Cassandra: If TRUNCATE table and restore backup for only one node, will I loose data?

The name of the pictureThe name of the pictureThe name of the pictureClash Royale CLAN TAG#URR8PPP



Cassandra: If TRUNCATE table and restore backup for only one node, will I loose data?



Suppose I have [3 nodes - 1 datacenter - 1 cluster] cassandra setup.



A keysapce with replication factor = 2



I am taking regular snapshots and incremental backups for all nodes.



One of my 3 node goes completely down with whatever reason and I want to restore backup.



Cassandra(datastax) documentation suggests to usually TRUNCATE table before restoring.



Question:
As I am only going to restore backup on one node, is TRUNCATE necessary? Because truncate will delete that table's data from ALL nodes as per my understanding. TRUNCATE Doc



So if I truncate table and restore backup only on one node, then wouldn't I loose data for that table which was stored on other nodes too?




1 Answer
1



First of all, in your scenario, you might not want to restore a backup at all. Since you have replication factor = 2, your data is still on one other node of the original three. Therefore, you could remove the node that went completely down and add it again. Cassandra will automatically get it up to speed and stream the data to it.



Alternatively or complementary, you can stream the data files from the backup into your cluster with SSTableLoader.



A few other points though for the sake of knowledge:



Why Truncate?



Truncate is recommended in certain scenarios because the data you restore will have older timestamps than the new data.



The example in the link you sent is rather apt to explain one of those scenarios.
If you accidently delete a lot of data and wish to restore your old data, you will need to remove the tombstones which mark those rows as deleted by truncating first.





#1 about NOT needing backup-restore at all in above case --: Thanks. I thought this too and was going to ask as another question. But you already answered it. #2 about truncate and restore only one node will not work --: I was looking for this. Thanks!
– simpleDev
Aug 10 at 11:04






By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.

-

Popular posts from this blog

Firebase Auth - with Email and Password - Check user already registered

Image
Clash Royale CLAN TAG #URR8PPP Firebase Auth - with Email and Password - Check user already registered I want to check when a user attempts to signup with createUserWithEmailAndPassword() in Firebase user Authentication method, this user is already registered with my app. createUserWithEmailAndPassword() 8 Answers 8 To detect whether a user with that email address already exists, you can detect when the call to createUserWithEmailAndPassword () fails with auth/email-already-in-use . I see that @Srinivasan just posted an answer for this. createUserWithEmailAndPassword () auth/email-already-in-use Alternatively, you can detect that an email address is already used by calling fetchSignInMethodsForEmail() (previous called fetchProvidersForEmail() ). fetchSignInMethodsForEmail() fetchProvidersForEmail() When the user trying to create an user with same email address, the task response will be "Response: The email address is already in use by another account." mFirebas...
Read more

Dynamically update html content plain JS

Image
Clash Royale CLAN TAG #URR8PPP Dynamically update html content plain JS So I have a script bound in my index.html, which literally has to fetch an array of jsons from an api, then dynamically update my page when get response. But as a result I'm getting an as the only update of my page. here is my script fetch(url) .then((resp) => resp.json()) .then((resp) => resp.results.forEach(item => fetch(item.url) .then((response)=> response.json()) .then((response) => pokeArr.push(response)) .catch(console.log) ) ).catch(console.log) const filler = () => if(!pokeArr) return 0 pokeArr.map((i,j)=> return `<tr>$i.name</tr>` ) const pokeindex = () => document.getElementById('a').appendChild(document.createElement(filler())) pokeindex() When I'm consoling it, I can see in the console all the responses I get, so I'm at least doing the fetching part right. What's parberakan ? What's pokeArr ? – T.J. Crowder Aug 8 at 12...
Read more

Creating a leaderboard in HTML/JS

Image
Clash Royale CLAN TAG #URR8PPP Creating a leaderboard in HTML/JS I'm trying to create a top 10 leaderboard, for now, I've only implemented 3 players, but I'm coming across an issue. My script doesn't seem to be outputting anything on webpage. The purpose of the script is to compare 3 arrays, player1,player2,and player3 solely based off of score. Which is the 2nd index of each array. I want the script to list the players in order of highest score. This method doesn't really seem to be efficient, especially when I'll have to add 7 more players. Could someone suggest perhaps an easier approach, as well as show me why my script wont output the info. Here's the JS function leaderboard() { var player1 = name:"Thomas",date:"01/23/18",score:"201"; var player2 = name:"Michael",date:"03/24/17",score:"943"; var player3 = Name:"Lisa",date:"06/04/18",Score:"79"; if(player1[2]...
Read more