What is the best way to export all of my data from a Cassandra Cluster?

user_12226869 0
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I am very new to Cassandra and any help here would be appreciated. I have a cluster of 6 nodes that spans 2 datacenters (3 nodes to each cluster). My client has decided that they do not want to renew their Cassandra license with Datastax anymore and want their data exported into a format that can be easily imported into another Database in the future. I was thinking of exporting the data as a CSV file, but since the data is distributed between all the nodes, I am not sure what is the best way to export all the data.

cassandra
4 Answers

One option - You should be able to use the CQL COPY command - which copies the data into a CSV format. The nice thing about copy is that you can run it from a single node (i.e. it is not a "node" level tool). Command would be (once in cqlsh):

CQL> COPY . to '/path/to/file'

If there is a LOT of data, or a lot of tables, this tool may not be a great fit. But for small number of tables that don't have HUGE rowcounts (< several million), this works well. Hope that helps.

-Jim

user_61148880

Since 2018 you can use DSBulk with DSE to export or import data to/from CSV (by default), or JSON. Since the end of 2019 it's possible to use it with open source Cassandra as well.

It could be as simple as:

dsbulk unload -k keyspace -t table -u user -p password -url filename

DSBulk is heavily optimized for fast data export, without putting too much load onto the coordinator node that happens when you just run select * from table.

You can control what columns to export, and even provide your own query, etc. DataStax blog has a series of blog posts about different aspects of using DSBulk:

  1. Introduction and Loading
  2. More Loading
  3. Common Settings
  4. Unloading
  5. Counting
  6. Examples for Loading From Other Locations
Alex_Ott_186270

You can use CQL COPY command for exporting the data from Cassandra cluster. However it is performant for small set of data if you are having big size of data this command is not useful cause it will give some error or timeout issue. Also, you may use sstabledump and export your node-wise date into JSON format. Hope, this will useful for you.

user_102077160

I have implemented small script for this purpose. It isn't the best way, since it slow and, in my experience, produces connection errors on system tables. But it could be useful for inspecting Cassandra on small datasets: https://github.com/kirillt/cassandra-utils

user_27577350
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