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log-cloudwatch.go
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log-cloudwatch.go
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// Licensed to NASA JPL under one or more contributor
// license agreements. See the NOTICE file distributed with
// this work for additional information regarding copyright
// ownership. NASA JPL licenses this file to you 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 logger
import (
"fmt"
"log"
"sync"
"time"
"github.com/aws/aws-sdk-go/aws"
"github.com/aws/aws-sdk-go/aws/awserr"
"github.com/aws/aws-sdk-go/aws/session"
"github.com/aws/aws-sdk-go/service/cloudwatchlogs"
)
// This is heavily based on: github.com/jcxplorer/cwlogger and github.com/mathisve/golang-cloudwatch-logs-example
// CloudwatchLogger - Structure holding API logger internals
type CloudwatchLogger struct {
cwClient *cloudwatchlogs.CloudWatchLogs
logGroupName string
logStreamName string
logLevel LogLevel
sequenceToken string
queue []string
lock sync.Mutex
retentionDays int
logIntervalSec time.Duration
running bool
}
// InitCloudWatchLogger - initialises the logger, given settings and AWS session
func InitCloudWatchLogger(sess *session.Session, logGroupName string, logStreamName string, logLevel LogLevel, retentionDays int, logIntervalSec time.Duration) (ILogger, error) {
result := CloudwatchLogger{
cwClient: cloudwatchlogs.New(sess),
logGroupName: logGroupName,
logStreamName: logStreamName,
logLevel: logLevel,
sequenceToken: "",
queue: []string{},
lock: sync.Mutex{},
retentionDays: retentionDays,
logIntervalSec: logIntervalSec,
running: true,
}
/*
tok := ""
totalDel := 0
for i := 0; i < 100; i++ {
var err error
var delcount int
tok, delcount, err = result.deleteOldGroups("/aws/lambda/", tok)
if err != nil {
return &result, err
}
totalDel += delcount
}
*/
// Make sure log group exists
err := result.ensureLogGroupExists(logGroupName, int64(retentionDays))
if err != nil {
return &result, err
}
// Now open the log stream
go result.processQueue(logIntervalSec)
return &result, nil
}
func (l *CloudwatchLogger) Close() {
// Sleep this thread for long enough that the other thread pumps any messages left in its queue to cloudwatch
time.Sleep(time.Second * l.logIntervalSec * 2)
}
/*
func (l *CloudwatchLogger) deleteOldGroups(prefix string, contToken string) (string, int, error) {
in := cloudwatchlogs.DescribeLogGroupsInput{
Limit: aws.Int64(50),
}
if len(contToken) > 0 {
in.NextToken = aws.String(contToken)
}
resp, err := l.cwClient.DescribeLogGroups(&in)
if err != nil {
return "", 0, err
}
delcount := 0
for _, logGroup := range resp.LogGroups {
if strings.HasPrefix(*logGroup.LogGroupName, prefix) {
_, err := l.cwClient.DeleteLogGroup(&cloudwatchlogs.DeleteLogGroupInput{
LogGroupName: logGroup.LogGroupName,
})
if err != nil {
fmt.Printf("DeleteLogGroup %v failed: %v\n", *logGroup.LogGroupName, err)
} else {
delcount++
}
}
}
return *resp.NextToken, delcount, nil
}
*/
func (l *CloudwatchLogger) ensureLogGroupExists(name string, retentionDays int64) error {
_, err := l.cwClient.CreateLogGroup(&cloudwatchlogs.CreateLogGroupInput{
LogGroupName: aws.String(name),
})
if err != nil {
// If it already exists, don't fail!
if aerr, ok := err.(awserr.Error); ok {
if aerr.Message() == "The specified log group already exists" {
return nil
}
}
return err
}
_, err = l.cwClient.PutRetentionPolicy(&cloudwatchlogs.PutRetentionPolicyInput{
RetentionInDays: aws.Int64(retentionDays),
LogGroupName: aws.String(name),
})
return err
}
func (l *CloudwatchLogger) createLogStream(name string) error {
// Ensure it exists here because it may be deleted at runtime from cloudwatch, if we're creating or re-creating
// our log stream, it's good to know that the group is there
err := l.ensureLogGroupExists(l.logGroupName, int64(l.retentionDays))
if err != nil {
return err
}
_, err = l.cwClient.CreateLogStream(&cloudwatchlogs.CreateLogStreamInput{
LogGroupName: aws.String(l.logGroupName),
LogStreamName: aws.String(name),
})
return err
}
// processQueue will process the log queue
func (l *CloudwatchLogger) processQueue(logIntervalSec time.Duration) error {
var logQueue []*cloudwatchlogs.InputLogEvent
for l.running {
l.lock.Lock()
if len(l.queue) > 0 {
for _, item := range l.queue {
logQueue = append(logQueue, &cloudwatchlogs.InputLogEvent{
Message: aws.String(item),
Timestamp: aws.Int64(time.Now().UnixNano() / int64(time.Millisecond)),
})
}
l.queue = []string{}
}
l.lock.Unlock()
if len(logQueue) > 0 {
input := cloudwatchlogs.PutLogEventsInput{
LogEvents: logQueue,
LogGroupName: aws.String(l.logGroupName),
}
if l.sequenceToken == "" {
err := l.createLogStream(l.logStreamName)
if err != nil {
// Write to stderr
log.Printf("createLogStream failed: %v", err)
}
} else {
input = *input.SetSequenceToken(l.sequenceToken)
}
input = *input.SetLogStreamName(l.logStreamName)
resp, err := l.cwClient.PutLogEvents(&input)
if err != nil {
// Write to stderr
log.Printf("PutLogEvents failed: %v", err)
}
if resp != nil {
if resp.NextSequenceToken != nil {
l.sequenceToken = *resp.NextSequenceToken
} else {
l.sequenceToken = ""
}
}
logQueue = []*cloudwatchlogs.InputLogEvent{}
}
time.Sleep(time.Second * logIntervalSec)
}
// Might be useful seeing this on shutdown...
fmt.Println("logger processQueue complete")
return nil
}
// Log enqueues a log message to be written to a log stream.
//
// The log message must be less than 1,048,550 bytes, and the time must not be
// more than 2 hours in the future, 14 days in the past, or older than the
// retention period of the log group.
//
// This method is safe for concurrent access by multiple goroutines.
func (l *CloudwatchLogger) Printf(level LogLevel, format string, a ...interface{}) {
// If we're not on this log level, skip
if l.logLevel > level {
return
}
txt := logLevelPrefix[level] + ": " + fmt.Sprintf(format, a...)
defer l.lock.Unlock()
l.lock.Lock()
// Add to the log queue
l.queue = append(l.queue, txt)
// Also write to local stdout
log.Println(txt)
}
// Debugf - Print debug to log, with format string
func (l *CloudwatchLogger) Debugf(format string, a ...interface{}) {
l.Printf(LogDebug, format, a...)
}
// Infof - Print info to log, with format string
func (l *CloudwatchLogger) Infof(format string, a ...interface{}) {
l.Printf(LogInfo, format, a...)
}
// Errorf - Print error to log, with format string
func (l *CloudwatchLogger) Errorf(format string, a ...interface{}) {
l.Printf(LogError, format, a...)
}
func (l *CloudwatchLogger) SetLogLevel(level LogLevel) {
l.logLevel = level
}
func (l *CloudwatchLogger) GetLogLevel() LogLevel {
return l.logLevel
}