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settings.go
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settings.go
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// Copyright 2017 The Cockroach Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
// implied. See the License for the specific language governing
// permissions and limitations under the License.
package cluster
import (
"math"
"sync/atomic"
"golang.org/x/net/context"
"golang.org/x/time/rate"
"github.com/cockroachdb/cockroach/pkg/roachpb"
"github.com/cockroachdb/cockroach/pkg/settings"
"github.com/cockroachdb/cockroach/pkg/util/log"
"github.com/cockroachdb/cockroach/pkg/util/tracing"
"github.com/pkg/errors"
)
// Settings is the collection of cluster settings. For a running CockroachDB
// node, there is a single instance of ClusterSetting which is shared across all
// of its components.
//
// The Version setting deserves an individual explanantion. During the node
// startup sequence, an initial version (persisted to the engines) is read and
// passed to InitializeVersion(). It is only after that that the Version field
// of this struct is ready for use (i.e. Version() and IsActive() can be
// called). In turn, the node usually registers itself as a callback to be
// notified of any further updates to the setting, which are then persisted.
//
// This dance is necessary because we cannot determine a safe default value for
// the version setting without looking at what's been persisted: The setting
// specifies the minimum binary version we have to expect to be in a mixed
// cluster with. We can't assume this binary's MinimumSupportedVersion as we
// could've started up earlier and enabled features that are not actually
// compatible with that version; we can't assume it's our binary's ServerVersion
// as that would enable features that may trip up older versions running in the
// same cluster. Hence, only once we get word of the "safe" version to use can
// we allow moving parts that actually need to know what's going on.
//
// Additionally, whenever the version changes, we want to persist that update to
// wherever the caller to InitializeVersion() got the initial version from
// (typically a collection of `engine.Engine`s), which the caller will do by
// registering itself via `(*Setting).Version.OnChange()`, which is invoked
// *before* exposing the new version to callers of `IsActive()` and `Version()`.
//
// For testing or one-off situations in which a ClusterSetting is needed, but
// cluster settings don't play a crucial role, MakeTestingClusterSetting() is
// provided; it is pre-initialized to the binary's ServerVersion.
type Settings struct {
SV settings.Values
// Manual defaults to false. If set, lets this ClusterSetting's MakeUpdater
// method return a dummy updater that simply throws away all values. This is
// for use in tests for which manual control is desired.
Manual atomic.Value // bool
Version ExposedClusterVersion
Tracer *tracing.Tracer
BulkIOWriteLimiter *rate.Limiter
Initialized bool
}
const keyVersionSetting = "version"
var version = settings.RegisterStateMachineSetting(keyVersionSetting,
"set the active cluster version in the format '<major>.<minor>'.", // hide optional `-<unstable>`
settings.TransformerFn(versionTransformer),
)
// BulkIOWriteLimit is defined here because it is used by BulkIOWriteLimiter.
var BulkIOWriteLimit = settings.RegisterByteSizeSetting(
"kv.bulk_io_write.max_rate",
"the rate limit (bytes/sec) to use for writes to disk on behalf of bulk io ops",
math.MaxInt64,
)
// BulkIOWriteLimiterBurst is the burst for the BulkIOWriteLimiter cluster setting.
const BulkIOWriteLimiterBurst = 2 * 1024 * 1024 // 2MB
// InitializeVersion initializes the Version field of this setting. Before this
// method has been called, usage of the Version field is illegal and leads to a
// fatal error.
func (s *Settings) InitializeVersion(cv ClusterVersion) error {
b, err := cv.Marshal()
if err != nil {
return err
}
// Note that we don't call `updater.ResetRemaining()`.
updater := settings.NewUpdater(&s.SV)
if err := updater.Set(keyVersionSetting, string(b), version.Typ()); err != nil {
return err
}
s.Version.baseVersion.Store(&cv)
return nil
}
// An ExposedClusterVersion exposes a cluster-wide minimum version which is
// assumed to be supported by all nodes. This in turn allows features which are
// incompatible with older versions to be used safely.
type ExposedClusterVersion struct {
MinSupportedVersion roachpb.Version
ServerVersion roachpb.Version
baseVersion atomic.Value // stores *ClusterVersion
cb func(ClusterVersion)
}
// OnChange registers (a single) callback that will be invoked whenever the
// cluster version changes. The new cluster version will only become "visible"
// after the callback has returned.
//
// The callback can be set at most once.
func (ecv *ExposedClusterVersion) OnChange(f func(cv ClusterVersion)) {
if ecv.cb != nil {
log.Fatal(context.TODO(), "cannot set callback twice")
}
ecv.cb = f
}
// Version returns the minimum cluster version the caller may assume is in
// effect. It must not be called until the setting has been initialized.
func (ecv *ExposedClusterVersion) Version() ClusterVersion {
v := *ecv.baseVersion.Load().(*ClusterVersion)
if (v == ClusterVersion{}) {
log.Fatal(context.Background(), "Version() was called before having been initialized")
}
return v
}
// BootstrapVersion returns the version a newly initialized cluster should have.
func (ecv *ExposedClusterVersion) BootstrapVersion() ClusterVersion {
return ClusterVersion{
MinimumVersion: ecv.ServerVersion,
UseVersion: ecv.ServerVersion,
}
}
// IsActive returns true if the features of the supplied version are active at
// the running version.
func (ecv *ExposedClusterVersion) IsActive(v roachpb.Version) bool {
return !ecv.Version().UseVersion.Less(v)
}
// MakeTestingClusterSettings returns a Settings object that has had its version
// initialized to BootstrapVersion().
func MakeTestingClusterSettings() *Settings {
st := MakeClusterSettings(BinaryServerVersion, BinaryServerVersion)
cv := st.Version.BootstrapVersion()
// Initialize with all features enabled.
if err := st.InitializeVersion(cv); err != nil {
log.Fatalf(context.TODO(), "unable to initialize version: %s", err)
}
return st
}
// MakeClusterSettings makes a new ClusterSettings object for the given minimum
// supported and server version, respectively.
func MakeClusterSettings(minVersion, serverVersion roachpb.Version) *Settings {
s := &Settings{}
// Initialize the setting. Note that baseVersion starts out with the zero
// cluster version, for which the transformer accepts any new version. After
// that, it'll only accept "valid bumps". We use this to initialize the
// variable lazily, after we have read the current version from the engines.
// After that, updates come from Gossip and need to be compatible with the
// engine version.
s.Version.MinSupportedVersion = minVersion
s.Version.ServerVersion = serverVersion
s.Version.baseVersion.Store(&ClusterVersion{})
sv := &s.SV
sv.Init(s)
s.Tracer = tracing.NewTracer()
s.Tracer.Configure(sv)
version.SetOnChange(sv, func() {
_, obj, err := version.Validate(sv, []byte(version.Get(sv)), nil)
if err != nil {
log.Fatal(context.Background(), err)
}
newV := *((*ClusterVersion)(obj.(*stringedVersion)))
// Call callback before exposing the new version to callers of
// IsActive() and Version(). Don't do this if the new version is
// trivial, which is the case as the setting is initialized.
if (newV != ClusterVersion{}) && s.Version.cb != nil {
s.Version.cb(newV)
}
s.Version.baseVersion.Store(&newV)
})
// TODO(dan): This limiting should be per-store and shared between any
// operations that need lots of disk throughput.
s.BulkIOWriteLimiter = rate.NewLimiter(rate.Limit(BulkIOWriteLimit.Get(sv)), BulkIOWriteLimiterBurst)
BulkIOWriteLimit.SetOnChange(sv, func() {
s.BulkIOWriteLimiter.SetLimit(rate.Limit(BulkIOWriteLimit.Get(sv)))
})
s.Initialized = true
return s
}
// MakeUpdater returns a new Updater, pre-alloced to the registry size. Note
// that if the Setting has the Manual flag set, this Updater simply ignores all
// updates.
func (s *Settings) MakeUpdater() settings.Updater {
if isManual, ok := s.Manual.Load().(bool); ok && isManual {
return &settings.NoopUpdater{}
}
return settings.NewUpdater(&s.SV)
}
type stringedVersion ClusterVersion
func (sv *stringedVersion) String() string {
if sv == nil {
sv = &stringedVersion{}
}
return sv.MinimumVersion.String()
}
// versionTransformer is the transformer function for the version StateMachine.
// It has access to the Settings struct via the opaque member of settings.Values.
func versionTransformer(
sv *settings.Values, curRawProto []byte, versionBump *string,
) (newRawProto []byte, versionStringer interface{}, _ error) {
opaque := sv.Opaque()
if opaque == settings.TestOpaque {
// This is a test where a cluster.Settings is not set up yet. In that case
// this function is ran only once, on initialization.
if curRawProto != nil || versionBump != nil {
panic("modifying version when TestOpaque is set")
}
return nil, nil, nil
}
s := opaque.(*Settings)
minSupportedVersion := s.Version.MinSupportedVersion
serverVersion := s.Version.ServerVersion
defer func() {
if versionStringer != nil {
versionStringer = (*stringedVersion)(versionStringer.(*ClusterVersion))
}
}()
var oldV ClusterVersion
// If no old value supplied, fill in the default.
if curRawProto == nil {
oldV = *s.Version.baseVersion.Load().(*ClusterVersion)
var err error
curRawProto, err = oldV.Marshal()
if err != nil {
return nil, nil, err
}
}
if err := oldV.Unmarshal(curRawProto); err != nil {
return nil, nil, err
}
if versionBump == nil {
// Round-trip the existing value, but only if it passes sanity
// checks. This is also the path taken when the setting gets updated
// via the gossip callback.
if serverVersion.Less(oldV.MinimumVersion) {
log.Fatalf(context.TODO(), "node at %s cannot run at %s", serverVersion, oldV.MinimumVersion)
}
if (oldV.MinimumVersion != roachpb.Version{}) && oldV.MinimumVersion.Less(minSupportedVersion) {
log.Fatalf(context.TODO(), "node at %s cannot run at %s (minimum version is %s)", serverVersion, oldV.MinimumVersion, minSupportedVersion)
}
return curRawProto, &oldV, nil
}
// We have a new proposed update to the value, validate it.
minVersion, err := roachpb.ParseVersion(*versionBump)
if err != nil {
return nil, nil, err
}
newV := oldV
newV.UseVersion = minVersion
newV.MinimumVersion = minVersion
if minVersion.Less(oldV.MinimumVersion) {
return nil, nil, errors.Errorf("cannot downgrade from %s to %s", oldV.MinimumVersion, minVersion)
}
if oldV != (ClusterVersion{}) && !oldV.MinimumVersion.CanBump(minVersion) {
return nil, nil, errors.Errorf("cannot upgrade directly from %s to %s", oldV.MinimumVersion, minVersion)
}
if serverVersion.Less(minVersion) {
// TODO(tschottdorf): also ask gossip about other nodes.
return nil, nil, errors.Errorf("cannot upgrade to %s: node running %s",
minVersion, serverVersion)
}
b, err := newV.Marshal()
return b, &newV, err
}