ApiRootResource — /api/v1 URI Handler-spark技术分享

ApiRootResource — /api/v1 URI Handler

ApiRootResource is the ApiRequestContext for the /v1 URI path.

ApiRootResource uses @Path("/v1") annotation at the class level. It is a partial URI path template relative to the base URI of the server on which the resource is deployed, the context root of the application, and the URL pattern to which the JAX-RS runtime responds.

Tip	Learn more about `@Path` annotation in The @Path Annotation and URI Path Templates.

ApiRootResource registers the /api/* context handler (with the REST resources and providers in org.apache.spark.status.api.v1 package).

With the @Path("/v1") annotation and after registering the /api/* context handler, ApiRootResource serves HTTP requests for paths under the /api/v1 URI paths for SparkUI and HistoryServer.

ApiRootResource gives the metrics of a Spark application in JSON format (using JAX-RS API).



// start spark-shell
$ http http://localhost:4040/api/v1/applications
HTTP/1.1 200 OK
Content-Encoding: gzip
Content-Length: 257
Content-Type: application/json
Date: Tue, 05 Jun 2018 18:36:16 GMT
Server: Jetty(9.3.z-SNAPSHOT)
Vary: Accept-Encoding, User-Agent

[
    {
        "attempts": [
            {
                "appSparkVersion": "2.3.1-SNAPSHOT",
                "completed": false,
                "duration": 0,
                "endTime": "1969-12-31T23:59:59.999GMT",
                "endTimeEpoch": -1,
                "lastUpdated": "2018-06-05T15:04:48.328GMT",
                "lastUpdatedEpoch": 1528211088328,
                "sparkUser": "jacek",
                "startTime": "2018-06-05T15:04:48.328GMT",
                "startTimeEpoch": 1528211088328
            }
        ],
        "id": "local-1528211089216",
        "name": "Spark shell"
    }
]

// Fixed in Spark 2.3.1
// https://issues.apache.org/jira/browse/SPARK-24188
$ http http://localhost:4040/api/v1/version
HTTP/1.1 200 OK
Content-Encoding: gzip
Content-Length: 43
Content-Type: application/json
Date: Thu, 14 Jun 2018 08:19:06 GMT
Server: Jetty(9.3.z-SNAPSHOT)
Vary: Accept-Encoding, User-Agent

{
    "spark": "2.3.1"
}

// start spark-shell

$ http http://localhost:4040/api/v1/applications

HTTP/1.1 200 OK

Content-Encoding: gzip

Content-Length: 257

Content-Type: application/json

Date: Tue, 05 Jun 2018 18:36:16 GMT

Server: Jetty(9.3.z-SNAPSHOT)

Vary: Accept-Encoding, User-Agent

[

{

"attempts": [

{

"appSparkVersion": "2.3.1-SNAPSHOT",

"completed": false,

"duration": 0,

"endTime": "1969-12-31T23:59:59.999GMT",

"endTimeEpoch": -1,

"lastUpdated": "2018-06-05T15:04:48.328GMT",

"lastUpdatedEpoch": 1528211088328,

"sparkUser": "jacek",

"startTime": "2018-06-05T15:04:48.328GMT",

"startTimeEpoch": 1528211088328

}

"id": "local-1528211089216",

"name": "Spark shell"

}

]

// Fixed in Spark 2.3.1

// https://issues.apache.org/jira/browse/SPARK-24188

$ http http://localhost:4040/api/v1/version

HTTP/1.1 200 OK

Content-Encoding: gzip

Content-Length: 43

Content-Type: application/json

Date: Thu, 14 Jun 2018 08:19:06 GMT

Server: Jetty(9.3.z-SNAPSHOT)

Vary: Accept-Encoding, User-Agent

{

"spark": "2.3.1"

}

Table 1. ApiRootResource’s Paths
Path	HTTP Method	Description
`applications`		Delegates to the ApplicationListResource resource class
`applications/{appId}`		Delegates to the OneApplicationResource resource class
`version`	GET	Creates a `VersionInfo` with the current version of Spark

Creating /api/* Context Handler — `getServletHandler` Method



getServletHandler(uiRoot: UIRoot): ServletContextHandler

getServletHandler(uiRoot: UIRoot): ServletContextHandler

getServletHandler creates a Jetty ServletContextHandler for /api context path.

Note	The Jetty `ServletContextHandler` created does not support HTTP sessions as REST API is stateless.

getServletHandler creates a Jetty ServletHolder with the resources and providers in org.apache.spark.status.api.v1 package. It then registers the ServletHolder to serve /* context path (under the ServletContextHandler for /api).

getServletHandler requests UIRootFromServletContext to setUiRoot with the ServletContextHandler and the input UIRoot.

Note	`getServletHandler` is used when SparkUI and HistoryServer are requested to initialize.

ApiRootResource — /api/v1 URI Handler