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spark-webui-JettyUtils.adoc

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JettyUtils

JettyUtils is a set of utility methods for creating Jetty HTTP Server-specific components.

Table 1. JettyUtils’s Utility Methods
Name Description

createServlet

Creates an HttpServlet

createStaticHandler

Creates a Handler for a static content

createServletHandler

Creates a ServletContextHandler for a path

createRedirectHandler

Creating ServletContextHandler for Path — createServletHandler Method

createServletHandler(
  path: String,
  servlet: HttpServlet,
  basePath: String): ServletContextHandler  // (1)
createServletHandler[T <: AnyRef](
  path: String,
  servletParams: ServletParams[T],
  securityMgr: SecurityManager,
  conf: SparkConf,
  basePath: String = ""): ServletContextHandler // (2)

  1. Calls the first three-argument createServletHandler with

createServletHandler…​FIXME

Note

createServletHandler is used when:

  • WebUI is requested to attachPage

  • MetricsServlet is requested to getHandlers

  • Spark Standalone’s WorkerWebUI is requested to initialize

Creating HttpServlet — createServlet Method

createServlet[T <: AnyRef](
  servletParams: ServletParams[T],
  securityMgr: SecurityManager,
  conf: SparkConf): HttpServlet

createServlet creates the X-Frame-Options header that can be either ALLOW-FROM with the value of spark.ui.allowFramingFrom configuration property if defined or SAMEORIGIN.

createServlet creates a Java Servlets HttpServlet with support for GET requests.

When handling GET requests, the HttpServlet first checks view permissions of the remote user (by requesting the SecurityManager to checkUIViewPermissions of the remote user).

Tip

Enable DEBUG logging level for org.apache.spark.SecurityManager logger to see what happens when SecurityManager does the security check.

Add the following line to conf/log4j.properties:

log4j.logger.org.apache.spark.SecurityManager=DEBUG

You should see the following DEBUG message in the logs:

DEBUG SecurityManager: user=[user] aclsEnabled=[aclsEnabled] viewAcls=[viewAcls] viewAclsGroups=[viewAclsGroups]

With view permissions check passed, the HttpServlet sends a response with the following:

  • FIXME

In case the view permissions didn’t allow to view the page, the HttpServlet sends an error response with the following:

  • Status 403

  • Cache-Control header with "no-cache, no-store, must-revalidate"

  • Error message: "User is not authorized to access this page."

Note
 createServlet is used exclusively when JettyUtils is requested to createServletHandler.

Creating Handler For Static Content — createStaticHandler Method

createStaticHandler(resourceBase: String, path: String): ServletContextHandler

createStaticHandler creates a handler for serving files from a static directory

Internally, createStaticHandler creates a Jetty ServletContextHandler and sets org.eclipse.jetty.servlet.Default.gzip init parameter to false.

createRedirectHandler creates a Jetty DefaultServlet.

Note

Quoting the official documentation of Jetty’s DefaultServlet:

DefaultServlet The default servlet. This servlet, normally mapped to /, provides the handling for static content, OPTION and TRACE methods for the context. The following initParameters are supported, these can be set either on the servlet itself or as ServletContext initParameters with a prefix of org.eclipse.jetty.servlet.Default.

With that, org.eclipse.jetty.servlet.Default.gzip is to configure gzip init parameter for Jetty’s DefaultServlet.

gzip If set to true, then static content will be served as gzip content encoded if a matching resource is found ending with ".gz" (default false) (deprecated: use precompressed)

createRedirectHandler resolves the resourceBase in the Spark classloader and, if successful, sets resourceBase init parameter of the Jetty DefaultServlet to the URL.

Note
 resourceBase init parameter is used to replace the context resource base.

createRedirectHandler requests the ServletContextHandler to use the path as the context path and register the DefaultServlet to serve it.

createRedirectHandler throws an Exception if the input resourceBase could not be resolved.

Could not find resource path for Web UI: [resourceBase]
Note
 createStaticHandler is used when SparkUI, HistoryServer, Spark Standalone’s MasterWebUI and WorkerWebUI, Spark on Mesos' MesosClusterUI are requested to initialize.

createRedirectHandler Method

createRedirectHandler(
  srcPath: String,
  destPath: String,
  beforeRedirect: HttpServletRequest => Unit = x => (),
  basePath: String = "",
  httpMethods: Set[String] = Set("GET")): ServletContextHandler

createRedirectHandler…​FIXME

Note
 createRedirectHandler is used when SparkUI and Spark Standalone’s MasterWebUI are requested to initialize.