Splunk logging driver
Estimated reading time: 7 minutesThe splunk
logging driver sends container logs to
HTTP Event Collector
in Splunk Enterprise and Splunk Cloud.
Usage
You can configure Docker logging to use the splunk
driver by default or on a
per-container basis.
To use the splunk
driver as the default logging driver, set the keys
log-driver
and log-opts
to appropriate values in the daemon.json
configuration file and restart Docker. For example:
{
"log-driver": "splunk",
"log-opts": {
"splunk-token": "",
"splunk-url": "",
...
}
}
The daemon.json file 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.
Note:
log-opt
configuration options in thedaemon.json
configuration file must be provided as strings. Boolean and numeric values (such as the value forsplunk-gzip
orsplunk-gzip-level
) must therefore be enclosed in quotes ("
).
To use the splunk
driver for a specific container, use the commandline flags
--log-driver
and log-opt
with docker run
:
docker run --log-driver=splunk --log-opt splunk-token=VALUE --log-opt splunk-url=VALUE ...
Splunk options
The following properties let you configure the splunk logging driver.
- To configure the
splunk
driver across the Docker environment, editdaemon.json
with the key,"log-opts": {"NAME": "VALUE", ...}
. - To configure the
splunk
driver for an individual container, usedocker run
with the flag,--log-opt NAME=VALUE ...
.
Option | Required | Description |
---|---|---|
splunk-token |
required | Splunk HTTP Event Collector token. |
splunk-url |
required | Path to your Splunk Enterprise, self-service Splunk Cloud instance, or Splunk Cloud managed cluster (including port and scheme used by HTTP Event Collector) in one of the following formats: https://your_splunk_instance:8088 or https://input-prd-p-XXXXXXX.cloud.splunk.com:8088 or https://http-inputs-XXXXXXXX.splunkcloud.com . |
splunk-source |
optional | Event source. |
splunk-sourcetype |
optional | Event source type. |
splunk-index |
optional | Event index. |
splunk-capath |
optional | Path to root certificate. |
splunk-caname |
optional | Name to use for validating server certificate; by default the hostname of the splunk-url is used. |
splunk-insecureskipverify |
optional | Ignore server certificate validation. |
splunk-format |
optional | Message format. Can be inline , json or raw . Defaults to inline . |
splunk-verify-connection |
optional | Verify on start, that docker can connect to Splunk server. Defaults to true. |
splunk-gzip |
optional | Enable/disable gzip compression to send events to Splunk Enterprise or Splunk Cloud instance. Defaults to false. |
splunk-gzip-level |
optional | Set compression level for gzip. Valid values are -1 (default), 0 (no compression), 1 (best speed) ... 9 (best compression). Defaults to DefaultCompression. |
tag |
optional | Specify tag for message, which interpret some markup. Default value is {{.ID}} (12 characters of the container ID). Refer to the log tag option documentation for customizing the log tag format. |
labels |
optional | Comma-separated list of keys of labels, which should be included in message, if these labels are specified for container. |
env |
optional | Comma-separated list of keys of environment variables, which should be included in message, if these variables are specified for container. |
env-regex |
optional | Similar to and compatible with env . A regular expression to match logging-related environment variables. Used for advanced log tag options. |
If there is collision between the label
and env
keys, the value of the env
takes precedence. Both options add additional fields to the attributes of a
logging message.
Below is an example of the logging options specified for the Splunk Enterprise instance. The instance is installed locally on the same machine on which the Docker daemon is running.
The path to the root certificate and Common Name is specified using an HTTPS
scheme. This is used for verification. The SplunkServerDefaultCert
is
automatically generated by Splunk certificates.
$ docker run --log-driver=splunk \
--log-opt splunk-token=176FCEBF-4CF5-4EDF-91BC-703796522D20 \
--log-opt splunk-url=https://splunkhost:8088 \
--log-opt splunk-capath=/path/to/cert/cacert.pem \
--log-opt splunk-caname=SplunkServerDefaultCert \
--log-opt tag="{{.Name}}/{{.FullID}}" \
--log-opt labels=location \
--log-opt env=TEST \
--env "TEST=false" \
--label location=west \
your/application
The splunk-url
for Splunk instances hosted on Splunk Cloud is in a format
like https://http-inputs-XXXXXXXX.splunkcloud.com
and does not include a
port specifier.
Message formats
There are three logging driver messaging formats: inline
(default), json
,
and raw
.
The default format is inline
where each log message is embedded as a string.
For example:
{
"attrs": {
"env1": "val1",
"label1": "label1"
},
"tag": "MyImage/MyContainer",
"source": "stdout",
"line": "my message"
}
{
"attrs": {
"env1": "val1",
"label1": "label1"
},
"tag": "MyImage/MyContainer",
"source": "stdout",
"line": "{\"foo\": \"bar\"}"
}
Note: If your messages are JSON objects, you may want to embed them in the message we send to Splunk.
To format messages as json
objects, set --log-opt splunk-format=json
. The
driver trys to parse every line as a JSON object and send it as an embedded
object. If it cannot parse the message, it is sent inline
. For example:
{
"attrs": {
"env1": "val1",
"label1": "label1"
},
"tag": "MyImage/MyContainer",
"source": "stdout",
"line": "my message"
}
{
"attrs": {
"env1": "val1",
"label1": "label1"
},
"tag": "MyImage/MyContainer",
"source": "stdout",
"line": {
"foo": "bar"
}
}
To format messages as raw
, set --log-opt splunk-format=raw
. Attributes
(environment variables and labels) and tags are prefixed to the message. For
example:
MyImage/MyContainer env1=val1 label1=label1 my message
MyImage/MyContainer env1=val1 label1=label1 {"foo": "bar"}
Advanced options
Splunk Logging Driver allows you to configure few advanced options by specifying next environment variables for the Docker daemon.
Environment variable name | Default value | Description |
---|---|---|
SPLUNK_LOGGING_DRIVER_POST_MESSAGES_FREQUENCY |
5s |
If there is nothing to batch how often driver posts messages. You can think about this as the maximum time to wait for more messages to batch. |
SPLUNK_LOGGING_DRIVER_POST_MESSAGES_BATCH_SIZE |
1000 |
How many messages driver should wait before sending them in one batch. |
SPLUNK_LOGGING_DRIVER_BUFFER_MAX |
10 * 1000 |
If driver cannot connect to remote server, what is the maximum amount of messages it can hold in buffer for retries. |
SPLUNK_LOGGING_DRIVER_CHANNEL_SIZE |
4 * 1000 |
How many pending messages can be in the channel which is used to send messages to background logger worker, which batches them. |