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docs HTTP API docs-agent-http The main interface to Consul is a RESTful HTTP API. The API can be used for CRUD for nodes, services, checks, and configuration. The endpoints are versioned to enable changes without breaking backwards compatibility.

HTTP API

The main interface to Consul is a RESTful HTTP API. The API can be used for CRUD for nodes, services, checks, and configuration. The endpoints are versioned to enable changes without breaking backwards compatibility.

All endpoints fall into one of several categories:

  • kv - Key/Value store
  • agent - Agent control
  • catalog - Manages nodes and services
  • health - Manages health checks
  • session - Session manipulation
  • acl - ACL creations and management
  • event - User Events
  • status - Consul system status
  • internal - Internal APIs. Purposely undocumented, subject to change.

Each of the categories and their respective endpoints are documented below.

Blocking Queries

Certain endpoints support a feature called a "blocking query." A blocking query is used to wait for a change to potentially take place using long polling.

Queries that support this will mention it specifically, however the use of this feature is the same for all. If supported, the query will set an HTTP header "X-Consul-Index". This is an opaque handle that the client will use.

To cause a query to block, the query parameters "?wait=<interval>&index=<idx>" are added to a request. The "?wait=" query parameter limits how long the query will potentially block for. It not set, it will default to 10 minutes. It can be specified in the form of "10s" or "5m", which is 10 seconds or 5 minutes respectively. The "?index=" parameter is an opaque handle, which is used by Consul to detect changes. The "X-Consul-Index" header for a query provides this value, and can be used to wait for changes since the query was run.

When provided, Consul blocks sending a response until there is an update that could have cause the output to change, and thus advancing the index. A critical note is that when the query returns there is no guarantee of a change. It is possible that the timeout was reached, or that there was an idempotent write that does not affect the result.

Consistency Modes

Most of the read query endpoints support multiple levels of consistency. These are to provide a tuning knob that clients can be used to find a happy medium that best matches their needs.

The three read modes are:

  • default - If not specified, this mode is used. It is strongly consistent in almost all cases. However, there is a small window in which an new leader may be elected, and the old leader may service stale values. The trade off is fast reads, but potentially stale values. This condition is hard to trigger, and most clients should not need to worry about the stale read. This only applies to reads, and a split-brain is not possible on writes.

  • consistent - This mode is strongly consistent without caveats. It requires that a leader verify with a quorum of peers that it is still leader. This introduces an additional round-trip to all server nodes. The trade off is always consistent reads, but increased latency due to an extra round trip. Most clients should not use this unless they cannot tolerate a stale read.

  • stale - This mode allows any server to service the read, regardless of if it is the leader. This means reads can be arbitrarily stale, but are generally within 50 milliseconds of the leader. The trade off is very fast and scalable reads but values will be stale. This mode allows reads without a leader, meaning a cluster that is unavailable will still be able to respond.

To switch these modes, either the "?stale" or "?consistent" query parameters are provided. It is an error to provide both.

To support bounding how stale data is, there is an "X-Consul-LastContact" which is the last time a server was contacted by the leader node in milliseconds. The "X-Consul-KnownLeader" also indicates if there is a known leader. These can be used to gauge if a stale read should be used.

Formatted JSON Output

By default, the output of all HTTP API requests return minimized JSON with all whitespace removed. By adding "?pretty" to the HTTP request URL, formatted JSON will be returned.

ACLs

Several endpoints in Consul use or require ACL tokens to operate. An agent can be configured to use a default token in requests using the acl_token configuration option. However, the token can also be specified per-request by using the "?token=" query parameter. This will take precedence over the default token.

KV

The KV endpoint is used to expose a simple key/value store. This can be used to store service configurations or other meta data in a simple way. It has only a single endpoint:

/v1/kv/<key>

This is the only endpoint that is used with the Key/Value store. Its use depends on the HTTP method. The GET, PUT and DELETE methods are all supported. It is important to note that each datacenter has its own K/V store, and that there is no replication between datacenters. By default the datacenter of the agent is queried, however the dc can be provided using the "?dc=" query parameter. If a client wants to write to all Datacenters, one request per datacenter must be made. The KV endpoint supports the use of ACL tokens.

If you are interested in Key/Value replication between datacenters, look at the consul-replicate project.

GET Method

When using the GET method, Consul will return the specified key, or if the "?recurse" query parameter is provided, it will return all keys with the given prefix.

Each object will look like:

[
  {
    "CreateIndex": 100,
    "ModifyIndex": 200,
    "LockIndex": 200,
    "Key": "zip",
    "Flags": 0,
    "Value": "dGVzdA==",
    "Session": "adf4238a-882b-9ddc-4a9d-5b6758e4159e"
  }
]

The CreateIndex is the internal index value that represents when the entry was created. The ModifyIndex is the last index that modified this key. This index corresponds to the X-Consul-Index header value that is returned. A blocking query can be used to wait for a value to change. If "?recurse" is used, the X-Consul-Index corresponds to the latest ModifyIndex and so a blocking query waits until any of the listed keys are updated. The LockIndex is the last index of a successful lock acquisition. If the lock is held, the Session key provides the session that owns the lock.

The Key is simply the full path of the entry. Flags are an opaque unsigned integer that can be attached to each entry. The use of this is left totally to the user. The Value is a base64 key value.

It is possible to also only list keys without their values by using the "?keys" query parameter along with a GET request. This will return a list of the keys under the given prefix. The optional "?separator=" can be used to list only up to a given separator.

For example, listing "/web/" with a "/" separator may return:

[
  "/web/bar",
  "/web/foo",
  "/web/subdir/"
]

Using the key listing method may be suitable when you do not need the values or flags, or want to implement a key-space explorer.

If the "?raw" query parameter is used with a non-recursive GET, then the response is just the raw value of the key, without any encoding.

If no entries are found, a 404 code is returned.

This endpoint supports blocking queries and all consistency modes.

PUT method

When using the PUT method, Consul expects the request body to be the value corresponding to the key. There are a number of parameters that can be used with a PUT request:

  • ?flags=<num> : This can be used to specify an unsigned value between 0 and 2^64-1. It is opaque to the user, but a client application may use it.

  • ?cas=<index> : This flag is used to turn the PUT into a Check-And-Set operation. This is very useful as it allows clients to build more complex synchronization primitives on top. If the index is 0, then Consul will only put the key if it does not already exist. If the index is non-zero, then the key is only set if the index matches the ModifyIndex of that key.

  • ?acquire=<session> : This flag is used to turn the PUT into a lock acquisition operation. This is useful as it allows leader election to be built on top of Consul. If the lock is not held and the session is valid, this increments the LockIndex and sets the Session value of the key in addition to updating the key contents. A key does not need to exist to be acquired.

  • ?release=<session> : This flag is used to turn the PUT into a lock release operation. This is useful when paired with "?acquire=" as it allows clients to yield a lock. This will leave the LockIndex unmodified but will clear the associated Session of the key. The key must be held by this session to be unlocked.

The return value is simply either true or false. If false is returned, then the update has not taken place.

DELETE method

The DELETE method can be used to delete a single key or all keys sharing a prefix. There are a number of query parameters that can be used with a DELETE request:

  • ?recurse : This is used to delete all keys which have the specified prefix. Without this, only a key with an exact match will be deleted.

  • ?cas=<index> : This flag is used to turn the DELETE into a Check-And-Set operation. This is very useful as it allows clients to build more complex synchronization primitives on top. If the index is 0, then Consul will only delete the key if it does not already exist (noop). If the index is non-zero, then the key is only deleted if the index matches the ModifyIndex of that key.

Agent

The Agent endpoints are used to interact with a local Consul agent. Usually, services and checks are registered with an agent, which then takes on the burden of registering with the Catalog and performing anti-entropy to recover from outages. There are also various control APIs that can be used instead of the msgpack RPC protocol.

The following endpoints are supported:

/v1/agent/checks

This endpoint is used to return the all the checks that are registered with the local agent. These checks were either provided through configuration files, or added dynamically using the HTTP API. It is important to note that the checks known by the agent may be different than those reported by the Catalog. This is usually due to changes being made while there is no leader elected. The agent performs active anti-entropy, so in most situations everything will be in sync within a few seconds.

This endpoint is hit with a GET and returns a JSON body like this:

{
  "service:redis": {
    "Node": "foobar",
    "CheckID": "service:redis",
    "Name": "Service 'redis' check",
    "Status": "passing",
    "Notes": "",
    "Output": "",
    "ServiceID": "redis",
    "ServiceName": "redis"
  }
}

/v1/agent/services

This endpoint is used to return the all the services that are registered with the local agent. These services were either provided through configuration files, or added dynamically using the HTTP API. It is important to note that the services known by the agent may be different than those reported by the Catalog. This is usually due to changes being made while there is no leader elected. The agent performs active anti-entropy, so in most situations everything will be in sync within a few seconds.

This endpoint is hit with a GET and returns a JSON body like this:

{
  "redis": {
    "ID": "redis",
    "Service": "redis",
    "Tags": null,
    "Address": "",
    "Port": 8000
  }
}

/v1/agent/members

This endpoint is hit with a GET and returns the members the agent sees in the cluster gossip pool. Due to the nature of gossip, this is eventually consistent and the results may differ by agent. The strongly consistent view of nodes is instead provided by "/v1/catalog/nodes".

For agents running in server mode, providing a "?wan=1" query parameter returns the list of WAN members instead of the LAN members which is default.

This endpoint returns a JSON body like:

[
  {
    "Name": "foobar",
    "Addr": "10.1.10.12",
    "Port": 8301,
    "Tags": {
      "bootstrap": "1",
      "dc": "dc1",
      "port": "8300",
      "role": "consul"
    },
    "Status": 1,
    "ProtocolMin": 1,
    "ProtocolMax": 2,
    "ProtocolCur": 2,
    "DelegateMin": 1,
    "DelegateMax": 3,
    "DelegateCur": 3
  }
]

/v1/agent/self

This endpoint is used to return configuration of the local agent and member information.

It returns a JSON body like this:

{
  "Config": {
    "Bootstrap": true,
    "Server": true,
    "Datacenter": "dc1",
    "DataDir": "/tmp/consul",
    "DNSRecursor": "",
    "DNSRecursors": [],
    "Domain": "consul.",
    "LogLevel": "INFO",
    "NodeName": "foobar",
    "ClientAddr": "127.0.0.1",
    "BindAddr": "0.0.0.0",
    "AdvertiseAddr": "10.1.10.12",
    "Ports": {
      "DNS": 8600,
      "HTTP": 8500,
      "RPC": 8400,
      "SerfLan": 8301,
      "SerfWan": 8302,
      "Server": 8300
    },
    "LeaveOnTerm": false,
    "SkipLeaveOnInt": false,
    "StatsiteAddr": "",
    "Protocol": 1,
    "EnableDebug": false,
    "VerifyIncoming": false,
    "VerifyOutgoing": false,
    "CAFile": "",
    "CertFile": "",
    "KeyFile": "",
    "StartJoin": [],
    "UiDir": "",
    "PidFile": "",
    "EnableSyslog": false,
    "RejoinAfterLeave": false
  },
  "Member": {
    "Name": "foobar",
    "Addr": "10.1.10.12",
    "Port": 8301,
    "Tags": {
      "bootstrap": "1",
      "dc": "dc1",
      "port": "8300",
      "role": "consul",
      "vsn": "1",
      "vsn_max": "1",
      "vsn_min": "1"
    },
    "Status": 1,
    "ProtocolMin": 1,
    "ProtocolMax": 2,
    "ProtocolCur": 2,
    "DelegateMin": 2,
    "DelegateMax": 4,
    "DelegateCur": 4
  }
}

/v1/agent/self/maintenance

The node maintenance endpoint allows placing the agent into "maintenance mode". During maintenance mode, the node will be marked as unavailable, and will not be present in DNS or API queries. This API call is idempotent. Maintenance mode is persistent and will be automatically restored on agent restart.

The ?enable flag is required, and its value must be true (to enter maintenance mode), or false (to resume normal operation).

The return code is 200 on success.

/v1/agent/join/<address>

This endpoint is hit with a GET and is used to instruct the agent to attempt to connect to a given address. For agents running in server mode, providing a "?wan=1" query parameter causes the agent to attempt to join using the WAN pool.

The endpoint returns 200 on successful join.

/v1/agent/force-leave/<node>

This endpoint is hit with a GET and is used to instructs the agent to force a node into the left state. If a node fails unexpectedly, then it will be in a "failed" state. Once in this state, Consul will attempt to reconnect, and additionally the services and checks belonging to that node will not be cleaned up. Forcing a node into the left state allows its old entries to be removed.

The endpoint always returns 200.

/v1/agent/check/register

The register endpoint is used to add a new check to the local agent. There is more documentation on checks here. Checks are of script, HTTP, or TTL type. The agent is responsible for managing the status of the check and keeping the Catalog in sync.

The register endpoint expects a JSON request body to be PUT. The request body must look like:

{
  "ID": "mem",
  "Name": "Memory utilization",
  "Notes": "Ensure we don't oversubscribe memory",
  "Script": "/usr/local/bin/check_mem.py",
  "HTTP": "http://example.com",
  "Interval": "10s",
  "TTL": "15s"
}

The Name field is mandatory, as is one of Script, HTTP or TTL. Script and HTTP also require that Interval be set.

If an ID is not provided, it is set to Name. You cannot have duplicate ID entries per agent, so it may be necessary to provide an ID. The Notes field is not used by Consul, and is meant to be human readable.

If a Script is provided, the check type is a script, and Consul will evaluate the script every Interval to update the status.

An HTTP check will preform an HTTP GET request to the value of HTTP (expected to be a URL) every Interval. If the response is any 2xx code the check is passing, if the response is 429 Too Many Requests the check is warning, otherwise the check is critical.

If a TTL type is used, then the TTL update APIs must be used to periodically update the state of the check.

It is also possible to associate a new check with an existing service registered on the agent by providing an additional ServiceID field. This type of request must look like:

{
  "ID": "service:redis:tx",
  "ServiceID": "redis",
  "Name": "Redis test transaction",
  "Notes": "Tests Redis SET, GET, and DELETE",
  "Script": "/usr/local/bin/check_redis_tx.py",
  "Interval": "1m"
}

The return code is 200 on success.

/v1/agent/check/deregister/<checkId>

The deregister endpoint is used to remove a check from the local agent. The CheckID must be passed after the slash. The agent will take care of deregistering the check with the Catalog.

The return code is 200 on success.

/v1/agent/check/pass/<checkId>

This endpoint is used with a check that is of the TTL type. When this endpoint is accessed via a GET, the status of the check is set to "passing", and the TTL clock is reset.

The optional "?note=" query parameter can be used to associate output with the status of the check. This should be human readable for operators.

The return code is 200 on success.

/v1/agent/check/warn/<checkId>

This endpoint is used with a check that is of the TTL type. When this endpoint is accessed via a GET, the status of the check is set to "warning", and the TTL clock is reset.

The optional "?note=" query parameter can be used to associate output with the status of the check. This should be human readable for operators.

The return code is 200 on success.

/v1/agent/check/fail/<checkId>

This endpoint is used with a check that is of the TTL type. When this endpoint is accessed via a GET, the status of the check is set to "critical", and the TTL clock is reset.

The optional "?note=" query parameter can be used to associate output with the status of the check. This should be human readable for operators.

The return code is 200 on success.

/v1/agent/service/register

The register endpoint is used to add a new service to the local agent. There is more documentation on services here. Services may also provide a health check. The agent is responsible for managing the status of the check and keeping the Catalog in sync.

The register endpoint expects a JSON request body to be PUT. The request body must look like:

{
  "ID": "redis1",
  "Name": "redis",
  "Tags": [
    "master",
    "v1"
  ],
  "Address": "127.0.0.1",
  "Port": 8000,
  "Check": {
    "Script": "/usr/local/bin/check_redis.py",
    "HTTP": "http://localhost:5000/health",
    "Interval": "10s",
    "TTL": "15s"
  }
}

The Name field is mandatory, If an ID is not provided, it is set to Name. You cannot have duplicate ID entries per agent, so it may be necessary to provide an ID. Tags, Address, Port and Check are optional. If Check is provided, only one of Script, HTTP or TTL should be provided. Script and HTTP also require Interval. There is more information about checks here. The Address will default to that of the agent if not provided.

The created check will be named "service:<ServiceId>".

The return code is 200 on success.

/v1/agent/service/deregister/<serviceId>

The deregister endpoint is used to remove a service from the local agent. The ServiceID must be passed after the slash. The agent will take care of deregistering the service with the Catalog. If there is an associated check, that is also deregistered.

The return code is 200 on success.

/v1/agent/service/maintenance/<serviceId>

The service maintenance endpoint allows placing a given service into "maintenance mode". During maintenance mode, the service will be marked as unavailable, and will not be present in DNS or API queries. This API call is idempotent. Maintenance mode is persistent and will be automatically restored on agent restart.

The ?enable flag is required, and its value must be true (to enter maintenance mode), or false (to resume normal operation).

The return code is 200 on success.

Catalog

The Catalog is the endpoint used to register and deregister nodes, services, and checks. It also provides a number of query endpoints.

The following endpoints are supported:

The last 4 endpoints of the catalog support blocking queries and consistency modes.

/v1/catalog/register

The register endpoint is a low level mechanism for directly registering or updating entries in the catalog. It is usually recommended to use the agent local endpoints, as they are simpler and perform anti-entropy.

The register endpoint expects a JSON request body to be PUT. The request body must look like:

{
  "Datacenter": "dc1",
  "Node": "foobar",
  "Address": "192.168.10.10",
  "Service": {
    "ID": "redis1",
    "Service": "redis",
    "Tags": [
      "master",
      "v1"
    ],
    "Address": "127.0.0.1",
    "Port": 8000
  },
  "Check": {
    "Node": "foobar",
    "CheckID": "service:redis1",
    "Name": "Redis health check",
    "Notes": "Script based health check",
    "Status": "passing",
    "ServiceID": "redis1"
  }
}

The behavior of the endpoint depends on what keys are provided. The endpoint requires Node and Address to be provided, while Datacenter will be defaulted to match that of the agent. If only those are provided, the endpoint will register the node with the catalog.

If the Service key is provided, then the service will also be registered. If ID is not provided, it will be defaulted to Service. It is mandated that the ID be node-unique. The Tags, Address and Port fields can be omitted.

If the Check key is provided, then a health check will also be registered. It is important to remember that this register API is very low level. This manipulates the health check entry, but does not setup a script or TTL to actually update the status. For that behavior, an agent local check should be setup.

The CheckID can be omitted, and will default to the Name. Like before, the CheckID must be node-unique. The Notes is an opaque field that is meant to hold human readable text. If a ServiceID is provided that matches the ID of a service on that node, then the check is treated as a service level health check, instead of a node level health check. The Status must be one of "unknown", "passing", "warning", or "critical". The "unknown" status is used to indicate that the initial check has not been performed yet.

It is important to note that Check does not have to be provided with Service and visa-versa. They can be provided or omitted at will.

If the API call succeeds a 200 status code is returned.

/v1/catalog/deregister

The deregister endpoint is a low level mechanism for directly removing entries in the catalog. It is usually recommended to use the agent local endpoints, as they are simpler and perform anti-entropy.

The deregister endpoint expects a JSON request body to be PUT. The request body must look like one of the following:

{
  "Datacenter": "dc1",
  "Node": "foobar",
}

{
  "Datacenter": "dc1",
  "Node": "foobar",
  "CheckID": "service:redis1"
}

{
  "Datacenter": "dc1",
  "Node": "foobar",
  "ServiceID": "redis1",
}

The behavior of the endpoint depends on what keys are provided. The endpoint requires Node to be provided, while Datacenter will be defaulted to match that of the agent. If only Node is provided, then the node, and all associated services and checks are deleted. If CheckID is provided, only that check belonging to the node is removed. If ServiceID is provided, then the service along with its associated health check (if any) is removed.

If the API call succeeds a 200 status code is returned.

/v1/catalog/datacenters

This endpoint is hit with a GET and is used to return all the datacenters that are known by the Consul server.

It returns a JSON body like this:

["dc1", "dc2"]

This endpoint does not require a cluster leader, and as such will succeed even during an availability outage. It can thus be a simple check to see if any Consul servers are routable.

/v1/catalog/nodes

This endpoint is hit with a GET and returns the nodes known about in a given DC. By default the datacenter of the agent is queried, however the dc can be provided using the "?dc=" query parameter.

It returns a JSON body like this:

[
  {
    "Node": "baz",
    "Address": "10.1.10.11"
  },
  {
    "Node": "foobar",
    "Address": "10.1.10.12"
  }
]

This endpoint supports blocking queries and all consistency modes.

/v1/catalog/services

This endpoint is hit with a GET and returns the services known about in a given DC. By default the datacenter of the agent is queried, however the dc can be provided using the "?dc=" query parameter.

It returns a JSON body like this:

{
  "consul": [],
  "redis": [],
  "postgresql": [
    "master",
    "slave"
  ]
}

The main object keys are the service names, while the array provides all the known tags for a given service.

This endpoint supports blocking queries and all consistency modes.

/v1/catalog/service/<service>

This endpoint is hit with a GET and returns the nodes providing a service in a given DC. By default the datacenter of the agent is queried, however the dc can be provided using the "?dc=" query parameter.

The service being queried must be provided after the slash. By default all nodes in that service are returned. However, the list can be filtered by tag using the "?tag=" query parameter.

It returns a JSON body like this:

[
  {
    "Node": "foobar",
    "Address": "10.1.10.12",
    "ServiceID": "redis",
    "ServiceName": "redis",
    "ServiceTags": null,
    "ServiceAddress": "",
    "ServicePort": 8000
  }
]

This endpoint supports blocking queries and all consistency modes.

/v1/catalog/node/<node>

This endpoint is hit with a GET and returns the node provided services. By default the datacenter of the agent is queried, however the dc can be provided using the "?dc=" query parameter. The node being queried must be provided after the slash.

It returns a JSON body like this:

{
  "Node": {
    "Node": "foobar",
    "Address": "10.1.10.12"
  },
  "Services": {
    "consul": {
      "ID": "consul",
      "Service": "consul",
      "Tags": null,
      "Port": 8300
    },
    "redis": {
      "ID": "redis",
      "Service": "redis",
      "Tags": [
        "v1"
      ],
      "Port": 8000
    }
  }
}

This endpoint supports blocking queries and all consistency modes.

Health

The Health used to query health related information. It is provided separately from the Catalog, since users may prefer to not use the health checking mechanisms as they are totally optional. Additionally, some of the query results from the Health system are filtered, while the Catalog endpoints provide the raw entries.

The following endpoints are supported:

All of the health endpoints supports blocking queries and all consistency modes.

/v1/health/node/<node>

This endpoint is hit with a GET and returns the node specific checks known. By default the datacenter of the agent is queried, however the dc can be provided using the "?dc=" query parameter. The node being queried must be provided after the slash.

It returns a JSON body like this:

[
  {
    "Node": "foobar",
    "CheckID": "serfHealth",
    "Name": "Serf Health Status",
    "Status": "passing",
    "Notes": "",
    "Output": "",
    "ServiceID": "",
    "ServiceName": ""
  },
  {
    "Node": "foobar",
    "CheckID": "service:redis",
    "Name": "Service 'redis' check",
    "Status": "passing",
    "Notes": "",
    "Output": "",
    "ServiceID": "redis",
    "ServiceName": "redis"
  }
]

In this case, we can see there is a system level check (no associated ServiceID, as well as a service check for Redis). The "serfHealth" check is special, in that all nodes automatically have this check. When a node joins the Consul cluster, it is part of a distributed failure detection provided by Serf. If a node fails, it is detected and the status is automatically changed to "critical".

This endpoint supports blocking queries and all consistency modes.

/v1/health/checks/<service>

This endpoint is hit with a GET and returns the checks associated with a service in a given datacenter. By default the datacenter of the agent is queried, however the dc can be provided using the "?dc=" query parameter. The service being queried must be provided after the slash.

It returns a JSON body like this:

[
  {
    "Node": "foobar",
    "CheckID": "service:redis",
    "Name": "Service 'redis' check",
    "Status": "passing",
    "Notes": "",
    "Output": "",
    "ServiceID": "redis",
    "ServiceName": "redis"
  }
]

This endpoint supports blocking queries and all consistency modes.

/v1/health/service/<service>

This endpoint is hit with a GET and returns the service nodes providing a given service in a given datacenter. By default the datacenter of the agent is queried, however the dc can be provided using the "?dc=" query parameter.

The service being queried must be provided after the slash. By default all nodes in that service are returned. However, the list can be filtered by tag using the "?tag=" query parameter.

This is very similar to the /v1/catalog/service endpoint however, this endpoint automatically returns the status of the associated health check, as well as any system level health checks. This allows a client to avoid sending traffic to nodes failing health tests, or who are reporting warnings.

Providing the "?passing" query parameter will filter results to only nodes with all checks in the passing state. This can be used to avoid some filtering logic on the client side. (Added in Consul 0.2)

Users can also built in support for dynamic load balancing and other features by incorporating the use of health checks.

It returns a JSON body like this:

[
  {
    "Node": {
      "Node": "foobar",
      "Address": "10.1.10.12"
    },
    "Service": {
      "ID": "redis",
      "Service": "redis",
      "Tags": null,
      "Port": 8000
    },
    "Checks": [
      {
        "Node": "foobar",
        "CheckID": "service:redis",
        "Name": "Service 'redis' check",
        "Status": "passing",
        "Notes": "",
        "Output": "",
        "ServiceID": "redis",
        "ServiceName": "redis"
      },
      {
        "Node": "foobar",
        "CheckID": "serfHealth",
        "Name": "Serf Health Status",
        "Status": "passing",
        "Notes": "",
        "Output": "",
        "ServiceID": "",
        "ServiceName": ""
      }
    ]
  }
]

This endpoint supports blocking queries and all consistency modes.

/v1/health/state/<state>

This endpoint is hit with a GET and returns the checks in a specific state for a given datacenter. By default the datacenter of the agent is queried, however the dc can be provided using the "?dc=" query parameter.

The state being queried must be provided after the slash. The supported states are "any", "unknown", "passing", "warning", or "critical". The "any" state is a wildcard that can be used to return all the checks.

It returns a JSON body like this:

[
  {
    "Node": "foobar",
    "CheckID": "serfHealth",
    "Name": "Serf Health Status",
    "Status": "passing",
    "Notes": "",
    "Output": "",
    "ServiceID": "",
    "ServiceName": ""
  },
  {
    "Node": "foobar",
    "CheckID": "service:redis",
    "Name": "Service 'redis' check",
    "Status": "passing",
    "Notes": "",
    "Output": "",
    "ServiceID": "redis",
    "ServiceName": "redis"
  }
]

This endpoint supports blocking queries and all consistency modes.

Session

The Session endpoints are used to create, destroy and query sessions. The following endpoints are supported:

All of the read session endpoints supports blocking queries and all consistency modes.

/v1/session/create

The create endpoint is used to initialize a new session. There is more documentation on sessions here. Sessions must be associated with a node, and optionally any number of checks. By default, the agent uses it's own node name, and provides the "serfHealth" check, along with a 15 second lock delay.

By default, the agent's local datacenter is used, but another datacenter can be specified using the "?dc=" query parameter. It is not recommended to use cross-region sessions.

The create endpoint expects a JSON request body to be PUT. The request body must look like:

{
  "LockDelay": "15s",
  "Name": "my-service-lock",
  "Node": "foobar",
  "Checks": ["a", "b", "c"],
  "Behavior": "release",
  "TTL": "0s"
}

None of the fields are mandatory, and in fact no body needs to be PUT if the defaults are to be used. The LockDelay field can be specified as a duration string using a "s" suffix for seconds. It can also be a numeric value. Small values are treated as seconds, and otherwise it is provided with nanosecond granularity.

The Node field must refer to a node that is already registered. By default, the agent will use it's own name. The Name field can be used to provide a human readable name for the Session. The Checks field is used to provide a list of associated health checks. By default the "serfHealth" check is provided. It is highly recommended that if you override this list, you include that check.

The Behavior field can be set to either "release" or "delete". This controls the behavior when a session is invalidated. By default this is "release", and this causes any locks that are held to be released. Changing this to "delete" causes any locks that are held to be deleted. This is useful to create ephemeral key/value entries.

The TTL field is a duration string, and like LockDelay it can use "s" as a suffix for seconds. If specified, it must be between 10s and 3600s currently. When provided, the session is invalidated if it is not renewed before the TTL expires. See the session internals page for more documentation.

The return code is 200 on success, along with a body like:

{
  "ID": "adf4238a-882b-9ddc-4a9d-5b6758e4159e"
}

This is used to provide the ID of the newly created session.

/v1/session/destroy/<session>

The destroy endpoint is hit with a PUT and destroys the given session. By default the local datacenter is used, but the "?dc=" query parameter can be used to specify the datacenter. The session being destroyed must be provided after the slash.

The return code is 200 on success.

/v1/session/info/<session>

This endpoint is hit with a GET and returns the session information by ID within a given datacenter. By default the datacenter of the agent is queried, however the dc can be provided using the "?dc=" query parameter. The session being queried must be provided after the slash.

It returns a JSON body like this:

[
  {
    "LockDelay": 1.5e+10,
    "Checks": [
      "serfHealth"
    ],
    "Node": "foobar",
    "ID": "adf4238a-882b-9ddc-4a9d-5b6758e4159e",
    "CreateIndex": 1086449
  }
]

If the session is not found, null is returned instead of a JSON list. This endpoint supports blocking queries and all consistency modes.

/v1/session/node/<node>

This endpoint is hit with a GET and returns the active sessions for a given node and datacenter. By default the datacenter of the agent is queried, however the dc can be provided using the "?dc=" query parameter. The node being queried must be provided after the slash.

It returns a JSON body like this:

[
  {
    "LockDelay": 1.5e+10,
    "Checks": [
      "serfHealth"
    ],
    "Node": "foobar",
    "ID": "adf4238a-882b-9ddc-4a9d-5b6758e4159e",
    "CreateIndex": 1086449
  },
  ...
]

This endpoint supports blocking queries and all consistency modes.

/v1/session/list

This endpoint is hit with a GET and returns the active sessions for a given datacenter. By default the datacenter of the agent is queried, however the dc can be provided using the "?dc=" query parameter.

It returns a JSON body like this:

[
  {
    "LockDelay": 1.5e+10,
    "Checks": [
      "serfHealth"
    ],
    "Node": "foobar",
    "ID": "adf4238a-882b-9ddc-4a9d-5b6758e4159e",
    "CreateIndex": 1086449
  },
  ...
]

This endpoint supports blocking queries and all consistency modes.

/v1/session/renew/<session>

The renew endpoint is hit with a PUT and renews the given session. This is used with sessions that have a TTL set, and it extends the expiration by the TTL. By default the local datacenter is used, but the "?dc=" query parameter can be used to specify the datacenter. The session being renewed must be provided after the slash.

The return code is 200 on success and a JSON body like this:

[
  {
    "LockDelay": 1.5e+10,
    "Checks": [
      "serfHealth"
    ],
    "Node": "foobar",
    "ID": "adf4238a-882b-9ddc-4a9d-5b6758e4159e",
    "CreateIndex": 1086449
    "Behavior": "release",
    "TTL": "15s"
  }
]

The response body includes the current session. Consul MAY return a TTL value higher than the one specified during session creation. This indicates the server is under high load and is requesting clients renew less often.

ACL

The ACL endpoints are used to create, update, destroy and query ACL tokens. The following endpoints are supported:

/v1/acl/create

The create endpoint is used to make a new token. A token has a name, type, and a set of ACL rules. The name is opaque to Consul, and type is either "client" or "management". A management token is effectively like a root user, and has the ability to perform any action including creating, modifying, and deleting ACLs. A client token can only perform actions as permitted by the rules associated, and may never manage ACLs. This means the request to this endpoint must be made with a management token.

In any Consul cluster, only a single datacenter is authoritative for ACLs, so all requests are automatically routed to that datacenter regardless of the agent that the request is made to.

The create endpoint expects a JSON request body to be PUT. The request body must look like:

{
  "Name": "my-app-token",
  "Type": "client",
  "Rules": ""
}

None of the fields are mandatory, and in fact no body needs to be PUT if the defaults are to be used. The Name and Rules default to being blank, and the Type defaults to "client". The format of Rules is documented here.

The return code is 200 on success, along with a body like:

{
  "ID": "adf4238a-882b-9ddc-4a9d-5b6758e4159e"
}

This is used to provide the ID of the newly created ACL token.

/v1/acl/update

The update endpoint is used to modify the policy for a given ACL token. It is very similar to the create endpoint, however instead of generating a new token ID, the ID field must be provided. Requests to this endpoint must be made with a management token.

In any Consul cluster, only a single datacenter is authoritative for ACLs, so all requests are automatically routed to that datacenter regardless of the agent that the request is made to.

The update endpoint expects a JSON request body to be PUT. The request body must look like:

{
  "ID": "adf4238a-882b-9ddc-4a9d-5b6758e4159e"
  "Name": "my-app-token-updated",
  "Type": "client",
  "Rules": "# New Rules",
}

Only the ID field is mandatory, the other fields provide defaults. The Name and Rules default to being blank, and the Type defaults to "client". The format of Rules is documented here.

The return code is 200 on success.

/v1/acl/destroy/<id>

The destroy endpoint is hit with a PUT and destroys the given ACL token. The request is automatically routed to the authoritative ACL datacenter. The token being destroyed must be provided after the slash, and requests to the endpoint must be made with a management token.

The return code is 200 on success.

/v1/acl/info/<id>

This endpoint is hit with a GET and returns the token information by ID. All requests are routed to the authoritative ACL datacenter The token being queried must be provided after the slash.

It returns a JSON body like this:

[
  {
    "CreateIndex": 3,
    "ModifyIndex": 3,
    "ID": "8f246b77-f3e1-ff88-5b48-8ec93abf3e05",
    "Name": "Client Token",
    "Type": "client",
    "Rules": "..."
  }
]

If the session is not found, null is returned instead of a JSON list.

/v1/acl/clone/<id>

The clone endpoint is hit with a PUT and returns a token ID that is cloned from an existing token. This allows a token to serve as a template for others, making it simple to generate new tokens without complex rule management. The source token must be provided after the slash. Requests to this endpoint require a management token.

The return code is 200 on success, along with a body like:

{
  "ID": "adf4238a-882b-9ddc-4a9d-5b6758e4159e"
}

This is used to provide the ID of the newly created ACL token.

/v1/acl/list

The list endpoint is hit with a GET and lists all the active ACL tokens. This is a privileged endpoint, and requires a management token.

It returns a JSON body like this:

[
  {
    "CreateIndex": 3,
    "ModifyIndex": 3,
    "ID": "8f246b77-f3e1-ff88-5b48-8ec93abf3e05",
    "Name": "Client Token",
    "Type": "client",
    "Rules": "..."
  },
  ...
]

Event

The Event endpoints are used to fire new events and to query the available events.

The following endpoints are supported:

/v1/event/fire/<name>

The fire endpoint is used to trigger a new user event. A user event needs a name, and optionally takes a number of parameters.

By default, the agent's local datacenter is used, but another datacenter can be specified using the "?dc=" query parameter.

The fire endpoint expects a PUT request, with an optional body. The body contents are opaque to Consul, and become the "payload" of the event. Any names starting with the "_" prefix should be considered reserved, and for Consul's internal use.

The ?node=, ?service=, and ?tag= query parameters may optionally be provided. They respectively provide a regular expression to filter by node name, service, and service tags.

The return code is 200 on success, along with a body like:

{
  "ID": "b54fe110-7af5-cafc-d1fb-afc8ba432b1c",
  "Name": "deploy",
  "Payload": null,
  "NodeFilter": "",
  "ServiceFilter": "",
  "TagFilter": "",
  "Version": 1,
  "LTime": 0
}

This is used to provide the ID of the newly fired event.

/v1/event/list

This endpoint is hit with a GET and returns the most recent events known by the agent. As a consequence of how the event command works, each agent may have a different view of the events. Events are broadcast using the gossip protocol, which means they have no total ordering, nor do they make a promise of delivery.

Additionally, each node applies the node, service and tag filters locally before storing the event. This means the events at each agent may be different depending on their configuration.

This endpoint does allow for filtering on events by name by providing the ?name= query parameter.

To support watches, this endpoint supports blocking queries. However, the semantics of this endpoint are slightly different. Most blocking queries provide a monotonic index, and block until a newer index is available. This can be supported as a consequence of the total ordering of the consensus protocol. With gossip, there is no ordering, and instead X-Consul-Index maps to the newest event that matches the query.

In practice, this means the index is only useful when used against a single agent, and has no meaning globally. Because Consul defines the index as being opaque, clients should not be expecting a natural ordering either.

Agents only buffer the most recent entries. The number of entries should not be depended upon, but currently defaults to 256. This value could change in the future. The buffer should be large enough for most clients and watches.

It returns a JSON body like this:

[
  {
    "ID": "b54fe110-7af5-cafc-d1fb-afc8ba432b1c",
    "Name": "deploy",
    "Payload": "MTYwOTAzMA==",
    "NodeFilter": "",
    "ServiceFilter": "",
    "TagFilter": "",
    "Version": 1,
    "LTime": 19
  },
  ...
]

Status

The Status endpoints are used to get information about the status of the Consul cluster. These are generally very low level, and not really useful for clients.

The following endpoints are supported:

/v1/status/leader

This endpoint is used to get the Raft leader for the datacenter the agent is running in. It returns only an address like:

"10.1.10.12:8300"

/v1/status/peers

This endpoint is used to get the Raft peers for the datacenter the agent is running in. It returns a list of addresses like:

[
  "10.1.10.12:8300",
  "10.1.10.11:8300",
  "10.1.10.10:8300"
]