open-nomad/website/source/docs/operating-a-job/accessing-logs.html.md

---
layout: "docs"
page_title: "Accessing Logs - Operating a Job"
sidebar_current: "docs-operating-a-job-accessing-logs"
description: |-
  Nomad provides a top-level mechanism for viewing application logs and data
  files via the command line interface. This section discusses the nomad logs
  command and API interface.
---

# Accessing Logs

Viewing application logs is critical for debugging issues, examining performance
problems, or even just verifying the application started correctly. To make this
as simple as possible, Nomad provides:

- Job specification for [log rotation](/docs/jobspec/index.html#log_rotation)
- CLI command for [log viewing](/docs/commands/logs.html)
- API for programatic [log access](/docs/http/client-fs.html#logs)

This section will utilize the job named "docs" from the [previous
sections](/docs/operating-a-job/submitting-jobs.html), but these operations
and command largely apply to all jobs in Nomad.

As a reminder, here is the output of the run command from the previous example:

```text
$ nomad run docs.nomad
==> Monitoring evaluation "42d788a3"
    Evaluation triggered by job "docs"
    Allocation "04d9627d" created: node "a1f934c9", group "example"
    Allocation "e7b8d4f5" created: node "012ea79b", group "example"
    Allocation "5cbf23a1" modified: node "1e1aa1e0", group "example"
    Evaluation status changed: "pending" -> "complete"
==> Evaluation "42d788a3" finished with status "complete"
```

The provided allocation ID (which is also available via the `nomad status`
command) is required to access the application's logs. To access the logs of our
application, we issue the following command:

```shell
$ nomad logs 04d9627d
```

The output will look something like this:

```text
<timestamp> 10.1.1.196:5678 10.1.1.196:33407 "GET / HTTP/1.1" 200 12 "curl/7.35.0" 21.809µs
<timestamp> 10.1.1.196:5678 10.1.1.196:33408 "GET / HTTP/1.1" 200 12 "curl/7.35.0" 20.241µs
<timestamp> 10.1.1.196:5678 10.1.1.196:33409 "GET / HTTP/1.1" 200 12 "curl/7.35.0" 13.629µs
```

By default, this will return the logs of the task. If more than one task is
defined in the job file, the name of the task is a required argument:

```shell
$ nomad logs 04d9627d server
```

The logs command supports both displaying the logs as well as following logs,
blocking for more output, similar to `tail -f`. To follow the logs, use the
`-tail` flag:

```shell
$ nomad logs -tail 04d9627d
```

This will stream logs to our console.

By default, only the logs on stdout are displayed. To show the log output from
stderr, use the `-stderr` flag:

```shell
$ nomad logs -stderr 04d9627d
```

## Log Shipper Pattern

While the logs command works well for quickly accessing application logs, it
generally does not scale to large systems or systems that produce a lot of log
output, especially for the long-term storage of logs. Nomad only retains log
files for a configurable period of time, so chatty applications should use a
better log retention strategy.

Since applications log to the `alloc/` directory, all tasks within the same task
group have access to each others logs. Thus it is possible to have a task group
as follows:

```hcl
group "my-group" {
  task "server" {
    # ...
  }

  task "log-shipper" {
    # ...
  }
}
```

In the above example, the `server` task is the application that should be run
and will be producing the logs. The `log-shipper` reads those logs from the
`alloc/logs/` directory and sends them to a longer-term storage solution such as
Amazon S3 or an internal log aggregation system.