---
title: Configuration
nav_icon: sliders
sort_rank: 1
---

# Configuration

Prometheus is configured via command-line flags and a configuration file. While
the command-line flags configure immutable system parameters (such as storage
locations, amount of data to keep on disk and in memory, etc.), the
configuration file defines everything related to scraping [jobs and their
instances](/docs/concepts/jobs_instances/), as well as which [rule files to
load](/docs/querying/rules/#configuring-rules).

To view all available command-line flags, run `prometheus -h`.

Prometheus can reload its configuration at runtime. If the new configuration
is not well-formed, the changes will not be applied.
A configuration reload is triggered by sending a `SIGHUP` to the Prometheus process.
This will also reload any configured rule files.


## Configuration file

To specify which configuration file to load, use the `-config.file` flag.

The file is written in [YAML format](http://en.wikipedia.org/wiki/YAML),
defined by the scheme described below.
Brackets indicate that a parameter is optional. For non-list parameters the
value is set to the specified default.

Generic placeholders are defined as follows:

* `<duration>`: a duration matching the regular expression `[0-9]+(ms|[smhdwy])`
* `<labelname>`: a string matching the regular expression `[a-zA-Z_][a-zA-Z0-9_]*`
* `<labelvalue>`: a string of unicode characters
* `<filename>`: a valid path in the current working directory
* `<boolean>`: a boolean that can take the values `true` or `false`

The other placeholders are specified separately.

A valid example file can be found [here](https://github.com/prometheus/prometheus/blob/master/config/testdata/conf.good.yml).

The global configuration specifies parameters that are valid in all other configuration
contexts. They also serve as defaults for other configuration sections.


```
global:
  # How frequently to scrape targets by default.
  [ scrape_interval: <duration> | default = 1m ]

  # How long until a scrape request times out.
  [ scrape_timeout: <duration> | default = 10s ]

  # How frequently to evaluate rules.
  [ evaluation_interval: <duration> | default = 1m ]

  # The labels to add to any time series or alerts when communicating with
  # external systems (federation, remote storage, Alertmanager).
  external_labels:
    [ <labelname>: <labelvalue> ... ]

# Rule files specifies a list of globs. Rules and alerts are read from
# all matching files.
rule_files:
  [ - <filepath_glob> ... ]

# A list of scrape configurations.
scrape_configs:
  [ - <scrape_config> ... ]

# Alerting specifies settings related to the Alertmanager.
alerting:
  alert_relabel_configs:
    [ - <relabel_config> ... ]
  alertmanagers:
    [- <alertmanager_config> ... ]

# Settings related to the experimental remote write feature.
remote_write:
  [ url: <string> ]
  [ remote_timeout: <duration> | default = 30s ]
  tls_config:
    [ <tls_config> ]
  [ proxy_url: <string> ]
  basic_auth:
    [ username: <string> ]
    [ password: <string> ]
  write_relabel_configs:
    [ - <relabel_config> ... ]
```

### `<scrape_config>`

A `scrape_config` section specifies a set of targets and parameters describing how
to scrape them. In the general case, one scrape configuration specifies a single
job. In advanced configurations, this may change.

Targets may be statically configured via the `static_configs` parameter or
dynamically discovered using one of the supported service-discovery mechanisms.

Additionally, `relabel_configs` allow advanced modifications to any
target and its labels before scraping.

```
# The job name assigned to scraped metrics by default.
job_name: <name>

# How frequently to scrape targets from this job.
[ scrape_interval: <duration> | default = <global_config.scrape_interval> ]

# Per-target timeout when scraping this job.
[ scrape_timeout: <duration> | default = <global_config.scrape_timeout> ]

# The HTTP resource path on which to fetch metrics from targets.
[ metrics_path: <path> | default = /metrics ]

# honor_labels controls how Prometheus handles conflicts between labels that are
# already present in scraped data and labels that Prometheus would attach
# server-side ("job" and "instance" labels, manually configured target
# labels, and labels generated by service discovery implementations).
#
# If honor_labels is set to "true", label conflicts are resolved by keeping label
# values from the scraped data and ignoring the conflicting server-side labels.
#
# If honor_labels is set to "false", label conflicts are resolved by renaming
# conflicting labels in the scraped data to "exported_<original-label>" (for
# example "exported_instance", "exported_job") and then attaching server-side
# labels. This is useful for use cases such as federation, where all labels
# specified in the target should be preserved.
#
# Note that any globally configured "external_labels" are unaffected by this
# setting. In communication with external systems, they are always applied only
# when a time series does not have a given label yet and are ignored otherwise.
[ honor_labels: <boolean> | default = false ]

# Configures the protocol scheme used for requests.
[ scheme: <scheme> | default = http ]

# Optional HTTP URL parameters.
params:
  [ <string>: [<string>, ...] ]

# Sets the `Authorization` header on every scrape request with the
# configured username and password.
basic_auth:
  [ username: <string> ]
  [ password: <string> ]

# Sets the `Authorization` header on every scrape request with
# the configured bearer token. It is mutually exclusive with `bearer_token_file`.
[ bearer_token: <string> ]

# Sets the `Authorization` header on every scrape request with the bearer token 
# read from the configured file. It is mutually exclusive with `bearer_token`.
[ bearer_token_file: /path/to/bearer/token/file ]

# Configures the scrape request's TLS settings.
tls_config:
  [ <tls_config> ]

# Optional proxy URL.
[ proxy_url: <string> ]

# List of Azure service discovery configurations.
azure_sd_configs:
  [ - <azure_sd_config> ... ]

# List of Consul service discovery configurations.
consul_sd_configs:
  [ - <consul_sd_config> ... ]

# List of DNS service discovery configurations.
dns_sd_configs:
  [ - <dns_sd_config> ... ]

# List of EC2 service discovery configurations.
ec2_sd_configs:
  [ - <ec2_sd_config> ... ]

# List of file service discovery configurations.
file_sd_configs:
  [ - <file_sd_config> ... ]

# List of GCE service discovery configurations.
gce_sd_configs:
  [ - <gce_sd_config> ... ]

# List of Kubernetes service discovery configurations.
kubernetes_sd_configs:
  [ - <kubernetes_sd_config> ... ]

# List of Marathon service discovery configurations.
marathon_sd_configs:
  [ - <marathon_sd_config> ... ]

# List of AirBnB's Nerve service discovery configurations.
nerve_sd_configs:
  [ - <nerve_sd_config> ... ]

# List of Zookeeper Serverset service discovery configurations.
serverset_sd_configs:
  [ - <serverset_sd_config> ... ]

# List of labeled statically configured targets for this job.
static_configs:
  [ - <static_config> ... ]

# List of target relabel configurations.
relabel_configs:
  [ - <relabel_config> ... ]

# List of metric relabel configurations.
metric_relabel_configs:
  [ - <relabel_config> ... ]
```

Where `<scheme>` may be `http` or `https` and `<path>` is a valid URL path.
`<job_name>` must be unique across all scrape configurations and adhere to the
regex `[a-zA-Z_][a-zA-Z0-9_-]`.

### `<tls_config>`

A `tls_config` allows configuring TLS connections.

```
# CA certificate to validate API server certificate with.
[ ca_file: <filename> ]

# Certificate and key files for client cert authentication to the server.
[ cert_file: <filename> ]
[ key_file: <filename> ]

# ServerName extension to indicate the name of the server.
# http://tools.ietf.org/html/rfc4366#section-3.1
[ server_name: <string> ]

# Disable validation of the server certificate.
[ insecure_skip_verify: <boolean> ]
```

### `<azure_sd_config>`

CAUTION: Azure SD is in beta: breaking changes to configuration are still
likely in future releases.

Azure SD configurations allow retrieving scrape targets from Azure VMs.

The following meta labels are available on targets during relabeling:

* `__meta_azure_machine_id`: the machine ID
* `__meta_azure_machine_resource_group`: the machine's resource group
* `__meta_azure_machine_location`: the location the machine runs in
* `__meta_azure_machine_private_ip`: the machine's private IP
* `__meta_azure_tag_<tagname>`: each tag value of the machine

See below for the configuration options for Azure discovery:

```
# The information to access the Azure API.
# The subscription ID.
subscription_id: <string>
# The tenant ID.
tenant_id: <string>
# The client ID.
client_id: <string>
# The client secret.
client_secret: <string>

# Refresh interval to re-read the instance list.
[ refresh_interval: <duration> | default = 300s ]

# The port to scrape metrics from. If using the public IP address, this must
# instead be specified in the relabeling rule.
[ port: <int> | default = 80 ]
```

### `<consul_sd_config>`

Consul SD configurations allow retrieving scrape targets from [Consul's](https://www.consul.io)
Catalog API.

The following meta labels are available on targets during relabeling:

* `__meta_consul_address`: the address of the target
* `__meta_consul_node`: the node name defined for the target
* `__meta_consul_tags`: the list of tags of the target joined by the tag separator
* `__meta_consul_service`: the name of the service the target belongs to
* `__meta_consul_service_address`: the service address of the target
* `__meta_consul_service_port`: the service port of the target
* `__meta_consul_service_id`: the service ID of the target
* `__meta_consul_dc`: the datacenter name for the target

```
# The information to access the Consul API. It is to be defined
# as the Consul documentation requires.
server: <host>
[ token: <string> ]
[ datacenter: <string> ]
[ scheme: <string> ]
[ username: <string> ]
[ password: <string> ]

# A list of services for which targets are retrieved. If omitted, all services
# are scraped.
services:
  [ - <string> ]

# The string by which Consul tags are joined into the tag label.
[ tag_separator: <string> | default = , ]
```

Note that the IP number and port used to scrape the targets is assembled as
`<__meta_consul_address>:<__meta_consul_service_port>`. However, in some
Consul setups, the relevant address is in `__meta_consul_service_address`.
In those cases, you can use the [relabel](#relabel_config)
feature to replace the special `__address__` label.

### `<dns_sd_config>`

A DNS-based service discovery configuration allows specifying a set of DNS
domain names which are periodically queried to discover a list of targets. The
DNS servers to be contacted are read from `/etc/resolv.conf`.

This service discovery method only supports basic DNS A, AAAA and SRV record
queries, but not the advanced DNS-SD approach specified in
[RFC6763](https://tools.ietf.org/html/rfc6763).

During the [relabeling phase](#relabel_config), the meta label
`__meta_dns_name` is available on each target and is set to the
record name that produced the discovered target.

```
# A list of DNS domain names to be queried.
names:
  [ - <domain_name> ]

# The type of DNS query to perform.
[ type: <query_type> | default = 'SRV' ]

# The port number used if the query type is not SRV.
[ port: <number>]

# The time after which the provided names are refreshed.
[ refresh_interval: <duration> | default = 30s ]
```

Where `<domain_name>` is a valid DNS domain name.
Where `<query_type>` is `SRV`, `A`, or `AAAA`.

### `<ec2_sd_config>`

EC2 SD configurations allow retrieving scrape targets from AWS EC2
instances. The private IP address is used by default, but may be changed to
the public IP address with relabeling.

The following meta labels are available on targets during relabeling:

* `__meta_ec2_availability_zone`: the availability zone in which the instance is running
* `__meta_ec2_instance_id`: the EC2 instance ID
* `__meta_ec2_instance_state`: the state of the EC2 instance
* `__meta_ec2_instance_type`: the type of the EC2 instance
* `__meta_ec2_private_ip`: the private IP address of the instance, if present
* `__meta_ec2_public_dns_name`: the public DNS name of the instance, if available
* `__meta_ec2_public_ip`: the public IP address of the instance, if available
* `__meta_ec2_subnet_id`: comma separated list of subnets IDs in which the instance is running, if available
* `__meta_ec2_tag_<tagkey>`: each tag value of the instance
* `__meta_ec2_vpc_id`: the ID of the VPC in which the instance is running, if available



See below for the configuration options for EC2 discovery:

```
# The information to access the EC2 API.

# The AWS Region.
region: <string>

# The AWS API keys. If blank, the environment variables `AWS_ACCESS_KEY_ID`
# and `AWS_SECRET_ACCESS_KEY` are used.
[ access_key: <string> ]
[ secret_key: <string> ]
# Named AWS profile used to connect to the API.
[ profile: <string> ]

# Refresh interval to re-read the instance list.
[ refresh_interval: <duration> | default = 60s ]

# The port to scrape metrics from. If using the public IP address, this must
# instead be specified in the relabeling rule.
[ port: <int> | default = 80 ]
```

### `<file_sd_config>`

File-based service discovery provides a more generic way to configure static targets
and serves as an interface to plug in custom service discovery mechanisms.

It reads a set of files containing a list of zero or more
`<static_config>`s. Changes to all defined files are detected via disk watches
and applied immediately. Files may be provided in YAML or JSON format. Only
changes resulting in well-formed target groups are applied.

The JSON file must contain a list of static configs, using this format:

```
[
  {
    "targets": [ "<host>", ... ],
    "labels": {
      "<labelname>": "<labelvalue>", ...
    }
  },
  ...
]
```

As a fallback, the file contents are also re-read periodically at the specified
refresh interval.

Each target has a meta label `__meta_filepath` during the
[relabeling phase](#relabel_config). Its value is set to the
filepath from which the target was extracted.

```
# Patterns for files from which target groups are extracted.
files:
  [ - <filename_pattern> ... ]

# Refresh interval to re-read the files.
[ refresh_interval: <duration> | default = 5m ]
```

Where `<filename_pattern>` may be a path ending in `.json`, `.yml` or `.yaml`. The last path segment
may contain a single `*` that matches any character sequence, e.g. `my/path/tg_*.json`.

NOTE: Prior to v0.20, `names:` was used instead of `files:`.

### `<gce_sd_config>`

CAUTION: GCE SD is in beta: breaking changes to configuration are still
likely in future releases.

[GCE](https://cloud.google.com/compute/) SD configurations allow retrieving scrape targets from GCP GCE instances.
The private IP address is used by default, but may be changed to the public IP
address with relabeling.

The following meta labels are available on targets during relabeling:

* `__meta_gce_project`: the GCP project in which the instance is running
* `__meta_gce_zone`: the GCE zone in which the instance is running
* `__meta_gce_network`: the network of the instance
* `__meta_gce_subnetwork`: the subnetwork of the instance
* `__meta_gce_public_ip`: the public IP address of the instance, if present
* `__meta_gce_private_ip`: the private IP address of the instance
* `__meta_gce_instance_name`: the name of the instance
* `__meta_gce_instance_tags`: comma separated list of instance tags



See below for the configuration options for GCE discovery:

```
# The information to access the GCE API.

# The GCP Project
project: <string>

# The zone of the scrape targets. If you need multiple zones use multiple
# gce_sd_configs.
zone: <string>

# Filter can be used optionally to filter the instance list by other criteria
[ filter: <string> ]

# Refresh interval to re-read the instance list
[ refresh_interval: <duration> | default = 60s ]

# The port to scrape metrics from. If using the public IP address, this must
# instead be specified in the relabeling rule.
[ port: <int> | default = 80 ]

# The tag separator is used to separate the tags on concatenation
[ tag_separator: <string> | default = , ]
```

Credentials are discovered by the Google Cloud SDK default client by looking
in the following places, preferring the first location found:

1. a JSON file specified by the `GOOGLE_APPLICATION_CREDENTIALS` environment variable
2. a JSON file in the well-known path `$HOME/.config/gcloud/application_default_credentials.json`
3. fetched from the GCE metadata server

If Prometheus is running within GCE, the service account associated with the
instance it is running on should have at least read-only permissions to the
compute resources. If running outside of GCE make sure to create an appropriate
service account and place the credential file in one of the expected locations.

### `<kubernetes_sd_config>`

CAUTION: Kubernetes SD is in beta: breaking changes to configuration are still
likely in future releases.

Kubernetes SD configurations allow retrieving scrape targets from
[Kubernetes'](http://kubernetes.io/) REST API and always staying synchronized with
the cluster state.

One of the following `role` types can be configured to discover targets:

#### `node`

The `node` role discovers one target per cluster node with the address defaulting
to the Kubelet's HTTP port.
The target address defaults to the first existing address of the Kubernetes
node object in the address type order of `NodeInternalIP`, `NodeExternalIP`,
`NodeLegacyHostIP`, and `NodeHostName`.

Available meta labels:

* `__meta_kubernetes_node_name`: The name of the node object.
* `__meta_kubernetes_node_label_<labelname>`: Each label from the node object.
* `__meta_kubernetes_node_annotation_<annotationname>`: Each annotation from the node object.
* `__meta_kubernetes_node_address_<address_type>`: The first address for each node address type, if it exists.

In addition, the `instance` label for the node will be set to the node name
as retrieved from the API server.

#### `service`

The `service` role discovers a target for each service port for each service.
This is generally useful for blackbox monitoring of a service.
The address will be set to the Kubernetes DNS name of the service and respective
service port.

Available meta labels:

* `__meta_kubernetes_namespace`: The namespace of the service object.
* `__meta_kubernetes_service_name`: The name of the service object.
* `__meta_kubernetes_service_label_<labelname>`: The label of the service object.
* `__meta_kubernetes_service_annotation_<annotationname>`: The annotation of the service object.
* `__meta_kubernetes_service_port_name`: Name of the service port for the target.
* `__meta_kubernetes_service_port_number`: Number of the service port for the target.
* `__meta_kubernetes_service_port_portocol`: Protocol of the service port for the target.

#### `pod`

The `pod` role discovers all pods and exposes their containers as targets. For each declared
port of a container, a single target is generated. If a container has no specified ports,
a port-free target per container is created for manually adding a port via relabeling.

Available meta labels:

* `__meta_kubernetes_namespace`: The namespace of the pod object.
* `__meta_kubernetes_pod_name`: The name of the pod object.
* `__meta_kubernetes_pod_ip`: The pod IP of the pod object.
* `__meta_kubernetes_pod_label_<labelname>`: The label of the pod object.
* `__meta_kubernetes_pod_annotation_<annotationname>`: The annotation of the pod object.
* `__meta_kubernetes_pod_container_name`: Name of the container the target address points to.
* `__meta_kubernetes_pod_container_port_name`: Name of the container port.
* `__meta_kubernetes_pod_container_port_number`: Number of the container port.
* `__meta_kubernetes_pod_container_port_protocol`: Protocol of the container port.
* `__meta_kubernetes_pod_ready`: Set to `true` or `false` for the pod's ready state.
* `__meta_kubernetes_pod_node_name`: The name of the node the pod is scheduled onto.
* `__meta_kubernetes_pod_host_ip`: The current host IP of the pod object.

#### `endpoints`

The `endpoints` role discovers targets from listed endpoints of a service. For each endpoint
address one target is discovered per port. If the endpoint is backed by a pod, all
additional container ports of the pod, not bound to an endpoint port, are discovered as targets as well.

Available meta labels:

* `__meta_kubernetes_namespace`: The namespace of the endpoints object.
* `__meta_kubernetes_endpoints_name`: The names of the endpoints object.
* For all targets discovered directly from the endpoints list (those not additionally inferred
  from underlying pods), the following labels are attached:
  * `__meta_kubernetes_endpoint_ready`: Set to `true` or `false` for the endpoint's ready state.
  * `__meta_kubernetes_endpoint_port_name`: Name of the endpoint port.
  * `__meta_kubernetes_endpoint_port_protocol`: Protocol of the endpoint port.
* If the endpoints belong to a service, all labels of the `role: service` discovery are attached.
* For all targets backed by a pod, all labels of the `role: pod` discovery are attached.


See below for the configuration options for Kubernetes discovery:

```
# The information to access the Kubernetes API.

# The API server addresses. If left empty, Prometheus is assumed to run inside
# of the cluster and will discover API servers automatically and use the pod's
# CA certificate and bearer token file at /var/run/secrets/kubernetes.io/serviceaccount/.
api_server: [<host>]

# The Kubernetes role of entities that should be discovered.
role: <role>

# Optional authentication information used to authenticate to the API server.
# Note that `basic_auth`, `bearer_token` and `bearer_token_file` options are
# mutually exclusive.

# Optional HTTP basic authentication information.
basic_auth:
  [ username: <string> ]
  [ password: <string> ]

# Optional bearer token authentication information.
[ bearer_token: <string> ]

# Optional bearer token file authentication information.
[ bearer_token_file: <filename> ]

# TLS configuration.
tls_config:
  [ <tls_config> ]
```

Where `<role>` must be `endpoints`, `service`, `pod`, or `node`.

See [this example Prometheus configuration file](https://github.com/prometheus/prometheus/blob/master/documentation/examples/prometheus-kubernetes.yml)
for a detailed example of configuring Prometheus for Kubernetes.

You may wish to check out the 3rd party [Prometheus Operator](https://github.com/coreos/prometheus-operator),
which automates the Prometheus setup on top of Kubernetes.

### `<marathon_sd_config>`

CAUTION: Marathon SD is in beta: breaking changes to configuration are still
likely in future releases.

Marathon SD configurations allow retrieving scrape targets using the
[Marathon](https://mesosphere.github.io/marathon/) REST API. Prometheus
will periodically check the REST endpoint for currently running tasks and
create a target group for every app that has at least one healthy task.

The following meta labels are available on targets during relabeling:

* `__meta_marathon_app`: the name of the app (with slashes replaced by dashes)
* `__meta_marathon_image`: the name of the Docker image used (if available)
* `__meta_marathon_task`: the ID of the Mesos task
* `__meta_marathon_app_label_<labelname>`: any Marathon labels attached to the app

See below for the configuration options for Marathon discovery:

```
# List of URLs to be used to contact Marathon servers.
# You need to provide at least one server URL, but should provide URLs for
# all masters you have running.
servers:
  - <string>

# Polling interval
[ refresh_interval: <duration> | default = 30s ]
```

By default every app listed in Marathon will be scraped by Prometheus. If not all
of your services provide Prometheus metrics, you can use a Marathon label and
Prometheus relabeling to control which instances will actually be scraped. Also
by default all apps will show up as a single job in Prometheus (the one specified
in the configuration file), which can also be changed using relabeling.

### `<nerve_sd_config>`

Nerve SD configurations allow retrieving scrape targets from [AirBnB's Nerve]
(https://github.com/airbnb/nerve) which are stored in
[Zookeeper](https://zookeeper.apache.org/).

The following meta labels are available on targets during relabeling:

* `__meta_nerve_path`: the full path to the endpoint node in Zookeeper
* `__meta_nerve_endpoint_host`: the host of the endpoint
* `__meta_nerve_endpoint_port`: the port of the endpoint
* `__meta_nerve_endpoint_name`: the name of the endpoint

```
# The Zookeeper servers.
servers:
  - <host>
# Paths can point to a single service, or the root of a tree of services.
paths:
  - <string>
[ timeout: <duration> | default = 10s ]
```

### `<serverset_sd_config>`

Serverset SD configurations allow retrieving scrape targets from [Serversets]
(https://github.com/twitter/finagle/tree/master/finagle-serversets) which are
stored in [Zookeeper](https://zookeeper.apache.org/). Serversets are commonly
used by [Finagle](https://twitter.github.io/finagle/) and
[Aurora](http://aurora.apache.org/).

The following meta labels are available on targets during relabeling:

* `__meta_serverset_path`: the full path to the serverset member node in Zookeeper
* `__meta_serverset_endpoint_host`: the host of the default endpoint
* `__meta_serverset_endpoint_port`: the port of the default endpoint
* `__meta_serverset_endpoint_host_<endpoint>`: the host of the given endpoint
* `__meta_serverset_endpoint_port_<endpoint>`: the port of the given endpoint
* `__meta_serverset_shard`: the shard number of the member
* `__meta_serverset_status`: the status of the member

```
# The Zookeeper servers.
servers:
  - <host>
# Paths can point to a single serverset, or the root of a tree of serversets.
paths:
  - <string>
[ timeout: <duration> | default = 10s ]
```

Serverset data must be in the JSON format, the Thrift format is not currently supported.

### `<static_config>`

A `static_config` allows specifying a list of targets and a common label set
for them.  It is the canonical way to specify static targets in a scrape
configuration.

```
# The targets specified by the static config.
targets:
  [ - '<host>' ]

# Labels assigned to all metrics scraped from the targets.
labels:
  [ <labelname>: <labelvalue> ... ]
```

Where `<host>` is a valid string consisting of a hostname or IP followed by a port
number.


### `<relabel_config>`

Relabeling is a powerful tool to dynamically rewrite the label set of a target before
it gets scraped. Multiple relabeling steps can be configured per scrape configuration.
They are applied to the label set of each target in order of their appearance
in the configuration file.

Initially, aside from the configured per-target labels, a target's `job`
label is set to the `job_name` value of the respective scrape configuration.
The `__address__` label is set to the `<host>:<port>` address of the target.
After relabeling, the `instance` label is set to the value of `__address__` by default if
it was not set during relabeling. The `__scheme__` and `__metrics_path__` labels
are set to the scheme and metrics path of the target respectively. The `__param_<name>`
label is set to the value of the first passed URL parameter called `<name>`.

Additional labels prefixed with `__meta_` may be available during the
relabeling phase. They are set by the service discovery mechanism that provided
the target and vary between mechanisms.

Labels starting with `__` will be removed from the label set after relabeling is completed.

If a relabeling step needs to store a label value only temporarily (as the
input to a subsequent relabeling step), use the `__tmp` label name prefix. This
prefix is guaranteed to never be used by Prometheus itself.

```
# The source labels select values from existing labels. Their content is concatenated
# using the configured separator and matched against the configured regular expression
# for the replace, keep, and drop actions.
[ source_labels: '[' <labelname> [, ...] ']' ]

# Separator placed between concatenated source label values.
[ separator: <string> | default = ; ]

# Label to which the resulting value is written in a replace action.
# It is mandatory for replace actions.
[ target_label: <labelname> ]

# Regular expression against which the extracted value is matched.
[ regex: <regex> | default = (.*) ]

# Modulus to take of the hash of the source label values.
[ modulus: <uint64> ]

# Replacement value against which a regex replace is performed if the
# regular expression matches.
[ replacement: <string> | default = $1 ]

# Action to perform based on regex matching.
[ action: <relabel_action> | default = replace ]
```

`<regex>` is any valid
[RE2 regular expression](https://github.com/google/re2/wiki/Syntax). It is
required for the `replace`, `keep`, `drop` and `labelmap` actions. The regex is
anchored on both ends. To un-anchor the regex, use `.*<regex>.*`.

`<relabel_action>` determines the relabeling action to take:

* `replace`: Match `regex` against the concatenated `source_labels`. Then, set
  `target_label` to `replacement`, with match group references
  (`${1}`, `${2}`, ...) in `replacement` substituted by their value. If `regex`
  does not match, no replacement takes place.
* `keep`: Drop targets for which `regex` does not match the concatenated `source_labels`.
* `drop`: Drop targets for which `regex` matches the concatenated `source_labels`.
* `hashmod`: Set `target_label` to the `modulus` of a hash of the concatenated `source_labels`.
* `labelmap`: Match `regex` against all label names. Then copy the values of the matching labels
   to label names given by `replacement` with match group references
  (`${1}`, `${2}`, ...) in `replacement` substituted by their value.

### `<metric_relabel_configs>`

Metric relabeling is applied to samples as the last step before ingestion. It
has the same configuration format and actions as target relabeling. Metric
relabeling does not apply to automatically generated timeseries such as `up`.

One use for this is to blacklist time series that are too expensive to ingest.

### `<alert_relabel_configs>`

Alert relabeling is applied to alerts before they are sent to the Alertmanager.
It has the same configuration format and actions as target relabeling. Alert
relabeling is applied after external labels.

One use for this is ensuring a HA pair of Prometheus servers with different
external labels send identical alerts.

### `<alertmanager_config>`

CAUTION: Dynamic discovery of Alertmanager instances is in alpha state. Breaking configuration
changes may happen in future releases. Use static configuration via the `-alertmanager.url` flag
as a stable alternative.

An `alertmanager_config` section specifies Alertmanager instances the Prometheus server sends 
alerts to. It also provides parameters to configure how to communicate with these Alertmanagers.

Alertmanagers may be statically configured via the `static_configs` parameter or
dynamically discovered using one of the supported service-discovery mechanisms.

Additionally, `relabel_configs` allow selecting Alertmanagers from discovered 
entities and provide advanced modifications to the used API path, which is exposed
through the `__alerts_path__` label.

```
# Per-target Alertmanager timeout when pushing alerts.
[ timeout: <duration> | default = 10s ]

# Prefix for the HTTP path alerts are pushed to. 
[ path_prefix: <path> | default = / ]

# Configures the protocol scheme used for requests.
[ scheme: <scheme> | default = http ]

# Sets the `Authorization` header on every request with the
# configured username and password.
basic_auth:
  [ username: <string> ]
  [ password: <string> ]

# Sets the `Authorization` header on every request with
# the configured bearer token. It is mutually exclusive with `bearer_token_file`.
[ bearer_token: <string> ]

# Sets the `Authorization` header on every request with the bearer token 
# read from the configured file. It is mutually exclusive with `bearer_token`.
[ bearer_token_file: /path/to/bearer/token/file ]

# Configures the scrape request's TLS settings.
tls_config:
  [ <tls_config> ]

# Optional proxy URL.
[ proxy_url: <string> ]

# List of Azure service discovery configurations.
azure_sd_configs:
  [ - <azure_sd_config> ... ]

# List of Consul service discovery configurations.
consul_sd_configs:
  [ - <consul_sd_config> ... ]

# List of DNS service discovery configurations.
dns_sd_configs:
  [ - <dns_sd_config> ... ]

# List of EC2 service discovery configurations.
ec2_sd_configs:
  [ - <ec2_sd_config> ... ]

# List of file service discovery configurations.
file_sd_configs:
  [ - <file_sd_config> ... ]

# List of GCE service discovery configurations.
gce_sd_configs:
  [ - <gce_sd_config> ... ]

# List of Kubernetes service discovery configurations.
kubernetes_sd_configs:
  [ - <kubernetes_sd_config> ... ]

# List of Marathon service discovery configurations.
marathon_sd_configs:
  [ - <marathon_sd_config> ... ]

# List of AirBnB's Nerve service discovery configurations.
nerve_sd_configs:
  [ - <nerve_sd_config> ... ]

# List of Zookeeper Serverset service discovery configurations.
serverset_sd_configs:
  [ - <serverset_sd_config> ... ]

# List of labeled statically configured Alertmanagers.
static_configs:
  [ - <static_config> ... ]

# List of Alertmanager relabel configurations.
relabel_configs:
  [ - <relabel_config> ... ]
```

Where `<scheme>` may be `http` or `https` and `<path>` is a valid URL path.

### `<remote_write>`
CAUTION: Remote write is experimental: breaking changes to configuration are
likely in future releases.

`url` is the URL of the endpoint to send samples to. `remote_timeout` specifies
the timeout for sending requests to the URL. There are no retries.

`basic_auth`, `tls_config` and `proxy_url` have the same meanings as in a
`scrape_config`.

`write_relabel_configs` is relabelling applied to samples before sending them
 to the URL. Write relabelling is applied after external labels. This could be
used to limit which samples are sent.

There is a [small
demo](https://github.com/prometheus/prometheus/tree/master/documentation/examples/remote_storage)
of how to use this functionality.
