# Trouble Shooting

## Look at Logs

If things aren't happening as expected, please first look at your logs. For td-agent (rpm/deb), the logs are located at `/var/log/td-agent/td-agent.log`.

## Turn on Verbose Logging

You can get more information about the logs if verbose logging is turned on. Please follow the steps below.

### rpm/deb

1. Open the service setting file for td-agent (see below for its file

   path).
2. Add `-vv` to TD\_AGENT\_OPTIONS.
3. Restart td-agent.

   ```
   # Add the following settings to:
   # - /etc/sysconfig/td-agent (CentOS/RedHat)
   # - /etc/default/td-agent (Debian/Ubuntu)
   TD_AGENT_OPTIONS="-vv"
   ```

Note: The environment variable TD\_AGENT\_OPTIONS has been introduced in td-agent v2.2.1. If you are using an older version of td-agent, you need to edit `/etc/init.d/td-agent` and insert `-vv` options to TD\_AGENT\_ARGS or DAEMON\_ARGS manually.

### gem

Please add `-vv` to your command line.

```
$ fluentd .. -vv
```

## Dump fluentd internal information

Fluentd uses [sigdump](https://github.com/frsyuki/sigdump) for dumping fluentd internal information to local file, e.g. thread dump, object allocation and etc. If you have a problem with fluentd like process hang, please send `SIGCONT` to fluentd parent and child processes.

## High CPU usage issue

If fluentd suddenly hits unexpected high CPU usage problem, there are several reasons:

* a plugin has a race condition or similar bug
* dependent gems have a bug
* regular expression with broken data
* system calls has a bug, e.g. `inotify` with lots of files

In such cases, you can use `perf` tool on recent Linux to investigate the problem. See [Linux perf Examples](http://www.brendangregg.com/perf.html) page. If you want to know which call causes the problem, [pid2line.rb](https://gist.github.com/nurse/0619b6af90df140508c2) is useful.

## Check uncaught logs

You sometimes hit unexpected shutdown with non-zero exit status like below.

```
2016-01-01 00:00:00 +0800 [info]: starting fluentd-0.12.28
2016-01-01 00:00:00 +0800 [info]: reading config file path="/etc/td-agent/td-agent.conf"
[...snip...]
2016-01-01 00:00:02 +0800 [info]: process finished code=6
```

If the problem happens inside ruby, e.g. segmentation fault, C extension bug, etc, you can't get entire log when fluentd process is daemonized. For example, td-agent launches fluentd with `--daemon` option. In td-agent case, you can get entire log using following command to simulate `/etc/init.d/td-agent start` without daemonize.

```
$ sudo LD_PRELOAD=/opt/td-agent/embedded/lib/libjemalloc.so /usr/sbin/td-agent -c /etc/td-agent/td-agent.conf --user td-agent --group td-agent
```

If this article is incorrect or outdated, or omits critical information, please [let us know](https://github.com/fluent/fluentd-docs-gitbook/issues?state=open). [Fluentd](http://www.fluentd.org/) is a open source project under [Cloud Native Computing Foundation (CNCF)](https://cncf.io/). All components are available under the Apache 2 License.


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