Service Map
The service map is a blueprint that Pedestal uses to create all the necessary parts to begin processing requests: a service function, server function, chain provider, router, routes, and default set of interceptors.
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Server vs. Service
A server is just the part of the overall system that listens for requests and sends responses; it’s the part most closely tied to your underlying servlet container (Jetty, Tomcat, and so forth). The service runs the show: it’s the server plus everything else: chain provider, the interceptors (including those responsible for routing), and so forth. |
An application creates the service map and passes it to api:create-server[ns=io.pedestal.http]. The result is a server map that is ready to be started.
Keep in mind, however, that this is strictly a convenience function
that assembles the parts for you. There are use cases where you would
not call create-server, but instead assemble a service function,
chain provider, and so forth, directly.
Pedestal may add other keys to this map for its own use. Other applications should treat any such keys and their values as implementation details and their behaviour will remain unspecified.
Service Map Keys
| In the details below, ::http is an alias to :io.pedestal.http. |
| Key | Always present? | Type | Description |
|---|---|---|---|
::http/allowed-origins | N | Function, map, or sequence of strings | Determines which origins are allowed for the api:allow-origin[ns=io.pedestal.http.cors] interceptor. See "CORS" below. |
::http/chain-provider | N | Function | Only assigned when replacing the servlet-interceptor.adoc. Receives the service-map.adoc, returns an updated map with whatever additional pieces the server function expects. (See ::http/type, below.) |
::http/container-options | N | Map | Map of options to pass to the container. Each container, such as jetty.adoc, defines it own container-specific options. |
::http/enable-csrf | N | Map | A settings map to pass to the api:anti-forgery[ns=io.pedestal.http.csrf] interceptor. See CSRF below. |
::http/enable-session | N | Map | A settings map to pass to the api:session[ns=io.pedestal.http.ring-middlewares] interceptor. Settings are session-store specific. If non- |
::http/file-path | N | String | File path used as root by the api:file[ns=io.pedestal.http.ring-middlewares] interceptor. If non- |
::http/host | N | String | Hostname, e.g., "localhost". Passed to the container. Defaults to |
::http/initial-context | N | Map | The initial context-map.adoc that is passed through the interceptor chain; This option makes it possible to place values into the context for all requests. |
::http/interceptors | N | Vector | Vector of items that satisfy the api:IntoInterceptor[ns=io.pedestal.interceptor] protocol. |
::http/join? | N | Boolean | If |
::http/method-param-name | N | Keyword | Query string parameter used to set the current HTTP verb. Default is :_method. |
::http/mime-types | N | Map of String → String | Mime-types map used by the api:content-type[ns=io.pedestal.http.ring-middlewares] interceptor. Default is |
::http/not-found-interceptor | N | Interceptor | Interceptor to use when returning a 404 Not Found response. Default is the api:not-found[] interceptor. |
::http/port | N | Integer | Port for the running server. If |
::http/resource-path | N | String | File path used as root by the api:resource[ns=io.pedestal.http.ring-middlewares] interceptor. If non- |
::http/router | N | Keyword or route constructor | The router implementation to use. Can be :linear-search, :map-tree :prefix-tree, or a custom api:Router[ns=io.pedestal.http.route.router] constructor function. Defaults to :map-tree, which falls back to :prefix-tree. |
::http/routes | Y | Function, | A route specification that can be processed by api:expand-routes[ns=io.pedestal.http.route] into a routing table. |
::http/secure-headers | N | Map of keyword → string | A settings map for various secure headers. See "Secure Headers" below |
::http/service-fn | N | Function | A function which can be used as an implementation of the |
::http/service-fn-options | N | Map | Service function options passed to api:http-interceptor-service-fn[io.pedestal.http.impl.servlet-interceptor]. |
::http/servlet | N |
| Present if the servlet is running. |
::http/start-fn | N | Function | Zero-arity function that starts the server. Part of the server map. |
::http/stop-fn | N | Function | Zero-arity function that stops the server. Part of the server map. |
::http/type | Y | Keyword or Function | Container for service or server function. As a keyword, names the container - currently, only :jetty is supported out of the box. As a function, acts as the server function. When omitted, Jetty is the default. |
::http/websockets | N | Map | Defines websocket routing. See websockets.adoc. |
default-interceptors
The api:default-interceptors[] function is the primary user of the majority of the service map keys; it builds and attaches the ::http/interceptors key (a list of interceptors) from the various other service map keys, but only if the ::http/interceptors is itself nil or missing.
default-interceptors is called automatically from api:create-server[].
You may find that you do not rely on default-interceptors logic, but build your own interceptor
chain directly; in that case, simply attach the interceptors as ::http/interceptors before calling
api:create-server[]. Many of the other service map keys will not be needed, beyond ::http/port and ::http/type.
Cross-Origin Resource Sharing (CORS)
If the ::http/allowed-origins key is non-nil, the
api:allow-origin[ns=io.pedestal.http.cors]
interceptor is added. The default is nil.
The allowed values are:
-
a function of one argument that returns a truthy value when an origin is allowed;
-
a map containing the following keys and values :allowed-origins sequence of strings or a function, :creds boolean indicating whether the client is allowed to send credentials, :max-age a long indicating the number of seconds a client should cache the response, and :methods, indicating the accepted HTTP methods, defaulting to "GET, POST, PUT, DELETE, HEAD, PATCH, OPTIONS";
-
a sequence of strings matching the scheme, host and port (
scheme://host:port) of allowed origins.
Cross-Site Request Forgery (CSRF)
When a value for ::http/enable-csrf is present, the api:anti-forgery[ns=io.pedestal.http.csrf] interceptor is added to the queue. This implies that support for HTTP sessions are enabled (Pedestal will add the necessary interceptor automatically).
The value must be a map with the following keys:
| Key | Value type | Description |
|---|---|---|
:read-token | Function | This function takes a request and returns an anti-forgery token or |
:cookie-token | any | truthy value for CSRF double-submit cookies |
:error-response | Function | This function takes the response body and returns a 403 Not Authorized response |
:error-handler | Function | This function takes the context and returns the appropriate response. |
Only one of :error-response or :error-handler may be specified.
Secure Headers
When the ::http/secure-headers value is present and non-nil, the api:secure-headers[ns=io.pedestal.http.secure-headers] interceptor is added.
If the key is simply not present in the service map, then a set of default secure headers will be provided:
| Key | HTTP Header | Content |
|---|---|---|
:hsts-settings | Strict-Transport-Security | "max-age=31536000; includeSubdomains" |
:frame-options-settings | X-Frame-Options | "DENY" |
:content-type-settings | X-Content-Type-Options | "nosniff" |
:xss-protection-settings | X-XSS-Protection | "1; mode=block" |
:download-options-settings | X-Download-Options | "noopen" |
:cross-domain-policies-settings | X-Permitted-Cross-Domain-Policies | "none" |
:content-security-policy-settings | Content-Security-Policy | "object-src 'none'; script-src 'unsafe-inline' 'unsafe-eval' 'strict-dynamic' https: http:;" |
If the value for ::http/secure-headers is present, it may contain keys and string values for the security headers. Any other keys will be ignored.
Server Map
The api:server[] function converts the service map to a server map; much of this is
the responsibility of the container-specific server function, such as
api:server[ns=io.pedestal.http.jetty] - the function is determined from the ::http/type key of the service map.
This function is passed the full service map, and a set of server options; these options are a subset of the service map keys: :host, :port, :join?, :container-options, and :websockets (each as a non-namespaced keyword).
The server function should create a service (e.g., a Jetty Server) and return a map with
at least keys :start-fn and :stop-fn. These are then qualified into the io.pedestal.http namespace
and merged into the service map.
The api:start[] and api:stop[] functions use the ::http/start-fn and ::http/stop-fn keys to start and stop the server instance.
Spec Validation
The service map can grow quite complex, with options controlling everything from routing, to security, to container-specific options.
The service map may be validated via {clojure_spec}; this involves loading the appropriate spec namespaces and using Clojure’s built-in instrumention and testing support.
localhost is a safe default and works with local testing, as your test code will be on the same host as the server. However, only connections originating on the local host will be accepted. For production deployments, however, you will usually set this to be 0.0.0.0, which accepts connections from anywhere. This is especially true when running Pedestal inside a Docker container, as all connections (even those from the host, or from another container on the same host) will be network, not localhost, connections.
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