Systemd Journal CloudWatch Writer

This utility reads from the systemd journal, and sends the data in batches to Cloudwatch.

This is an alternative process to the AWS-provided logs agent. The AWS logs agent copies data from on-disk text log files into Cloudwatch. This utility systemd-cloud-watch reads the systemd journal and writes that data in batches to CloudWatch.

There are other ways to do this using various techniques. But depending on the size of log messages and size of the core parts these other methods are fragile. This utility allows you cap the log field size, include only the fields that you want, or exclude the fields you don't want. We find that this is not only useful but essential.

Log format

The journal event data is written to CloudWatch Logs in JSON format, making it amenable to filtering using the JSON filter syntax. Log records are translated to CloudWatch JSON events using a structure like the following:

Sample log

{
    "instanceId": "i-xxxxxxxx",
    "pid": 12354,
    "uid": 0,
    "gid": 0,
    "cmdName": "cron",
    "exe": "/usr/sbin/cron",
    "cmdLine": "/usr/sbin/CRON -f",
    "systemdUnit": "cron.service",
    "bootId": "fa58079c7a6d12345678b6ebf1234567",
    "hostname": "ip-10-1-0-15",
    "transport": "syslog",
    "priority": "INFO",
    "message": "pam_unix(cron:session): session opened for user root by (uid=0)",
    "syslog": {
        "facility": 10,
        "ident": "CRON",
        "pid": 12354
    },
    "kernel": {}
}

The JSON-formatted log events could also be exported into an AWS ElasticSearch instance using the CloudWatch sync mechanism. Once in ElasticSearch, you can use an ELK stack to obtain more elaborate filtering and query capabilities.

Installation

If you have a binary distribution, you just need to drop the executable file somewhere.

This tool assumes that it is running on an EC2 instance.

This tool uses libsystemd to access the journal. systemd-based distributions generally ship with this already installed, but if yours doesn't you must manually install the library somehow before this tool will work.

There are instructions on how to install the Linux requirements for development below see - Setting up a Linux env for testing/developing (CentOS7).

We also have two excellent examples of setting up a dev environment using bin.packer for both AWS EC2 and Docker. We setup CentoOS 7. The EC2 instance bin.packer build uses the aws command line to create and connect to a running image. These should be instructive for how to setup this utility in your environment to run with systemd as we provide all of the systemd scripts in the bin.packer provision scripts for EC2. An example is good. A running example is better.

Configuration

This tool uses a small configuration file to set some values that are required for its operation. Most of the configuration values are optional and have default settings, but a couple are required.

The configuration file uses a syntax like this:

log_group = "my-awesome-app"

The following configuration settings are supported:

aws_region: (Optional) The AWS region whose CloudWatch Logs API will be written to. If not provided, this defaults to the region where the host EC2 instance is running.
ec2_instance_id: (Optional) The id of the EC2 instance on which the tool is running. There is very little reason to set this, since it will be automatically set to the id of the host EC2 instance.
journal_dir: (Optional) Override the directory where the systemd journal can be found. This is useful in conjunction with remote log aggregation, to work with journals synced from other systems. The default is to use the local system's journal.
log_group: (Required) The name of the cloudwatch log group to write logs into. This log group must be created before running the program.
log_priority: (Optional) The highest priority of the log messages to read (on a 0-7 scale). This defaults to DEBUG (all messages). This has a behaviour similar to journalctl -p <priority>. At the moment, only a single value can be specified, not a range. Possible values are: 0,1,2,3,4,5,6,7 or one of the corresponding "emerg", "alert", "crit", "err", "warning", "notice", "info", "debug". When a single log level is specified, all messages with this log level or a lower (hence more important) log level are read and pushed to CloudWatch. For more information about priority levels, look at https://www.freedesktop.org/software/systemd/man/journalctl.html
log_stream: (Optional) The name of the cloudwatch log stream to write logs into. This defaults to the EC2 instance id. Each running instance of this application (along with any other applications writing logs into the same log group) must have a unique log_stream value. If the given log stream doesn't exist then it will be created before writing the first set of journal events.
buffer_size: (Optional) The size of the local event buffer where journal events will be kept in order to write batches of events to the CloudWatch Logs API. The default is 100. A batch of new events will be written to CloudWatch Logs every second even if the buffer does not fill, but this setting provides a maximum batch size to use when clearing a large backlog of events, e.g. from system boot when the program starts for the first time.
fields: (Optional) Specifies which fields should be included in the JSON map that is sent to CloudWatch.
omit_fields: (Optional) Specifies which fields should NOT be included in the JSON map that is sent to CloudWatch.
field_length: (Optional) Specifies how long string fileds can be in the JSON map that is sent to CloudWatch. The default is 255 characters.
debug: (Optional) Turns on debug logging.
local: (Optional) Used for unit testing. Will not try to create an AWS meta-data client to read region and AWS credentials.

AWS API access

This program requires access to call some of the Cloudwatch API functions. The recommended way to achieve this is to create an IAM Instance Profile that grants your EC2 instance a role that has Cloudwatch API access. The program will automatically discover and make use of instance profile credentials.

The following IAM policy grants the required access across all log groups in all regions:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "logs:CreateLogStream",
                "logs:PutLogEvents",
                "logs:DescribeLogStreams"
            ],
            "Resource": [
                "arn:aws:logs:*:*:log-group:*",
                "arn:aws:logs:*:*:log-group:*:log-stream:*"
            ]
        }
    ]
}

In more complex environments you may want to restrict further which regions, groups and streams the instance can write to. You can do this by adjusting the two ARN strings in the "Resource" section:

The first * in each string can be replaced with an AWS region name like us-east-1 to grant access only within the given region.
The * after log-group in each string can be replaced with a Cloudwatch Logs log group name to grant access only to the named group.
The * after log-stream in the second string can be replaced with a Cloudwatch Logs log stream name to grant access only to the named stream.

Other combinations are possible too. For more information, see the reference on ARNs and namespaces.

Coexisting with the official Cloudwatch Logs agent

This application can run on the same host as the official Cloudwatch Logs agent but care must be taken to ensure that they each use a different log stream name. Only one process may write into each log stream.

Running on System Boot

This program is best used as a persistent service that starts on boot and keeps running until the system is shut down. If you're using journald then you're presumably using systemd; you can create a systemd unit for this service. For example:

[Unit]
Description=journald-cloudwatch-logs
Wants=basic.target
After=basic.target network.target

[Service]
User=nobody
Group=nobody
ExecStart=/usr/local/bin/journald-cloudwatch-logs /usr/local/etc/journald-cloudwatch-logs.conf
KillMode=process
Restart=on-failure
RestartSec=42s

This program is designed under the assumption that it will run constantly from some point during system boot until the system shuts down.

If the service is stopped while the system is running and then later started again, it will "lose" any journal entries that were written while it wasn't running. However, on the initial run after each boot it will clear the backlog of logs created during the boot process, so it is not necessary to run the program particularly early in the boot process unless you wish to promptly capture startup messages.

Building

Test cloud-watch package

go test -v  github.com/advantageous/systemd-cloud-watch/cloud-watch

Build and Test on Linux (Centos7)

 ./run_build_linux.sh

The above starts up a docker container, runs go get, go build, go test and then copies the binary to systemd-cloud-watch_linux.

Debug process running Linux

 ./run_test_container.sh

The above starts up a docker container that you can develop with that has all the prerequisites needed to compile and test this project.

Sample debug session

$ ./run_test_container.sh
latest: Pulling from advantageous/golang-cloud-watch
Digest: sha256:eaf5c0a387aee8cc2d690e1c5e18763e12beb7940ca0960ce1b9742229413e71
Status: Image is up to date for advantageous/golang-cloud-watch:latest
[root@6e0d1f984c03 /]# cd gopath/src/github.com/advantageous/systemd-cloud-watch/
.git/                      README.md                  cloud-watch/               bin.packer/                    sample.conf
.gitignore                 build_linux.sh             main.go                    run_build_linux.sh         systemd-cloud-watch.iml    
.idea/                     cgroup/                    output.json                run_test_container.sh      systemd-cloud-watch_linux  

[root@6e0d1f984c03 /]# cd gopath/src/github.com/advantageous/systemd-cloud-watch/

[root@6e0d1f984c03 systemd-cloud-watch]# ls
README.md  build_linux.sh  cgroup  cloud-watch  main.go  output.json  bin.packer  run_build_linux.sh
run_test_container.sh  sample.conf  systemd-cloud-watch.iml  systemd-cloud-watch_linux

[root@6e0d1f984c03 systemd-cloud-watch]# source ~/.bash_profile

[root@6e0d1f984c03 systemd-cloud-watch]# export GOPATH=/gopath

[root@6e0d1f984c03 systemd-cloud-watch]# /usr/lib/systemd/systemd-journald &
[1] 24

[root@6e0d1f984c03 systemd-cloud-watch]# systemd-cat echo "RUNNING JAVA BATCH JOB - ADF BATCH from `pwd`"

[root@6e0d1f984c03 systemd-cloud-watch]# echo "Running go clean"
Running go clean

[root@6e0d1f984c03 systemd-cloud-watch]# go clean

[root@6e0d1f984c03 systemd-cloud-watch]# echo "Running go get"
Running go get

[root@6e0d1f984c03 systemd-cloud-watch]# go get

[root@6e0d1f984c03 systemd-cloud-watch]# echo "Running go build"
Running go build
[root@6e0d1f984c03 systemd-cloud-watch]# go build

[root@6e0d1f984c03 systemd-cloud-watch]# echo "Running go test"
Running go test

[root@6e0d1f984c03 systemd-cloud-watch]# go test -v github.com/advantageous/systemd-cloud-watch/cloud-watch
=== RUN   TestRepeater
config DEBUG: 2016/11/30 08:53:34 config.go:66: Loading log...
aws INFO: 2016/11/30 08:53:34 aws.go:42: Config set to local
aws INFO: 2016/11/30 08:53:34 aws.go:72: Client missing credentials not looked up
aws INFO: 2016/11/30 08:53:34 aws.go:50: Client missing using config to set region
aws INFO: 2016/11/30 08:53:34 aws.go:52: AWSRegion missing using default region us-west-2
repeater ERROR: 2016/11/30 08:53:44 cloudwatch_journal_repeater.go:141: Error from putEvents NoCredentialProviders: no valid providers in chain. Deprecated.
    For verbose messaging see aws.Config.CredentialsChainVerboseErrors
--- SKIP: TestRepeater (10.01s)
    cloudwatch_journal_repeater_test.go:43: Skipping WriteBatch, you need to setup AWS credentials for this to work
=== RUN   TestConfig
test DEBUG: 2016/11/30 08:53:44 config.go:66: Loading log...
test INFO: 2016/11/30 08:53:44 config_test.go:33: [Foo Bar]
--- PASS: TestConfig (0.00s)
=== RUN   TestLogOmitField
test DEBUG: 2016/11/30 08:53:44 config.go:66: Loading log...
--- PASS: TestLogOmitField (0.00s)
=== RUN   TestNewJournal
--- PASS: TestNewJournal (0.00s)
=== RUN   TestSdJournal_Operations
--- PASS: TestSdJournal_Operations (0.00s)
    journal_linux_test.go:41: Read value=Runtime journal is using 8.0M (max allowed 4.0G, trying to leave 4.0G free of 55.1G available → current limit 4.0G).
=== RUN   TestNewRecord
test DEBUG: 2016/11/30 08:53:44 config.go:66: Loading log...
--- PASS: TestNewRecord (0.00s)
=== RUN   TestLimitFields
test DEBUG: 2016/11/30 08:53:44 config.go:66: Loading log...
--- PASS: TestLimitFields (0.00s)
=== RUN   TestOmitFields
test DEBUG: 2016/11/30 08:53:44 config.go:66: Loading log...
--- PASS: TestOmitFields (0.00s)
PASS
ok      github.com/advantageous/systemd-cloud-watch/cloud-watch 10.017s

Building the docker image to build the linux instance to build this project

# from project root
cd bin.packer
bin.packer build packer_docker.json

To run docker dev image

# from project root
cd bin.packer
./run.sh

Building the ec2 image with bin.packer to build the linux instance to build this project

# from project root
cd bin.packer
bin.packer build packer_ec2.json

We use the docker support for bin.packer. ("Packer is a tool for creating machine and container images for multiple platforms from a single source configuration.")

Use ec2_env.sh_example to create a ec2_env.sh with the instance id that was just created.

ec2_env.sh_example

#!/usr/bin/env bash
export ami=ami-YOURAMI
export subnet=subnet-YOURSUBNET
export security_group=sg-YOURSG
export iam_profile=YOUR_IAM_ROLE
export key_name=MY_PEM_FILE_KEY_NAME

Using EC2 image (assumes you have ~/.ssh config setup)

# from project root
cd bin.packer

# Run and log into dev env running in EC2
./runEc2Dev.sh

# Log into running server
./loginIntoEc2Dev.sh

Setting up a Linux env for testing/developing (CentOS7).

yum -y install wget
yum install -y git
yum install -y gcc
yum install -y systemd-devel


echo "installing go"
cd /tmp
wget https://storage.googleapis.com/golang/go1.7.3.linux-amd64.tar.gz
tar -C /usr/local/ -xzf go1.7.3.linux-amd64.tar.gz
rm go1.7.3.linux-amd64.tar.gz
echo 'export PATH=$PATH:/usr/local/go/bin' >> ~/.bash_profile

Setting up Java to write to systemd journal

gradle build

compile 'org.gnieh:logback-journal:0.2.0'

logback.xml

<?xml version="1.0" encoding="UTF-8"?>
<configuration>

    <appender name="journal" class="org.gnieh.logback.SystemdJournalAppender" />

    <root level="INFO">
        <appender-ref ref="journal" />
        <customFields>{"serviceName":"adfCalcBatch","serviceHost":"${HOST}"}</customFields>
    </root>


    <logger name="com.mycompany" level="INFO"/>

</configuration>

Commands for controlling systemd service EC2 dev env

# Get status
sudo systemctl status journald-cloudwatch
# Stop Service
sudo systemctl stop journald-cloudwatch
# Find the service
ps -ef | grep cloud
# Run service manually
/usr/bin/systemd-cloud-watch_linux /etc/journald-cloudwatch.conf

Derived

This is based on advantageous journald-cloudwatch-logs which was forked from saymedia journald-cloudwatch-logs.

Status

It is close to being done.

Improvements:

Added unit tests (there were none).
Added cross compile so I can develop/test on my laptop (MacOS).
Made logging stateless. No more need for a state file.
No more getting out of sync with CloudWatch.
Detects being out of sync and recovers.
Fixed error with log messages being too big.
Added ability to include or omit logging fields.
Created docker image and scripts to test on Linux (CentOS7).
Created EC2 image and scripts to test on Linux running in AWS EC2 (CentOS7).
Code organization (we use a package).
Added comprehensive logging which includes debug logging by config.
Uses actual timestamp from journal log record instead of just current time
Auto-creates CloudWatch log group if it does not exist

License

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.