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15
website/source/docs/jobops/index.html.md
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@ -1,15 +0,0 @@
---
layout: "docs"
page_title: "Operating a Job"
sidebar_current: "docs-jobops"
description: |-
Learn how to operate a Nomad Job.
---
# Operating a Job
Once a job has been submitted to Nomad, users must be able to inspect the state
of tasks, understand resource usage and access task logs. Further, for services,
performing zero downtime updates is critical. This section provides some best
practices and guidance for operating jobs under Nomad. Please navigate the
appropriate sub-sections for more information.

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---
layout: "docs"
page_title: "Operating a Job: Inspecting State"
sidebar_current: "docs-jobops-inspection"
description: |-
Learn how to inspect a Nomad Job.
---
# Inspecting state
Once a job is submitted, the next step is to ensure it is running. This section
will assume we have submitted a job with the name _example_.
To get a high-level over view of our job we can use the [`nomad status`
command](/docs/commands/status.html). This command will display the list of
running allocations, as well as any recent placement failures. An example below
shows that the job has some allocations placed but did not have enough resources
to place all of the desired allocations. We run with `-evals` to see that there
is an outstanding evaluation for the job:
```
$ nomad status example
ID = example
Name = example
Type = service
Priority = 50
Datacenters = dc1
Status = running
Periodic = false
Evaluations
ID Priority Triggered By Status Placement Failures
5744eb15 50 job-register blocked N/A - In Progress
8e38e6cf 50 job-register complete true
Placement Failure
Task Group "cache":
* Resources exhausted on 1 nodes
* Dimension "cpu exhausted" exhausted on 1 nodes
Allocations
ID Eval ID Node ID Task Group Desired Status Created At
12681940 8e38e6cf 4beef22f cache run running 08/08/16 21:03:19 CDT
395c5882 8e38e6cf 4beef22f cache run running 08/08/16 21:03:19 CDT
4d7c6f84 8e38e6cf 4beef22f cache run running 08/08/16 21:03:19 CDT
843b07b8 8e38e6cf 4beef22f cache run running 08/08/16 21:03:19 CDT
a8bc6d3e 8e38e6cf 4beef22f cache run running 08/08/16 21:03:19 CDT
b0beb907 8e38e6cf 4beef22f cache run running 08/08/16 21:03:19 CDT
da21c1fd 8e38e6cf 4beef22f cache run running 08/08/16 21:03:19 CDT
```
In the above example we see that the job has a "blocked" evaluation that is in
progress. When Nomad can not place all the desired allocations, it creates a
blocked evaluation that waits for more resources to become available. We can use
the [`eval-status` command](/docs/commands/eval-status.html) to examine any
evaluation in more detail. For the most part this should never be necessary but
can be useful to see why all of a job's allocations were not placed. For
example if we run it on the _example_ job, which had a placement failure
according to the above output, we see:
```
nomad eval-status 8e38e6cf
ID = 8e38e6cf
Status = complete
Status Description = complete
Type = service
TriggeredBy = job-register
Job ID = example
Priority = 50
Placement Failures = true
Failed Placements
Task Group "cache" (failed to place 3 allocations):
* Resources exhausted on 1 nodes
* Dimension "cpu exhausted" exhausted on 1 nodes
Evaluation "5744eb15" waiting for additional capacity to place remainder
```
More interesting though is the [`alloc-status`
command](/docs/commands/alloc-status.html). This command gives us the most
recent events that occurred for a task, its resource usage, port allocations and
more:
```
nomad alloc-status 12
ID = 12681940
Eval ID = 8e38e6cf
Name = example.cache[1]
Node ID = 4beef22f
Job ID = example
Client Status = running
Created At = 06/28/16 15:37:44 UTC
Task "redis" is "running"
Task Resources
CPU Memory Disk IOPS Addresses
2/500 6.3 MiB/256 MiB 300 MiB 0 db: 127.0.0.1:57161
Recent Events:
Time Type Description
06/28/16 15:46:42 UTC Started Task started by client
06/28/16 15:46:10 UTC Restarting Task restarting in 30.863215327s
06/28/16 15:46:10 UTC Terminated Exit Code: 137, Exit Message: "Docker container exited with non-zero exit code: 137"
06/28/16 15:37:46 UTC Started Task started by client
06/28/16 15:37:44 UTC Received Task received by client
```
In the above example we forced killed the Docker container so that we could see
in the event history that Nomad detected the failure and restarted the
allocation.
The `alloc-status` command is a good starting to point for debugging an
application that did not start. In this example task we are trying to start a
redis image using `redis:2.8` but the user has accidentally put a comma instead
of a period, typing `redis:2,8`.
When the job is run, it produces an allocation that fails. The `alloc-status`
command gives us the reason why:
```
nomad alloc-status c0f1
ID = c0f1b34c
Eval ID = 4df393cb
Name = example.cache[0]
Node ID = 13063955
Job ID = example
Client Status = failed
Created At = 06/28/16 15:50:22 UTC
Task "redis" is "dead"
Task Resources
CPU Memory Disk IOPS Addresses
500 256 MiB 300 MiB 0 db: 127.0.0.1:23285
Recent Events:
Time Type Description
06/28/16 15:50:22 UTC Not Restarting Error was unrecoverable
06/28/16 15:50:22 UTC Driver Failure failed to create image: Failed to pull `redis:2,8`: API error (500): invalid tag format
06/28/16 15:50:22 UTC Received Task received by client
```
Not all failures are this easily debuggable. If the `alloc-status` command shows
many restarts occurring as in the example below, it is a good hint that the error
is occurring at the application level during start up. These failures can be
debugged by looking at logs which is covered in the [Nomad Job Logging
documentation](/docs/jobops/logs.html).
```
$ nomad alloc-status e6b6
ID = e6b625a1
Eval ID = 68b742e8
Name = example.cache[0]
Node ID = 83ef596c
Job ID = example
Client Status = pending
Created At = 06/28/16 15:55:48
Task "redis" is "pending"
Task Resources
CPU Memory Disk IOPS Addresses
500 256 MiB 300 MiB 0 db: 127.0.0.1:30153
Recent Events:
Time Type Description
06/28/16 15:56:16 UTC Restarting Task restarting in 5.178426031s
06/28/16 15:56:16 UTC Terminated Exit Code: 1, Exit Message: "Docker container exited with non-zero exit code: 1"
06/28/16 15:56:16 UTC Started Task started by client
06/28/16 15:56:00 UTC Restarting Task restarting in 5.00123931s
06/28/16 15:56:00 UTC Terminated Exit Code: 1, Exit Message: "Docker container exited with non-zero exit code: 1"
06/28/16 15:55:59 UTC Started Task started by client
06/28/16 15:55:48 UTC Received Task received by client
```

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---
layout: "docs"
page_title: "Operating a Job: Accessing Logs"
sidebar_current: "docs-jobops-logs"
description: |-
Learn how to operate a Nomad Job.
---
# Accessing Logs
Accessing applications logs is critical when debugging issues, performance
problems or even for verifying the application is starting correctly. To make
this as simple as possible, Nomad provides [log
rotation](/docs/jobspec/index.html#log_rotation) in the jobspec, provides a [CLI
command](/docs/commands/logs.html) and an [API](/docs/http/client-fs.html#logs)
for accessing application logs and data files.
To see this in action we can just run the example job which created using `nomad
init`:
```
$ nomad init
Example job file written to example.nomad
```
This job will start a redis instance in a Docker container. We can run it now:
```
$ nomad run example.nomad
==> Monitoring evaluation "7a3b78c0"
Evaluation triggered by job "example"
Allocation "c3c58508" created: node "b5320e2d", group "cache"
Evaluation status changed: "pending" -> "complete"
==> Evaluation "7a3b78c0" finished with status "complete"
```
We can grab the allocation ID from above and use the [`nomad logs`
command](/docs/commands/logs.html) to access the applications logs. The `logs`
command supports both displaying the logs as well as following logs, blocking
for more output.
Thus to access the `stdout` we can issue the below command:
```
$ nomad logs c3c58508 redis
_._
_.-``__ ''-._
_.-`` `. `_. ''-._ Redis 3.2.1 (00000000/0) 64 bit
.-`` .-```. ```\/ _.,_ ''-._
( ' , .-` | `, ) Running in standalone mode
|`-._`-...-` __...-.``-._|'` _.-'| Port: 6379
| `-._ `._ / _.-' | PID: 1
`-._ `-._ `-./ _.-' _.-'
|`-._`-._ `-.__.-' _.-'_.-'|
| `-._`-._ _.-'_.-' | http://redis.io
`-._ `-._`-.__.-'_.-' _.-'
|`-._`-._ `-.__.-' _.-'_.-'|
| `-._`-._ _.-'_.-' |
`-._ `-._`-.__.-'_.-' _.-'
`-._ `-.__.-' _.-'
`-._ _.-'
`-.__.-'
1:M 28 Jun 19:49:30.504 # WARNING: The TCP backlog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of 128.
1:M 28 Jun 19:49:30.505 # Server started, Redis version 3.2.1
1:M 28 Jun 19:49:30.505 # WARNING overcommit_memory is set to 0! Background save may fail under low memory condition. To fix this issue add 'vm.overcommit_memory = 1' to /etc/sysctl.conf and then reboot or run the command 'sysctl vm.overcommit_memory=1' for this to take effect.
1:M 28 Jun 19:49:30.505 # WARNING you have Transparent Huge Pages (THP) support enabled in your kernel. This will create latency and memory usage issues with Redis. To fix this issue run the command 'echo never > /sys/kernel/mm/transparent_hugepage/enabled' as root, and add it to your /etc/rc.local in order to retain the setting after a reboot. Redis must be restarted after THP is disabled.
1:M 28 Jun 19:49:30.505 * The server is now ready to accept connections on port 6379
```
To display the `stderr` for the task we would run the following:
```
$ nomad logs -stderr c3c58508 redis
```
While this works well for quickly accessing logs, we recommend running a
log-shipper for long term storage of logs. In many cases this will not be needed
and the above will suffice but for use cases in which log retention is needed
Nomad can accommodate.
Since we place application logs inside the `alloc/` directory, all tasks within
the same task group have access to each others logs. Thus we can have a task
group as follows:
```
group "my-group" {
task "log-producer" {...}
task "log-shipper" {...}
}
```
In the above example, the `log-producer` task is the application that should be
run and will be producing the logs we would like to ship and the `log-shipper`
reads these logs from the `alloc/logs/` directory and ships them to a long term
storage such as S3.

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@ -1,9 +1,11 @@
--- ---
layout: "docs" layout: "docs"
page_title: "Operating a Job: Resource Utilization" page_title: "Resource Utilization - Operating a Job"
sidebar_current: "docs-jobops-resource-utilization" sidebar_current: "docs-operating-a-job-resource-utilization"
description: |- description: |-
Learn how to see resource utilization of a Nomad Job. Nomad supports reporting detailed job statistics and resource utilization
metrics for most task drivers. This section describes the ways to inspect a
job's resource consumption and utilization.
--- ---
# Determining Resource Utilization # Determining Resource Utilization
@ -16,7 +18,7 @@ command](/docs/commands/alloc-status.html) by specifying the `-stats` flag.
In the below example we are running `redis` and can see its resource utilization In the below example we are running `redis` and can see its resource utilization
below: below:
``` ```text
$ nomad alloc-status c3e0 $ nomad alloc-status c3e0
ID = c3e0e3e0 ID = c3e0e3e0
Eval ID = 617e5e39 Eval ID = 617e5e39
@ -49,10 +51,10 @@ Here we can see that we are near the limit of our configured CPU but we have
plenty of memory headroom. We can use this information to alter our job's plenty of memory headroom. We can use this information to alter our job's
resources to better reflect is actually needs: resources to better reflect is actually needs:
``` ```hcl
resource { resource {
cpu = 2000 cpu = 2000
memory = 100 memory = 100
} }
``` ```

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@ -1,16 +0,0 @@
---
layout: "docs"
page_title: "Operating a Job: Service Discovery"
sidebar_current: "docs-jobops-service-discovery"
description: |-
Learn how to use service discovery with Nomad Jobs.
---
# Using Service Discovery
Service discovery is key for applications in a dynamic environment to discover
each other. As such, Nomad has built in support for registering services and
health checks with [Consul](http://consul.io).
For more details on using service discovery with your application, see
the [Service Discovery documentation](/docs/jobspec/servicediscovery.html).

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---
layout: "docs"
page_title: "Submitting Jobs - Operating a Job"
sidebar_current: "docs-operating-a-job-submitting"
description: |-
The job file is the unit of work in Nomad. Upon authoring, the job file is
submitted to the server for evaluation and scheduling. This section discusses
some techniques for submitting jobs.
---
# Submitting Jobs
In Nomad, the description of the job and all its requirements are maintained in
a single file called the "job file". This job file resides locally on disk and
it is highly recommended that you check job files into source control.
The general flow for submitting a job in Nomad is:
1. Author a job file according to the job specification
1. Plan and review changes with a Nomad server
1. Submit the job file to a Nomad server
1. (Optional) Review job status and logs
Here is a very basic example to get you started.
## Author a Job File
Authoring a job file is very easy. For more detailed information, please see the
[job specification](/docs/jobspec/index.html). Here is a sample job file which
runs a small docker container web server.
```hcl
job "docs" {
datacenters = ["dc1"]
group "example" {
task "server" {
driver = "docker"
config {
image = "hashicorp/http-echo"
args = ["-text", "hello world"]
}
resources {
memory = 32
}
}
}
}
```
This job file exists on your local workstation in plain text. When you are
satisfied with this job file, you will plan and review the scheduler decision.
It is generally a best practice to commit job files to source control,
especially if you are working in a team.
## Planning the Job
Once the job file is authored, we need to plan out the changes. The `nomad plan`
command may be used to perform a dry-run of the scheduler and inform us of
which scheduling decisions would take place.
```shell
$ nomad plan example.nomad
```
The resulting output will look like:
```text
TODO: Output
```
Note that no action has been taken. This is a complete dry-run and no
allocations have taken place.
## Submitting the Job
Assuming the output of the plan looks acceptable, we can ask Nomad to execute
this job. This is done via the `nomad run` command. We can optionally supply
the modify index provided to us by the plan command to ensure no changes to this
job have taken place between our plan and now.
```shell
$ nomad run -check-index=123 example.nomad
```
The resulting output will look like:
```text
TODO: Output
```
Now that the job is scheduled, it may or may not be running. We need to inspect
the allocation status and logs to make sure the job started correctly. The next
section on [inspecting state](/docs/operating-a-job/inspecting-state.html) details ways to
examine this job.

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@ -1,103 +0,0 @@
---
layout: "docs"
page_title: "Operating a Job: Task Configuration"
sidebar_current: "docs-jobops-task-config"
description: |-
Learn how to ship task configuration in a Nomad Job.
---
# Task Configurations
Most tasks need to be parameterized in some way. The simplest is via
command-line arguments but often times tasks consume complex configurations via
config files. Here we explore how to configure Nomad jobs to support many
common configuration use cases.
## Command-line Arguments
The simplest type of configuration to support is tasks which take their
configuration via command-line arguments that will not change.
Nomad has many [drivers](/docs/drivers/index.html) and most support passing
arguments to their tasks via the `args` parameter. To configure these simply
provide the appropriate arguments. Below is an example using the [`docker`
driver](/docs/drivers/docker.html) to launch `memcached(8)` and set its thread count
to 4, increase log verbosity, as well as assign the correct port and address
bindings using interpolation:
```
task "memcached" {
driver = "docker"
config {
image = "memcached:1.4.27"
args = [
# Set thread count
"-t", "4",
# Enable the highest verbosity logging mode
"-vvv",
# Use interpolations to limit memory usage and bind
# to the proper address
"-m", "${NOMAD_MEMORY_LIMIT}",
"-p", "${NOMAD_PORT_db}",
"-l", "${NOMAD_ADDR_db}"
]
network_mode = "host"
}
resources {
cpu = 500 # 500 MHz
memory = 256 # 256MB
network {
mbits = 10
port "db" {
}
}
}
}
```
In the above example, we see how easy it is to pass configuration options using
the `args` section and even see how
[interpolation](/docs/jobspec/interpreted.html) allows us to pass arguments
based on the dynamic port and address Nomad chose for this task.
## Config Files
Often times applications accept their configurations using configuration files
or have so many arguments to be set it would be unwieldy to pass them via
arguments. Nomad supports downloading
[`artifacts`](/docs/jobspec/index.html#artifact_doc) prior to launching tasks.
This allows shipping of configuration files and other assets that the task
needs to run properly.
An example can be seen below, where we download two artifacts, one being the
binary to run and the other beings its configuration:
```
task "example" {
driver = "exec"
config {
command = "my-app"
args = ["-config", "local/config.cfg"]
}
# Download the binary to run
artifact {
source = "http://example.com/example/my-app"
}
# Download the config file
artifact {
source = "http://example.com/example/config.cfg"
}
}
```
Here we can see a basic example of downloading static configuration files. By
default, an `artifact` is downloaded to the task's `local/` directory but is
[configurable](/docs/jobspec/index.html#artifact_doc).

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@ -1,7 +1,7 @@
--- ---
layout: "docs" layout: "docs"
page_title: "Operating a Job: Updating Jobs" page_title: "Update Strategies - Operating a Job"
sidebar_current: "docs-jobops-updating" sidebar_current: "docs-operating-a-job-updating"
description: |- description: |-
Learn how to do safely update Nomad Jobs. Learn how to do safely update Nomad Jobs.
--- ---
@ -21,14 +21,16 @@ support for rolling updates. When a job specifies a rolling update, with the
below syntax, Nomad will only update `max-parallel` number of task groups at a below syntax, Nomad will only update `max-parallel` number of task groups at a
time and will wait `stagger` duration before updating the next set. time and will wait `stagger` duration before updating the next set.
``` ```hcl
job "rolling" { job "example" {
... # ...
update {
stagger = "30s" update {
max_parallel = 1 stagger = "30s"
} max_parallel = 1
... }
# ...
} }
``` ```
@ -37,7 +39,7 @@ jobs to ensure the scheduler will do as we expect. In this example, we have 3
web server instances that we want to update their version. After the job file web server instances that we want to update their version. After the job file
was modified we can run `plan`: was modified we can run `plan`:
``` ```text
$ nomad plan my-web.nomad $ nomad plan my-web.nomad
+/- Job: "my-web" +/- Job: "my-web"
+/- Task Group: "web" (3 create/destroy update) +/- Task Group: "web" (3 create/destroy update)
@ -83,33 +85,33 @@ traffic.
In this case we would consider version 1 to be the live set and we want to In this case we would consider version 1 to be the live set and we want to
transition to version 2. We can model this workflow with the below job: transition to version 2. We can model this workflow with the below job:
``` ```hcl
job "my-api" { job "my-api" {
... # ...
group "api-green" { group "api-green" {
count = 10 count = 10
task "api-server" { task "api-server" {
driver = "docker" driver = "docker"
config { config {
image = "api-server:v1" image = "api-server:v1"
} }
}
} }
}
group "api-blue" { group "api-blue" {
count = 0 count = 0
task "api-server" { task "api-server" {
driver = "docker" driver = "docker"
config { config {
image = "api-server:v2" image = "api-server:v2"
} }
}
} }
}
} }
``` ```
@ -127,33 +129,33 @@ operators be confident that deployments will not cause down time. If the deploy
is successful and we fully transition from v1 to v2 the job file will look like is successful and we fully transition from v1 to v2 the job file will look like
this: this:
``` ```hcl
job "my-api" { job "my-api" {
... # ...
group "api-green" { group "api-green" {
count = 0 count = 0
task "api-server" { task "api-server" {
driver = "docker" driver = "docker"
config { config {
image = "api-server:v1" image = "api-server:v1"
} }
}
} }
}
group "api-blue" { group "api-blue" {
count = 10 count = 10
task "api-server" { task "api-server" {
driver = "docker" driver = "docker"
config { config {
image = "api-server:v2" image = "api-server:v2"
} }
}
} }
}
} }
``` ```

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@ -0,0 +1,105 @@
---
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.

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---
layout: "docs"
page_title: "Configuring Tasks - Operating a Job"
sidebar_current: "docs-operating-a-job-configuring-tasks"
description: |-
Most applications require some kind of configuration. Whether this
configuration is provided via the command line or via a configuration file,
Nomad has built-in functionality for configuration. This section details two
common patterns for configuring tasks.
---
# Configuring Tasks
Most applications require some kind of configuration. The simplest way is via
command-line arguments, but often times tasks consume complex configurations via
config files. This section explores how to configure Nomad jobs to support many
common configuration use cases.
## Command-line Arguments
Many tasks accept configuration via command-line arguments that do not change
over time.
For example, consider the [http-echo](https://github.com/hashicorp/http-echo)
server which is a small go binary that renders the provided text as a webpage. The binary accepts two parameters:
* `-listen` - the address:port to listen on
* `-text` - the text to render as the HTML page
Outside of Nomad, the server is started like this:
```shell
$ http-echo -listen=":5678" -text="hello world"
```
The Nomad equivalent job file might look something like this:
```hcl
job "docs" {
datacenters = ["dc1"]
group "example" {
task "server" {
driver = "exec"
config {
command = "/bin/http-echo"
args = [
"-listen", ":5678",
"-text", "hello world",
]
}
resources {
network {
mbits = 10
port "http" {
static = "5678"
}
}
}
}
}
}
```
~> **This assumes** the <tt>http-echo</tt> binary is already installed and available in the system path. Nomad can also optionally fetch the binary using the <tt>artifact</tt> resource.
Nomad has many [drivers](/docs/drivers/index.html), and most support passing
arguments to their tasks via the `args` parameter. This option also optionally
accepts [Nomad interpolation](/docs/jobspec/interpreted.html). For example, if
you wanted Nomad to dynamically allocate a high port to bind the service on
intead of relying on a static port for the previous job:
```hcl
job "docs" {
datacenters = ["dc1"]
group "example" {
task "server" {
driver = "exec"
config {
command = "/bin/http-echo"
args = [
"-listen", ":${NOMAD_PORT_http}",
"-text", "hello world",
]
}
resources {
network {
mbits = 10
port "http" {}
}
}
}
}
}
```
## Configuration Files
Not all applications accept their configuration via command-line flags.
Sometimes applications accept their configurations using files instead. Nomad
supports downloading [artifacts](/docs/jobspec/index.html#artifact_doc) prior to
launching tasks. This allows shipping of configuration files and other assets
that the task needs to run properly.
Here is an example job which pulls down a configuration file as an artifact:
```hcl
job "docs" {
datacenters = ["dc1"]
group "example" {
task "server" {
driver = "exec"
artifact {
source = "http://example.com/config.hcl"
destination = "local/config.hcl"
}
config {
command = "my-app"
args = [
"-config", "local/config.hcl",
]
}
}
}
}
```
For more information on the artifact resource, please see the [artifact documentation](/docs/jobspec/index.html#artifact_doc).Zz

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---
layout: "docs"
page_title: "Operating a Job"
sidebar_current: "docs-operating-a-job"
description: |-
Learn how to operate a Nomad Job.
---
# Operating a Job
The general flow for operating a job in Nomad is:
1. Author the job file according to the [job specification](/docs/jobspec/index.html)
1. Plan and review the changes with a Nomad server
1. Submit the job file to a Nomad server
1. (Optional) Review job status and logs
When updating a job, there are a number of built-in update strategies which may
be defined in the job file. The general flow for updating an existing job in
Nomad is:
1. Modify the existing job file with the desired changes
1. Plan and review the changes with a Nomad server
1. Submit the job file to a Nomad server
1. (Optional) Review job status and logs
Because the job file defines the update strategy (blue-green, rolling updates,
etc.), the workflow remains the same regardless of whether this is an initial
deployment or a long-running job.
This section provides some best practices and guidance for operating jobs under
Nomad. Please navigate the appropriate sub-sections for more information.

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---
layout: "docs"
page_title: "Inspecting State - Operating a Job"
sidebar_current: "docs-operating-a-job-inspecting-state"
description: |-
Nomad exposes a number of tools and techniques for inspecting a running job.
This is helpful in ensuring the job started successfully. Additionally, it
can inform us of any errors that occurred while starting the job.
---
# Inspecting State
A successful job submission is not an indication of a successfully-running job.
This is the nature of a highly-optimistic scheduler. A successful job submission
means the server was able to issue the proper scheduling commands. It does not
indicate the job is actually running. To verify the job is running, we need to
inspect its state.
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.
## Job Status
After a job is submitted, you can query the status of that job using the status
command:
```shell
$ nomad status
```
Here is some sample output:
```text
ID Type Priority Status
docs service 50 running
```
At a high level, we can see that our job is currently running, but what does
"running" actually mean. By supplying the name of a job to the status command,
we can ask Nomad for more detailed job information:
```shell
$ nomad status docs
```
Here is some sample output
```text
ID = docs
Name = docs
Type = service
Priority = 50
Datacenters = dc1
Status = running
Periodic = false
Summary
Task Group Queued Starting Running Failed Complete Lost
example 0 0 3 0 0 0
Allocations
ID Eval ID Node ID Task Group Desired Status Created At
04d9627d 42d788a3 a1f934c9 example run running <timestamp>
e7b8d4f5 42d788a3 012ea79b example run running <timestamp>
5cbf23a1 42d788a3 1e1aa1e0 example run running <timestamp>
```
Here we can see that there are three instances of this task running, each with
its own allocation. For more information on the `status` command, please see the
[CLI documentation for <tt>status</tt>](/docs/commands/status.html).
## Evaluation Status
You can think of an evaluation as a submission to the scheduler. An example
below shows status output for a job where some allocations were placed
successfully, but did not have enough resources to place all of the desired
allocations.
If we issue the status command with the `-evals` flag, we could see there is an
outstanding evaluation for this hypothetical job:
```text
$ nomad status -evals docs
ID = docs
Name = docs
Type = service
Priority = 50
Datacenters = dc1
Status = running
Periodic = false
Evaluations
ID Priority Triggered By Status Placement Failures
5744eb15 50 job-register blocked N/A - In Progress
8e38e6cf 50 job-register complete true
Placement Failure
Task Group "example":
* Resources exhausted on 1 nodes
* Dimension "cpu exhausted" exhausted on 1 nodes
Allocations
ID Eval ID Node ID Task Group Desired Status Created At
12681940 8e38e6cf 4beef22f example run running <timestamp>
395c5882 8e38e6cf 4beef22f example run running <timestamp>
4d7c6f84 8e38e6cf 4beef22f example run running <timestamp>
843b07b8 8e38e6cf 4beef22f example run running <timestamp>
a8bc6d3e 8e38e6cf 4beef22f example run running <timestamp>
b0beb907 8e38e6cf 4beef22f example run running <timestamp>
da21c1fd 8e38e6cf 4beef22f example run running <timestamp>
```
In the above example we see that the job has a "blocked" evaluation that is in
progress. When Nomad can not place all the desired allocations, it creates a
blocked evaluation that waits for more resources to become available.
The `eval-status` command enables us to examine any evaluation in more detail.
For the most part this should never be necessary but can be useful to see why
all of a job's allocations were not placed. For example if we run it on the job
named docs, which had a placement failure according to the above output, we
might see:
```text
$ nomad eval-status 8e38e6cf
ID = 8e38e6cf
Status = complete
Status Description = complete
Type = service
TriggeredBy = job-register
Job ID = docs
Priority = 50
Placement Failures = true
Failed Placements
Task Group "example" (failed to place 3 allocations):
* Resources exhausted on 1 nodes
* Dimension "cpu exhausted" exhausted on 1 nodes
Evaluation "5744eb15" waiting for additional capacity to place remainder
```
For more information on the `eval-status` command, please see the [CLI documentation for <tt>eval-status</tt>](/docs/commands/eval-status.html).
## Allocation Status
You can think of an allocation as an instruction to schedule. Just like an
application or service, an allocation has logs and state. The `alloc-status`
command gives us the most recent events that occurred for a task, its resource
usage, port allocations and more:
```text
$ nomad alloc-status 04d9627d
ID = 04d9627d
Eval ID = 42d788a3
Name = docs.example[2]
Node ID = a1f934c9
Job ID = docs
Client Status = running
Task "server" is "running"
Task Resources
CPU Memory Disk IOPS Addresses
0/100 MHz 728 KiB/10 MiB 300 MiB 0 http: 10.1.1.196:5678
Recent Events:
Time Type Description
10/09/16 00:36:06 UTC Started Task started by client
10/09/16 00:36:05 UTC Received Task received by client
```
The `alloc-status` command is a good starting to point for debugging an
application that did not start. Hypothetically assume a user meant to start a
Docker container named "redis:2.8", but accidentally put a comma instead of a
period, typing "redis:2,8".
When the job is executed, it produces a failed allocation. The `alloc-status`
command will give us the reason why:
```text
$ nomad alloc-status 04d9627d
# ...
Recent Events:
Time Type Description
06/28/16 15:50:22 UTC Not Restarting Error was unrecoverable
06/28/16 15:50:22 UTC Driver Failure failed to create image: Failed to pull `redis:2,8`: API error (500): invalid tag format
06/28/16 15:50:22 UTC Received Task received by client
```
Unfortunately not all failures are as easily debuggable. If the `alloc-status`
command shows many restarts, there is likely an application-level issue during
start up. For example:
```
$ nomad alloc-status 04d9627d
# ...
Recent Events:
Time Type Description
06/28/16 15:56:16 UTC Restarting Task restarting in 5.178426031s
06/28/16 15:56:16 UTC Terminated Exit Code: 1, Exit Message: "Docker container exited with non-zero exit code: 1"
06/28/16 15:56:16 UTC Started Task started by client
06/28/16 15:56:00 UTC Restarting Task restarting in 5.00123931s
06/28/16 15:56:00 UTC Terminated Exit Code: 1, Exit Message: "Docker container exited with non-zero exit code: 1"
06/28/16 15:55:59 UTC Started Task started by client
06/28/16 15:55:48 UTC Received Task received by client
```
To debug these failures, we will need to utilize the "logs" command, which is
discussed in the [accessing logs](/docs/operating-a-job/accessing-logs.html)
section of this documentation.
For more information on the `alloc-status` command, please see the [CLI
documentation for <tt>alloc-status</tt>](/docs/commands/alloc-status.html).

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---
layout: "docs"
page_title: "Resource Utilization - Operating a Job"
sidebar_current: "docs-operating-a-job-resource-utilization"
description: |-
Nomad supports reporting detailed job statistics and resource utilization
metrics for most task drivers. This section describes the ways to inspect a
job's resource consumption and utilization.
---
# Resource Utilization
Understanding the resource utilization of an application is important, and Nomad
supports reporting detailed statistics in many of its drivers. The main
interface for seeing resource utilization is the `alloc-status` command with the
`-stats` flag.
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"
```
To see the detailed usage statistics, we can issue the command:
```shell
$ nomad alloc-status -stats 04d9627d
```
And here is some sample output:
```text
$ nomad alloc-status c3e0
ID = 04d9627d
Eval ID = 42d788a3
Name = docs.example[2]
Node ID = a1f934c9
Job ID = docs
Client Status = running
Task "server" is "running"
Task Resources
CPU Memory Disk IOPS Addresses
75/100 MHz 784 KiB/10 MiB 300 MiB 0 http: 10.1.1.196:5678
Memory Stats
Cache Max Usage RSS Swap
56 KiB 1.3 MiB 784 KiB 0 B
CPU Stats
Percent Throttled Periods Throttled Time
0.00% 0 0
Recent Events:
Time Type Description
<timestamp> Started Task started by client
<timestamp> Received Task received by client
```
Here we can see that we are near the limit of our configured CPU but we have
plenty of memory headroom. We can use this information to alter our job's
resources to better reflect is actually needs:
```hcl
resource {
cpu = 200
memory = 10
}
```
Adjusting resources is very important for a variety of reasons:
* Ensuring your application does not get OOM killed if it hits its memory limit.
* Ensuring the application performs well by ensuring it has some CPU allowance.
* Optimizing cluster density by reserving what you need and not over-allocating.
While single point in time resource usage measurements are useful, it is often
more useful to graph resource usage over time to better understand and estimate
resource usage. Nomad supports outputting resource data to statsite and statsd
and is the recommended way of monitoring resources. For more information about
outputting telemetry see the [telemetry
documentation](/docs/agent/telemetry.html).
For more advanced use cases, the resource usage data is also accessible via the
client's HTTP API. See the documentation of the Client's [allocation HTTP
API](/docs/http/client-allocation-stats.html).

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---
layout: "docs"
page_title: "Submitting Jobs - Operating a Job"
sidebar_current: "docs-operating-a-job-submitting-jobs"
description: |-
The job file is the unit of work in Nomad. Upon authoring, the job file is
submitted to the server for evaluation and scheduling. This section discusses
some techniques for submitting jobs.
---
# Submitting Jobs
In Nomad, the description of the job and all its requirements are maintained in
a single file called the "job file". This job file resides locally on disk and
it is highly recommended that you check job files into source control.
The general flow for submitting a job in Nomad is:
1. Author a job file according to the job specification
1. Plan and review changes with a Nomad server
1. Submit the job file to a Nomad server
1. (Optional) Review job status and logs
Here is a very basic example to get you started.
## Author a Job File
Authoring a job file is very easy. For more detailed information, please see the
[job specification](/docs/jobspec/index.html). Here is a sample job file which
runs a small docker container web server to get us started.
```hcl
job "docs" {
datacenters = ["dc1"]
group "example" {
task "server" {
driver = "docker"
config {
image = "hashicorp/http-echo"
args = [
"-listen", ":5678",
"-text", "hello world",
]
}
resources {
network {
mbits = 10
port "http" {
static = "5678"
}
}
}
}
}
}
```
This job file exists on your local workstation in plain text. When you are
satisfied with this job file, you will plan and review the scheduler decision.
It is generally a best practice to commit job files to source control,
especially if you are working in a team.
## Planning the Job
Once the job file is authored, we need to plan out the changes. The `nomad plan`
command invokes a dry-run of the scheduler and inform us of which scheduling
decisions would take place.
```shell
$ nomad plan docs.nomad
```
The resulting output will look like:
```text
+ Job: "docs"
+ Task Group: "example" (1 create)
+ Task: "server" (forces create)
Scheduler dry-run:
- All tasks successfully allocated.
Job Modify Index: 0
To submit the job with version verification run:
nomad run -check-index 0 docs.nomad
When running the job with the check-index flag, the job will only be run if the
server side version matches the the job modify index returned. If the index has
changed, another user has modified the job and the plan's results are
potentially invalid.
```
Note that no action was taken. This job is not running. This is a complete
dry-run and no allocations have taken place.
## Submitting the Job
Assuming the output of the plan looks acceptable, we can ask Nomad to execute
this job. This is done via the `nomad run` command. We can optionally supply
the modify index provided to us by the plan command to ensure no changes to this
job have taken place between our plan and now.
```shell
$ nomad run docs.nomad
```
The resulting output will look like:
```text
==> Monitoring evaluation "0d159869"
Evaluation triggered by job "docs"
Allocation "5cbf23a1" created: node "1e1aa1e0", group "example"
Evaluation status changed: "pending" -> "complete"
==> Evaluation "0d159869" finished with status "complete"
```
Now that the job is scheduled, it may or may not be running. We need to inspect
the allocation status and logs to make sure the job started correctly. The next
section on [inspecting state](/docs/operating-a-job/inspecting-state.html)
details ways to examine this job's state.
## Updating the Job
When making updates to the job, it is best to always run the plan command and
then the run command. For example:
```diff
@@ -2,6 +2,8 @@ job "docs" {
datacenters = ["dc1"]
group "example" {
+ count = "3"
+
task "server" {
driver = "docker"
```
After we save these changes to disk, run the plan command:
```text
$ nomad plan docs.nomad
+/- Job: "docs"
+/- Task Group: "example" (2 create, 1 in-place update)
+/- Count: "1" => "3" (forces create)
Task: "server"
Scheduler dry-run:
- All tasks successfully allocated.
Job Modify Index: 131
To submit the job with version verification run:
nomad run -check-index 131 docs.nomad
When running the job with the check-index flag, the job will only be run if the
server side version matches the the job modify index returned. If the index has
changed, another user has modified the job and the plan's results are
potentially invalid.
```
And then run the run command, assuming the output looks okay. Note that we are
including the "check-index" parameter. This will ensure that no remote changes
have taken place to the job between our plan and run phases.
```text
nomad run -check-index 131 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"
```
For more details on advanced job updating strategies such as canary builds and
build-green deployments, please see the documentation on [job update
strategies](/docs/operating-a-job/update-strategies.html).

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---
layout: "docs"
page_title: "Update Strategies - Operating a Job"
sidebar_current: "docs-operating-a-job-updating"
description: |-
Learn how to do safely update Nomad Jobs.
---
# Update Strategies
When operating a service, updating the version of the job will be a common task.
Under a cluster scheduler the same best practices apply for reliably deploying
new versions including: rolling updates, blue-green deploys and canaries which
are special cased blue-green deploys. This section will explore how to do each
of these safely with Nomad.
## Rolling Updates
In order to update a service without introducing down-time, Nomad has build in
support for rolling updates. When a job specifies a rolling update, with the
below syntax, Nomad will only update `max-parallel` number of task groups at a
time and will wait `stagger` duration before updating the next set.
```hcl
job "example" {
# ...
update {
stagger = "30s"
max_parallel = 1
}
# ...
}
```
We can use the "nomad plan" command while updating jobs to ensure the scheduler
will do as we expect. In this example, we have 3 web server instances that we
want to update their version. After the job file was modified we can run `plan`:
```text
$ nomad plan my-web.nomad
+/- Job: "my-web"
+/- Task Group: "web" (3 create/destroy update)
+/- Task: "web" (forces create/destroy update)
+/- Config {
+/- image: "nginx:1.10" => "nginx:1.11"
port_map[0][http]: "80"
}
Scheduler dry-run:
- All tasks successfully allocated.
- Rolling update, next evaluation will be in 10s.
Job Modify Index: 7
To submit the job with version verification run:
nomad run -check-index 7 my-web.nomad
When running the job with the check-index flag, the job will only be run if the
server side version matches the the job modify index returned. If the index has
changed, another user has modified the job and the plan's results are
potentially invalid.
```
Here we can see that Nomad will destroy the 3 existing tasks and create 3
replacements but it will occur with a rolling update with a stagger of `10s`.
For more details on the update block, see
the [Jobspec documentation](/docs/jobspec/index.html#update).
## Blue-green and Canaries
Blue-green deploys have several names, Red/Black, A/B, Blue/Green, but the
concept is the same. The idea is to have two sets of applications with only one
of them being live at a given time, except while transitioning from one set to
another. What the term "live" means is that the live set of applications are
the set receiving traffic.
So imagine we have an API server that has 10 instances deployed to production
at version 1 and we want to upgrade to version 2. Hopefully the new version has
been tested in a QA environment and is now ready to start accepting production
traffic.
In this case we would consider version 1 to be the live set and we want to
transition to version 2. We can model this workflow with the below job:
```hcl
job "my-api" {
# ...
group "api-green" {
count = 10
task "api-server" {
driver = "docker"
config {
image = "api-server:v1"
}
}
}
group "api-blue" {
count = 0
task "api-server" {
driver = "docker"
config {
image = "api-server:v2"
}
}
}
}
```
Here we can see the live group is "api-green" since it has a non-zero count. To
transition to v2, we up the count of "api-blue" and down the count of
"api-green". We can now see how the canary process is a special case of
blue-green. If we set "api-blue" to `count = 1` and "api-green" to `count = 9`,
there will still be the original 10 instances but we will be testing only one
instance of the new version, essentially canarying it.
If at any time we notice that the new version is behaving incorrectly and we
want to roll back, all that we have to do is drop the count of the new group to
0 and restore the original version back to 10. This fine control lets job
operators be confident that deployments will not cause down time. If the deploy
is successful and we fully transition from v1 to v2 the job file will look like
this:
```hcl
job "my-api" {
# ...
group "api-green" {
count = 0
task "api-server" {
driver = "docker"
config {
image = "api-server:v1"
}
}
}
group "api-blue" {
count = 10
task "api-server" {
driver = "docker"
config {
image = "api-server:v2"
}
}
}
}
```
Now "api-blue" is the live group and when we are ready to update the api to v3,
we would modify "api-green" and repeat this process. The rate at which the count
of groups are incremented and decremented is totally up to the user. It is
usually good practice to start by transition one at a time until a certain
confidence threshold is met based on application specific logs and metrics.
## Handling Drain Signals
On operating systems that support signals, Nomad will signal the application
before killing it. This gives the application time to gracefully drain
connections and conduct any other cleanup that is necessary. Certain
applications take longer to drain than others and as such Nomad lets the job
file specify how long to wait in-between signaling the application to exit and
forcefully killing it. This is configurable via the `kill_timeout`. More details
can be seen in the [Jobspec documentation](/docs/jobspec/index.html#kill_timeout).

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@ -21,6 +21,6 @@ We recommend reading the following as next steps.
* [Creating a Cluster](/docs/cluster/bootstrapping.html) - Additional details on * [Creating a Cluster](/docs/cluster/bootstrapping.html) - Additional details on
creating a production worthy Nomad Cluster. creating a production worthy Nomad Cluster.
* [Operating a Job](/docs/jobops/index.html) - Additional details on how to * [Operating a Job](/docs/operating-a-job/index.html) - Additional details on how to
run a job in production. run a job in production.

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</ul> </ul>
</li> </li>
<li<%= sidebar_current("docs-jobops") %>>
<a href="/docs/jobops/index.html">Operating a Job</a>
<ul class="nav">
<li<%= sidebar_current("docs-jobops-task-config") %>>
<a href="/docs/jobops/taskconfig.html">Task Configuration</a>
</li>
<li<%= sidebar_current("docs-jobops-inspection") %>>
<a href="/docs/jobops/inspecting.html">Inspecting State</a>
</li>
<li<%= sidebar_current("docs-jobops-resource-utilization") %>>
<a href="/docs/jobops/resources.html">Resource Utilization</a>
</li>
<li<%= sidebar_current("docs-jobops-service-discovery") %>>
<a href="/docs/jobops/servicediscovery.html">Service Discovery</a>
</li>
<li<%= sidebar_current("docs-jobops-logs") %>>
<a href="/docs/jobops/logs.html">Accessing Logs</a>
</li>
<li<%= sidebar_current("docs-jobops-updating") %>>
<a href="/docs/jobops/updating.html">Updating Jobs</a>
</li>
</ul>
</li>
<li<%= sidebar_current("docs-upgrade") %>>
<a href="/docs/upgrade/index.html">Upgrading</a>
<ul class="nav">
<li<%= sidebar_current("docs-upgrade-upgrading") %>>
<a href="/docs/upgrade/index.html">Upgrading Nomad</a>
</li>
<li<%= sidebar_current("docs-upgrade-specific") %>>
<a href="/docs/upgrade/upgrade-specific.html">Specific Version Details</a>
</li>
</ul>
</li>
<li<%= sidebar_current("docs-jobspec") %>> <li<%= sidebar_current("docs-jobspec") %>>
<a href="/docs/jobspec/index.html">Job Specification</a> <a href="/docs/jobspec/index.html">Job Specification</a>
<ul class="nav"> <ul class="nav">
@ -88,6 +51,42 @@
</ul> </ul>
</li> </li>
<li<%= sidebar_current("docs-operating-a-job") %>>
<a href="/docs/operating-a-job/index.html">Operating a Job</a>
<ul class="nav">
<li<%= sidebar_current("docs-operating-a-job-configuring-tasks") %>>
<a href="/docs/operating-a-job/configuring-tasks.html">Configuring Tasks</a>
</li>
<li<%= sidebar_current("docs-operating-a-job-submitting-jobs") %>>
<a href="/docs/operating-a-job/submitting-jobs.html">Submitting Jobs</a>
</li>
<li<%= sidebar_current("docs-operating-a-job-inspecting-state") %>>
<a href="/docs/operating-a-job/inspecting-state.html">Inspecting State</a>
</li>
<li<%= sidebar_current("docs-operating-a-job-accessing-logs") %>>
<a href="/docs/operating-a-job/accessing-logs.html">Accessing Logs</a>
</li>
<li<%= sidebar_current("docs-operating-a-job-resource-utilization") %>>
<a href="/docs/operating-a-job/resource-utilization.html">Resource Utilization</a>
</li>
<li<%= sidebar_current("docs-operating-a-job-updating") %>>
<a href="/docs/operating-a-job/update-strategies.html">Update Strategies</a>
</li>
</ul>
</li>
<li<%= sidebar_current("docs-upgrade") %>>
<a href="/docs/upgrade/index.html">Upgrading</a>
<ul class="nav">
<li<%= sidebar_current("docs-upgrade-upgrading") %>>
<a href="/docs/upgrade/index.html">Upgrading Nomad</a>
</li>
<li<%= sidebar_current("docs-upgrade-specific") %>>
<a href="/docs/upgrade/upgrade-specific.html">Specific Version Details</a>
</li>
</ul>
</li>
<li<%= sidebar_current("docs-drivers") %>> <li<%= sidebar_current("docs-drivers") %>>
<a href="/docs/drivers/index.html">Task Drivers</a> <a href="/docs/drivers/index.html">Task Drivers</a>
<ul class="nav"> <ul class="nav">