--- layout: "docs" page_title: "service Stanza - Job Specification" sidebar_current: "docs-job-specification-service" description: |- The "service" stanza instructs Nomad to register the task as a service using the service discovery integration. --- # `service` Stanza
Placement job -> group -> task -> **service**
The `service` stanza instructs Nomad to register the task as a service using the service discovery integration. This section of the documentation will discuss the configuration, but please also read the [Nomad service discovery documentation][service-discovery] for more detailed information about the integration. ```hcl job "docs" { group "example" { task "server" { service { tags = ["leader", "mysql"] port = "db" check { type = "tcp" port = "db" interval = "10s" timeout = "2s" } check { type = "script" name = "check_table" command = "/usr/local/bin/check_mysql_table_status" args = ["--verbose"] interval = "60s" timeout = "5s" } } } } } ``` This section of the documentation only covers the job file options for configuring service discovery. For more information on the setup and configuration to integrate Nomad with service discovery, please see the [Nomad service discovery documentation][service-discovery]. There are steps you must take to configure Nomad. Simply adding this configuration to your job file does not automatically enable service discovery. ## `service` Parameters - `check` ([Check](#check-parameters): nil) - Specifies a health check associated with the service. This can be specified multiple times to define multiple checks for the service. At this time, Nomad supports the `script`1, `http` and `tcp` checks. - `name` `(string: "--")` - Specifies the name of this service. If not supplied, this will default to the name of the job, group, and task concatenated together with a dash, like `"docs-example-server"`. Each service must have a unique name within the cluster. Names must adhere to [RFC-1123 ยง2.1](https://tools.ietf.org/html/rfc1123#section-2) and are limited to alphanumeric and hyphen characters (i.e. `[a-z0-9\-]`), and be less than 64 characters in length. In addition to the standard [Nomad interpolation][interpolation], the following keys are also available: - `${JOB}` - the name of the job - `${GROUP}` - the name of the group - `${TASK}` - the name of the task - `${BASE}` - shorthand for `${JOB}-${GROUP}-${TASK}` - `port` `(string: required)` - Specifies the label of the port on which this service is running. Note this is the _label_ of the port and not the port number. The port label must match one defined in the [`network`][network] stanza. - `tags` `(array: [])` - Specifies the list of tags to associate with this service. If this is not supplied, no tags will be assigned to the service when it is registered. ### `check` Parameters - `args` `(array: [])` - Specifies additional arguments to the `command`. This only applies to script-based health checks. - `command` `(string: )` - Specifies the command to run for performing the health check. The script must exit: 0 for passing, 1 for warning, or any other value for a failing health check. This is required for script-based health checks. ~> **Caveat:** The command must be the path to the command on disk, and no shell exists by default. That means operators like `||` or `&&` are not available. Additionally, all arguments must be supplied via the `args` parameter. The achieve the behavior of shell operators, specify the command as a shell, like `/bin/bash` and then use `args` to run the check. - `initial_status` `(string: )` - Specifies the originating status of the service. Valid options are the empty string, `passing`, `warning`, and `critical`. - `interval` `(string: )` - Specifies the frequency of the health checks that Consul will perform. This is specified using a label suffix like "30s" or "1h". This must be greater than or equal to "1s" - `name` `(string: "service: check")` - Specifies the name of the health check. - `path` `(string: )` - Specifies the path of the HTTP endpoint which Consul will query to query the health of a service. Nomad will automatically add the IP of the service and the port, so this is just the relative URL to the health check endpoint. This is required for http-based health checks. - `port` `(string: )` - Specifies the label of the port on which the check will be performed. Note this is the _label_ of the port and not the port number. The port label must match one defined in the [`network`][network] stanza. If a port value was declared on the `service`, this will inherit from that value if not supplied. If supplied, this value takes precedence over the `service.port` value. This is useful for services which operate on multiple ports. - `protocol` `(string: "http")` - Specifies the protocol for the http-based health checks. Valid options are `http` and `https`. - `timeout` `(string: )` - Specifies how long Consul will wait for a health check query to succeed. This is specified using a label suffix like "30s" or "1h". This must be greater than or equal to "1s" - `type` `(string: )` - This indicates the check types supported by Nomad. Valid options are `script`, `http`, and `tcp`. ## `service` Examples The following examples only show the `service` stanzas. Remember that the `service` stanza is only valid in the placements listed above. ### Basic Service This example registers a service named "load-balancer" with no health checks. ```hcl service { name = "load-balancer" port = "lb" } ``` This example must be accompanied by a [`network`][network] stanza which defines a static or dynamic port labeled "lb". For example: ```hcl resources { network { mbits = 10 port "lb" {} } } ``` ### Check with Bash-isms This example shows a common mistake and correct behavior for custom checks. Suppose a health check like this: ```shell $ test -f /tmp/file.txt ``` In this example `test` is not actually a command (binary) on the system; it is a built-in shell function to bash. Thus, the following **would not work**: ```hcl service { check { type = "script" command = "test -f /tmp/file.txt" # THIS IS NOT CORRECT } } ``` Nomad will attempt to find an executable named `test` on your system, but it does not exist. It is actually just a function of bash. Additionally, it is not possible to specify the arguments in a single string. Here is the correct solution: ```hcl service { check { type = "script" command = "/bin/bash" args = ["-c", "test -f /tmp/file.txt"] } } ``` The `command` is actually `/bin/bash`, since that is the actual process we are running. The arguments to that command are the script itself, which each argument provided as a value to the `args` array. ### HTTP Health Check This example shows a service with an HTTP health check. This will query the service on the IP and port registered with Nomad at `/_healthz` every 5 seconds, giving the service a maximum of 2 seconds to return a response. Any non-2xx code is considered a failure. ```hcl service { check { type = "http" port = "lb" path = "/_healthz" interval = "5s" timeout = "2s" } } ``` ### Multiple Health Checks This example shows a service with multiple health checks defined. All health checks must be passing in order for the service to register as healthy. ```hcl service { check { type = "http" port = "lb" path = "/_healthz" interval = "5s" timeout = "2s" } check { type = "https" port = "lb" path = "/_healthz" interval = "5s" timeout = "2s" } check { type = "script" command = "/usr/local/bin/pg-tools" args = ["verify", "database" "prod", "up"] interval = "5s" timeout = "2s" } } ``` - - - 1 Script checks are not supported for the [qemu driver][qemu] since the Nomad client does not have access to the file system of a task for that driver. [service-discovery]: /docs/service-discovery/index.html "Nomad Service Discovery" [interpolation]: /docs/runtime/interpolation.html "Nomad Runtime Interpolation" [network]: /docs/job-specification/network.html "Nomad network Job Specification" [qemu]: /docs/drivers/qemu.html "Nomad qemu Driver"