topic Re: How to stream JSON with Kafka? in Talend Studio

How to stream JSON with Kafka?

Anonymous — Sat, 16 Nov 2024 09:43:12 GMT

Hi,

I'm trying to stream the JSON message in Kafka and save it as the .json file. However the output file is empty.

If somebody can help, I will be grateful.

I'm using TOS for Big Data 6.4

Kafka ver.: 0.9.0.1

Kafka ver. set in TOS: 0.9.0.1

I'm also looking for examples of solutions where Kafka is used to catch the message in JSON format and the output is in .json file.
I want to evaluate whether TOS is a good tool for reading JSON using Kafka.

Kafka producer and consumer input/output (example):

My simple jobs.

Re: How to stream JSON with Kafka?

vapukov — Mon, 29 May 2017 23:46:20 GMT

Hi,

if Output file empty, it mean - You wrong parse JSON

You can attache screenshots for tExtractJSON and tWriteJSON, it would be better

Re: How to stream JSON with Kafka?

Anonymous — Thu, 01 Jun 2017 13:43:53 GMT

Hi,

I've checked two options of the same job.

1. with Kafka input. No data in .jsonfile (file is empty) or no data i .txt file as an output (tFileOutputRaw component)

2. with tFixedFlowInput component. All the data and structure is in the .json file. I've checked also export to .xls file and it works as well.

In both cases I'm not using tWriteJSON component. Should I use it?

1. Kafka input job

tExtractJSON config

tFileOutputJSON

Output schema, columns 1:1

2. Job where I used tFixedFlowInput component

tFixedFlowInput

JSON here:

{"data":[{"Service_Description":"Pets Allowed","Service_Code":"PET"},{"Service_Description":"Swimming Pool","Service_Code":"SWI"},{"Service_Description":"Tennis Court","Service_Code":"TEN"},{"Service_Description":"Dry Cleaning","Service_Code":"DRY"},{"Service_Description":"Internet Access","Service_Code":"INT"},{"Service_Description":"WIFI Internet Access","Service_Code":"WIF"},{"Service_Description":"Fitness Room","Service_Code":"FIT"},{"Service_Description":"Concierge","Service_Code":"CON"}]}

output .json file

output .xlsx file

Please NOTE that tLogRow_2 displays the same output in both cases/jobs.

Re: How to stream JSON with Kafka?

vapukov — Thu, 01 Jun 2017 22:58:59 GMT

I will check later with your sample
generally I use JSONPath for parse JSON

Re: How to stream JSON with Kafka?

vapukov — Sun, 04 Jun 2017 14:51:45 GMT

I make few test, with Your schema.

My Jobs use little different and this is was not affected for me, but look like all depend from configuration of KafkaInput component

Kafka as any MQ oriented for non stop work, and depending how Your component setup, it open and close output file different.

If You use auto-disconnect by timeout or by number of received messages - all fine:

if You manual stop Job - file not closed properly

as alternative possible use tFlowToIterate and route output in different JSON files, or append in same delimited, something like:

in this case - each file contain single message from Kafka, all of them closed independent and could be processed after

Re: How to stream JSON with Kafka?

Anonymous — Wed, 27 May 2020 10:59:26 GMT

Hello

May you kindly help me with this please, I have a problem with my first experience working with Talend OS_BD, I'm consuming Kafka messages (JSON format) into Talend where I need to eventually output it into PostgreSQL data warehouse (in JSON format as well). My problem is, the PostgreSQL table is not created, if I create it manually no data is inserted in the table but It can acknowledge that the table already exists. I can not also save the Kafka messages to .json file, its always empty. Do i have to first convert this JSON string to object so that i insert it to PostgreSQL ? I'm stuck for days and I hope you can help me out. if you have any better solution to register these data in the data warehouse (PostgreSQL) I will appreciate it. below is the brief description of my set-up

here is the JSON I'm receiving from the Kafka topic before any extraction

another one

I then put in place a pipeline as follows

I'm just selecting 2 columns from the JSON for the PostgreSQL table, here is the output in tlogRow

here is my configuration for tkafkaInput

and the tExtractJsonFields is as follows

I hope you can help me with ideas on how to solve this

Regards

Re: How to stream JSON with Kafka?

vapukov — Wed, 27 May 2020 11:38:14 GMT

I think you problem in tPostgreSQL component.

By default it commits and inserts data by 10000 rows, you need to disable this in Advanced tab of component settings, to make an insert for each row.

In the original solution, it special split for 2 sub-jobs to be sure sub-job finish it work before next iteration started. Same issue could be and with saving to file (not sure)

Re: How to stream JSON with Kafka?

Anonymous — Wed, 27 May 2020 11:57:38 GMT

Thank for the response

the problem now is , the "commit every" setting should not be empty

Re: How to stream JSON with Kafka?

vapukov — Wed, 27 May 2020 11:59:29 GMT

what prevents you from using 1 ? 🙂

Re: How to stream JSON with Kafka?

Anonymous — Wed, 27 May 2020 15:02:55 GMT

Thank you Sir it worked , and i have also noted in Kafka configuration timeout precision by default its -1.

Now do you know how i can convert this json string in Talend OS for BD

to be like this one below without the backslashes

Regards