APM Plugins
APMs are used to store metrics about an applications performance and current state. The APM (Application Performance Management) plugin is responsible for querying the APM and returning a value which will be used to determine if scaling should occur.
Prometheus APM Plugin
Use Prometheus metrics to scale your Nomad job task groups or cluster.
Agent Configuration Options
apm "prometheus" { driver = "prometheus" config = { address = "http://prometheus.my.endpoint.io:9090" }}address(string: "http://127.0.0.1:9090")- The address of the Prometheus endpoint used to perform queries.
Policy Configuration Options
check { source = "prometheus" query = "avg((haproxy_server_current_sessions{backend=\"http_back\"}) and (haproxy_server_up{backend=\"http_back\"} == 1))" ...}Datadog APM Plugin
The Datadog APM allows using time series data to make scaling decisions.
Agent Configuration Options
apm "datadog" { driver = "datadog" config = { dd_api_key = "<api key>" dd_app_key = "<app key>" }}dd_api_key(string: "")- The Datadog API key to use for authentication.dd_app_key(string: "")- The Datadog APP key to use for authentication.
The Datadog plugin can also read its configuration options via environment
variables. The accepted keys are DD_API_KEY and DD_APP_KEY. The agent
configuration parameters take precedence over the environment variables.
Policy Configuration Options
check { source = "datadog" query = "avg:proxy.backend.response.time{proxy-service:web-app}" ...}Nomad APM Plugin
The Nomad APM plugin allows querying the Nomad API for metric data. This provides an immediate starting point without addition applications but comes at the price of efficiency. When using this APM, it is advised to monitor Nomad carefully ensuring it is not put under excessive load pressure.
Agent Configuration Options
apm "nomad-apm" { driver = "nomad-apm"}When using a Nomad cluster with ACLs enabled, following ACL policy will provide the appropriate permissions for obtaining task group metrics:
namespace "default" { policy = "read" capabilities = ["read-job"]}In order to obtain cluster level metrics, the following ACL policy will be required:
node { policy = "read"} namespace "default" { policy = "read" capabilities = ["read-job"]}Policy Configuration Options - Task Groups
The Nomad APM allows querying Nomad to understand the current resource usage of a task group.
check { source = "nomad-apm" query = "avg_cpu" ...}Querying Nomad task group metrics is be done using the operation_metric syntax,
where valid operations are:
avg- returns the average of the metric value across allocations in the task group.min- returns the lowest metric value among the allocations in the task group.max- returns the highest metric value among the allocations in the task group.sum- returns the sum of all the metric values for the allocations in the task group.
The metric value can be:
cpu- CPU usage as reported by thenomad.client.allocs.cpu.total_percentmetric.memory- Memory usage as reported by thenomad.client.allocs.memory.usagemetric.
Policy Configuration Options - Client Nodes
The Nomad APM allows querying Nomad to understand the current allocated resource as a percentage of the total available.
check { source = "nomad-apm" query = "percentage-allocated_cpu" ...}Querying Nomad client node metrics is be done using the operation_metric syntax,
where valid operations are:
percentage-allocated- returns the allocated percentage of the desired resource.
The metric value can be: