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Filters

A Filter is a request/response processor. Multiple filters can be orchestrated together to form a pipeline, each filter returns a string result after it finishes processing the input request/response. An empty result means the input was successfully processed by the current filter and can go forward to the next filter in the pipeline, while a non-empty result means the pipeline or preceding filter needs to take extra action.

Proxy

The Proxy filter is a proxy of the backend service.

Below is one of the simplest Proxy configurations, it forward requests to http://127.0.0.1:9095.

kind: Proxy
name: proxy-example-1
pools:
- servers:
  - url: http://127.0.0.1:9095

Pool without filter is considered the main pool, other pools with filter are considered candidate pools. Proxy first checks if one of the candidate pools can process a request. For example, the first candidate pool in the below configuration selects and processes requests with the header X-Candidate:candidate, the second candidate pool randomly selects and processes 400‰ of requests, and the main pool processes the other 600‰ of requests.

kind: Proxy
name: proxy-example-2
pools:
- servers:
  - url: http://127.0.0.1:9095
- filter:
    headers:
      X-Candidate:
        exact: candidate
  servers:
  - url: http://127.0.0.1:9096
- filter:
    permil: 400 # between 0 and 1000
    policy: random
  servers:
  - url: http://127.0.0.1:9097

Servers of a pool can also be dynamically configured via service discovery, the below configuration gets a list of servers by serviceRegistry & serviceName, and only servers that have tag v2 are selected.

kind: Proxy
name: proxy-example-3
pools:
- serverTags: ["v2"]
  serviceName: service-001
  serviceRegistry: eureka-service-registry-example

When there are multiple servers in a pool, the Proxy can do a load balance between them:

kind: Proxy
name: proxy-example-4
pools:
- serverTags: ["v2"]
  serviceName: service-001
  serviceRegistry: eureka-service-registry-example
  loadBalance:
    policy: roundRobin

Configuration

Name Type Description Required
pools proxy.ServerPoolSpec The pool without filter is considered the main pool, other pools with filter are considered candidate pools, and a Proxy must contain exactly one main pool. When Proxy gets a request, it first goes through the candidate pools, and if one of the pool's filter matches the request, servers of this pool handle the request, otherwise, the request is passed to the main pool. Yes
mirrorPool proxy.ServerPoolSpec Define a mirror pool, requests are sent to this pool simultaneously when they are sent to candidate pools or main pool No
compression proxy.CompressionSpec Response compression options No
mtls proxy.MTLS mTLS configuration No
maxIdleConns int Controls the maximum number of idle (keep-alive) connections across all hosts. Default is 10240 No
maxIdleConnsPerHost int Controls the maximum idle (keep-alive) connections to keep per-host. Default is 1024 No
serverMaxBodySize int64 Max size of response body. the default value is 4MB. Responses with a body larger than this option are discarded. When this option is set to -1, Easegress takes the response body as a stream and the body can be any size, but some features are not possible in this case, please refer Stream for more information. No

Results

Value Description
internalError Encounters an internal error
clientError Client-side (Easegress) network error
serverError Server-side network error
failureCode Resp failure code matches failureCodes set in poolSpec

WebSocketProxy

The WebSocketProxy filter is a proxy of the websocket backend service.

Below is one of the simplest WebSocketProxy configurations, it forwards the websocket connection to ws://127.0.0.1:9095.

kind: WebSocketProxy
name: proxy-example-1
pools:
- servers:
  - url: ws://127.0.0.1:9095

Same as the Proxy filter:

  • a filter can be configured on a pool.
  • the servers of a pool can be dynamically configured via service discovery.
  • When there are multiple servers in a pool, the pool can do a load balance between them.

Note, when routing traffic to a pipeline with a WebSocketProxy, the HTTPServer must set the corresponding clientMaxBodySize to -1, as below:

name: demo-server
kind: HTTPServer
port: 8080
rules:
- paths:
  path: /ws
  clientMaxBodySize: -1          # REQUIRED!
  backend: websocket-pipeline

Configuration

Name Type Description Required
pools websocketproxy.WebSocketServerPoolSpec The pool without filter is considered the main pool, other pools with filter are considered candidate pools, and a Proxy must contain exactly one main pool. When WebSocketProxy gets a request, it first goes through the candidate pools, and if it matches one of the pool's filter, servers of this pool handle the connection, otherwise, it is passed to the main pool. Yes
defaultOrigin string Easegress need to set the Origin header when connecting to the backend service, if the client request does not have this header, this value is used. No

Results

Value Description
internalError Encounters an internal error
clientError Client-side network error

CORSAdaptor

The CORSAdaptor handles the CORS preflight, simple and not so simple request for the backend service.

The below example configuration handles the CORS GET request from *.megaease.com.

kind: CORSAdaptor
name: cors-adaptor-example
allowedOrigins: ["http://*.megaease.com"]
allowedMethods: [GET]

Configuration

Name Type Description Required
allowedOrigins []string An array of origins a cross-domain request can be executed from. If the special * value is present in the list, all origins will be allowed. An origin may contain a wildcard () to replace 0 or more characters (i.e.: http://.domain.com). Usage of wildcards implies a small performance penalty. Only one wildcard can be used per origin. Default value is * No
allowedMethods []string An array of methods the client is allowed to use with cross-domain requests. The default value is simple methods (HEAD, GET, and POST) No
allowedHeaders []string An array of non-simple headers the client is allowed to use with cross-domain requests. If the special * value is present in the list, all headers will be allowed. The default value is [] but "Origin" is always appended to the list No
allowCredentials bool Indicates whether the request can include user credentials like cookies, HTTP authentication, or client-side SSL certificates No
exposedHeaders []string Indicates which headers are safe to expose to the API of a CORS API specification No
maxAge int Indicates how long (in seconds) the results of a preflight request can be cached. The default is 0 stands for no max age No

Results

Value Description
preflighted The request is a preflight one and has been processed successfully.
rejected The request was rejected by CORS checking.

Fallback

The Fallback filter mocks a response as the fallback action of other filters. The below example configuration mocks the response with a specified status code, headers, and body.

kind: Fallback
name: fallback-example
mockCode: 200
mockHeaders:
  Content-Type: application/json
mockBody: '{"message": "The feature turned off, please try it later."}'

Configuration

Name Type Description Required
mockCode int This code overwrites the status code of the original response Yes
mockHeaders map[string]string Headers to be added/set to the original response No
mockBody string Default is an empty string, overwrite the body of the original response if specified No

Results

Value Description
fallback The fallback steps have been executed, this filter always return this result
responseNotFound No response found

Mock

The Mock filter mocks responses according to configured rules, mainly for testing purposes.

Below is an example configuration to mock response for requests to path /users/1 with specified status code, headers, and body, also with a 100ms delay to mock the time for request processing.

kind: Mock
name: mock-example
rules:
- match:
    path: /users/1
  code: 200
  headers:
    Content-Type: application/json
  body: '{"name": "alice", "age": 30}'
  delay: 100ms

Configuration

Name Type Description Required
rules []mock.Rule Mocking rules Yes

Results

Value Description
mocked The request matches one of the rules and response has been mocked

RemoteFilter

The RemoteFilter is a filter making remote service act as an internal filter. It forwards original request & response information to the remote service and returns a result according to the response of the remote service.

The below example configuration forwards request & response information to http://127.0.0.1:9096/verify.

kind: RemoteFilter
name: remote-filter-example
url: http://127.0.0.1:9096/verify
timeout: 500ms

Configuration

Name Type Description Required
url string Address of remote service Yes
timeout string Timeout duration of the remote service No

Results

Value Description
failed Failed to send the request to remote service, or remote service returns a non-2xx status code
responseAlready The remote service returns status code 205

RequestAdaptor

The RequestAdaptor modifies the original request according to configuration.

The example configuration below adds prefix /v3 to the request path.

kind: RequestAdaptor
name: request-adaptor-example
path:
  addPrefix: /v3

The example configuration below removes header X-Version from all GET requests.

kind: RequestAdaptor
name: request-adaptor-example
method: GET
header:
  del: ["X-Version"]

The example configuration below modifies the request path using regular expressions.

kind: RequestAdaptor
name: request-adaptor-example
path:
  regexpReplace:
    regexp: "^/([a-z]+)/([a-z]+)" # groups /$1/$2 for lowercase alphabet
    replace: "/$2/$1" # changes the order of groups

The example configuration below signs the request using the Amazon Signature V4 signing process, with the default configuration of this signing process.

kind: RequestAdaptor
name: request-adaptor-example
path:
  signer:
    for: "aws4"

Configuration

Name Type Description Required
method string If provided, the method of the original request is replaced by the value of this option No
path pathadaptor.Spec Rules to revise request path No
header httpheader.AdaptSpec Rules to revise request header No
body string If provided the body of the original request is replaced by the value of this option. No
host string If provided the host of the original request is replaced by the value of this option. No
decompress string If provided, the request body is replaced by the value of decompressed body. Now support "gzip" decompress No
compress string If provided, the request body is replaced by the value of compressed body. Now support "gzip" compress No
sign requestadaptor.SignerSpec If provided, sign the request using the Amazon Signature V4 signing process with the configuration No

Results

Value Description
decompressFail the request body can not be decompressed
compressFail the request body can not be compressed
signFail the request body can not be signed

RequestBuilder

The RequestBuilder creates a new request from existing requests/responses according to the configuration, and saves the new request into the namespace it is bound.

The example configuration below creates a reference to the request of namespace DEFAULT.

name: requestbuilder-example-1
kind: RequestBuilder
protocol: http
sourceNamespace: DEFAULT

The example configuration below creates an HTTP request with method GET, url http://127.0.0.1:8080, header X-Mock-Header:mock-value, and body this is the body.

name: requestbuilder-example-1
kind: RequestBuilder
protocol: http
template: |
  method: get
  url: http://127.0.0.1:8080
  headers:
    X-Mock-Header:
    - mock-value
  body: "this is the body"

Configuration

Name Type Description Required
protocol string protocol of the request to build, default is http. No
sourceNamespace string add a reference to the request of the source namespace No
template string template to create request, the schema of this option must conform with protocol, please refer the template for more information No
leftDelim string left action delimiter of the template, default is {{ No
rightDelim string right action delimiter of the template, default is }} No

NOTE: sourceNamespace and template are mutually exclusive, you must set one and only one of them.

Results

Value Description
buildErr error happens when build request

RateLimiter

RateLimiter protects backend service for high availability and reliability by limiting the number of requests sent to the service in a configured duration.

Below example configuration limits GET, POST, PUT, DELETE requests to path which matches regular expression ^/pets/\d+$ to 50 per 10ms, and a request fails if it cannot be permitted in 100ms due to high concurrency requests count.

kind: RateLimiter
name: rate-limiter-example
policies:
- name: policy-example
  timeoutDuration: 100ms
  limitRefreshPeriod: 10ms
  limitForPeriod: 50
defaultPolicyRef: policy-example
urls:
- methods: [GET, POST, PUT, DELETE]
  url:
    regex: ^/pets/\d+$
  policyRef: policy-example

Configuration

Name Type Description Required
policies []urlrule.URLRule Policy definitions Yes
defaultPolicyRef string The default policy, if no policyRef is configured in one of the urls, it uses this policy No
urls []resilience.URLRule An array of request match criteria and policy to apply on matched requests. Note that a standalone RateLimiter instance is created for each item of the array, even two or more items can refer to the same policy Yes

Results

Value Description
rateLimited The request has been rejected as a result of rate limiting

ResponseAdaptor

The ResponseAdaptor modifies the input response according to the configuration.

Below is an example configuration that adds a header named X-Response-Adaptor with the value response-adaptor-example to the input response.

kind: ResponseAdaptor
name: response-adaptor-example
header:
  add:
    X-Response-Adaptor: response-adaptor-example

Configuration

Name Type Description Required
header httpheader.AdaptSpec Rules to revise request header No
body string If provided the body of the original request is replaced by the value of this option. No
compress string compress body, currently only support gzip No
decompress string decompress body, currently only support gzip No

Results

Value Description
responseNotFound responseNotFound response is not found
decompressFailed error happens when decompress body
compressFailed error happens when compress body

ResponseBuilder

The ResponseBuilder creates a new response from existing requests/responses according to the configuration, and saves the new response into the namespace it is bound.

The example configuration below creates a reference to the response of namespace DEFAULT.

name: responsebuilder-example-1
kind: ResponseBuilder
protocol: http
sourceNamespace: DEFAULT

The example configuration below creates an HTTP response with status code 200, header X-Mock-Header:mock-value, and body this is the body.

name: responsebuilder-example-1
kind: ResponseBuilder
protocol: http
template: |
  statusCode: 200
  headers:
    X-Mock-Header:
    - mock-value
  body: "this is the body"

Configuration

Name Type Description Required
protocol string protocol of the response to build, default is http. No
sourceNamespace string add a reference to the response of the source namespace No
template string template to create response, the schema of this option must conform with protocol, please refer the template for more information No
leftDelim string left action delimiter of the template, default is {{ No
rightDelim string right action delimiter of the template, default is }} No

NOTE: sourceNamespace and template are mutually exclusive, you must set one and only one of them.

Results

Value Description
buildErr error happens when build response.

Validator

The Validator filter validates requests, forwards valid ones, and rejects invalid ones. Four validation methods (headers, jwt, signature, oauth2 and basicAuth) are supported up to now, and these methods can either be used together or alone. When two or more methods are used together, a request needs to pass all of them to be forwarded.

Below is an example configuration for the headers validation method. Requests which has a header named Is-Valid with value abc or goodplan or matches regular expression ^ok-.+$ are considered to be valid.

kind: Validator
name: header-validator-example
headers:
  Is-Valid:
    values: ["abc", "goodplan"]
    regexp: "^ok-.+$"

Below is an example configuration for the jwt validation method.

kind: Validator
name: jwt-validator-example
jwt:
  cookieName: auth
  algorithm: HS256
  secret: 6d79736563726574

Below is an example configuration for the signature validation method, note multiple access keys id/secret pairs can be listed in accessKeys, but there's only one pair here as an example.

kind: Validator
name: signature-validator-example
signature:
  accessKeys:
    AKID: SECRET

Below is an example configuration for the oauth2 validation method which uses a token introspection server for validation.

kind: Validator
name: oauth2-validator-example
oauth2:
  tokenIntrospect:
    endPoint: https://127.0.0.1:8443/auth/realms/test/protocol/openid-connect/token/introspect
    clientId: easegress
    clientSecret: 42620d18-871d-465f-912a-ebcef17ecb82
    insecureTls: false

Here's an example of basicAuth validation method which uses Apache2 htpasswd formatted encrypted password file for validation.

kind: Validator
name: basicAuth-validator-example
basicAuth:
  mode: "FILE"
  userFile: /etc/apache2/.htpasswd

Configuration

Name Type Description Required
headers map[string]httpheader.ValueValidator Header validation rules, the key is the header name and the value is validation rule for corresponding header value, a request needs to pass all of the validation rules to pass the headers validation No
jwt validator.JWTValidatorSpec JWT validation rule, validates JWT token string from the Authorization header or cookies No
signature signer.Spec Signature validation rule, implements an Amazon Signature V4 compatible signature validation validator, with customizable literal strings No
oauth2 validator.OAuth2ValidatorSpec The OAuth/2 method support Token Introspection mode and Self-Encoded Access Tokens mode, only one mode can be configured at a time No
basicAuth basicauth.BasicAuthValidatorSpec The BasicAuth method support FILE mode and ETCD mode, only one mode can be configured at a time. No

Results

Value Description
invalid The request doesn't pass validation

WasmHost

The WasmHost filter implements a host environment for user-developed WebAssembly code. Below is an example configuration that loads wasm code from a file, and more details could be found in this document.

name: wasm-host-example
kind: WasmHost
maxConcurrency: 2
code: /home/megaease/wasm/hello.wasm
timeout: 200ms

Note: this filter is disabled in the default build of Easegress, it can be enabled by:

$ make GOTAGS=wasmhost

or

$ make wasm

Configuration

Name Type Description Required
maxConcurrency int32 The maximum requests the filter can process concurrently. Default is 10 and minimum value is 1. Yes
code string The wasm code, can be the base64 encoded code, or path/url of the file which contains the code. Yes
timeout string Timeout for wasm execution, default is 100ms. Yes
parameters map[string]string Parameters to initialize the wasm code. No

Results

Value Description
outOfVM Can not found an available wasm VM.
wasmError An error occurs during the execution of wasm code.
wasmResult1 Results defined and returned by wasm code.
...
wasmResult9

Kafka

The Kafka filter converts HTTP Requests to Kafka messages and sends them to the Kafka backend. The topic of the Kafka message comes from the HTTP header, if not found, then the default topic will be used. The payload of the Kafka message comes from the body of the HTTP Request.

Below is an example configuration.

kind: Kafka
name: kafka-example
backend: [":9093"]
topic:
  default: kafka-topic
  dynamic:
    header: X-Kafka-Topic

Configuration

Name Type Description Required
backend []string Addresses of Kafka backend Yes
topic Kafka.Topic the topic is Spec used to get Kafka topic used to send message to the backend Yes

Results

Value Description
parseErr Failed to get Kafka message from the HTTP request

HeaderToJSON

The HeaderToJSON converts HTTP headers to JSON and combines it with the HTTP request body. To use this filter, make sure your HTTP Request body is empty or JSON schema.

Below is an example configuration.

kind: HeaderToJSON
name: headertojson-example
headerMap:
  - header: X-User-Name
    json: username
  - header: X-Type
    json: type

Configuration

Name Type Description Required
headerMap []HeaderToJSON.HeaderMap headerMap defines a map between HTTP header name and corresponding JSON field name Yes

Results

Value Description
jsonEncodeDecodeErr Failed to convert HTTP headers to JSON.
bodyReadErr Request body is stream

CertExtractor

CertExtractor extracts a value from requests TLS certificates Subject or Issuer metadata (https://pkg.go.dev/crypto/x509/pkix#Name) and adds the value to headers. Request can contain zero or multiple certificates so the position (first, second, last, etc) of the certificate in the chain is required.

Here's an example configuration, that adds a new header tls-cert-postalcode, based on the PostalCode of the last TLS certificate's Subject:

kind: "CertExtractor"
name: "postalcode-extractor"
certIndex: -1 # take last certificate in chain
target: "subject"
field: "PostalCode"
headerKey: "tls-cert-postalcode"

Configuration

Name Type Description Required
certIndex int16 The index of the certificate in the chain. Negative indexes from the end of the chain (-1 is the last index, -2 second last etc.) Yes
target string Either subject or issuer of the x509.Certificate Yes
field string One of the string or string slice fields from https://pkg.go.dev/crypto/x509/pkix#Name Yes
headerKey string Extracted value is added to this request header key. Yes

Results

The CertExtractor is always success and returns no results.

HeaderLookup

HeaderLookup checks custom data stored in etcd and put them into HTTP header.

Suppose you create a custom data kind of client-info and post a data key client1 with the value:

name: client1
id: 123
kind: vip

Then HeaderLookup with the following configuration adds X-Id:123 and X-Kind:vip to HTTP request header.

name: headerlookup-example-1
kind: HeaderLookup
etcdPrefix: client-info # get custom data kind
headerKey: client1      # get custom data name
headerSetters:
- etcdKey: id           # custom data value of id
  headerKey: X-Id
- etcdKey: kind         # custom data value of kind
  headerKey: X-Kind

You can also use pathRegExp to check different keys for different requests. When pathRegExp is defined, pathRegExp is used with regexp.FindStringSubmatch to identify a group from the path. The first captured group is appended to the etcd key in the following format: {headerKey's value}-{regex group}.

Suppose you create a custom data kind of client-info and post several data:

name: client-abc
id: 123
kind: vip

name: client-def
id: 124
kind: vvip

Then HeaderLookup with the following configuration adds X-Id:123 and X-Kind:vip for requests with path /api/abc, adds X-Id:124 and X-Kind:vvip for requests with path /api/def.

name: headerlookup-example-1
kind: HeaderLookup
etcdPrefix: client-info # get custom data kind
headerKey: client      # get custom data name
pathRegExp: "^/api/([a-z]+)"
headerSetters:
- etcdKey: id           # custom data value of id
  headerKey: X-Id
- etcdKey: kind         # custom data value of kind
  headerKey: X-Kind

Configuration

Name Type Description Required
etcdPrefix string Kind of custom data Yes
headerKey string Name of custom data in given kind Yes
pathRegExp string Reg used to get key from request path No
headerSetters []headerlookup.HeaderSetterSpec Set custom data value to http header Yes

Results

HeaderLookup has no results.

ResultBuilder

ResultBuilder generates a string, which will be the result of the filter. This filter exists to work with the jumpIf mechanism for conditional jumping.

Currently, the result string can only be result0 - result9, this will be changed in the future to allow arbitrary result string.

For example, we can use the following configuration to check if the request body contains an image field, and forward it to proxy1 or proxy2 conditionally.

name: demo-pipeline
kind: Pipeline
flow:
- filter: resultBuilder
  jumpIf:
    result1: proxy1
    result2: proxy2
- filter: proxy1
- filter: END
- filter: proxy2

filters:
- name: resultBuilder
  kind: ResultBuilder
  template: |
    {{- if .requests.DEFAULT.JSONBody.image}}result1{{else}}result2{{end -}}

Configuration

Name Type Description Required
template string template to create result, please refer the template for more information No
leftDelim string left action delimiter of the template, default is {{ No
rightDelim string right action delimiter of the template, default is }} No

Results

Value Description
unknown The ResultBuilder generates an unknown result.
buildErr Error happens when build the result.
result0 Results defined and returned by the template .
...
result9

DataBuilder

DataBuilder is used to manipulate and store data. The data from the previous filter can be transformed and stored in the context so that the data can be used in subsequent filters.

The example below shows how to use DataBuilder to store the request body in the context.

- name: requestBodyDataBuilder
  kind: DataBuilder
  dataKey: requestBody
  template: |
    {{.requests.DEFAULT.JSONBody | jsonEscape}}

Configuration

Name Type Description Required
template string template to create data, please refer the template for more information Yes
dataKey string key to store data Yes
leftDelim string left action delimiter of the template, default is {{ No
rightDelim string right action delimiter of the template, default is }} No

Results

Value Description
buildErr Error happens when building the data

OIDCAdaptor

OpenID Connect(OIDC) is an identity layer on top of the OAuth 2.0 protocol. It enables Clients to verify the identity of the End-User based on the authentication performed by an Authorization Server, as well as to obtain basic profile information about the End-User.

For identity platforms that implement standard OIDC specification like Google Accounts、OKTA、 Auth0、Authing. configure discovery endpoint as below example:

name: demo-pipeline
kind: Pipeline
flow:
  - filter: oidc
    jumpIf: { oidcFiltered: END }
filters:
  - name: oidc
    kind: OIDCAdaptor
    cookieName: oidc-auth-cookie
    clientId: <Your ClientId>
    clientSecret: <Your clientSecret>
    discovery: https://accounts.google.com/.well-known/openid-configuration  #Replace your own discovery
    redirectURI: /oidc/callback

For third platforms that only implement OAuth2.0 like GitHub, users should configure authorizationEndpoint、 tokenEndpoint、userinfoEndpoint at the same time as below example:

name: demo-pipeline
kind: Pipeline
flow:
  - filter: oidc
    jumpIf: { oidcFiltered: END }
filters:
  - name: oidc
    kind: OIDCAdaptor
    cookieName: oidc-auth-cookie
    clientId: <Your ClientId>
    clientSecret: <Your clientSecret>
    authorizationEndpoint: https://github.com/login/oauth/authorize
    tokenEndpoint: https://github.com/login/oauth/access_token
    userinfoEndpoint: https://api.github.com/user
    redirectURI: /oidc/callback

Configuration

Name Type Description Required
clientId string The OAuth2.0 app client id Yes
clientSecret string The OAuth2.0 app client secret Yes
cookieName string Used to check if necessary to launch OpenIDConnect flow No
discovery string Standard OpenID Connect discovery endpoint URL of the identity server No
authorizationEndpoint string OAuth2.0 authorization endpoint URL No
tokenEndpoint string OAuth2.0 token endpoint URL No
userInfoEndpoint string OAuth2.0 user info endpoint URL No
redirectURI string The callback uri registered in identity server, for example:
https://example.com/oidc/callback or /oidc/callback		 Yes

Results

Value Description
oidcFiltered The request is handled by OIDCAdaptor.

After OIDCAdaptor handled, following OIDC related information can be obtained from Easegress HTTP request headers:

  • X-User-Info: Base64 encoded OIDC End-User basic profile.
  • X-Origin-Request-URL: End-User origin request URL before OpenID Connect or OAuth2.0 flow.
  • X-Id-Token: The ID Token returned by OpenID Connect flow.
  • X-Access-Token: The AccessToken returned by OpenId Connect or OAuth2.0 flow.

OPAFilter

The Open Policy Agent (OPA) is an open source, general-purpose policy engine that unifies policy enforcement across the stack. It provides a high-level declarative language, we can specify policy as code to enforce policies in Easegress API Gateway. There are 185 builtin operators including functions we can use like examples net.cidr_contains and contains.

name: demo-pipeline
kind: Pipeline
flow:
  - filter: opa-filter
    jumpIf: { opaDenied: END }
filters:
  - name: opa-filter
    kind: OPAFilter
    defaultStatus: 403
    readBody: true
    includedHeaders: a,b,c
    policy: |
      package http
      default allow = false
      allow {
         input.request.method == "POST"
         input.request.scheme == "https"
         contains(input.request.path, "/")               
         net.cidr_contains("127.0.0.0/24",input.request.realIP)          
      }

The following table input request fields can be used in OPA policy to help make policy decision enforcement

Name Type Description Example
input.request.method string The current http request method "POST"
input.request.path string The current http request URL path "/a/b/c"
input.request.path_parts array The current http request URL path parts ["a","b","c"]
input.request.raw_query string The current http request raw query "a=1&b=2&c=3"
input.request.query map The current http request query map {"a":1,"b":2,"c":3}
input.request.headers map The current http request header map targeted by
includedHeaders		 {"Content-Type":"application/json"}
input.request.scheme string The current http request scheme "https"
input.request.realIP string The current http request client real IP "127.0.0.1"
input.request.body string The current http request body string data {"data":"xxx"}

Configuration

Name Type Description Required
defaultStatus int The default http status code when request is denied by OPA policy decision No
readBody bool Whether to read request body as OPA policy data on condition than body can be cast to string No
includedHeaders string Used to configure which HTTP headers should be included in input.request.headers,
comma-separated header names		 No
policy string The OPA policy written using Rego declarative language Yes

Results

Value Description
opaDenied The request is denied by OPA policy decision.

Common Types

pathadaptor.Spec

Name Type Description Required
replace string Replaces request path with the value of this option when specified No
addPrefix string Prepend the value of this option to request path when specified No
trimPrefix string Trims the value of this option if request path start with it when specified No
regexpReplace pathadaptor.RegexpReplace Revise request path with regular expression No

pathadaptor.RegexpReplace

Name Type Description Required
regexp string Regular expression to match request path. The syntax of the regular expression is RE2 Yes
replace string Replacement when the match succeeds. Placeholders like $1, $2 can be used to represent the sub-matches in regexp Yes

httpheader.AdaptSpec

Rules to revise request header.

Name Type Description Required
del []string Name of the headers to be removed No
set map[string]string Name & value of headers to be set No
add map[string]string Name & value of headers to be added No

proxy.ServerPoolSpec

Name Type Description Required
spanName string Span name for tracing, if not specified, the url of the target server is used No
serverTags []string Server selector tags, only servers have tags in this array are included in this pool No
servers []proxy.Server An array of static servers. If omitted, serviceName and serviceRegistry must be provided, and vice versa No
serviceName string This option and serviceRegistry are for dynamic server discovery No
serviceRegistry string This option and serviceName are for dynamic server discovery No
loadBalance proxy.LoadBalance Load balance options Yes
memoryCache proxy.MemoryCacheSpec Options for response caching No
filter proxy.RequestMatcherSpec Filter options for candidate pools No
serverMaxBodySize int64 Max size of response body, will use the option of the Proxy if not set. Responses with a body larger than this option are discarded. When this option is set to -1, Easegress takes the response body as a stream and the body can be any size, but some features are not possible in this case, please refer Stream for more information. No
timeout string Request calceled when timeout No
retryPolicy string Retry policy name No
circuitBreakerPolicy string CircuitBreaker policy name No
failureCodes []int Proxy return result of failureCode when backend resposne's status code in failureCodes. The default value is 5xx No

proxy.Server

Name Type Description Required
url string Address of the server. The address should start with http:// or https:// (when used in the WebSocketProxy, it can also start with ws:// and wss://), followed by the hostname or IP address of the server, and then optionally followed by :{port number}, for example: https://www.megaease.com, http://10.10.10.10:8080. When host name is used, the Host of a request sent to this server is always the hostname of the server, and therefore using a RequestAdaptor in the pipeline to modify it will not be possible; when IP address is used, the Host is the same as the original request, that can be modified by a RequestAdaptor. See also KeepHost. Yes
tags []string Tags of this server, refer serverTags in proxy.PoolSpec No
weight int When load balance policy is weightedRandom, this value is used to calculate the possibility of this server No
keepHost bool If true, the Host is the same as the original request, no matter what is the value of url. Default value is false. No

proxy.LoadBalanceSpec

Name Type Description Required
policy string Load balance policy, valid values are roundRobin, random, weightedRandom, ipHash ,and headerHash Yes
headerHashKey string When policy is headerHash, this option is the name of a header whose value is used for hash calculation No
stickySession proxy.StickySession Sticky session spec No

proxy.StickySessionSpec

Name Type Description Required
mode string Mode of session stickiness, support CookieConsistentHash,DurationBased,ApplicationBased Yes
appCookieName string Name of the application cookie, its value will be used as the session identifier for stickiness in CookieConsistentHash and ApplicationBased mode No
lbCookieName string Name of the cookie generated by load balancer, its value will be used as the session identifier for stickiness in DurationBased and ApplicationBased mode, default is EG_SESSION No
lbCookieExpire string Expire duration of the cookie generated by load balancer, its value will be used as the session expire time for stickiness in DurationBased and ApplicationBased mode, default is 2 hours No

proxy.MemoryCacheSpec

Name Type Description Required
codes []int HTTP status codes to be cached Yes
expiration string Expiration duration of cache entries Yes
maxEntryBytes uint32 Maximum size of the response body, response with a larger body is never cached Yes
methods []string HTTP request methods to be cached Yes

proxy.RequestMatcherSpec

Polices:

  • If the policy is empty or general, matcher match requests with headers and urls.
  • If the policy is ipHash, the matcher match requests if their IP hash value is less than `permil``.
  • If the policy is headerHash, the matcher match requests if their header hash value is less than permil, use the key of headerHashKey.
  • If the policy is random, the matcher matches requests with probability permil/1000.
Name Type Description Required
｜ policy string Policy used to match requests, support general, ipHash, headerHash, random No
headers map[string]proxy.StringMatcher Request header filter options. The key of this map is header name, and the value of this map is header value match criteria No
urls []proxy.MethodAndURLMatcher Request URL match criteria No
permil uint32 the probability of requests been matched. Value between 0 to 1000 No
matchAllHeaders bool All rules in headers should be match No
headerHashKey string Used by policy headerHash. No

proxy.StringMatcher

The relationship between exact, prefix, and regex is OR.

Name Type Description Required
exact string The string must be identical to the value of this field. No
prefix string The string must begin with the value of this field No
regex string The string must the regular expression specified by the value of this field No
empty bool The string must be empty No

proxy.MethodAndURLMatcher

The relationship between methods and url is AND.

Name Type Description Required
methods []string HTTP method criteria, Default is an empty list means all methods No
url proxy.StringMatcher Criteria to match a URL Yes

urlrule.URLRule

The relationship between methods and url is AND.

Name Type Description Required
methods []string HTTP method criteria, Default is an empty list means all methods No
url urlrule.StringMatch Criteria to match a URL Yes
policyRef string Name of resilience policy for matched requests No

proxy.Compression

Name Type Description Required
minLength int Minimum response body size to be compressed, response with a smaller body is never compressed Yes

proxy.MTLS

Name Type Description Required
certBase64 string Base64 encoded certificate Yes
keyBase64 string Base64 encoded key Yes
rootCertBase64 string Base64 encoded root certificate Yes

websocketproxy.WebSocketServerPoolSpec

Name Type Description Required
serverTags []string Server selector tags, only servers have tags in this array are included in this pool No
servers []proxy.Server An array of static servers. If omitted, serviceName and serviceRegistry must be provided, and vice versa No
serviceName string This option and serviceRegistry are for dynamic server discovery No
serviceRegistry string This option and serviceName are for dynamic server discovery No
loadBalance proxy.LoadBalance Load balance options Yes
filter proxy.RequestMatcherSpec Filter options for candidate pools No

mock.Rule

Name Type Description Required
code int HTTP status code of the mocked response Yes
match MatchRule Rule to match a request Yes
delay string Delay duration, for the request processing time mocking No
headers map[string]string Headers of the mocked response No
body string Body of the mocked response, default is an empty string No

mock.MatchRule

Name Type Description Required
path string Path match criteria, if request path is the value of this option, then the response of the request is mocked according to this rule No
pathPrefix string Path prefix match criteria, if request path begins with the value of this option, then the response of the request is mocked according to this rule No
matchAllHeaders bool Whether to match all headers No
headers map[string]url.StringMatch Headers to match, key is a header name, value is the rule to match the header value No

ratelimiter.Policy

Name Type Description Required
name string Name of the policy. Must be unique in one RateLimiter configuration Yes
timeoutDuration string Maximum duration a request waits for permission to pass through the RateLimiter. The request fails if it cannot get permission in this duration. Default is 100ms No
limitRefreshPeriod string The period of a limit refresh. After each period the RateLimiter sets its permissions count back to the limitForPeriod value. Default is 10ms No
limitForPeriod int The number of permissions available in one limitRefreshPeriod. Default is 50 No

httpheader.ValueValidator

Name Type Description Required
values []string An array of strings, if one of the header values of any header of the request is found in the array, the request is considered to pass the validation of current rule No
regexp string A regular expression, if one of the header values of any header of the request matches this regular expression, the request is considered to pass the validation of current rule No

validator.JWTValidatorSpec

Name Type Description Required
cookieName string The name of a cookie, if this option is set and the cookie exists, its value is used as the token string, otherwise, the Authorization header is used No
algorithm string The algorithm for validation:HS256,HS384,HS512,RS256,RS384,RS512,ES256,ES384,ES512,EdDSA are supported Yes
publicKey string The public key is used for RS256,RS384,RS512,ES256,ES384,ES512 or EdDSA validation in hex encoding Yes
secret string The secret is for HS256,HS384,HS512 validation in hex encoding Yes

signer.Spec

Name Type Description Required
literal signer.Literal Literal strings for customization, default value is used if omitted No
excludeBody bool Exclude request body from the signature calculation, default is false No
ttl string Time to live of a signature, default is 0 means a signature never expires No
accessKeys map[string]string A map of access key id to access key secret Yes
accessKeyId string ID used to set credential No
accessKeySecret string Value usd to set credential No
ignoredHeaders []string Headers to be ignored No
headerHoisting signer.HeaderHoisting HeaderHoisting defines which headers are allowed to be moved from header to query in presign: header with name has one of the allowed prefixes, but hasn't any disallowed prefixes and doesn't match any of disallowed names are allowed to be hoisted No

signer.HeaderHoisting

| Name | Type | Description | Required | | allowedPrefix | []string | Allowed prefix for headers | No | | disallowedPrefix | []string | Disallowed prefix for headers | No | | disallowed | []string | Disallowed headers | No |

signer.Literal

Name Type Description Required
scopeSuffix string The last part to build credential scope, default is request, in Amazon Signature V4, it is aws4_request No
algorithmName string The query name of the signature algorithm in the request, default is X-Algorithm, in Amazon Signature V4, it is X-Amz-Algorithm No
algorithmValue string The header/query value of the signature algorithm for the request, default is "HMAC-SHA256", in Amazon Signature V4, it is AWS4-HMAC-SHA256 No
signedHeaders string The header/query headers of the signed headers, default is X-SignedHeaders, in Amazon Signature V4, it is X-Amz-SignedHeaders No
signature string The query name of the signature, default is X-Signature, in Amazon Signature V4, it is X-Amz-Signature No
date string The header/query name of the request time, default is X-Date, in Amazon Signature V4, it is X-Amz-Date No
expires string The query name of expire duration, default is X-Expires, in Amazon Signature V4, it is X-Amz-Date No
credential string The query name of credential, default is X-Credential, in Amazon Signature V4, it is X-Amz-Credential No
contentSha256 string The header name of body/payload hash, default is X-Content-Sha256, in Amazon Signature V4, it is X-Amz-Content-Sha256 No
signingKeyPrefix string The prefix is prepended to access key secret when deriving the signing key, default is an empty string, in Amazon Signature V4, it is AWS4 No

validator.OAuth2ValidatorSpec

Name Type Description Required
tokenIntrospect validator.OAuth2TokenIntrospect Configuration for Token Introspection mode No
jwt validator.OAuth2JWT Configuration for Self-Encoded Access Tokens mode No

validator.OAuth2TokenIntrospect

Name Type Description Required
endPoint string The endpoint of the token introspection server Yes
clientId string Client id of Easegress in the token introspection server No
clientSecret string Client secret of Easegress No
basicAuth string If clientId not specified and this option is specified, its value is used for basic authorization with the token introspection server No
insecureTls bool Whether the connection between Easegress and the token introspection server need to be secure or not, default is false means the connection need to be a secure one No

validator.OAuth2JWT

Name Type Description Required
algorithm string The algorithm for validation, HS256, HS384 and HS512 are supported Yes
secret string The secret for validation, in hex encoding Yes

kafka.Topic

Name Type Description Required
default string Default topic for Kafka backend Yes
dynamic.header string The HTTP header that contains Kafka topic Yes

headertojson.HeaderMap

Name Type Description Required
header string The HTTP header that contains JSON value Yes
json string The field name to put JSON value into HTTP body Yes

headerlookup.HeaderSetterSpec

Name Type Description Required
etcdKey string Key used to get data No
headerKey string Key used to set data into http header No

requestadaptor.SignerSpec

This type is derived from signer.Spec, with the following two more fields.

Name Type Description Required
apiProvider string The RequestAdaptor pre-defines the Literal and HeaderHoisting configuration for some API providers, specify the provider name in this field to use one of them, only aws4 is supported at present. No
scopes []string Scopes of the input request No

Template Of Builder Filters

The content of the template field in the builder filters' spec is a a template defined in Golang text/template, with extra functions from the sprig package, and extra functions defined by Easegress:

  • addf: calculate the sum of the input two numbers.
  • subf: calculate the difference of the two input numbers.
  • mulf: calculate the product of the two input numbers.
  • divf: calculate the quotient of the two input numbers.
  • log: write a log message to Easegress log, the first argument must be debug, info, warn or error, and the second argument is the message.
  • mergeObject: merge two or more objects into one, the type of the input objects must be map[string]interface{}, and if one of their field is also an object, its type must also be map[string]interface{}.
  • jsonEscape: escape a string so that it can be used as the key or value in JSON text.

Easegress injects existing requests/responses of the current context into the template engine at runtime, so we can use .requests.<namespace>.<field> or .responses.<namespace>.<field> to read the information out (the available fields vary from the protocol of the request or response, and please refer Pipeline for what is namespace). For example, if the request of the DEFAULT namespace is an HTTP one, we can access its method via .requests.DEFAULT.Method.

Easegress also injects other data into the template engine, which can be accessed with .data.<name>, for example, we can use .data.PIPELINE to read the data defined in the pipeline spec.

The template should generate a string in YAML format, the schema of the result YAML varies from filters and protocols.

HTTP Specific

  • Available fields of existing requests

    All exported fields of the http.Request. And RawBody is the body as bytes; Body is the body as string; JSONBody is the body as a JSON object; YAMLBody is the body as a YAML object.

  • Available fields of existing responses

    All exported fields of the http.Response. And RawBody is the body as bytes; Body is the body as string; JSONBody is the body as a JSON object; YAMLBody is the body as a YAML object.

  • Schema of result request

    Name Type Description Required
    method string HTTP Method of the result request, default is GET. No
    url string URL of the result request, default is /. No
    headers map[string][]string Headers of the result request. No
    body string Body of the result request. No
    formData map[string]field Body of the result request, in form data pattern. No

    Please note body takes higher priority than formData, and the schema of field in formData is:

    Name Type Description Required
    value string value of the field. No
    fileName string the file name, if value is the content of a file. No

  • Schema of result response

    Name Type Description Required
    statusCode int HTTP status code, default is 200. No
    headers map[string][]string Headers of the result request. No
    body string Body of the result request. No