cwl-mount

Mount AWS CloudWatch logs as a file system.

Key Features • How To Use • Installation • Credits • License

cwl-mount mounts an AWS CloudWatch Logs log group as a file system. This lets you use everyday utilities like cat, grep, and shell globbing and query your logs.

What problem does cwl-mount solve

AWS CloudWatch Logs Insights is powerful but only returns a maximum of 10,000 results with no option to paginate results [1]. AWS CloudWatch Logs lets you filter logs but does not allow you to show logs before and after matches. You can export CloudWatch logs to S3 but this can take up to 12 hours [3]. You can stream your CloudWatch Logs to another data store but will pay for the streaming out and extra infrastructure [4].

Filling in the gap, cwl-mount has no upper limit on the number of logs you can search over, allows you to run grep -C to search with context, can be used immediately, and does not require additional infrastructure.

[1] https://docs.aws.amazon.com/AmazonCloudWatchLogs/latest/APIReference/API_StartQuery.html#API_StartQuery_RequestSyntax

[2] https://docs.aws.amazon.com/AmazonCloudWatch/latest/logs/cloudwatch_limits_cwl.html

[3] https://docs.aws.amazon.com/AmazonCloudWatch/latest/logs/S3Export.html

[4] https://docs.aws.amazon.com/AmazonCloudWatch/latest/logs/Subscriptions.html

Key Features

• Access CloudWatch logs as if they are files. Use cat on certain time ranges, grep --context, etc.
• Query latest logs instantaneouly; don't wait for S3 exports or transferring to a stream.
• Cross platform
  • Natively supports Linux and Mac OS X.
  • Run on Windows via a Docker container.

How To Use

You need IAM credentials for a IAM user or IAM role that can call logs:FilterLogEvents and logs:DescribeLogGroups.

Natively on Linux and Mac OS X

In one Terminal tab:

mkdir /tmp/foo
cwl-mount --region us-west-2 mount --log-group-name babynames-preprod-log-group-syslog /tmp/foo

In a second tab:

➜  ~ ls -l /tmp/foo

total 0
drwxrwxrwx  2 asimi  staff  0 Dec 31  1969 2021

➜  ~ ls -l /tmp/foo/2021/12/04/00-{00,01,02,03,04,05}
-rwxrwxrwx  1 asimi  staff  2147483647 Dec 31  1969 /tmp/foo/2021/12/04/00-00
-rwxrwxrwx  1 asimi  staff  2147483647 Dec 31  1969 /tmp/foo/2021/12/04/00-01
-rwxrwxrwx  1 asimi  staff  2147483647 Dec 31  1969 /tmp/foo/2021/12/04/00-02
-rwxrwxrwx  1 asimi  staff  2147483647 Dec 31  1969 /tmp/foo/2021/12/04/00-03
-rwxrwxrwx  1 asimi  staff  2147483647 Dec 31  1969 /tmp/foo/2021/12/04/00-04
-rwxrwxrwx  1 asimi  staff  2147483647 Dec 31  1969 /tmp/foo/2021/12/04/00-05

➜  ~ cat /tmp/foo/2021/12/04/00-{00,01,02,03,04,05}
[i-03e71e7954a899acb] Dec  4 00:00:07 ip-10-0-0-62 systemd[1]: Starting Rotate log files...
[i-03e71e7954a899acb] Dec  4 00:00:07 ip-10-0-0-62 systemd[1]: Starting Daily man-db regeneration...
[i-03e71e7954a899acb] Dec  4 00:00:07 ip-10-0-0-62 systemd[1]: logrotate.service: Succeeded.
[i-03e71e7954a899acb] Dec  4 00:00:07 ip-10-0-0-62 systemd[1]: Finished Rotate log files.
[i-03e71e7954a899acb] Dec  4 00:00:07 ip-10-0-0-62 systemd[1]: man-db.service: Succeeded.
[i-03e71e7954a899acb] Dec  4 00:00:07 ip-10-0-0-62 systemd[1]: Finished Daily man-db regeneration.[i-03e71e7954a899acb] Dec  4 00:03:01 ip-10-0-0-62 CRON[40987]: (root) CMD (/bin/sleep $[ ( $RANDOM % 3000 ) + 1 ]s; rm -f /var/log/awsagent-update.log; umask 037 && /opt/aws/awsagent/bin/update > /var/log/awsagent-update.log 2>&1)%

Docker, for any OS

Since cwl-mount requires FUSE it will not work out of the box on Windows. You can instead use a Docker container:

docker run \
    --privileged \
    --interactive \
    --tty \
    --env-file $HOME/.aws_kitten_cat_credentials_docker \
    public.ecr.aws/b5u6b4p0/cwl-mount:latest

The contents of env-file are some IAM role credentials that have access to logs:FilterLogEvents and logs:DescribeLogGroups, and look like:

AWS_ACCESS_KEY_ID=ABCDE
AWS_SECRET_ACCESS_KEY=fghij
AWS_REGION=us-west-2

Usage help

cwl-mount 0.1.2

USAGE:
    cwl-mount [FLAGS] [OPTIONS] --region <region> [SUBCOMMAND]

FLAGS:
    -h, --help       Prints help information
    -V, --version    Prints version information
    -v, --verbose    Verbose output. Set three times for maximum verbosity.

OPTIONS:
        --region <region>    AWS region, e.g. 'us-west-2'
        --tps <tps>          Transactions per second (TPS) at which to call AWS CloudWatch Logs. [default: 5]

SUBCOMMANDS:
    help               Prints this message or the help of the given subcommand(s)
    list-log-groups    List AWS CloudWatch Logs log groups then quit.
    mount              Mount AWS CloudWatch Logs to a directory.

You can list log groups using cwl-mount list-log-groups:

cwl-mount-list-log-groups
List AWS CloudWatch Logs log groups then quit.

USAGE:
    cwl-mount --region <region> list-log-groups

FLAGS:
    -h, --help       Prints help information
    -V, --version    Prints version information

You can mount logs using cwl-mount mount:

cwl-mount-mount
Mount AWS CloudWatch Logs to a directory.

USAGE:
    cwl-mount --region <region> mount [FLAGS] [OPTIONS] <mount-point> <--log-group-name <log-group-name>|--log-group-filter <log-group-filter>>

FLAGS:
        --allow-root    Allow root user to access filesystem
    -h, --help          Prints help information
    -V, --version       Prints version information

OPTIONS:
        --log-group-filter <log-group-filter>    CloudWatch Logs log group filter, a regular expression
        --log-group-name <log-group-name>        CloudWatch Logs log group name
        --output-format <output-format>
            Output format string. Valid parameters to use are [log_group_name, event_id, ingestion_time,
            log_stream_name, message, timestamp]. [default: [${log_stream_name}] ${message}]

ARGS:
    <mount-point>    Mount the AWS CloudWatch logs at the given directory

Troubleshooting

If you get an error about the directory already being mounted, try umount /tmp/foo first.

I recommend always passing in the AWS region in --region, even if you have the AWS_REGION environment variable set, otherwise STS temporary credentials may not work.

Installation

Linux with RPM:

wget https://github.com/asimihsan/cwl-mount/releases/download/v0.1.2/cwl-mount-0.1.2-1-x86_64.rpm
yum localinstall cwl-mount-0.1.2-1-x86_64.rpm
cwl-mount --help

Linux with DEB:

wget https://github.com/asimihsan/cwl-mount/releases/download/v0.1.2/cwl-mount-0.1.2-1-x86_64.deb
apt -y install gdebi
gdebi cwl-mount-0.1.2-1-x86_64.deb
cwl-mount --help

Mac:

# If this is the first time you've installed macfuse, you will need to restart after this.
brew install macfuse

mkdir $HOME/bin
wget https://github.com/asimihsan/cwl-mount/releases/download/v0.1.2/cwl-mount-0.1.2-darwin-x64_64.tar.gz
tar xvf cwl-mount-0.1.2-darwin-x64_64.tar.gz --directory $HOME/bin
$HOME/bin/cwl-mount --help

Credits

• This README file is based off of electron-markdownify.

Maintainer instructions

./release.sh combines all the steps below in the correct order.

Building runnable Docker container and publishing it

docker build --squash . --file Dockerfile.runnable --tag cwl-mount:latest

source ~/.aws_kitten_cat_credentials
aws ecr-public get-login-password --region us-east-1 | docker login --username AWS --password-stdin public.ecr.aws/kittencat
docker tag cwl-mount:latest public.ecr.aws/kittencat/cwl-mount:latest
docker push public.ecr.aws/kittencat/cwl-mount:latest

To run it:

docker run \
    --privileged \
    --interactive \
    --tty \
    --env-file $HOME/.aws_kitten_cat_credentials_docker \
    cwl-mount:latest

The contents of env-file are some credentials like:

AWS_ACCESS_KEY_ID=ABCDE
AWS_SECRET_ACCESS_KEY=fghij
AWS_REGION=us-west-2

Building RPM

docker build . --file Dockerfile.amazonlinux2 --tag cwl-mount-al2:latest

docker run \
    --privileged \
    --interactive \
    --tty \
    --volume "$(pwd):/workspace" \
    --workdir /workspace \
    --env-file $HOME/.aws_kitten_cat_credentials_docker \
    cwl-mount-al2:latest ./build_rpm.sh

rmdir /tmp/foo ; mkdir /tmp/foo
docker run \
    --cap-add SYS_ADMIN \
    --device /dev/fuse \
    --privileged \
    --interactive \
    --tty \
    --volume "$(pwd):/workspace" \
    --volume "/tmp/foo:/tmp/foo" \
    --workdir /workspace \
    --env-file $HOME/.aws_kitten_cat_credentials_docker \
    public.ecr.aws/amazonlinux/amazonlinux:2 ./test_rpm.sh

Building DEB

docker build . --file Dockerfile.debian --tag cwl-mount-debian:latest

docker run \
    --privileged \
    --interactive \
    --tty \
    --volume "$(pwd):/workspace" \
    --workdir /workspace \
    --env-file $HOME/.aws_kitten_cat_credentials_docker \
    cwl-mount-debian:latest ./build_deb.sh

Building for Mac

./build_mac.sh

Recording a demo

See: https://terminalizer.com/docs

npm install -g terminalizer

[ ! -d $HOME/demo ] && mkdir $HOME/demo
cd $HOME/demo
terminalizer record demo

# inside the demo...

tmux
# ...

cwl-mount --region us-west-2 list-log-groups
cwl-mount --region us-west-2 mount --log-group-filter '^babynames-preprod' --output-format '[$log_group_name] [$log_stream_name] [$timestamp] $message' /tmp/foo

# when you're done
CTRL-D

terminalizer render demo

# optimize it
brew install gifsicle

gifsicle --info render1639870257301.gif
gifsicle render1639870257301.gif \
    --colors 64 \
    --optimize=3 \
    --lossy=80 \
    --threads=4 \
    --disposal background \
    --no-conserve-memory \
    --output demo2.gif

References

How to set up Rust actors

• Rust actors, channels, tasks: https://ryhl.io/blog/actors-with-tokio/
• Rust channels and tasks: https://tokio.rs/tokio/tutorial/channels

License

Apache License 2.0