91 lines
2.9 KiB
Markdown
91 lines
2.9 KiB
Markdown
---
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layout: "docs"
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page_title: "logs Stanza - Job Specification"
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sidebar_current: "docs-job-specification-logs"
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description: |-
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The "logs" stanza configures the log rotation policy for a task's stdout and
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stderr. Logging is enabled by default with sane defaults. The "logs" stanza
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allows for finer-grained control over how Nomad handles log files.
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---
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# `logs` Stanza
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<table class="table table-bordered table-striped">
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<tr>
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<th width="120">Placement</th>
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<td>
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<code>job -> group -> task -> **logs**</code>
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</td>
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</tr>
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</table>
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The `logs` stanza configures the log rotation policy for a task's `stdout` and
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`stderr`. Logging is enabled by default with sane defaults (provided in the
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parameters section below), and there is currently no way to disable logging for
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tasks. The `logs` stanza allows for finer-grained control over how Nomad handles
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log files.
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Nomad's log rotation works by writing stdout/stderr output from tasks to a file
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inside the `alloc/logs/` directory with the following format:
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`<task-name>.<stdout/stderr>.<index>`. Output is written to a particular index,
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starting at zero, till that log file hits the configured `max_file_size`. After,
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a new file is created at `index + 1` and logs will then be written there. A log
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file is never rolled over, instead Nomad will keep up to `max_files` worth of
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logs and once that is exceeded, the log file with the lowest index is deleted.
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```hcl
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job "docs" {
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group "example" {
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task "server" {
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logs {
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max_files = 10
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max_file_size = 10
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}
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}
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}
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}
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```
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For information on how to interact with logs after they have been configured,
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please see the [`nomad logs`][logs-command] command.
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## `logs` Parameters
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- `max_files` `(int: 10)` - Specifies the maximum number of rotated files Nomad
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will retain for `stdout` and `stderr`. Each stream is tracked individually, so
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specifying a value of 2 will create 4 files - 2 for stdout and 2 for stderr
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- `max_file_size` `(int: 10)` - Specifies the maximum size of each rotated file
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in `MB`. If the amount of disk resource requested for the task is less than
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the total amount of disk space needed to retain the rotated set of files,
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Nomad will return a validation error when a job is submitted.
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## `logs` Examples
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The following examples only show the `logs` stanzas. Remember that the
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`logs` stanza is only valid in the placements listed above.
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### Configure Defaults
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This example shows a default logging configuration. Yes, it is empty on purpose.
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Nomad automatically enables logging with sane defaults as described in the
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parameters section above.
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```hcl
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```
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### Customization
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This example asks Nomad to retain 3 rotated files for each of `stderr` and
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`stdout`, each a maximum size of 5 MB per file. The minimum disk space this
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would require is 30 MB (3 `stderr` + 3 `stdout` × 5 MB = 30 MB).
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```hcl
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logs {
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max_files = 3
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max_file_size = 5
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}
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```
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[logs-command]: /docs/commands/logs.html "Nomad logs command"
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