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Optimizely Agent

Optimizely Agent is a service which exposes the functionality of the Full Stack and Rollouts SDKs as a highly available and distributed web application.

Optimizely Full Stack is A/B testing and feature flag management for product development teams. Experiment in any application. Make every feature on your roadmap an opportunity to learn. Learn more at, or see the documentation.

Getting Started

To get started with Optimizely Agent, follow the Quickstart guide and view example usage in our examples folder.


Optimizely Agent is implemented in Golang. Golang version 1.13+ is required for developing and compiling from source. Installers and binary archives for most platforms can be downloaded directly from the Go downloads page.

Running from source (Linux / OSX)

Once Go is installed, the Optimizely Agent can be started via the following make command:

make setup
make run

This will start the Optimizely Agent with the default configuration in the foreground.

Running from source (Windows)

A helper script is available under scripts/build.ps1 to automate compiling Agent in a Windows environment. The script will download and install both Git and Golang and then attempt to compile Agent. Open a Powershell terminal and run

Set-ExecutionPolicy -ExecutionPolicy Unrestricted -Scope CurrentUser



Running via Docker

If you have Docker installed, Optimizely Agent can be started as a container. First pull the Docker image with:

docker pull optimizely/agent

By default this will pull the "latest" tag. You can also specify a specific version of Agent by providing the version as a tag to the docker command:

docker pull optimizely/agent:X.Y.Z

Then run the docker container with:

docker run -p 8080:8080 --env OPTIMIZELY_LOG_PRETTY=true --env OPTIMIZELY_SERVER_HOST= --env OPTIMIZELY_SERVER_ALLOWEDHOSTS= optimizely/agent

This will start Agent in the foreground and expose the container API port 8080 to the host.

Note that when a new version is released, 2 images are pushed to dockerhub, they are distinguished by their tags:

  • :latest (same as :X.Y.Z)
  • :alpine (same as :X.Y.Z-alpine)

The difference between latest and alpine is that latest is built FROM scratch while alpine is FROM alpine.

Configuration Options

Optimizely Agent configuration can be overridden by a yaml configuration file provided at runtime.

By default the configuration file will be sourced from the current active directory e.g. ./config.yaml. Alternative configuration locations can be specified at runtime via environment variable or command line flag.


The default configuration can be found here.

Below is a comprehensive list of available configuration properties.

Property Name Env Variable Description
admin.auth.clients N/A Credentials for requesting access tokens. See: Authorization Guide
admin.auth.hmacSecrets OPTIMIZELY_ADMIN_AUTH_HMACSECRETS Signing secret for issued access tokens. See: Authorization Guide
admin.auth.jwksUpdateInterval OPTIMIZELY_ADMIN_AUTH_JWKSUPDATEINTERVAL JWKS Update Interval for caching the keys in the background. See: Authorization Guide
admin.auth.jwksURL OPTIMIZELY_ADMIN_AUTH_JWKSURL JWKS URL for validating access tokens. See: Authorization Guide
admin.auth.ttl OPTIMIZELY_ADMIN_AUTH_TTL Time-to-live of issued access tokens. See: Authorization Guide
admin.port OPTIMIZELY_ADMIN_PORT Admin listener port. Default: 8088
api.auth.clients N/A Credentials for requesting access tokens. See: Authorization Guide
api.auth.hmacSecrets OPTIMIZELY_API_AUTH_HMACSECRETS Signing secret for issued access tokens. See: Authorization Guide
api.auth.jwksUpdateInterval OPTIMIZELY_API_AUTH_JWKSUPDATEINTERVAL JWKS Update Interval for caching the keys in the background. See: Authorization Guide
api.auth.jwksURL OPTIMIZELY_API_AUTH_JWKSURL JWKS URL for validating access tokens. See: Authorization Guide
api.auth.ttl OPTIMIZELY_API_AUTH_TTL Time-to-live of issued access tokens. See: Authorization Guide
api.enableNotifications OPTIMIZELY_API_ENABLENOTIFICATIONS Enable streaming notification endpoint. Default: false
api.enableOverrides OPTIMIZELY_API_ENABLEOVERRIDES Enable bucketing overrides endpoint. Default: false
api.maxConns OPTIMIZELY_API_MAXCONNS Maximum number of concurrent requests
api.port OPTIMIZELY_API_PORT Api listener port. Default: 8080
author OPTIMIZELY_AUTHOR Agent author. Default: Optimizely Inc.
client.batchSize OPTIMIZELY_CLIENT_BATCHSIZE The number of events in a batch. Default: 10
client.datafileURLTemplate OPTIMIZELY_CLIENT_DATAFILEURLTEMPLATE Template URL for SDK datafile location. Default:
client.eventURL OPTIMIZELY_CLIENT_EVENTURL URL for dispatching events. Default:
client.flushInterval OPTIMIZELY_CLIENT_FLUSHINTERVAL The maximum time between events being dispatched. Default: 30s
client.pollingInterval OPTIMIZELY_CLIENT_POLLINGINTERVAL The time between successive polls for updated project configuration. Default: 1m
client.queueSize OPTIMIZELY_CLIENT_QUEUESIZE The max number of events pending dispatch. Default: 1000
client.sdkKeyRegex OPTIMIZELY_CLIENT_SDKKEYREGEX Regex to validate SDK keys provided in request header. Default: ^\w+(:\w+)?$
client.userProfileService OPTIMIZELY_CLIENT_USERPROFILESERVICE Property used to enable and set UserProfileServices. Default: ./config.yaml
config.filename OPTIMIZELY_CONFIG_FILENAME Location of the configuration YAML file. Default: ./config.yaml
log.level OPTIMIZELY_LOG_LEVEL The log level for the agent. Default: info
log.pretty OPTIMIZELY_LOG_PRETTY Flag used to set colorized console output as opposed to structured json logs. Default: false
name OPTIMIZELY_NAME Agent name. Default: optimizely
sdkKeys OPTIMIZELY_SDKKEYS Comma delimited list of SDK keys used to initialize on startup
server.allowedHosts OPTIMIZELY_SERVER_ALLOWEDHOSTS List of allowed request host values. Requests whose host value does not match either the configured, or one of these, will be rejected with a 404 response. To match all subdomains, you can use a leading dot (for example matches,, etc.). You can use the value . to disable allowed host checking, allowing requests with any host. Request host is determined in the following priority order: 1. X-Forwarded-Host header value, 2. Forwarded header host= directive value, 3. Host property of request (see Host under Note: don't include port in these hosts values - port is stripped from the request host before comparing against these.
server.batchRequests.maxConcurrency OPTIMIZELY_SERVER_BATCHREQUESTS_MAXCONCURRENCY Number of requests running in parallel. Default: 10
server.batchRequests.operationsLimit OPTIMIZELY_SERVER_BATCHREQUESTS_OPERATIONSLIMIT Number of allowed operations. ( will flag an error if the number of operations exeeds this parameter) Default: 500
server.certfile OPTIMIZELY_SERVER_CERTFILE Path to a certificate file, used to run Agent with HTTPS
server.disabledCiphers OPTIMIZELY_SERVER_DISABLEDCIPHERS List of TLS ciphers to disable when accepting HTTPS connections
server.healthCheckPath OPTIMIZELY_SERVER_HEALTHCHECKPATH Path for the health status api. Default: /health OPTIMIZELY_SERVER_HOST Host of server. Default:
server.interceptors N/A Property used to enable and set Interceptor plugins
server.keyfile OPTIMIZELY_SERVER_KEYFILE Path to a key file, used to run Agent with HTTPS
server.readTimeout OPTIMIZELY_SERVER_READTIMEOUT The maximum duration for reading the entire body. Default: “5s”
server.writeTimeout OPTIMIZELY_SERVER_WRITETIMEOUT The maximum duration before timing out writes of the response. Default: “10s”
version OPTIMIZELY_VERSION Agent version. Default: git describe --tags
webhook.port OPTIMIZELY_WEBHOOK_PORT Webhook listener port: Default: 8085
webhook.projects.<projectId>.sdkKeys N/A Comma delimited list of SDK Keys applicable to the respective projectId
webhook.projects.<projectId>.secret N/A Webhook secret used to validate webhook requests originating from the respective projectId
webhook.projects.<projectId>.skipSignatureCheck N/A Boolean to indicate whether the signature should be validated. TODO remove in favor of empty secret.

More information about configuring Agent can be found in the Advanced Configuration Notes.


The core API is implemented as a REST service configured on it's own HTTP listener port (default 8080). The full API specification is defined in an OpenAPI 3.0 (aka Swagger) spec.

Each request made into the API must include a X-Optimizely-SDK-Key in the request header to identify the context the request should be evaluated. The SDK key maps to a unique Optimizely Project and Environment allowing multiple Environments to be serviced by a single Agent. For a secure environment, this header should include both the SDK key and the datafile access token separated by a colon. For example, if SDK key is my_key and datafile access token is my_token then set header's value to my_key:my_token.

Enabling CORS

CORS can be enabled for the core API service by setting the the appropriate cors properties.

      - "HEAD"
      - "GET"
      - "POST"
      - "OPTIONS"

For more advanced options please refer to the go-chi/cors middleware documentation.

NOTE: To avoid any potential security issues, and reduce risk to your data it's recommended that authentication is enabled alongside CORS.


The webhook listener used to receive inbound Webhook requests from These webhooks enable PUSH style notifications triggering immediate project configuration updates. The webhook listener is configured on its own port (default: 8085) since it can be configured to select traffic from the internet.

To accept webhook requests Agent must be configured by mapping an Optimizely Project Id to a set of SDK keys along with the associated secret used for validating the inbound request. An example webhook configuration can be found in the the provided config.yaml.

Admin API

The Admin API provides system information about the running process. This can be used to check the availability of the service, runtime information and operational metrics. By default the admin listener is configured on port 8088.


The /info endpoint provides basic information about the Optimizely Agent instance.

Example Request:

curl localhost:8088/info

Example Response:

    "version": "v0.10.0",
    "author": "Optimizely Inc.",
    "app_name": "optimizely"

Health Check

The /health endpoint is used to determine service availability.

Example Request:

curl localhost:8088/health

Example Response:

    "status": "ok"

Agent will return a HTTP 200 - OK response if and only if all configured listeners are open and all external dependent services can be reached. A non-healthy service will return a HTTP 503 - Unavailable response with a descriptive message to help diagnose the issue.

This endpoint can used when placing Agent behind a load balancer to indicate whether a particular instance can receive inbound requests.


The /metrics endpoint exposes telemetry data of the running Optimizely Agent. The core runtime metrics are exposed via the go expvar package. Documentation for the various statistics can be found as part of the mstats package.

Example Request:

curl localhost:8088/metrics

Example Response:

    "cmdline": [
    "memstats": {
        "Alloc": 924136,
        "TotalAlloc": 924136,
        "Sys": 71893240,
        "Lookups": 0,
        "Mallocs": 4726,
        "HeapAlloc": 924136,
        "Frees": 172

Custom metrics are also provided for the individual service endpoints and follow the pattern of:

"timers.<metric-name>.counts": 0,
"timers.<metric-name>.responseTime": 0,
"timers.<metric-name>.responseTimeHist.p50": 0,
"timers.<metric-name>.responseTimeHist.p90": 0,
"timers.<metric-name>.responseTimeHist.p95": 0,
"timers.<metric-name>.responseTimeHist.p99": 0,


Agent exposes the runtime profiling data in the format expected by the pprof visualization tool.

You can use the pprof tool to look at the heap profile:

go tool pprof http://localhost:6060/debug/pprof/heap

Or to look at a 5-second CPU profile: (higher durations require configuring the server.writeTimeout)

go tool pprof http://localhost:6060/debug/pprof/profile?seconds=5

Or to look at the goroutine blocking profile, after setting runtime.blockProfileRate in the configuration:

go tool pprof http://localhost:8088/debug/pprof/block

Or to collect a 5-second execution trace:

wget "http://localhost:8088/debug/pprof/trace?seconds=5"

Or to look at the holders of contended mutexes, after setting runtime.mutexProfileFraction in your configuration:

go tool pprof http://localhost:6060/debug/pprof/mutex

To view all available profiles can be found at http://localhost:8088/debug/pprof/ in your browser.

Agent Plugins

Optimizely Agent can be extended through the use of plugins. Plugins are distinct from the standard Agent packages to provide a namespaced environment for custom logic. Plugins must be compiled as part of the Agent distribution and are enabled through configuration.

Interceptor Plugins

UserProfileService Plugins


Optimizely Agent supports authorization workflows based on OAuth and JWT standards, allowing you to protect access to its API and Admin interfaces. For details, see Authorization Guide.


Just as you can use Notification Listeners to subscribe to events of interest with Optimizely SDKs, you can use the Notifications endpoint to subscribe to events in Agent. For more information, see the Notifications Guide.

Package Structure

Following best practice for go project layout as defined here

  • api - OpenAPI/Swagger specs, JSON schema files, protocol definition files.
  • bin - Compiled application binaries.
  • cmd - Main applications for this project.
  • config - Application configuration.
  • docs - User documentation files.
  • pkg - Library code that can be used by other applications.
  • plugins - Plugin libraries for extending Agent functionality.
  • scripts - Scripts to perform various build, install, analysis, etc operations.

Make targets

The following make targets can be used to build and run the application:

  • build - builds optimizely and installs binary in bin/optimizely
  • clean - runs go clean and removes the bin/ dir
  • cover - runs test suite with coverage profiling
  • cover-html - generates test coverage html report
  • install - installs all dev and ci dependencies, but does not install golang
  • lint - runs golangci-lint linters defined in .golangci.yml file
  • run - builds and executes the optimizely binary
  • test - recursively tests all .go files


This software is used with additional code that is separately downloaded by you. These components are subject to their own license terms which you should review carefully.

Gohistogram (c) 2013 VividCortex License (MIT):

Chi (c) 2015-present Peter Kieltyka (, Google Inc. License (MIT):

chi-render (c) 2016-Present ‑ authors License (MIT):

hostrouter (c) 2016-Present - authors License (MIT):

go-chi/cors (c) 2014 Olivier Poitrey License (MIT):

go-kit (c) 2015 Peter Bourgon License (MIT):

guuid (c) 2009,2014 Google Inc. All rights reserved. License (BSD 3-Clause):

optimizely go sdk (c) 2016-2017, Optimizely, Inc. and contributors License (Apache 2):

concurrent-map (c) 2014 streamrail License (MIT):

zerolog (c) 2017 Olivier Poitrey License (MIT):

viper (c) 2014 Steve Francia License (MIT):

testify (c) 2012-2018 Mat Ryer and Tyler Bunnell License (MIT):

net (c) 2009 The Go Authors License (BSD 3-Clause):

sync (c) 2009 The Go Authors License (BSD 3-Clause):

statik (c) 2014 rakyll License (Apache 2): v0.1.7

sys (c) 2009 The Go Authors License (BSD 3-Clause):

Apache Copyright Notice

Copyright 2019-present, Optimizely, Inc. and contributors

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.