exec
The
in_exec Input plugin executes external programs to receive or pull event logs. It will then read TSV (tab-separated values), JSON or MessagePack from the standard output of the program.You can run a program periodically or permanently. To run periodically, please use the
run_interval parameter.It is included in Fluentd's core.
<source>
@type exec
command cmd arg arg
<parse>
keys k1,k2,k3
</parse>
<extract>
tag_key k1
time_key k2
time_format %Y-%m-%d %H:%M:%S
</extract>
run_interval 10s
</source>
Refer to the Configuration File article for the basic structure and syntax of the configuration file.
The value must be
exec.type | default | version |
string | required parameter | 0.14.0 |
The command (program) to execute.
type | default | version |
string | required if extract/tag_key is not specified | 0.14.0 |
The tag of the output events.
type | default | version |
time | nil | 0.14.0 |
The interval time between periodic program runs. If not specified, command script runs only once.
type | default | version |
size | 10240 | 0.14.9 |
The default block size to read if parser requires partial read.
type | default | available values | version |
enum | read | read/read_with_stderr | 1.11.3 |
Control target IO:
read: Read logs from stdioread_with_stderr: Read logs from stdio and stderr.
read_with_stderr is mainly for debug.required | multi | version |
false | false | 0.14.9 |
Refer these for more details about
parse section:type | default | version |
string | tsv | 0.14.9 |
Overwrites the default value in this plugin.
type | default | version |
string | float | 0.14.9 |
Overwrites the default value in this plugin.
type | default | version |
string | nil | 0.14.9 |
Overwrites the default value in this plugin.
type | default | version |
bool | false | 0.14.9 |
Overwrites the default value in this plugin.
required | multi | version |
false | false | 0.14.9 |
type | default | version |
string | float | 0.14.9 |
Overwrites the default value in this plugin.
Here is a simple example to fetch load average stats on Linux systems. This configuration instructs Fluentd to read
/proc/loadavg once per minute and emit the file content as events.<source>
@type exec
tag system.loadavg
command cat /proc/loadavg | cut -d ' ' -f 1,2,3
run_interval 1m
<parse>
@type tsv
keys avg1,avg5,avg15
delimiter " "
</parse>
</source>
This configuration emits events like this one:
2018-06-29 17:27:35.115878527 +0900 system.loadavg: {"avg1":"0.30","avg5":"0.20","avg15":"0.05"}
If you already have a script that runs periodically (say, via
cron) that you wish to store the output to multiple backend systems (HDFS, AWS, Elasticsearch, etc.), in_exec is a great choice.The only requirement for the script is that it outputs TSV, JSON or MessagePack.
For example, this script scrapes the front page of Hacker News and scrapes information about each post:
Suppose that script is called
hn.rb. Then, you can run it every 5 minutes with the following configuration:<source>
@type exec
<parse>
@type json
</parse>
tag hackernews
command ruby /path/to/hn.rb
run_interval 5m # don't hit HN too frequently!
</source>
<match hackernews>
@type stdout
</match>
And if you run Fluentd with it, you will see the following output (if you are impatient,
CTRL+C to flush the stdout buffer):2017-12-08 14:19:33.160567411 +0900 hackernews: {"time":1512710373,"rank":1,"title":"Japan eyes startup visa program","points":160,"user_name":"benguild","duration":"4 hours ago ","num_comments":0,"unique_id":"item?id=15875627","hiring_notice":false}
2017-12-08 14:19:33.160735378 +0900 hackernews: {"time":1512710373,"rank":2,"title":"Bookbinding: A Tutorial","points":46,"user_name":"jstrieb","duration":"2 hours ago ","num_comments":0,"unique_id":"item?id=15876260","hiring_notice":false}
2017-12-08 14:19:33.160769125 +0900 hackernews: {"time":1512710373,"rank":3,"title":"My Quadriplegic Husband and Me","points":92,"user_name":"mooreds","duration":"4 hours ago ","num_comments":0,"unique_id":"item?id=15875772","hiring_notice":false}
2017-12-08 14:19:33.160799115 +0900 hackernews: {"time":1512710373,"rank":4,"title":"Wall Street banks hit pause button on Bitcoin","points":16,"user_name":"tadasv","duration":"1 hour ago ","num_comments":0,"unique_id":"item?id=15876497","hiring_notice":false}
2017-12-08 14:19:33.160824386 +0900 hackernews: {"time":1512710373,"rank":5,"title":"A Spectator Who Threw a Wrench in the Waymo/Uber Lawsuit","points":107,"user_name":"kynthelig","duration":"4 hours ago ","num_comments":0,"unique_id":"item?id=15875685","hiring_notice":false}
Of course, you can use Fluentd's many output plugins to store the data into various backend systems like Elasticsearch, HDFS, MongoDB, AWS, etc.
If this article is incorrect or outdated, or omits critical information, please let us know. Fluentd is an open-source project under Cloud Native Computing Foundation (CNCF). All components are available under the Apache 2 License.
Last modified 2yr ago