How to read data from Kinesis stream using AWS CLI? - json

Question

I have a Kinesis stream in AWS and can send data to it (JSON) using kinesis command and can get it back from a stream with:
SHARD_ITERATOR=$(aws kinesis get-shard-iterator --shard-id shardId-000000000000 --shard-iterator-type TRIM_HORIZON --stream-name mystream --query 'ShardIterator' --profile myprofile)
aws kinesis get-records --shard-iterator $SHARD_ITERATOR --profile myprofile
Output of this looks like something like:
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
How do I get actual JSON message in raw format (to look as JSON) - same way as it was in original when I sent it?
Thanks

Answer 1

As per the docs, you need to use a Base64 decoding tool or use KCL library to get the data in the format it was sent:
The first thing you'll likely notice about your record in this part of the tutorial is that the data appears to be garbage –; it's not the clear text testdata we sent. This is due to the way put-record uses Base64 encoding to allow you to send binary data. However, the Kinesis Data Streams support in the AWS CLI does not provide Base64 decoding because Base64 decoding to raw binary content printed to stdout can lead to undesired behavior and potential security issues on certain platforms and terminals. If you use a Base64 decoder (for example, https://www.base64decode.org/) to manually decode dGVzdGRhdGE= you will see that it is, in fact, testdata. This is sufficient for the sake of this tutorial because, in practice, the AWS CLI is rarely used to consume data, but more often to monitor the state of the stream and obtain information, as shown previously (describe-stream and list-streams). Future tutorials will show you how to build production-quality consumer applications using the Kinesis Client Library (KCL), where Base64 is taken care of for you. For more information about the KCL, see Developing KCL 1.x Consumers.

Answer 2

on unix, you can use the base64 --decode command to decode the base64 encoded kinesis record data.
for example, to decode the data of the first record:
# define the name of the stream you want to read
KINESIS_STREAM_NAME='__your_stream_name_goes_here__';
# define the shard iterator to use
SHARD_ITERATOR=$(aws kinesis get-shard-iterator --shard-id shardId-000000000000 --shard-iterator-type TRIM_HORIZON --stream-name $KINESIS_STREAM_NAME --query 'ShardIterator');
# read the records, use `jq` to grab the data of the first record, and base64 decode it
aws kinesis get-records --shard-iterator $SHARD_ITERATOR | jq -r '.Records[0].Data' | base64 --decode