Google Cloud Data Fusion——从 REST API 端点源构建管道

Question

Attempting to build a pipeline to read from a 3rd party REST API endpoint data source.

I am using the HTTP (version 1.2.0) plugin found in the Hub.

The response request URL is: https://api.example.io/v2/somedata?return_count=false

A sample of response body:

{
  "paging": {
    "token": "12456789",
    "next": "https://api.example.io/v2/somedata?return_count=false&__paging_token=123456789"
  },
  "data": [
    {
      "cID": "aerrfaerrf",
      "first": true,
      "_id": "aerfaerrfaerrf",
      "action": "aerrfaerrf",
      "time": "1970-10-09T14:48:29+0000",
      "email": "example@aol.com"
    },
    {...}
  ]
}

The main error in the logs is:

java.lang.NullPointerException: null
    at io.cdap.plugin.http.source.common.pagination.BaseHttpPaginationIterator.getNextPage(BaseHttpPaginationIterator.java:118) ~[1580429892615-0/:na]
    at io.cdap.plugin.http.source.common.pagination.BaseHttpPaginationIterator.ensurePageIterable(BaseHttpPaginationIterator.java:161) ~[1580429892615-0/:na]
    at io.cdap.plugin.http.source.common.pagination.BaseHttpPaginationIterator.hasNext(BaseHttpPaginationIterator.java:203) ~[1580429892615-0/:na]
    at io.cdap.plugin.http.source.batch.HttpRecordReader.nextKeyValue(HttpRecordReader.java:60) ~[1580429892615-0/:na]
    at io.cdap.cdap.etl.batch.preview.LimitingRecordReader.nextKeyValue(LimitingRecordReader.java:51) ~[cdap-etl-core-6.1.1.jar:na]
    at org.apache.spark.rdd.NewHadoopRDD$$anon$1.hasNext(NewHadoopRDD.scala:214) ~[spark-core_2.11-2.3.3.jar:2.3.3]
    at org.apache.spark.InterruptibleIterator.hasNext(InterruptibleIterator.scala:37) ~[spark-core_2.11-2.3.3.jar:2.3.3]
    at scala.collection.Iterator$$anon$12.hasNext(Iterator.scala:439) ~[scala-library-2.11.8.jar:na]
    at scala.collection.Iterator$$anon$12.hasNext(Iterator.scala:439) ~[scala-library-2.11.8.jar:na]
    at scala.collection.Iterator$$anon$12.hasNext(Iterator.scala:439) ~[scala-library-2.11.8.jar:na]
    at org.apache.spark.internal.io.SparkHadoopWriter$$anonfun$4.apply(SparkHadoopWriter.scala:128) ~[spark-core_2.11-2.3.3.jar:2.3.3]
    at org.apache.spark.internal.io.SparkHadoopWriter$$anonfun$4.apply(SparkHadoopWriter.scala:127) ~[spark-core_2.11-2.3.3.jar:2.3.3]
    at org.apache.spark.util.Utils$.tryWithSafeFinallyAndFailureCallbacks(Utils.scala:1415) ~[spark-core_2.11-2.3.3.jar:2.3.3]
    at org.apache.spark.internal.io.SparkHadoopWriter$.org$apache$spark$internal$io$SparkHadoopWriter$$executeTask(SparkHadoopWriter.scala:139) [spark-core_2.11-2.3.3.jar:2.3.3]
    at org.apache.spark.internal.io.SparkHadoopWriter$$anonfun$3.apply(SparkHadoopWriter.scala:83) [spark-core_2.11-2.3.3.jar:2.3.3]
    at org.apache.spark.internal.io.SparkHadoopWriter$$anonfun$3.apply(SparkHadoopWriter.scala:78) [spark-core_2.11-2.3.3.jar:2.3.3]
    at org.apache.spark.scheduler.ResultTask.runTask(ResultTask.scala:87) [spark-core_2.11-2.3.3.jar:2.3.3]
    at org.apache.spark.scheduler.Task.run(Task.scala:109) [spark-core_2.11-2.3.3.jar:2.3.3]
    at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:345) [spark-core_2.11-2.3.3.jar:2.3.3]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_232]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_232]
    at java.lang.Thread.run(Thread.java:748) [na:1.8.0_232]

Possible issues

After trying to troubleshoot this for awhile, I'm thinking the issue might be with

Pagination

• Data Fusion HTTP plugin has a lot of methods to deal with pagination
  • Based on the response body above, it seems like the best option for Pagination Type is Link in Response Body
  • For the required Next Page JSON/XML Field Path parameter, I've tried $.paging.next and paging/next . Neither work.
  • I have verified that the link in /paging/next works when opening in Chrome

Authentication

• When simply trying to view the response URL in Chrome, a prompt will pop up asking for username and password
  • Only need to input API key for username to get past this prompt in Chrome
  • To do this in the Data Fusion HTTP plugin, the API Key is used for Username in the Basic Authentication section

Anyone have any success in creating a pipeline in Google Cloud Data Fusion where the data source is a REST API?

Answer 1

In answer to

Anyone have any success in creating a pipeline in Google Cloud Data Fusion where the data source is a REST API?

This is not the optimal way to achieve this the best way would be to ingest data Service APIs Overview to pub/sub your would then use pub/sub as the source for your pipeline this would provide a simple and reliable staging location for your data on its for processing, storage, and analysis, see the documentation for the pub/sub API . In order to use this in conjunction with Dataflow, the steps to follow are in the official documentation here Using Pub/Sub with Dataflow

Answer 2

I think your problem is in the data format that you receive. The exception:

java.lang.NullPointerException: null

occurs when you do not specify a correct output schema (no schema in this case I believe)

Solution 1

To solve it, try configuring the HTTP Data Fusion plugin to:

• Receive format: Text.
• Output Schema: name: user Type: String

This should work to obtain the response from the API in string format. Once that is done, use a JSONParser to convert the string into a table like object.

Solution 2

Configure the HTTP Data Fusion plugin to:

• Receive format: json
• JSON/XML Result Path : data
• JSON/XML Fields Mapping : Include the fields you presented (see attached foto).