alertmanager/nflog/nflog.go

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// Copyright 2016 Prometheus Team
// 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 nflog implements a garbage-collected and snapshottable append-only log of
// active/resolved notifications. Each log entry stores the active/resolved state,
// the notified receiver, and a hash digest of the notification's identifying contents.
// The log can be queried along different paramters.
package nflog
import (
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"bytes"
"errors"
"fmt"
"io"
"math/rand"
"os"
"sync"
"time"
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"github.com/go-kit/kit/log"
"github.com/golang/protobuf/ptypes"
"github.com/matttproud/golang_protobuf_extensions/pbutil"
pb "github.com/prometheus/alertmanager/nflog/nflogpb"
"github.com/weaveworks/mesh"
)
// ErrNotFound is returned for empty query results.
var ErrNotFound = errors.New("not found")
// Log stores and serves information about notifications
// about byte-slice addressed alert objects to different receivers.
type Log interface {
// The Log* methods store a notification log entry for
// a fully qualified receiver and a given IDs identifying the
// alert object.
LogActive(r *pb.Receiver, key, hash []byte) error
LogResolved(r *pb.Receiver, key, hash []byte) error
// Query the log along the given Paramteres.
//
// TODO(fabxc):
// - extend the interface by a `QueryOne` method?
// - return an iterator rather than a materialized list?
Query(p ...QueryParam) ([]*pb.Entry, error)
// Snapshot the current log state and return the number
// of bytes written.
Snapshot(w io.Writer) (int, error)
// GC removes expired entries from the log. It returns
// the total number of deleted entries.
GC() (int, error)
}
// query currently allows filtering by and/or receiver group key.
// It is configured via QueryParameter functions.
//
// TODO(fabxc): Future versions could allow querying a certain receiver
// group or a given time interval.
type query struct {
recv *pb.Receiver
groupKey []byte
}
// QueryParam is a function that modifies a query to incorporate
// a set of parameters. Returns an error for invalid or conflicting
// parameters.
type QueryParam func(*query) error
// QReceiver adds a receiver parameter to a query.
func QReceiver(r *pb.Receiver) QueryParam {
return func(q *query) error {
q.recv = r
return nil
}
}
// QGroupKey adds a group key as querying argument.
func QGroupKey(gk []byte) QueryParam {
return func(q *query) error {
q.groupKey = gk
return nil
}
}
type nlog struct {
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logger log.Logger
now func() time.Time
retention time.Duration
runInterval time.Duration
snapf string
stopc chan struct{}
done func()
gossip mesh.Gossip // gossip channel for sharing log state.
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// For now we only store the most recently added log entry.
// The key is a serialized concatenation of group key and receiver.
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// Currently our memory state is equivalent to the mesh.GossipData
// representation. This may change in the future as we support history
// and indexing.
mtx sync.RWMutex
st gossipData
}
// Option configures a new Log implementation.
type Option func(*nlog) error
// WithMesh registers the log with a mesh network with which
// the log state will be shared.
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func WithMesh(create func(g mesh.Gossiper) mesh.Gossip) Option {
return func(l *nlog) error {
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l.gossip = create(l)
return nil
}
}
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// WithRetention sets the retention time for log st.
func WithRetention(d time.Duration) Option {
return func(l *nlog) error {
l.retention = d
return nil
}
}
// WithNow overwrites the function used to retrieve a timestamp
// for the current point in time.
// This is generally useful for injection during tests.
func WithNow(f func() time.Time) Option {
return func(l *nlog) error {
l.now = f
return nil
}
}
// WithLogger configures a logger for the notification log.
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func WithLogger(logger log.Logger) Option {
return func(l *nlog) error {
l.logger = logger
return nil
}
}
// WithMaintenance configures the Log to run garbage collection
// and snapshotting, if configured, at the given interval.
//
// The maintenance terminates on receiving from the provided channel.
// The done function is called after the final snapshot was completed.
func WithMaintenance(d time.Duration, stopc chan struct{}, done func()) Option {
return func(l *nlog) error {
if d == 0 {
return fmt.Errorf("maintenance interval must not be 0")
}
l.runInterval = d
l.stopc = stopc
l.done = done
return nil
}
}
// WithSnapshot configures the log to be initialized from a given snapshot file.
// If maintenance is configured, a snapshot will be saved periodically and on
// shutdown as well.
func WithSnapshot(sf string) Option {
return func(l *nlog) error {
l.snapf = sf
return nil
}
}
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func utcNow() time.Time {
return time.Now().UTC()
}
// New creates a new notification log based on the provided options.
// The snapshot is loaded into the Log if it is set.
func New(opts ...Option) (Log, error) {
l := &nlog{
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logger: log.NewNopLogger(),
now: utcNow,
st: map[string]*pb.MeshEntry{},
}
for _, o := range opts {
if err := o(l); err != nil {
return nil, err
}
}
if l.snapf != "" {
if f, err := os.Open(l.snapf); !os.IsNotExist(err) {
if err != nil {
return l, err
}
defer f.Close()
if err := l.loadSnapshot(f); err != nil {
return l, err
}
}
}
go l.run()
return l, nil
}
// run periodic background maintenance.
func (l *nlog) run() {
if l.runInterval == 0 || l.stopc == nil {
return
}
t := time.NewTicker(l.runInterval)
defer t.Stop()
if l.done != nil {
defer l.done()
}
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f := func() error {
if _, err := l.GC(); err != nil {
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return err
}
if l.snapf == "" {
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return nil
}
f, err := openReplace(l.snapf)
if err != nil {
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return err
}
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// TODO(fabxc): potentially expose snapshot size in log message.
if _, err := l.Snapshot(f); err != nil {
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return err
}
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return f.Close()
}
for {
select {
case <-l.stopc:
break
case <-t.C:
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if err := f(); err != nil {
l.logger.Log("msg", "running maintenance failed", "err", err)
}
}
}
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// No need to run final maintenance if we don't want to snapshot.
if l.snapf == "" {
return
}
if err := f(); err != nil {
l.logger.Log("msg", "creating shutdown snapshot failed", "err", err)
}
}
// LogActive implements the Log interface.
func (l *nlog) LogActive(r *pb.Receiver, key, hash []byte) error {
return l.log(r, key, hash, false)
}
// LogResolved implements the Log interface.
func (l *nlog) LogResolved(r *pb.Receiver, key, hash []byte) error {
return l.log(r, key, hash, true)
}
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// stateKey returns a string key for a log entry consisting of the group key
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// and receiver.
func stateKey(k []byte, r *pb.Receiver) string {
return fmt.Sprintf("%s:%s", k, r)
}
func (l *nlog) log(r *pb.Receiver, gkey, ghash []byte, resolved bool) error {
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// Write all st with the same timestamp.
now := l.now()
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key := stateKey(gkey, r)
l.mtx.Lock()
defer l.mtx.Unlock()
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if prevle, ok := l.st[key]; ok {
// Entry already exists, only overwrite if timestamp is newer.
// This may with raciness or clock-drift across AM nodes.
prevts, err := ptypes.Timestamp(prevle.Entry.Timestamp)
if err != nil {
return err
}
if prevts.After(now) {
return nil
}
}
ts, err := ptypes.TimestampProto(now)
if err != nil {
return err
}
expts, err := ptypes.TimestampProto(now.Add(l.retention))
if err != nil {
return err
}
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l.st[key] = &pb.MeshEntry{
Entry: &pb.Entry{
Receiver: r,
GroupKey: gkey,
GroupHash: ghash,
Resolved: resolved,
Timestamp: ts,
},
ExpiresAt: expts,
}
return nil
}
// GC implements the Log interface.
func (l *nlog) GC() (int, error) {
now := l.now()
var n int
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l.mtx.Lock()
defer l.mtx.Unlock()
for k, le := range l.st {
if ets, err := ptypes.Timestamp(le.ExpiresAt); err != nil {
return n, err
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} else if !ets.After(now) {
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delete(l.st, k)
n++
}
}
return n, nil
}
// Query implements the Log interface.
func (l *nlog) Query(params ...QueryParam) ([]*pb.Entry, error) {
q := &query{}
for _, p := range params {
if err := p(q); err != nil {
return nil, err
}
}
// TODO(fabxc): For now our only query mode is the most recent entry for a
// receiver/group_key combination.
if q.recv == nil || q.groupKey == nil {
// TODO(fabxc): allow more complex queries in the future.
// How to enable pagination?
return nil, errors.New("no query parameters specified")
}
l.mtx.RLock()
defer l.mtx.RUnlock()
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if le, ok := l.st[stateKey(q.groupKey, q.recv)]; ok {
return []*pb.Entry{le.Entry}, nil
}
return nil, ErrNotFound
}
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// loadSnapshot loads a snapshot generated by Snapshot() into the state.
func (l *nlog) loadSnapshot(r io.Reader) error {
l.mtx.Lock()
defer l.mtx.Unlock()
st := gossipData{}
for {
var e pb.MeshEntry
if _, err := pbutil.ReadDelimited(r, &e); err != nil {
if err == io.EOF {
break
}
return err
}
st[stateKey(e.Entry.GroupKey, e.Entry.Receiver)] = &e
}
l.st = st
return nil
}
// Snapshot implements the Log interface.
func (l *nlog) Snapshot(w io.Writer) (int, error) {
l.mtx.RLock()
defer l.mtx.RUnlock()
var n int
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for _, e := range l.st {
m, err := pbutil.WriteDelimited(w, e)
if err != nil {
return n + m, err
}
n += m
}
return n, nil
}
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// Gossip implements the mesh.Gossiper interface.
func (l *nlog) Gossip() mesh.GossipData {
l.mtx.RLock()
defer l.mtx.RUnlock()
gd := make(gossipData, len(l.st))
for k, v := range l.st {
gd[k] = v
}
return gd
}
// OnGossip implements the mesh.Gossiper interface.
func (l *nlog) OnGossip(msg []byte) (mesh.GossipData, error) {
gd, err := decodeGossipData(msg)
if err != nil {
return nil, err
}
l.mtx.Lock()
defer l.mtx.Unlock()
if delta := l.st.mergeDelta(gd); len(delta) > 0 {
return delta, nil
}
return nil, nil
}
// OnGossipBroadcast implements the mesh.Gossiper interface.
func (l *nlog) OnGossipBroadcast(src mesh.PeerName, msg []byte) (mesh.GossipData, error) {
gd, err := decodeGossipData(msg)
if err != nil {
return nil, err
}
l.mtx.Lock()
defer l.mtx.Unlock()
return l.st.mergeDelta(gd), nil
}
// OnGossipUnicast implements the mesh.Gossiper interface.
func (l *nlog) OnGossipUnicast(src mesh.PeerName, msg []byte) error {
panic("not implemented")
}
// gossipData is a representation of the current log state that
// implements the mesh.GossipData interface.
type gossipData map[string]*pb.MeshEntry
func decodeGossipData(msg []byte) (gossipData, error) {
gd := gossipData{}
rd := bytes.NewReader(msg)
for {
var e pb.MeshEntry
if _, err := pbutil.ReadDelimited(rd, &e); err != nil {
if err == io.EOF {
break
}
return gd, err
}
gd[stateKey(e.Entry.GroupKey, e.Entry.Receiver)] = &e
}
return gd, nil
}
// Encode implements the mesh.GossipData interface.
func (gd gossipData) Encode() [][]byte {
// Split into sub-messages of ~1MB.
const maxSize = 1024 * 1024
var (
buf bytes.Buffer
res [][]byte
n int
)
for _, e := range gd {
m, err := pbutil.WriteDelimited(&buf, e)
n += m
if err != nil {
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// TODO(fabxc): log error and skip entry. Or can this really not happen with a bytes.Buffer?
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panic(err)
}
if n > maxSize {
res = append(res, buf.Bytes())
buf = bytes.Buffer{}
}
}
if buf.Len() > 0 {
res = append(res, buf.Bytes())
}
return res
}
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func (gd gossipData) clone() gossipData {
res := make(gossipData, len(gd))
for k, e := range gd {
res[k] = e
}
return res
}
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// Merge the notification set with gossip data and return a new notification
// state.
// TODO(fabxc): can we just return the receiver. Does it have to remain
// unmodified. Needs to be clarified upstream.
func (gd gossipData) Merge(other mesh.GossipData) mesh.GossipData {
for k, e := range other.(gossipData) {
prev, ok := gd[k]
if !ok {
gd[k] = e
continue
}
pts, err := ptypes.Timestamp(prev.Entry.Timestamp)
if err != nil {
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// TODO(fabxc): log error and skip entry. What can actually error here?
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panic(err)
}
ets, err := ptypes.Timestamp(e.Entry.Timestamp)
if err != nil {
// TODO(fabxc): see above.
panic(err)
}
if pts.Before(ets) {
gd[k] = e
}
}
return gd
}
// mergeDelta behaves like Merge but returns a gossipData only containing
// things that have changed.
func (gd gossipData) mergeDelta(od gossipData) gossipData {
delta := gossipData{}
for k, e := range od {
prev, ok := gd[k]
if !ok {
gd[k] = e
delta[k] = e
continue
}
pts, err := ptypes.Timestamp(prev.Entry.Timestamp)
if err != nil {
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// TODO(fabxc): log error and skip entry. What can actually error here?
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panic(err)
}
ets, err := ptypes.Timestamp(e.Entry.Timestamp)
if err != nil {
// TODO(fabxc): see above.
panic(err)
}
if pts.Before(ets) {
gd[k] = e
delta[k] = e
}
}
return delta
}
// replaceFile wraps a file that is moved to another filename on closing.
type replaceFile struct {
*os.File
filename string
}
func (f *replaceFile) Close() error {
if err := f.File.Sync(); err != nil {
return err
}
if err := f.File.Close(); err != nil {
return err
}
return os.Rename(f.File.Name(), f.filename)
}
// openReplace opens a new temporary file that is moved to filename on closing.
func openReplace(filename string) (*replaceFile, error) {
tmpFilename := fmt.Sprintf("%s.%x", filename, uint64(rand.Int63()))
f, err := os.Create(tmpFilename)
if err != nil {
return nil, err
}
rf := &replaceFile{
File: f,
filename: filename,
}
return rf, nil
}