Re: Priority for cassandra nodes in cluster

If u ask conceptually, it is possible but not recommended. If u really want to do it use the initial token setting and provide the broad range to the nodes where u want more data. But u need to understand about the replication factor consideration, if u keep rf as 3 on a 3 node cluster that means

Re: Priority for cassandra nodes in cluster

Hi, Thanks all for your valuable suggestion. Thanks and Regards A.SathishKumar On Sat, Nov 12, 2016 at 2:59 PM, Ben Bromhead wrote: > +1 w/ Benjamin. > > However if you wish to make use of spare hardware capacity, look to > something like mesos DC/OS or kubernetes. You

Re: Consistency when adding data to collections concurrently?

Hi, Instead of using a collection, consider making label a clustered column. With this each request will essentially append a column (label) to the partition. To get all labels would be a simple query select label from table where partitionkey = "value". In general , read + update of a

Re: Priority for cassandra nodes in cluster

+1 w/ Benjamin. However if you wish to make use of spare hardware capacity, look to something like mesos DC/OS or kubernetes. You can run multiple services across a fleet of hardware, but provision equal resources to Cassandra and have somewhat reliable hardware sharing mechanisms. On Sat, 12

Re: Priority for cassandra nodes in cluster

Agreed w/ Benjamin. Trying to diagnose issues in prod will be a nightmare. Keep your DB servers homogeneous. > On Nov 12, 2016, at 1:52 PM, Benjamin Roth wrote: > > 1. From a 15 year experience of running distributed Services: dont Mix > Services on machines if

Re: Priority for cassandra nodes in cluster

1. From a 15 year experience of running distributed Services: dont Mix Services on machines if you don't have to. Dedicate each server to a single task if you can afford it. It is easier to manage and reduces risks in case of overload or failure 2. You can assign a different number of tokens for

Priority for cassandra nodes in cluster

Hi, We are planning to install 3 node cluster in production environment. Is it possible to provide weightage or priority to the nodes in cluster. Eg., We want more more records to be written to first 2 nodes and less to the 3rd node. We are thinking of this approach because we want to install

Re: Consistency when adding data to collections concurrently?

"doing mapper.save() will do an insert rather than an update? " --> Yes The java driver mapper has no update method. To do an update you need to use the Accessor and roll out your own update statement On Sat, Nov 12, 2016 at 5:37 PM, Ali Akhtar wrote: > Just to be clear,

Re: Consistency when adding data to collections concurrently?

Just to be clear, doing mapper.save() will do an insert rather than an update? On Sat, Nov 12, 2016 at 9:36 PM, Andrew Tolbert wrote: > I believe you are correct that the implementation taking the Set is the > right one to use. > > On Sat, Nov 12, 2016 at 9:44 AM

Re: Consistency when adding data to collections concurrently?

I believe you are correct that the implementation taking the Set is the right one to use. On Sat, Nov 12, 2016 at 9:44 AM Ali Akhtar wrote: > Or it could even take Set as the first bound var: > > void addLabel(Set label, String id); > > > On Sat, Nov 12, 2016 at 8:41 PM,

Re: Consistency when adding data to collections concurrently?

Or it could even take Set as the first bound var: void addLabel(Set label, String id); On Sat, Nov 12, 2016 at 8:41 PM, Ali Akhtar wrote: > Andrew, > > I was thinking about setting up an accessor with that query and a bound > variable ? which binds to the instance being

Re: Consistency when adding data to collections concurrently?

Andrew, I was thinking about setting up an accessor with that query and a bound variable ? which binds to the instance being added, e.g: @Query("UPDATE my_table SET labels = labels + ? WHERE id = ?") void addLabel(Label label, String id); Will that work? On Sat, Nov 12, 2016 at 8:38 PM,

Re: Consistency when adding data to collections concurrently?

You can do it in a SimpleStatement assuming you provide the CQL exactly as you provided, but in a PreparedStatement it will not work because cql prohibits provide bind values in collection literals. For it to work you could provide a List of UDT values in a bound prepared statement, i.e.:

Re: Deadlock in callbacks to async operations (Java)

> > Will the above example work if instead of session.execute, it was doing > session.executeAsync()? > It will work as executeAsync will not block waiting on behavior in a I/O thread (that may also happen to be the calling thread), so it is not susceptible to deadlock. To be extra safe, you

Re: Consistency when adding data to collections concurrently?

Looks like the trick was to use [] around the udt value literal. Any way to do this using the java driver? On Sat, Nov 12, 2016 at 7:58 PM, Ali Akhtar wrote: > Changing the double quotes to single quotes gives: > > UPDATE my_table SET labels = labels + {id: 'foo'} where

Re: Consistency when adding data to collections concurrently?

Changing the double quotes to single quotes gives: UPDATE my_table SET labels = labels + {id: 'foo'} where id = ''; InvalidRequest: Error from server: code=2200 [Invalid query] message="Invalid user type literal for labels of type list" On Sat, Nov 12, 2016 at 7:50 PM, Ali Akhtar

Re: Consistency when adding data to collections concurrently?

The question is about appending to a set of frozen and how to do that while avoiding the race condition. If I run: UPDATE my_table SET labels = labels + {id: "foo"} where id = 'xx'; I get: SyntaxException: line 1:57 no viable alternative at input '}' (...= labels + {id: ["fo]o"}...) Here

Re: Consistency when adding data to collections concurrently?

If I used consistency = ALL both when getting the record, and when saving the record, will that avoid the race condition? If I use consistency level = all, will that cause it to end up with [1,2]? No. Even if you have only one host it's possible that two threads first both read data and than

Re: Consistency when adding data to collections concurrently?

The labels collection is of the type set , where label is a udt containing: id, name, description , all text fields. On Sat, Nov 12, 2016 at 5:54 PM, Ali Akhtar wrote: > The problem isn't just the update / insert though, right? Don't frozen > entities get

Re: Consistency when adding data to collections concurrently?

The problem isn't just the update / insert though, right? Don't frozen entities get overwritten completely? So if I had [1] [2] being written as updates, won't each update overwrite the set completely, so i'll end up with either one of them instead of [1,2]? On Sat, Nov 12, 2016 at 5:50 PM,

Re: Consistency when adding data to collections concurrently?

Maybe you should use my Achilles mapper, which does generates UPDATE statements on collections and not only INSERT Le 12 nov. 2016 13:08, "Ali Akhtar" a écrit : > I am using the Java Cassandra mapper for all of these cases, so my code > looks like this: > > Item myItem =

Deadlock in callbacks to async operations (Java)

At https://datastax.github.io/java-driver/manual/async/ the docs say to not do any blocking operations within the callback of an async operation. This example is given as one that can cause a deadlock: ListenableFuture resultSet = Futures.transform(session, new Function()

Re: Consistency when adding data to collections concurrently?

I am using the Java Cassandra mapper for all of these cases, so my code looks like this: Item myItem = myaccessor.get( itemId ); Mapper mapper = mappingManager.create( Item.class ); myItem.labels.add( newLabel ); mapper.save( myItem ); On Sat, Nov 12, 2016 at 5:06 PM, Ali Akhtar

Re: Consistency when adding data to collections concurrently?

Thanks DuyHai, I will switch to using a set. But I'm still not sure how to resolve the original question. - Original labels = [] - Request 1 arrives with label = 1, and request 2 arrives with label = 2 - Updates are sent to c* with labels = [1] and labels = [2] simultaneously. What will happen

Re: Consistency when adding data to collections concurrently?

Don't use list, use set instead. If you need ordering of insertion, use a map where timeuuid is generated by the client to guarantee insertion order When setting a new value to a list, C* will do a read-delete-write internally e.g. read the current list, remove all its value (by a

Re: Consistency when adding data to collections concurrently?

If I used consistency = ALL both when getting the record, and when saving the record, will that avoid the race condition? On Sat, Nov 12, 2016 at 4:26 PM, Ali Akhtar wrote: > I'm responding to a 3rd party API, so I have no control over sending the > labels together instead

Re: Consistency when adding data to collections concurrently?

I'm responding to a 3rd party API, so I have no control over sending the labels together instead of one by one. In this case, the API will send them one by one. The list is actually of a list and not a text (I used text for simplification, apologies). In that case, will updates still

Re: Consistency when adding data to collections concurrently?

Could you not send both labels in one request? Race conditions should still be handled as Vladimir suggests. But in this specific case the client could send both as 1 request thus simplifying the solution. /Oskar > On 12 nov. 2016, at 12:05, Vladimir Yudovin wrote: > >

Re: Consistency when adding data to collections concurrently?

Hi Ali, What can I do so I end up with [1, 2] instead of either [1] or [2] after both requests have been processed? Use UPDATE, not INSERT. Thus new labels will be added to list, without overwriting old ones. Also consider usage of SET instead of LIST to avoid duplicates. Best regards,

Consistency when adding data to collections concurrently?

I have a table where each record contains a list of labels. I have an endpoint which responds to new labels being added to a record by the user. Consider the following scenario: - Record X, labels = [] - User selects 2 labels, clicks a button, and 2 http requests are generated. - The server