintf("txn%d", txnIdx)
	err := db.Txn(func(txn *client.Txn) error {
		txn.SetDebugName(txnName, 0)
		if isolation == roachpb.SNAPSHOT {
			if err := txn.SetIsolation(roachpb.SNAPSHOT); err != nil {
				return err
			}
		}
		txn.InternalSetPriority(priority)

		env := map[string]int64{}
		// TODO(spencer): restarts must create additional histories. They
		// look like: given the current partial history and a restart on
		// txn txnIdx, re-enumerate a set of all histories containing the
		// remaining commands from extant txns and all commands from this
		// restarted txn.

		// If this is attempt > 1, reset cmds so no waits.
		if retry++; retry == 2 {
			for _, c := range cmds {
				c.done()
			}
		}
		if log.V(2) {
			log.Infof("%s, retry=%d", txnName, retry)
		}
		for i := range cmds {
			cmds[i].env = env
			if err := hv.runCmd(txn, txnIdx, retry, i, cmds, t); err != nil {
				if log.V(1) {
					log.Infof("%s encountered error: %s", cmds[i], err)
				}
				return err
			}
		}
		return nil
	})
	hv.wg.Done()
	return err
}

// refreshLease tries to refresh the node's table lease.
func (m *LeaseManager) refreshLease(db *client.DB, id ID, minVersion DescriptorVersion) error {
	// Only attempt to update a lease for a table that is already leased.
	if t := m.findTableState(id, false); t == nil {
		return nil
	}
	// Acquire and release a lease on the table at a version >= minVersion.
	var lease *LeaseState
	if pErr := db.Txn(func(txn *client.Txn) *roachpb.Error {
		var pErr *roachpb.Error
		// Acquire() can only acquire a lease at a version if it has
		// already been acquired at that version, or that version
		// is the latest version. If the latest version is > minVersion
		// then the node acquires a lease at the latest version but
		// Acquire() itself returns an error. This is okay, because
		// we want to update the node lease.
		lease, pErr = m.Acquire(txn, id, minVersion)
		return pErr
	}); pErr != nil {
		return pErr.GoError()
	}
	return m.Release(lease)
}

func (hv *historyVerifier) runHistory(historyIdx int, priorities []int32,
	isolations []roachpb.IsolationType, cmds []*cmd, db *client.DB, t *testing.T) error {
	plannedStr := historyString(cmds)
	if log.V(1) {
		log.Infof("attempting iso=%v pri=%v history=%s", isolations, priorities, plannedStr)
	}

	hv.actual = []string{}
	hv.wg.Add(len(priorities))
	txnMap := map[int][]*cmd{}
	var prev *cmd
	for _, c := range cmds {
		c.historyIdx = historyIdx
		txnMap[c.txnIdx] = append(txnMap[c.txnIdx], c)
		c.init(prev)
		prev = c
	}
	for i, txnCmds := range txnMap {
		go func(i int, txnCmds []*cmd) {
			if err := hv.runTxn(i, priorities[i-1], isolations[i-1], txnCmds, db, t); err != nil {
				t.Errorf("(%s): unexpected failure running %s: %v", cmds, cmds[i], err)
			}
		}(i, txnCmds)
	}
	hv.wg.Wait()

	// Construct string for actual history.
	actualStr := strings.Join(hv.actual, " ")

	// Verify history.
	var verifyStrs []string
	verifyEnv := map[string]int64{}
	for _, c := range hv.verifyCmds {
		c.historyIdx = historyIdx
		c.env = verifyEnv
		c.init(nil)
		pErr := db.Txn(func(txn *client.Txn) *roachpb.Error {
			fmtStr, pErr := c.execute(txn, t)
			if pErr != nil {
				return pErr
			}
			cmdStr := fmt.Sprintf(fmtStr, 0, 0)
			verifyStrs = append(verifyStrs, cmdStr)
			return nil
		})
		if pErr != nil {
			t.Errorf("failed on execution of verification cmd %s: %s", c, pErr)
			return pErr.GoError()
		}
	}

	err := hv.verify.checkFn(verifyEnv)
	if err == nil {
		if log.V(1) {
			log.Infof("PASSED: iso=%v, pri=%v, history=%q", isolations, priorities, actualStr)
		}
	}
	if hv.expSuccess && err != nil {
		verifyStr := strings.Join(verifyStrs, " ")
		t.Errorf("%d: iso=%v, pri=%v, history=%q: actual=%q, verify=%q: %s",
			historyIdx, isolations, priorities, plannedStr, actualStr, verifyStr, err)
	}
	return err
}

// concurrentIncrements starts two Goroutines in parallel, both of which
// read the integers stored at the other's key and add it onto their own.
// It is checked that the outcome is serializable, i.e. exactly one of the
// two Goroutines (the later write) sees the previous write by the other.
func concurrentIncrements(db *client.DB, t *testing.T) {
	// wgStart waits for all transactions to line up, wgEnd has the main
	// function wait for them to finish.
	var wgStart, wgEnd sync.WaitGroup
	wgStart.Add(2 + 1)
	wgEnd.Add(2)

	for i := 0; i < 2; i++ {
		go func(i int) {
			// Read the other key, write key i.
			readKey := []byte(fmt.Sprintf(testUser+"/value-%d", (i+1)%2))
			writeKey := []byte(fmt.Sprintf(testUser+"/value-%d", i))
			defer wgEnd.Done()
			wgStart.Done()
			// Wait until the other goroutines are running.
			wgStart.Wait()

			if pErr := db.Txn(func(txn *client.Txn) *roachpb.Error {
				txn.SetDebugName(fmt.Sprintf("test-%d", i), 0)

				// Retrieve the other key.
				gr, pErr := txn.Get(readKey)
				if pErr != nil {
					return pErr
				}

				otherValue := int64(0)
				if gr.Value != nil {
					otherValue = gr.ValueInt()
				}

				_, pErr = txn.Inc(writeKey, 1+otherValue)
				return pErr
			}); pErr != nil {
				t.Error(pErr)
			}
		}(i)
	}

	// Kick the goroutines loose.
	wgStart.Done()
	// Wait for the goroutines to finish.
	wgEnd.Wait()
	// Verify that both keys contain something and, more importantly, that
	// one key actually contains the value of the first writer and not only
	// its own.
	total := int64(0)
	results := []int64(nil)
	for i := 0; i < 2; i++ {
		readKey := []byte(fmt.Sprintf(testUser+"/value-%d", i))
		gr, pErr := db.Get(readKey)
		if pErr != nil {
			t.Fatal(pErr)
		}
		if gr.Value == nil {
			t.Fatalf("unexpected empty key: %s=%v", readKey, gr.Value)
		}
		total += gr.ValueInt()
		results = append(results, gr.ValueInt())
	}

	// First writer should have 1, second one 2
	if total != 3 {
		t.Fatalf("got unserializable values %v", results)
	}
}

// concurrentIncrements starts two Goroutines in parallel, both of which
// read the integers stored at the other's key and add it onto their own.
// It is checked that the outcome is serializable, i.e. exactly one of the
// two Goroutines (the later write) sees the previous write by the other.
// The isMultiphase option runs the transaction in multiple phases recreating
// the transaction from the transaction protobuf returned from the server.
func concurrentIncrements(db *client.DB, t *testing.T, isMultiphase bool) {
	// wgStart waits for all transactions to line up, wgEnd has the main
	// function wait for them to finish.
	var wgStart, wgEnd sync.WaitGroup
	wgStart.Add(2 + 1)
	wgEnd.Add(2)

	for i := 0; i < 2; i++ {
		go func(i int) {
			// Read the other key, write key i.
			readKey := []byte(fmt.Sprintf(testUser+"/value-%d", (i+1)%2))
			writeKey := []byte(fmt.Sprintf(testUser+"/value-%d", i))
			defer wgEnd.Done()
			wgStart.Done()
			// Wait until the other goroutines are running.
			wgStart.Wait()

			if isMultiphase {
				applyInc := func(txn *client.Txn) (error, proto.Transaction) {
					txn.SetDebugName(fmt.Sprintf("test-%d", i))
					b := client.Batch{}
					// Retrieve the other key.
					b.Get(readKey)
					if err := txn.Run(&b); err != nil {
						return err, txn.GetState()
					}
					otherValue := int64(0)
					gr := b.Results[0].Rows[0]
					if gr.Value != nil {
						otherValue = gr.ValueInt()
					}
					// New txn.
					txn = db.ReconstructTxn(txn.GetState())
					// Write our key.
					b = client.Batch{}
					b.Inc(writeKey, 1+otherValue)
					if err := txn.Run(&b); err != nil {
						return err, txn.GetState()
					}
					// New txn.
					txn = db.ReconstructTxn(txn.GetState())
					err := txn.Commit(&client.Batch{})
					return err, txn.GetState()
				}
				for r := retry.Start(client.DefaultTxnRetryOptions); r.Next(); {
					txn := db.ReconstructTxn(proto.Transaction{})
					if err, txnProto := applyInc(txn); err != nil {
						// New txn.
						txn = db.ReconstructTxn(txnProto)
						if err := txn.Rollback(); err != nil {
							t.Error(err)
						} else {
							// retry
							continue
						}
					}
					// exit retry
					break
				}
			} else {
				if err := db.Txn(func(txn *client.Txn) error {
					txn.SetDebugName(fmt.Sprintf("test-%d", i))

					// Retrieve the other key.
					gr, err := txn.Get(readKey)
					if err != nil {
						return err
					}

					otherValue := int64(0)
					if gr.Value != nil {
						otherValue = gr.ValueInt()
					}

					_, err = txn.Inc(writeKey, 1+otherValue)
					return err
				}); err != nil {
					t.Error(err)
				}
			}
		}(i)
	}

	// Kick the goroutines loose.
	wgStart.Done()
	// Wait for the goroutines to finish.
	wgEnd.Wait()
	// Verify that both keys contain something and, more importantly, that
	// one key actually contains the value of the first writer and not only
	// its own.
	total := int64(0)
	results := []int64(nil)
	for i := 0; i < 2; i++ {
		readKey := []byte(fmt.Sprintf(testUser+"/value-%d", i))
//.........這裏部分代碼省略.........