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From Stephan Ewen <se...@apache.org>
Subject Re: Program crashes trying to read JSON file
Date Wed, 26 Nov 2014 08:48:23 GMT
There must be something simple mixed up somewhere. The string output from
your previous mail suggests that the output is the name of the data reading
operator object. Not sure how you achieved that, but that is pretty mixed
up.

My gut feeling is that you call "toString()" on a DataSet somewhere and use
that as actual data. Something like

DataSet<String> text = env.fromElements(env.readTextFile(...).toString())

Reading JSON entries as strings (assuming they contain no linebreaks) and
extracting fields is one of the "hello world" examples, there should be no
strange surprises. I would have a look at examples like WordCount and check
where you use different types of opetations.

Btw: I would look into the Jackson library for json parsing and field
extraction. Very easy to use, good performance.
 Am 26.11.2014 09:01 schrieb "Anirvan BASU" <anirvan.basu@inria.fr>:

> Ciao Stefano !
>
> Thanks for this early morning information, very helpful.
> Yes, for outputting the data we are using WriteAsCSV which is stable over
> different versions of Flink.
>
> Our current concern is "reading" a JSON file into a dataset.
> As you can see, we have a simple 2-level JSON hierarchy that can be easily
> mapped to a fixed-column CSV.
> But the place we are stuck at currently is in reading the file correctly
> into a tuple-based dataset in memory.
> Once this is achieved, the rest will be fairly simple dataset
> transformations.
>
> As you can see from the pasted code, we used functions developed from the
> stream connector for our purposes. (Thanks to Gyula and Marton for that
> information)
>
> If reading a JSON file using functions already developed is not possible
> then we will have to develop some custom functions on hardcore string
> operations to do the same.
> That would be like reinventing the wheel ... :-((
>
> Any advice in this regard will be highly appreciated.
>
> Thanks in advance to all,
> Anirvan
>
> ------------------------------
>
> *From: *"Stefano Bortoli" <s.bortoli@gmail.com>
> *To: *"user" <user@flink.incubator.apache.org>
> *Sent: *Wednesday, November 26, 2014 8:37:59 AM
> *Subject: *Re: Program crashes trying to read JSON file
>
> You can output your results in different ways. If all you need is to write
> a file, I normally use the writeAsText method (however, there is the
> writeAsCSV, writeAsFormattedText. Of write according to your custom
> FileOutputFormat.
>
> datasetToPrint.writeAsText("/path/to/file/with/permission",
> WriteMode.OVERWRITE);
>
> Keep in mind that this will output your tuple dataset. Therefore, if you
> want to shape your output differently, It may be necessary to have further
> processing.
>
> saluti,
> Stefano
>
> 2014-11-25 22:04 GMT+01:00 Anirvan BASU <anirvan.basu@inria.fr>:
>
>> Thanks to Aljoscha and Stefano for pointing out the flaw.
>>
>> We corrected the issue as follows:
>>
>> [CODE]
>>
>> import org.apache.flink.api.java.tuple.*Tuple4*;
>> import org.apache.flink.util.Collector;
>> import org.apache.flink.api.java.DataSet;
>> import org.apache.flink.api.java.ExecutionEnvironment;
>> import org.apache.flink.streaming.connectors.json.JSONParseFlatMap;
>> import org.apache.sling.commons.json.JSONException;
>> ...
>>
>>     public static void main(String[] args) throws Exception {
>>
>>         if(!parseParameters(args)) {
>>             return;
>>         }
>>
>>         // set up the execution environment
>>         final ExecutionEnvironment env =
>> ExecutionEnvironment.getExecutionEnvironment();
>>
>>         // get input data
>>         DataSet<String> text = getTextDataSet(env);
>>
>>         DataSet<Tuple4<Integer, String, String, *Integer*>> counts =
>>                 // split up the lines in pairs (4-tuples) containing:
>> (timestamp,uuid,event,*count*)
>>                 text.flatMap(new SelectDataFlatMap())
>>                 // group by the tuple field "1" (an event - string) and
>> sum up tuple field "3" (integer - value 1)
>>                 .*groupBy(1)*
>>                 .*sum(3*);
>>
>>
>>         // emit result
>>         if(fileOutput) {
>>             counts.writeAsCsv(outputPath, "\n", " ");
>>         } else {
>>             counts.print();
>>         }
>>
>>         // execute program
>>         env.execute("Weblogs Programme");
>>     }
>>
>> ...
>>
>>     public static class SelectDataFlatMap extends
>>     JSONParseFlatMap<String, *Tuple4*<Integer, String, String, Integer>>
>> {
>>
>>         private static final long serialVersionUID = 1L;
>>
>>         @Override
>>         public void flatMap(String value, Collector<Tuple4<Integer,
>> String, String, Integer>> record)
>>                 throws Exception {
>>             try {
>>                 record.collect(new Tuple4<Integer, String, String,
>> Integer>(
>>                         getInt(value, "timestamp"),
>>                         getString(value, "uuid"),
>>                         getString(value, "event"),
>>                         1));
>>             } catch (JSONException e) {
>>                 System.err.println("Field not found");
>>             }
>>         }
>>     }
>>
>>
>> [/CODE]
>>
>> However, this time the issue was different.
>> The programme executed correctly till status FINISHED.
>> However, there was no output :-((
>> i.e. For each Task Manager, an empty file is written.
>>
>> When we checked further about the input text file that is read using
>> env.readTextFile() we find that instead of a text string (full text
>> dataset) only a small string is written!
>> Something as :
>> org.apache.flink.api.java.operators.DataSource@6bd8b476
>>
>> Worse still ! this string value sometimes remains the same over multiple
>> runs of the programme ....
>> Is this natural ? Is this just the handle to the file or the dataset ?
>> Is the Collector() working correctly also ?
>>
>>
>> Note :
>> The actual JSON file (i.e. the text file that should be read) is of the
>> following nature, with a 2-level hierarchy for one field:
>> [JSON]
>> {timestamp: 1397731764 <callto:1397731764>     payload: {product:
>> Younited     uuid:
>> 754726549cec3968a60ffffa2f8ccdc1da27e57a01af4bb2b11841803a25eadd
>>  platform: native     version: 6aa54aca95fb1b8ef2290136ab12df2e4b011241
>>  type: can-usage-v1     event: General,Login,Success}}
>> {timestamp: 1397731765 <callto:1397731765>     payload: {product:
>> Younited     uuid:
>> e0b3dad557ca77dc035fd22d1e8608c4248526ab9318a85637dbf88228a4034e
>>  platform: native     version: 7b4b767060b62537b63c5d10d911870a14d2b84e
>>  type: can-usage-v1     event: General,App,Opened}}
>> [/JSON]
>>
>>
>> So now again, we are confused if we are doing it correctly :-((
>>
>> Thanks in advance for helping us to understand where we are going wrong.
>> Anirvan
>>
>> ------------------------------
>>
>> *From: *"Stefano Bortoli" <s.bortoli@gmail.com>
>> *To: *"user" <user@flink.incubator.apache.org>
>> *Cc: *dev@flink.incubator.apache.org
>> *Sent: *Tuesday, November 25, 2014 5:05:34 PM
>> *Subject: *Re: Program crashes trying to read JSON file
>>
>>
>> Very quickly, it seems you are trying to sum on Strings
>>
>> Caused by: org.apache.flink.api.java.
>> aggregation.UnsupportedAggregationTypeException: The type
>> java.lang.String has currently not supported for built-in sum aggregations.
>>
>> Check your tuple types and be sure that you are not summing on strings.
>>
>>
>> 2014-11-25 16:55 GMT+01:00 Anirvan BASU <anirvan.basu@inria.fr>:
>>
>>> Hello all,
>>>
>>> We are using Flink 0.7 and trying to read a large JSON file, reading
>>> some fields into a flink  (3-tuple based) dataset, then performing some
>>> operations.
>>>
>>> We encountered the following runtime error:
>>>
>>> [QUOTE]
>>> Error: The main method caused an error.
>>> org.apache.flink.client.program.ProgramInvocationException: The main
>>> method caused an error.
>>>     at
>>> org.apache.flink.client.program.PackagedProgram.callMainMethod(PackagedProgram.java:404)
>>>     at
>>> org.apache.flink.client.program.PackagedProgram.invokeInteractiveModeForExecution(PackagedProgram.java:307)
>>>     at org.apache.flink.client.program.Client.run(Client.java:244)
>>>     at
>>> org.apache.flink.client.CliFrontend.executeProgram(CliFrontend.java:347)
>>>     at org.apache.flink.client.CliFrontend.run(CliFrontend.java:334)
>>>     at
>>> org.apache.flink.client.CliFrontend.parseParameters(CliFrontend.java:1001)
>>>     at org.apache.flink.client.CliFrontend.main(CliFrontend.java:1025)
>>> Caused by:
>>> org.apache.flink.api.java.aggregation.UnsupportedAggregationTypeException:
>>> The type java.lang.String has currently not supported for built-in sum
>>> aggregations.
>>>     at
>>> org.apache.flink.api.java.aggregation.SumAggregationFunction$SumAggregationFunctionFactory.createAggregationFunction(SumAggregationFunction.java:186)
>>>     at
>>> org.apache.flink.api.java.operators.AggregateOperator.<init>(AggregateOperator.java:109)
>>>     at
>>> org.apache.flink.api.java.operators.UnsortedGrouping.aggregate(UnsortedGrouping.java:61)
>>>     at
>>> org.apache.flink.api.java.operators.UnsortedGrouping.sum(UnsortedGrouping.java:72)
>>>     at
>>> org.apache.flink.examples.java.wordcount.WordCount.main(WordCount.java:75)
>>>     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
>>>     at
>>> sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
>>>     at
>>> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
>>>     at java.lang.reflect.Method.invoke(Method.java:606)
>>>     at
>>> org.apache.flink.client.program.PackagedProgram.callMainMethod(PackagedProgram.java:389)
>>>     ... 6 more
>>> [/QUOTE]
>>>
>>>
>>>
>>> The code snippet that could have caused this error (i.e. that we edited)
>>> is the following
>>>
>>> [CODE]
>>>
>>> import org.apache.flink.api.java.tuple.Tuple3;
>>> import org.apache.flink.util.Collector;
>>> import org.apache.flink.api.java.DataSet;
>>> import org.apache.flink.api.java.ExecutionEnvironment;
>>> import org.apache.flink.streaming.connectors.json.JSONParseFlatMap;
>>> import org.apache.sling.commons.json.JSONException;
>>> ...
>>>
>>>     public static void main(String[] args) throws Exception {
>>>
>>>         if(!parseParameters(args)) {
>>>             return;
>>>         }
>>>
>>>         // set up the execution environment
>>>         final ExecutionEnvironment env =
>>> ExecutionEnvironment.getExecutionEnvironment();
>>>
>>>         // get input data
>>>         DataSet<String> text = getTextDataSet(env);
>>>
>>>         DataSet<Tuple3<Integer, String, String>> counts =
>>>                 // split up the lines in pairs (3-tuples) containing:
>>> (timestamp,uuid,event)
>>>                 text.flatMap(new *SelectDataFlatMap()*)
>>>                 // group by the tuple field "0" and sum up tuple field
>>> "1"
>>>                 .groupBy(2)
>>>                 .sum(2);
>>>
>>>         // emit result
>>>         if(fileOutput) {
>>>             counts.writeAsCsv(outputPath, "\n", " ");
>>>         } else {
>>>             counts.print();
>>>         }
>>>
>>>         // execute program
>>>         env.execute("Weblogs Programme");
>>>     }
>>>
>>> ...
>>>
>>>     public static class *SelectDataFlatMap* extends
>>>     JSONParseFlatMap<String, Tuple3<Integer, String, String>> {
>>>
>>>         @Override
>>>         public void flatMap(String value, Collector<Tuple3<Integer,
>>> String, String>> out)
>>>                 throws Exception {
>>>             try {
>>>                 out.collect(new Tuple3<Integer, String, String>(
>>>                         getInt(value, "timestamp"),
>>>                         getString(value, "uuid"),
>>>                         getString(value, "event")));
>>>             } catch (JSONException e) {
>>>                 System.err.println("Field not found");
>>>             }
>>>         }
>>>     }
>>>
>>> [/CODE]
>>>
>>>
>>>
>>> [QUOTE]
>>> Error: The main method caused an error.
>>> org.apache.flink.client.program.ProgramInvocationException: The main
>>> method caused an error.
>>>     at
>>> org.apache.flink.client.program.PackagedProgram.callMainMethod(PackagedProgram.java:404)
>>>     at
>>> org.apache.flink.client.program.PackagedProgram.invokeInteractiveModeForExecution(PackagedProgram.java:307)
>>>     at org.apache.flink.client.program.Client.run(Client.java:244)
>>>     at
>>> org.apache.flink.client.CliFrontend.executeProgram(CliFrontend.java:347)
>>>     at org.apache.flink.client.CliFrontend.run(CliFrontend.java:334)
>>>     at
>>> org.apache.flink.client.CliFrontend.parseParameters(CliFrontend.java:1001)
>>>     at org.apache.flink.client.CliFrontend.main(CliFrontend.java:1025)
>>> Caused by:
>>> org.apache.flink.api.java.aggregation.UnsupportedAggregationTypeException:
>>> The type java.lang.String has currently not supported for built-in sum
>>> aggregations.
>>>     at
>>> org.apache.flink.api.java.aggregation.SumAggregationFunction$SumAggregationFunctionFactory.createAggregationFunction(SumAggregationFunction.java:186)
>>>     at
>>> org.apache.flink.api.java.operators.AggregateOperator.<init>(AggregateOperator.java:109)
>>>     at
>>> org.apache.flink.api.java.operators.UnsortedGrouping.aggregate(UnsortedGrouping.java:61)
>>>     at
>>> org.apache.flink.api.java.operators.UnsortedGrouping.sum(UnsortedGrouping.java:72)
>>>     at
>>> org.apache.flink.examples.java.wordcount.WordCount.main(WordCount.java:75)
>>>     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
>>>     at
>>> sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
>>>     at
>>> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
>>>     at java.lang.reflect.Method.invoke(Method.java:606)
>>>     at
>>> org.apache.flink.client.program.PackagedProgram.callMainMethod(PackagedProgram.java:389)
>>>     ... 6 more
>>> [/QUOTE]
>>>
>>>
>>> The JSON file is of the following nature, with a 2-level hierarchy for
>>> one field:
>>> [JSON]
>>> {timestamp: 1397731764 <callto:1397731764>     payload: {product:
>>> Younited     uuid:
>>> 754726549cec3968a60ffffa2f8ccdc1da27e57a01af4bb2b11841803a25eadd
>>>  platform: native     version: 6aa54aca95fb1b8ef2290136ab12df2e4b011241
>>>  type: can-usage-v1     event: General,Login,Success}}
>>> {timestamp: 1397731765 <callto:1397731765>     payload: {product:
>>> Younited     uuid:
>>> e0b3dad557ca77dc035fd22d1e8608c4248526ab9318a85637dbf88228a4034e
>>>  platform: native     version: 7b4b767060b62537b63c5d10d911870a14d2b84e
>>>  type: can-usage-v1     event: General,App,Opened}}
>>> [/JSON]
>>>
>>>
>>>
>>> Thanks in advance for helping us to understand where we are going wrong.
>>>
>>> Anirvan
>>>
>>
>>
>>
>
>

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