AWS Cloudwatch Log - Is it possible to export existing log data from it?

Question

I have managed to push my application logs to AWS Cloudwatch by using the AWS CloudWatch log agent. But the CloudWatch web console does not seem to provide a button to allow you to download/export the log data from it.

Any idea how I can achieve this goal?

score 133 · Accepted Answer · edited Jun 15 '21 at 14:35

133

The latest AWS CLI has a CloudWatch Logs cli, that allows you to download the logs as JSON, text file or any other output supported by AWS CLI.

For example to get the first 1MB up to 10,000 log entries from the stream a in group A to a text file, run:

aws logs get-log-events \
   --log-group-name A --log-stream-name a \
   --output text > a.log

The command is currently limited to a response size of maximum 1MB (up to 10,000 records per request), and if you have more you need to implement your own page stepping mechanism using the --next-token parameter. I expect that in the future the CLI will also allow full dump in a single command.

Update

Here's a small Bash script to list events from all streams in a specific group, since a specified time:

#!/bin/bash
function dumpstreams() {
  aws $AWSARGS logs describe-log-streams \
    --order-by LastEventTime --log-group-name $LOGGROUP \
    --output text | while read -a st; do 
      [ "${st[4]}" -lt "$starttime" ] && continue
      stname="${st[1]}"
      echo ${stname##*:}
    done | while read stream; do
      aws $AWSARGS logs get-log-events \
        --start-from-head --start-time $starttime \
        --log-group-name $LOGGROUP --log-stream-name $stream --output text
    done
}

AWSARGS="--profile myprofile --region us-east-1"
LOGGROUP="some-log-group"
TAIL=
starttime=$(date --date "-1 week" +%s)000
nexttime=$(date +%s)000
dumpstreams
if [ -n "$TAIL" ]; then
  while true; do
    starttime=$nexttime
    nexttime=$(date +%s)000
    sleep 1
    dumpstreams
  done
fi

That last part, if you set TAIL will continue to fetch log events and will report newer events as they come in (with some expected delay).

edited Jun 15 '21 at 14:35

saputkin

13
4

answered Feb 23 '15 at 15:19

Guss

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In the first command of `aws cli` what is the backslash intended for? I think it brakes the command and that it is not needed. It should be `aws logs get-log-events --log-group-name A --log-stream-name a --output text > a.log` – Drubio Apr 29 '19 at 10:28
1

You are obviously correct, but I'm using backslashes to break the command into multiple lines so it's easier to read in Stack Overflow's narrow display, and still be copy&pastable to your command line. – Guss Apr 29 '19 at 10:40
The `TAIL` logic doesn't really work when you have a large number of log files. For me, it takes several minutes to enumerate the log files in each iteration. (Also probably replace the fugly `while read -a` loop with an Awk one-liner; `awk -v after="$starttime" '$5 >= after { s = $2; gsub(/.*:/, "", s); print s }'` ... and [quote your variables.](https://stackoverflow.com/questions/10067266/when-to-wrap-quotes-around-a-shell-variable) – tripleee Aug 25 '20 at 09:00
@tripleee: (a) thank you for your comment, I'd appreciate seeing your full solution in an answer here :-) (b) Some people like AWK, I use it sparingly and Iike my `read -a` better - it is just a matter of style (c) some variables require quoting, others (like `$AWSARGS` here) require not-quoting - as per the link you provided, I don't quote my variables when they are numbers or otherwise safe. `$LOGGROUP` could probably use some quoting, though it is hardcoded and safe in this example. – Guss Aug 25 '20 at 09:15
Thanks for the quick feedback. I'm not critizising your code so much as adding a caveat for visitors whose scenario resembles mine. I don't think I can come up with a better solution; my workaround is to fetch the logs from the previous 24 hours in one go and then analyze them locally in batch. – tripleee Aug 25 '20 at 10:39
2

@tripleee (a) that's cool. (b) I'm still pretty sure that if you post your code here, people will appreciate it – Guss Aug 25 '20 at 13:01

Jan Vlcinsky · Answer 2 · 2015-11-09T22:25:41.423

48

There is also a python project called awslogs, allowing to get the logs: https://github.com/jorgebastida/awslogs

There are things like:

list log groups:

$ awslogs groups

list streams for given log group:

$ awslogs streams /var/log/syslog

get the log records from all streams:

$ awslogs get /var/log/syslog

get the log records from specific stream :

$ awslogs get /var/log/syslog stream_A

and much more (filtering for time period, watching log streams...

I think, this tool might help you to do what you want.

edited Nov 09 '15 at 22:25

answered Nov 09 '15 at 21:41

Jan Vlcinsky

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I don't see the timestamp for each record. Any reason why this is suppressed? It's visible via CloudWatch Logs in the AWS console. – sharmil Jul 02 '19 at 09:00
1

@sharmil try the `--timestamp` option – Jan Vlcinsky Jul 03 '19 at 18:39
How foolish of me. I see it in the documents. Thank you for pointing it out. – sharmil Jul 04 '19 at 12:22
@JanVlcinsky sir I want to ask one thing, How we can log our form data over cloudwatch using php ? – Chitrang Sharma Jun 25 '21 at 11:06
1

@ChitrangSharma I am not expert on PHP, but I have found, there is an PHP AWS SDK and there is client to interact with AwsCloudWatchLogs: https://docs.aws.amazon.com/aws-sdk-php/v3/api/class-Aws.CloudWatchLogs.CloudWatchLogsClient.html – Jan Vlcinsky Jun 26 '21 at 12:13

score 24 · Answer 3 · answered Aug 30 '17 at 21:18

It seems AWS has added the ability to export an entire log group to S3.

You'll need to setup permissions on the S3 bucket to allow cloudwatch to write to the bucket by adding the following to your bucket policy, replacing the region with your region and the bucket name with your bucket name.

    {
        "Effect": "Allow",
        "Principal": {
            "Service": "logs.us-east-1.amazonaws.com"
        },
        "Action": "s3:GetBucketAcl",
        "Resource": "arn:aws:s3:::tsf-log-data"
    },
    {
        "Effect": "Allow",
        "Principal": {
            "Service": "logs.us-east-1.amazonaws.com"
        },
        "Action": "s3:PutObject",
        "Resource": "arn:aws:s3:::tsf-log-data/*",
        "Condition": {
            "StringEquals": {
                "s3:x-amz-acl": "bucket-owner-full-control"
            }
        }
    }

Details can be found in Step 2 of this AWS doc

score 9 · Answer 4 · answered Sep 08 '22 at 08:44

9

The other answers were not useful with AWS Lambda logs since they create many log streams and I just wanted to dump everything in the last week. I finally found the following command to be what I needed:

aws logs tail --since 1w  LOG_GROUP_NAME > output.log

Note that LOG_GROUP_NAME is the lambda function path (e.g. /aws/lambda/FUNCTION_NAME) and you can replace the since argument with a variety of times (1w = 1 week, 5m = 5 minutes, etc)

answered Sep 08 '22 at 08:44

Mike McKay

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We can also use `... --log-stream-names STREAM_NAME ...` to retrieve specific instances logs. Final: `aws logs tail --since 1w LOG_GROUP_NAME --log-stream-names STREAM_NAME > output.log` – voiski Apr 20 '23 at 03:07

score 5 · Answer 5 · answered Apr 26 '18 at 17:48

I would add that one liner to get all logs for a stream :

aws logs get-log-events --log-group-name my-log-group --log-stream-name my-log-stream | grep '"message":' | awk -F '"' '{ print $(NF-1) }' > my-log-group_my-log-stream.txt

Or in a slightly more readable format :

aws logs get-log-events \
    --log-group-name my-log-group\
    --log-stream-name my-log-stream \
    | grep '"message":' \
    | awk -F '"' '{ print $(NF-1) }' \
    > my-log-group_my-log-stream.txt

And you can make a handy script out of it that is admittedly less powerful than @Guss's but simple enough. I saved it as getLogs.sh and invoke it with ./getLogs.sh log-group log-stream

#!/bin/bash

if [[ "${#}" != 2 ]]
then
    echo "This script requires two arguments!"
    echo
    echo "Usage :"
    echo "${0} <log-group-name> <log-stream-name>"
    echo
    echo "Example :"
    echo "${0} my-log-group my-log-stream"

    exit 1
fi

OUTPUT_FILE="${1}_${2}.log"
aws logs get-log-events \
    --log-group-name "${1}"\
    --log-stream-name "${2}" \
    | grep '"message":' \
    | awk -F '"' '{ print $(NF-1) }' \
    > "${OUTPUT_FILE}"

echo "Logs stored in ${OUTPUT_FILE}"

Remember, anything which looks like `grep 'x' | awk '{ y }'` can and probably should be refactored to `awk '/x/ { y }'` — tripleee, Aug 25 '20 at 09:03

score 3 · Answer 6 · answered Jan 21 '15 at 07:30

Apparently there isn't an out-of-box way from AWS Console where you can download the CloudWatchLogs. Perhaps you can write a script to perform the CloudWatchLogs fetch using the SDK / API.

The good thing about CloudWatchLogs is that you can retain the logs for infinite time(Never Expire); unlike the CloudWatch which just keeps the logs for just 14 days. Which means you can run the script in monthly / quarterly frequency rather than on-demand.

More information about the CloudWatchLogs API, http://docs.aws.amazon.com/AmazonCloudWatchLogs/latest/APIReference/Welcome.html http://awsdocs.s3.amazonaws.com/cloudwatchlogs/latest/cwl-api.pdf

score 3 · Answer 7 · answered Nov 13 '19 at 21:43

You can now perform exports via the Cloudwatch Management Console with the new Cloudwatch Logs Insights page. Full documentation here https://docs.aws.amazon.com/AmazonCloudWatch/latest/logs/CWL_ExportQueryResults.html. I had already started ingesting my Apache logs into Cloudwatch with JSON, so YMMV if you haven't set it up in advance.

Add Query to Dashboard or Export Query Results

After you run a query, you can add the query to a CloudWatch dashboard, or copy the results to the clipboard.

Queries added to dashboards automatically re-run every time you load the dashboard and every time that the dashboard refreshes. These queries count toward your limit of four concurrent CloudWatch Logs Insights queries.

To add query results to a dashboard

Open the CloudWatch console at https://console.aws.amazon.com/cloudwatch/.

In the navigation pane, choose Insights.

Choose one or more log groups and run a query.

Choose Add to dashboard.

Select the dashboard, or choose Create new to create a new dashboard for the query results.

Choose Add to dashboard.

To copy query results to the clipboard

Open the CloudWatch console at https://console.aws.amazon.com/cloudwatch/.

In the navigation pane, choose Insights.

Choose one or more log groups and run a query.

Choose Actions, Copy query results.

score 2 · Answer 8 · answered Sep 16 '21 at 14:21

Inspired by saputkin I have created a pyton script that downloads all the logs for a log group in given time period.

The script itself: https://github.com/slavogri/aws-logs-downloader.git

In case there are multiple log streams for that period multiple files will be created. Downloaded files will be stored in current directory, and will be named by the log streams that has a log events in given time period. (If the group name contains forward slashes, they will be replaced by underscores. Each file will be overwritten if it already exists.)

Prerequisite: You need to be logged in to your aws profile. The Script itself is going to use on behalf of you the AWS command line APIs: "aws logs describe-log-streams" and "aws logs get-log-events"

Usage example: python aws-logs-downloader -g /ecs/my-cluster-test-my-app -t "2021-09-04 05:59:50 +00:00" -i 60

optional arguments:
   -h, --help         show this help message and exit
   -v, --version      show program's version number and exit
   -g , --log-group   (required) Log group name for which the log stream events needs to be downloaded
   -t , --end-time    (default: now) End date and time of the downloaded logs in format: %Y-%m-%d %H:%M:%S %z (example: 2021-09-04 05:59:50 +00:00)
   -i , --interval    (default: 30) Time period in minutes before the end-time. This will be used to calculate the time since which the logs will be downloaded.
   -p , --profile     (default: dev) The aws profile that is logged in, and on behalf of which the logs will be downloaded.
   -r , --region      (default: eu-central-1) The aws region from which the logs will be downloaded.

Please let me now if it was useful to you. :)

After I did it I learned that there is another option using Boto3: https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/logs.html#CloudWatchLogs.Client.get_log_events

Still the command line API seems to me like a good option.

score 1 · Answer 9 · answered Nov 11 '21 at 17:26

export LOGGROUPNAME=[SOME_LOG_GROUP_NAME]; for LOGSTREAM in `aws --output text logs describe-log-streams --log-group-name ${LOGGROUPNAME} |awk '{print $7}'`; do aws --output text logs get-log-events --log-group-name ${LOGGROUPNAME} --log-stream-name ${LOGSTREAM} >> ${LOGGROUPNAME}_output.txt; done

score 0 · Answer 10 · answered Nov 19 '20 at 00:40

Adapted @Guyss answer to macOS. As I am not really a bash guy, had to use python, to convert dates to a human-readable form.

runaswslog -1w gets last week and so on

runawslog() { sh awslogs.sh $1 | grep "EVENTS" | python parselogline.py; }

awslogs.sh:

#!/bin/bash
#set -x
function dumpstreams() {
  aws $AWSARGS logs describe-log-streams \
    --order-by LastEventTime --log-group-name $LOGGROUP \
    --output text | while read -a st; do 
      [ "${st[4]}" -lt "$starttime" ] && continue
      stname="${st[1]}"
      echo ${stname##*:}
    done | while read stream; do
      aws $AWSARGS logs get-log-events \
        --start-from-head --start-time $starttime \
        --log-group-name $LOGGROUP --log-stream-name $stream --output text
    done
}
AWSARGS=""
#AWSARGS="--profile myprofile --region us-east-1"
LOGGROUP="/aws/lambda/StockTrackFunc"
TAIL=
FROMDAT=$1
starttime=$(date -v ${FROMDAT} +%s)000
nexttime=$(date +%s)000
dumpstreams
if [ -n "$TAIL" ]; then
  while true; do
    starttime=$nexttime
    nexttime=$(date +%s)000
    sleep 1
    dumpstreams
  done
fi

parselogline.py:

import sys
import datetime
dat=sys.stdin.read()
for k in dat.split('\n'):
    d=k.split('\t')
    if len(d)<3:
        continue
    d[2]='\t'.join(d[2:])
    print( str(datetime.datetime.fromtimestamp(int(d[1])/1000)) + '\t' + d[2] )

score 0 · Answer 11 · answered Feb 22 '22 at 06:46

I had a similar use case where i had to download all the streams for a given log group. See if this script helps.

#!/bin/bash

if [[ "${#}" != 1 ]]
then
    echo "This script requires two arguments!"
    echo
    echo "Usage :"
    echo "${0} <log-group-name>"

    exit 1
fi

streams=`aws logs describe-log-streams --log-group-name "${1}"`


for stream in $(jq '.logStreams | keys | .[]' <<< "$streams"); do 
    record=$(jq -r ".logStreams[$stream]" <<< "$streams")
    streamName=$(jq -r ".logStreamName" <<< "$record")
    echo "Downloading ${streamName}";
    echo `aws logs get-log-events --log-group-name "${1}" --log-stream-name "$streamName" --output json > "${stream}.log" `
    echo "Completed dowload:: ${streamName}";
done;

You have have pass log group name as an argument.

Eg: bash <name_of_the_bash_file>.sh <group_name>

Pavel Voropaev · Answer 12 · 2023-05-24T15:50:56.317

For stream with more than 10000 events, it is more resilient to use the forward token and start-from-head for the log stream. It avoids issues with empty/duplicate events if time not exactly right or events are too dense.

#!/bin/bash

# Required parameters
REGION="PLACEHOLDER"
LOG_GROUP_NAME="PLACEHOLDER"
LOG_STREAM_NAME="PLACEHOLDER"

# Temporary files
TEMP_FILE="temp_output.txt"
FINAL_OUTPUT_FILE="final_output.txt"

# Initial command
aws logs get-log-events --region $REGION --log-group-name $LOG_GROUP_NAME --log-stream-name $LOG_STREAM_NAME --start-from-head --output text > $TEMP_FILE

# Check number of lines in the file
while [ $(wc -l <"$TEMP_FILE") -gt 1 ]
do
  # Get the next token
  NEXT_TOKEN=$(grep -o -E "^b/[0-9]+/s\s+f/[0-9]+/s$" $TEMP_FILE |awk '{print $2}')

  # If we didn't find a next token, exit the loop
  if [ -z "$NEXT_TOKEN" ]; then
    break
  fi

  # Remove token line from temp file and append to final output file
  grep -v -o -E "^b/[0-9]+/s\s+f/[0-9]+/s$" temp_output.txt  $TEMP_FILE >> $FINAL_OUTPUT_FILE
  
  # Fetch more logs with the next token
  aws logs get-log-events --region $REGION --log-group-name $LOG_GROUP_NAME --log-stream-name $LOG_STREAM_NAME --next-token $NEXT_TOKEN --output text > $TEMP_FILE
done

# Append remaining content in temp file to final output file
grep -v -o -E "^b/[0-9]+/s\s+f/[0-9]+/s$" temp_output.txt  $TEMP_FILE >> $FINAL_OUTPUT_FILE

# Cleanup
rm $TEMP_FILE

score -1 · Answer 13 · answered Aug 19 '20 at 01:41

-1

I found AWS Documentation to be complete and accurate. https://docs.aws.amazon.com/AmazonCloudWatch/latest/logs/S3ExportTasks.html This laid down steps for exporting logs from Cloudwatch to S3

answered Aug 19 '20 at 01:41

Chaitanya Bapat

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AWS Cloudwatch Log - Is it possible to export existing log data from it?

13 Answers13

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