tag parameter is required

[Aaron Todd]

Hello all!

Just starting out with fluentd and am attempting to configure for inbound tcp using the tcp input plugin.  When I add the config t throws an error about the 'tag' parameter being required.  Unfortunately I do not see anything about the tag parameter in the documentation.  Anyone have any ideas about this message?  The config is below:

<source>
  type tcp
  port 514
<source>

And the error:

# /etc/init.d/td-agent start
Starting td-agent: 2015-05-18 13:13:41 -0400 [error]: fluent/supervisor.rb:273:rescue in main_process: config error file="/etc/td-agent/td-agent.conf" error="'tag' parameter is required"

[Mr. Fiber]

Hi Aaron,

Sorry, this is the mistake of fluentd document.

in_tcp article didn't mention tag parameter.

I just updated the document.

http://docs.fluentd.org/articles/in_tcp

Masahiro

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[Aaron Todd]

Masahiro,

Thanks!  Do  you have a quick link to the different types of "tags"?  I've been poking around the docs, but haven't found anything that describes the different strings and their meaning.

Thanks again!

Aaron

[Mr. Fiber]

For tag and routing,

http://docs.fluentd.org/articles/config-file article describes how to use tag with input plugins.

Masahiro

--

[Aaron Todd]

Masahiro,

Thanks for the link.  I believe I skimed over that, but since you linked me back to that page i've given it a good read.  I still dont quite understand though... 

I understand how the following config:

<match debug.**>
  type stdout
</match>
<source>
  type debug_agent
  bind 127.0.0.1
  port 24230
</source>

would match the command:  curl -X POST -d 'json={"json":"message"}' http://localhost:8888/debug.test

But if I add the following to the config:

<match at.test>
  type file
  path /var/log/td-agent/test
</match>

and change my command to curl -X POST -d 'json={"json":"message"}' http://localhost:8888/at.test nothing happens.  Any idea what am I missing?

Thanks again!

[Aaron Todd]

Masahiro,

As usual, the more I tinker the more I figure it out.  I think its starting to make sense.  I think the problem with my previous post is a separate issue with the  out_file plugin.  I changed it to the out_stdout plugin and now it matches and writes to the main log file.  So I'm not sure why it didn't write to the test file I specified, but its not a huge concern as it was only a test.  

So correct me if I'm wrong, but the "tag" parameter inside the in_tcp plugin seems to be only used for internal routing.  I can send anything at it on the listening port and it seems to match because of the "tag" parameter inside the tcp_plugin config.  Is that a safe assumption?

Thanks!

Aaron

[Mr. Fiber]

> I think the problem with my previous post is a separate issue with the  out_file plugin.

file output plugin is buffered output and it takes a time to flush.

See article: http://docs.fluentd.org/articles/out_file

>  Is that a safe assumption?

Yes. in_tcp receives logs and parses it. Parsed events are send to output plugin with 'tag' value.

--

[Lance N.]

There are 3 kinds of data passed between plugins: keys, values, and tag wildcards. Different plugins let you add, delete keys and change key values. Wildcards on tags give you a third "channel" to pass data. The channel is at the record level instead of the field level, and is narrow. 

As an example, the in_file plugin adds the full path of the file to the tag if you use a wildcard:

<source>

  type tail

  format json

  path /var/log/bugs/*.log

  pos_file /var/log/td-agent/bugs.pos

  tag bugs_infile.*

</source>

<match bugs_infile.*>

        filename ${tag_parts[4]}.log

</match>

If this fetches a new line from /var/log/bugs/alpha.log, the second tag will match "bugs_infile.var.log.bugs.alpha.log" and will add a field "filename":"alpha.log" because tag_parts[4] (counting from 0) is "alpha".

I have used tag wildcards to do complex matrix-based dispatching.