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

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

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).

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.

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

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}"

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.

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

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] )

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.

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

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>

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)