Amazon CloudWatch Logs logging driver
Estimated reading time: 8 minutesThe awslogs
logging driver sends container logs to
Amazon CloudWatch Logs.
Log entries can be retrieved through the AWS Management
Console or the AWS SDKs
and Command Line Tools.
Usage
To use the awslogs
driver as the default logging driver, set the log-driver
and log-opt
keys to appropriate values in the daemon.json
file, which is
located in /etc/docker/
on Linux hosts or
C:\ProgramData\docker\config\daemon.json
on Windows Server. For more about
configuring Docker using daemon.json
, see
daemon.json.
The following example sets the log driver to awslogs
and sets the
awslogs-region
option.
{
"log-driver": "awslogs",
"log-opts": {
"awslogs-region": "us-east-1"
}
}
Restart Docker for the changes to take effect.
You can set the logging driver for a specific container by using the
--log-driver
option to docker run
:
docker run --log-driver=awslogs ...
Amazon CloudWatch Logs options
You can add logging options to the daemon.json
to set Docker-wide defaults,
or use the --log-opt NAME=VALUE
flag to specify Amazon CloudWatch Logs
logging driver options when starting a container.
awslogs-region
The awslogs
logging driver sends your Docker logs to a specific region. Use
the awslogs-region
log option or the AWS_REGION
environment variable to set
the region. By default, if your Docker daemon is running on an EC2 instance
and no region is set, the driver uses the instance’s region.
docker run --log-driver=awslogs --log-opt awslogs-region=us-east-1 ...
awslogs-group
You must specify a
log group
for the awslogs
logging driver. You can specify the log group with the
awslogs-group
log option:
docker run --log-driver=awslogs --log-opt awslogs-region=us-east-1 --log-opt awslogs-group=myLogGroup ...
awslogs-stream
To configure which
log stream
should be used, you can specify the awslogs-stream
log option. If not
specified, the container ID is used as the log stream.
Note: Log streams within a given log group should only be used by one container at a time. Using the same log stream for multiple containers concurrently can cause reduced logging performance.
awslogs-create-group
Log driver returns an error by default if the log group does not exist. However, you can set the
awslogs-create-group
to true
to automatically create the log group as needed.
The awslogs-create-group
option defaults to false
.
$ docker run --log-driver=awslogs \
--log-opt awslogs-region=us-east-1 \
--log-opt awslogs-group=myLogGroup \
--log-opt awslogs-create-group=true \
...
Note: Your AWS IAM policy must include the
logs:CreateLogGroup
permission before you attempt to useawslogs-create-group
.
awslogs-datetime-format
The awslogs-datetime-format
option defines a multiline start pattern in Python
strftime
format. A log message consists of a line that
matches the pattern and any following lines that don’t match the pattern. Thus
the matched line is the delimiter between log messages.
One example of a use case for using this format is for parsing output such as a stack dump, which might otherwise be logged in multiple entries. The correct pattern allows it to be captured in a single entry.
This option always takes precedence if both awslogs-datetime-format
and
awslogs-multiline-pattern
are configured.
Note: Multiline logging performs regular expression parsing and matching of all log messages, which may have a negative impact on logging performance.
Consider the following log stream, where new log messages start with a timestamp:
[May 01, 2017 19:00:01] A message was logged
[May 01, 2017 19:00:04] Another multiline message was logged
Some random message
with some random words
[May 01, 2017 19:01:32] Another message was logged
The format can be expressed as a strftime
expression of
[%b %d, %Y %H:%M:%S]
, and the awslogs-datetime-format
value can be set to
that expression:
$ docker run --log-driver=awslogs \
--log-opt awslogs-region=us-east-1 \
--log-opt awslogs-group=myLogGroup \
--log-opt awslogs-datetime-format='\[%b %d, %Y %H:%M:%S\]' \
...
This parses the logs into the following CloudWatch log events:
# First event
[May 01, 2017 19:00:01] A message was logged
# Second event
[May 01, 2017 19:00:04] Another multiline message was logged
Some random message
with some random words
# Third event
[May 01, 2017 19:01:32] Another message was logged
The following strftime
codes are supported:
Code | Meaning | Example |
---|---|---|
%a |
Weekday abbreviated name. | Mon |
%A |
Weekday full name. | Monday |
%w |
Weekday as a decimal number where 0 is Sunday and 6 is Saturday. | 0 |
%d |
Day of the month as a zero-padded decimal number. | 08 |
%b |
Month abbreviated name. | Feb |
%B |
Month full name. | February |
%m |
Month as a zero-padded decimal number. | 02 |
%Y |
Year with century as a decimal number. | 2008 |
%y |
Year without century as a zero-padded decimal number. | 08 |
%H |
Hour (24-hour clock) as a zero-padded decimal number. | 19 |
%I |
Hour (12-hour clock) as a zero-padded decimal number. | 07 |
%p |
AM or PM. | AM |
%M |
Minute as a zero-padded decimal number. | 57 |
%S |
Second as a zero-padded decimal number. | 04 |
%L |
Milliseconds as a zero-padded decimal number. | .123 |
%f |
Microseconds as a zero-padded decimal number. | 000345 |
%z |
UTC offset in the form +HHMM or -HHMM. | +1300 |
%Z |
Time zone name. | PST |
%j |
Day of the year as a zero-padded decimal number. | 363 |
awslogs-multiline-pattern
The awslogs-multiline-pattern
option defines a multiline start pattern using a
regular expression. A log message consists of a line that matches the pattern
and any following lines that don’t match the pattern. Thus the matched line is
the delimiter between log messages.
This option is ignored if awslogs-datetime-format
is also configured.
Note: Multiline logging performs regular expression parsing and matching of all log messages. This may have a negative impact on logging performance.
For example, to process the following log stream where new log messages start with the pattern INFO
:
Consider the following log stream, where each log message should start with the
patther INFO
:
INFO A message was logged
INFO Another multiline message was logged
Some random message
INFO Another message was logged
You can use the regular expression of ^INFO
:
$ docker run --log-driver=awslogs \
--log-opt awslogs-region=us-east-1 \
--log-opt awslogs-group=myLogGroup \
--log-opt awslogs-multiline-pattern='^INFO' \
...
This parses the logs into the following CloudWatch log events:
# First event
INFO A message was logged
# Second event
INFO Another multiline message was logged
Some random message
# Third event
INFO Another message was logged
tag
Specify tag
as an alternative to the awslogs-stream
option. tag
interprets Go template markup, such as {{.ID}}
, {{.FullID}}
or {{.Name}}
docker.{{.ID}}
.
See the tag option documentation for details on all supported template substitutions.
When both awslogs-stream
and tag
are specified, the value supplied for awslogs-stream
overrides the template specified with tag
.
If not specified, the container ID is used as the log stream.
Note: The CloudWatch log API doesn’t support
:
in the log name. This can cause some issues when using the{{ .ImageName }}
as a tag, since a docker image has a format ofIMAGE:TAG
, such asalpine:latest
. Template markup can be used to get the proper format. To get the image name and the first 12 characters of the container ID, you can use:--log-opt tag='{{ with split .ImageName ":" }}{{join . "_"}}{{end}}-{{.ID}}'
the output is something like:alpine_latest-bf0072049c76
Credentials
You must provide AWS credentials to the Docker daemon to use the awslogs
logging driver. You can provide these credentials with the AWS_ACCESS_KEY_ID
,
AWS_SECRET_ACCESS_KEY
, and AWS_SESSION_TOKEN
environment variables, the
default AWS shared credentials file (~/.aws/credentials
of the root user), or
(if you are running the Docker daemon on an Amazon EC2 instance) the Amazon EC2
instance profile.
Credentials must have a policy applied that allows the logs:CreateLogStream
and logs:PutLogEvents
actions, as shown in the following example.
{
"Version": "2012-10-17",
"Statement": [
{
"Action": [
"logs:CreateLogStream",
"logs:PutLogEvents"
],
"Effect": "Allow",
"Resource": "*"
}
]
}