Skip to content
Switch branches/tags

Latest commit


Git stats


Failed to load latest commit information.
Latest commit message
Commit time

Go Report Card


This repository contains the source code for the Cloud Foundry L7 HTTP router. Gorouter is deployed by default with Cloud Foundry (cf-deployment) which includes routing-release as submodule.

Note: This repository should be imported as

Reporting issues and requesting features

Please report all issues and feature requests in cloudfoundry/routing-release.


Please read the contributors' guide and our Development Guide for Gorouter.


The following instructions may help you get started with gorouter.


  • Go should be installed and in the PATH.
  • nats-server should be installed and in the PATH.
  • direnv should be installed and in the PATH.


Gorouter dependencies are managed with routing-release. Do not clone the gorouter repo directly; instead, follow instructions at (summarized below).

git clone
cd routing-release
cd src/

Note: direnv will automatically set your GOPATH when you cd into the routing-release directory. You will need to run direnv allow the first time.

Running Tests

Tests in this repo cannot be run on their own, only as part of Routing Release.

Follow the instructions for running tests in docker in the routing release readme.


Building creates an executable in the gorouter/ dir:

go build


Installing creates an executable in the $GOPATH/bin dir:

go install


# Start NATS server in daemon mode
go get
nats-server &

# Start gorouter


See [Routing Release 0.144.0 Release Notes] (

Dynamic Routing Table

Gorouters routing table is updated dynamically via the NATS message bus. NATS can be deployed via BOSH with (cf-deployment) or standalone using nats-release.

To add or remove a record from the routing table, a NATS client must send register or unregister messages. Records in the routing table have a maximum TTL of 120 seconds, so clients must heartbeat registration messages periodically; we recommend every 20s. Route Registrar is a BOSH job that comes with Routing Release that automates this process.

When deployed with Cloud Foundry, registration of routes for apps pushed to CF occurs automatically without user involvement. For details, see [Routes and Domains] (

Registering Routes via NATS

When the gorouter starts, it sends a router.start message to NATS. This message contains an interval that other components should then send router.register on, minimumRegisterIntervalInSeconds. It is recommended that clients should send router.register messages on this interval. This minimumRegisterIntervalInSeconds value is configured through the start_response_delay_interval configuration property. Gorouter will prune routes that it considers to be stale based upon a separate "staleness" value, droplet_stale_threshold, which defaults to 120 seconds. Gorouter will check if routes have become stale on an interval defined by prune_stale_droplets_interval, which defaults to 30 seconds. All of these values are represented in seconds and will always be integers.

The format of the router.start message is as follows:

  "id": "some-router-id",
  "hosts": [""],
  "minimumRegisterIntervalInSeconds": 20,
  "prunteThresholdInSeconds": 120

After a router.start message is received by a client, the client should send router.register messages. This ensures that the new router can update its routing table and synchronize with existing routers.

If a component comes online after the router, it must make a NATS request called router.greet in order to determine the interval. The response to this message will be the same format as router.start.

The format of the router.register message is as follows:

  "host": "",
  "port": 4567,
  "tls_port": 1234,
  "uris": [
  "tags": {
    "another_key": "another_value",
    "some_key": "some_value"
  "app": "some_app_guid",
  "stale_threshold_in_seconds": 120,
  "private_instance_id": "some_app_instance_id",
  "isolation_segment": "some_iso_seg_name",
  "server_cert_domain_san": "some_subject_alternative_name"

stale_threshold_in_seconds is the custom staleness threshold for the route being registered. If this value is not sent, it will default to the router's default staleness threshold.

app is a unique identifier for an application that the endpoint is registered for. This value will be included in router access logs with the label app_id, as well as being sent with requests to the endpoint in an HTTP header X-CF-ApplicationId.

private_instance_id is a unique identifier for an instance associated with the app identified by the app field. Gorouter includes an HTTP header X-CF-InstanceId set to this value with requests to the registered endpoint.

isolation_segment determines which routers will register route. Only Gorouters configured with the matching isolation segment will register the route. If a value is not provided, the route will be registered only by Gorouters set to the all or shared-and-segments router table sharding modes. Refer to the job properties for [Gorouter] ( for more information.

tls_port is the port that Gorouter will use to attempt TLS connections with the registered backends. Supported only when router.backend.enable_tls: true is configured in the manifest. router.ca_certs may be optionally configured with a CA, for backends certificates signed by custom CAs. For mutual authentication with backends, router.backends.tls_pem may be optionally provided. When router.backend.enable_tls: true, Gorouter will prefer tls_port over port if present in the NATS message. Otherwise, port will be preferred, and messages with only tls_port will be rejected and an error message logged.

server_cert_domain_san (required when tls_port is present) Indicates a string that Gorouter will look for in a Subject Alternative Name (SAN) of the TLS certificate hosted by the backend to validate instance identity. When the value of server_cert_domain_san does not match a SAN in the server certificate, Gorouter will prune the backend and retry another backend for the route if one exists, or return a 503 if it cannot validate the identity of any backend in three tries.

Additionally, if the host and tls_port pair matches an already registered host and port pair, the previously registered route will be overwritten and Gorouter will now attempt TLS connections with the host and tls_port pair. The same is also true if the host and port pair matches an already registered host and tls_port pair, except Gorouter will no longer attempt TLS connections with the backend.

Such a message can be sent to both the router.register subject to register URIs, and to the router.unregister subject to unregister URIs, respectively.

Deleting a Route

Routes can be deleted with the router.unregister nats message. The format of the router.unregister message the same as the router.register message, but most information is ignored. Any route that matches the host, port and uris fields will be deleted.


Create a simple app

$ nohup ruby -rsinatra -e 'get("/") { "Hello!" }' &

Send a register message

$ nats-pub 'router.register' '{"host":"","port":4567,"uris":["",""],"tags":{"another_key":"another_value","some_key":"some_value"}}'

Published [router.register] : '{"host":"","port":4567,"uris":["",""],"tags":{"another_key":"another_value","some_key":"some_value"}}'

See that it works!

$ curl

Unregister the route

$ nats-pub 'router.unregister' '{"host":"","port":4567,"tls_port":1234,"uris":["",""]}'

Published [router.unregister] : '{"host":"","port":4567,"tls_port":1234,"uris":["",""]}'

See that the route is gone

$ curl
404 Not Found: Requested route ('') does not exist.

If router.backends.enable_tls has been set to true, tls_port will be used as the definitive port when unregistering a route if present, otherwise port will be used. If router.backends.enable_tls is set to false, port will be preferred and any requests with only tls_port will be rejected and an error logged to the gorouter logs.

Note that if router.backends.enable_tls is true and host and tls_port happens to match a registered host and port pair, this host and port pair will be unregistered. The reverse is also true.

Note: In order to use nats-pub to register a route, you must install the gem on a Cloud Foundry VM. It's easiest on a VM that has ruby as a package, such as the API VM. Find the ruby installed in /var/vcap/packages, export your PATH variable to include the bin directory, and then run gem install nats. Find the nats login info from your gorouter config and use it to connect to the nats cluster.

Healthchecking from a Load Balancer

To scale Gorouter horizontally for high-availability or throughput capacity, you must deploy it behind a highly-available load balancer (F5, AWS ELB, etc).

Gorouter has a health endpoint /health on port 8080 that returns a 200 OK which indicates the Gorouter instance is healthy; any other response indicates unhealthy. This port can be configured via the router.status.port property in the BOSH deployment manifest or via the status.port property under /var/vcap/jobs/gorouter/config/gorouter.yml

$ curl -v
*   Trying
* Connected to ( port 8080 (#0)
> GET /health HTTP/1.1
> Host:
> User-Agent: curl/7.43.0
> Accept: */*
< HTTP/1.1 200 OK
< Cache-Control: private, max-age=0
< Expires: 0
< Date: Thu, 22 Sep 2016 00:13:54 GMT
< Content-Length: 3
< Content-Type: text/plain; charset=utf-8
* Connection #0 to host left intact

DEPRECATED: Your load balancer can be configured to send an HTTP healthcheck on port 80 with the User-Agent HTTP header set to HTTP-Monitor/1.1. A 200 response indicates the Gorouter instance is healthy; any other response indicates unhealthy. Gorouter can be configured to accept alternate values for the User Agent header using the healthcheck_user_agent configuration property; as an example, AWS ELBS send User-Agent: ELB-HealthChecker/1.0.

$ curl -v -A "HTTP-Monitor/1.1" ""
* Rebuilt URL to:
* Hostname was NOT found in DNS cache
*   Trying
* Connected to ( port 80 (#0)
> GET / HTTP/1.1
> User-Agent: HTTP-Monitor/1.1
> Host:
> Accept: */*
< HTTP/1.1 200 OK
< Cache-Control: private, max-age=0
< Expires: 0
< X-Vcap-Request-Id: 04ad84c6-43dd-4d20-7818-7c47595d9442
< Date: Thu, 07 Jan 2016 22:30:02 GMT
< Content-Length: 3
< Content-Type: text/plain; charset=utf-8
* Connection #0 to host left intact

DEPRECATED: The /healthz endpoint is now an alias for the /health endpoint to ensure backward compatibility.


The Routing Table

The /routes endpoint returns the entire routing table as JSON. This endpoint requires basic authentication and is served on port 8080. Each route has an associated array of host:port entries.

$ curl "http://someuser:somepass@"
  "": [
      "address": "",
      "ttl": 0,
      "tags": {
        "component": "CloudController"
  "": [
      "address": "",
      "ttl": 0,
      "tags": {
        "component": "route-emitter"
      "address": "",
      "ttl": 0,
      "tags": {
        "component": "route-emitter"

Because of the nature of the data present in /varz and /routes, they require http basic authentication credentials. These credentials can be found the BOSH manifest for cf-deployment under the router job:

      password: zed292_bevesselled
      user: paronymy61-polaric

If router.status.user is not set in the manifest, the default is router-status as can be seen from the job spec.

Or on the Gorouter VM under /var/vcap/jobs/gorouter/config/gorouter.yml:

  port: 8080
  user: some_user
  pass: some_password


The /varz endpoint provides status and metrics. This endpoint requires basic authentication.

Metrics response (click to expand)
$ curl "http://someuser:somepass@"
  "bad_gateways": 0,
  "bad_requests": 20,
  "cpu": 0,
  "credentials": [
  "droplets": 26,
  "host": "",
  "index": 0,
  "latency": {
    "50": 0.001418144,
    "75": 0.00180639025,
    "90": 0.0070607187,
    "95": 0.009561058849999996,
    "99": 0.01523927838000001,
    "samples": 1,
    "value": 5e-07
  "log_counts": {
    "info": 9,
    "warn": 40
  "mem": 19672,
  "ms_since_last_registry_update": 1547,
  "num_cores": 2,
  "rate": [
  "requests": 13832,
  "requests_per_sec": 1.1361328993362565,
  "responses_2xx": 13814,
  "responses_3xx": 0,
  "responses_4xx": 9,
  "responses_5xx": 0,
  "responses_xxx": 0,
  "start": "2016-01-07 19:04:40 +0000",
  "tags": {
    "component": {
      "CloudController": {
        "latency": {
          "50": 0.009015199,
          "75": 0.0107408015,
          "90": 0.015104917100000005,
          "95": 0.01916497394999999,
          "99": 0.034486261410000024,
          "samples": 1,
          "value": 5e-07
        "rate": [
        "requests": 1686,
        "responses_2xx": 1684,
        "responses_3xx": 0,
        "responses_4xx": 2,
        "responses_5xx": 0,
        "responses_xxx": 0
      "HM9K": {
        "latency": {
          "50": 0.0033354,
          "75": 0.00751815875,
          "90": 0.011916812100000005,
          "95": 0.013760064,
          "99": 0.013760064,
          "samples": 1,
          "value": 5e-07
        "rate": [
        "requests": 12,
        "responses_2xx": 6,
        "responses_3xx": 0,
        "responses_4xx": 6,
        "responses_5xx": 0,
        "responses_xxx": 0
      "dea-0": {
        "latency": {
          "50": 0.001354994,
          "75": 0.001642107,
          "90": 0.0020699939000000003,
          "95": 0.0025553900499999996,
          "99": 0.003677146940000006,
          "samples": 1,
          "value": 5e-07
        "rate": [
        "requests": 12103,
        "responses_2xx": 12103,
        "responses_3xx": 0,
        "responses_4xx": 0,
        "responses_5xx": 0,
        "responses_xxx": 0
      "uaa": {
        "latency": {
          "50": 0.038288465,
          "75": 0.245610809,
          "90": 0.2877324668,
          "95": 0.311816554,
          "99": 0.311816554,
          "samples": 1,
          "value": 5e-07
        "rate": [
        "requests": 17,
        "responses_2xx": 17,
        "responses_3xx": 0,
        "responses_4xx": 0,
        "responses_5xx": 0,
        "responses_xxx": 0
  "top10_app_requests": [
      "application_id": "063f95f9-492c-456f-b569-737f69c04899",
      "rpm": 60,
      "rps": 1
  "type": "Router",
  "uptime": "0d:3h:22m:31s",
  "urls": 21,
  "uuid": "0-c7fd7d76-f8d8-46b7-7a1c-7a59bcf7e286"

Profiling the Server

The Gorouter runs the debugserver, which is a wrapper around the go pprof tool. In order to generate this profile, do the following:

# Establish a SSH tunnel to your server (not necessary if you can connect directly)
ssh -L localhost:8080:[INTERNAL_SERVER_IP]:17001 vcap@[BOSH_DIRECTOR]
# Run the profile tool.
go tool pprof http://localhost:8080/debug/pprof/profile

Load Balancing

The Gorouter is, in simple terms, a reverse proxy that load balances between many backend instances. The default load balancing algorithm that Gorouter will use is a simple round-robin strategy. Gorouter will retry a request if the chosen backend does not accept the TCP connection.


Default load balancing algorithm that gorouter will use or may be explicitly set in gorouter.yml yaml default_balancing_algorithm: round-robin


The Gorouter also supports least connection based routing and this can be enabled in gorouter.yml

default_balancing_algorithm: least-connection

Least connection based load balancing will select the endpoint with the least number of connections. If multiple endpoints match with the same number of least connections, it will select a random one within those least connections.

NOTE: Gorouter currently only supports changing the load balancing strategy at the gorouter level and does not yet support a finer-grained level such as route-level. Therefore changing the load balancing algorithm from the default (round-robin) should be proceeded with caution.

When terminating TLS in front of Gorouter with a component that does not support sending HTTP headers

Enabling apps and CF to detect that request was encrypted using X-Forwarded-Proto

If you terminate TLS in front of Gorouter, your component should send the X-Forwarded-Proto HTTP header in order for applications and Cloud Foundry system components to correctly detect when the original request was encrypted. As an example, UAA will reject requests that do not include X-Forwarded-Proto: https.

If your TLS-terminating component does not support sending HTTP headers, we recommend also terminating TLS at Gorouter. In this scenario you should only disable TLS at Gorouter if your TLS-terminating component rejects unencrypted requests and your private network is completely trusted. In this case, use the following property to inform applications and CF system components that requests are secure.

    force_forwarded_proto_https: true

Enabling apps to detect the requestor's IP address using PROXY Protocol

If you terminate TLS in front of Gorouter, your component should also send the X-Forwarded-Proto HTTP header in order for X-Forwarded-For header to applications can detect the requestor's IP address.

If your TLS-terminating component does not support sending HTTP headers, you can use the PROXY protocol to send Gorouter the requestor's IP address.

If your TLS-terminating component supports the PROXY protocol, enable the PROXY protocol on Gorouter using the following cf-deployment manifest property:

    enable_proxy: true

You can test this feature manually:

echo -e "PROXY TCP4 [GOROUTER IP] 12345 [GOROUTER PORT]\r\nGET / HTTP/1.1\r\nHost: [APP URL]\r\n" | nc [GOROUTER IP] [GOROUTER PORT]

You should see in the access logs on the Gorouter that the X-Forwarded-For header is You can read more about the PROXY Protocol here.

HTTP/2 Support

The Gorouter does not currently support proxying HTTP/2 connections, even over TLS. Connections made using HTTP/1.1, either by TLS or cleartext, will be proxied to backends over cleartext.


The router's logging is specified in its YAML configuration file. It supports the following log levels:

  • fatal - A fatal error has occurred that makes gorouter unable to handle any requests. Examples: the router can't bind to its TCP port, a CF component has published invalid data to the router.
  • error - An unexpected error has occurred. Examples: the router failed to fetch token from UAA service.
  • info - An expected event has occurred. Examples: the router started or exited, the router has begun to prune routes for stale droplets.
  • debug - A lower-level event has occurred. Examples: route registration, route unregistration.

Sample log message in gorouter.

[2017-02-01 22:54:08+0000] {"log_level":0,"timestamp":"2019-11-21T22:16:18.750673404Z","message":"endpoint-registered","source":"vcap.gorouter.registry","data":{"uri":"0-*","backend":"","modification_tag":{"guid":"","index":0}}}

  • log_level: This represents logging level of the message
  • timestamp: Time of the log in either RFC 3339 (default) or epoch format
  • message: Content of the log line
  • source: The function within Gorouter that initiated the log message
  • data: Additional information that varies based on the message

Route table change logs

The following log messages are emitted any time the routing table changes:

  • route-registered: a new route is added to the table
  • route-unregistred: an existing route is removed from the table
  • endpoint-registered: a new backend is added to the table e.g. an app is scaled up and a new app instance is started
  • endpoint-unregistered: a backend is removed from the table e.g. an app is scaled down and an app instance is stopped


Route mapped to existing application with 1 app instance:


App with two mapped routes scaled up from 1 instance to 2:


App with two mapped routes scaled down from 2 instances to 1:


Route unmapped from application with 1 app instance:


Access logs

Access logs provide information for the following fields when receiving a request:

<Request Host> - [<Start Date>] "<Request Method> <Request URL> <Request Protocol>" <Status Code> <Bytes Received> <Bytes Sent> "<Referer>" "<User-Agent>" <Remote Address> <Backend Address> x_forwarded_for:"<X-Forwarded-For>" x_forwarded_proto:"<X-Forwarded-Proto>" vcap_request_id:<X-Vcap-Request-ID> response_time:<Response Time> gorouter_time:<Gorouter Time> app_id:<Application ID> app_index:<Application Index> x_cf_routererror:<X-Cf-RouterError> <Extra Headers>

  • Status Code, Response Time, Gorouter Time, Application ID, Application Index, X-Cf-RouterError, and Extra Headers are all optional fields. The absence of Status Code, Response Time, Application ID, Application Index, or X-Cf-RouterError will result in a "-" in the corresponding field.

  • Response Time is the total time it takes for the request to go through the Gorouter to the app and for the response to travel back through the Gorouter. This includes the time the request spends traversing the network to the app and back again to the Gorouter. It also includes the time the app spends forming a response.

  • Gorouter Time is the total time it takes for the request to go through the Gorouter initially plus the time it takes for the response to travel back through the Gorouter. This does not include the time the request spends traversing the network to the app. This also does not include the time the app spends forming a response.

  • X-CF-RouterError is populated if the Gorouter encounters an error. This can help distinguish if a non-2xx response code is due to an error in the Gorouter or the backend. For more information on the possible Router Error causes go to the #router-errors section.

Access logs are also redirected to syslog.


If a user wants to send requests to a specific app instance, the header X-CF-APP-INSTANCE can be added to indicate the specific instance to be targeted. The format of the header value should be X-Cf-App-Instance: APP_GUID:APP_INDEX. If the instance cannot be found or the format is wrong, a 400 status code is returned. In addition, Gorouter will return a X-Cf-Routererror header. If the instance guid provided is incorrectly formatted, the value of the header will be invalid_cf_app_instance_header. If the instance guid provided is correctly formatted, but the guid does not exist, the value of this header will be unknown_route, and the request body will contain 400 Bad Request: Requested instance ('1') with guid ('aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa') does not exist for route ('').

Usage of the X-Cf-App-Instance header is only available for users on the Diego architecture.

Router Errors

The value of the X-Cf-Routererror header can be one of the following:

Value Description
invalid_cf_app_instance_header The provided value for the "X-Cf-App-Instance" header does not match the required format of APP_GUID:INSTANCE_ID.
empty_host The value for the "Host" header is empty, or the "Host" header is equivalent to the remote address. Some LB's optimistically set the "Host" header value with their IP address when there is no value present.
unknown_route The desired route does not exist in the gorouter's route table.
no_endpoints There is an entry in the route table for the desired route, but there are no healthy endpoints available.
Connection Limit Reached The backends associated with the route have reached their max number of connections. The max connection number is set via the spec property router.backends.max_conns.
route_service_unsupported Route services are not enabled. This can be configured via the spec property router.route_services_secret. If the property is empty, route services are disabled.
endpoint_failure The registered endpoint for the desired route failed to handle the request.

Supported Cipher Suites

The Gorouter supports both RFC and OpenSSL formatted values. Refer to golang 1.9 for the list of supported cipher suites for Gorouter. Refer to this documentation for a list of OpenSSL RFC mappings. Example configurations enabling the TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 cipher suite for Gorouter:

enable_ssl: true
cipher_suite: "ECDHE-ECDSA-AES128-GCM-SHA256"


enable_ssl: true
cipher_suite: "TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256"


There is a separate docs folder which contains more advanced topics.


Refer doc to learn more troubleshooting slow requests.


CF Router




No releases published


No packages published