Yes, it is one read request.
Since Cassandra does not support GROUP BY, I was trying to implement it in our
application. Hence the need to read large amount of data. I guess that was a
bad idea.
Mohammed
On Jun 27, 2013, at 9:54 PM, aaron morton
If our application tries to read 80,000 columns each from 10 or more rows at
the same time, some of the nodes run out of heap space and terminate with OOM
error.
Is this in one read request ?
Reading 80K columns is too many, try reading a few hundred at most.
Cheers
-
Your young gen is 1/4 of 1.8G which is 450MB. Also in slice queries, the
co-ordinator will get the results from replicas as per consistency level
used and merge the results before returning to the client.
What is the replication in your keyspace and what consistency you are
reading with.
Also 55MB
Replication is 3 and read consistency level is one. One of the non-cordinator
mode is crashing, so the OOM is happening before aggregation of the data to be
returned.
Thanks for the info about the space allocated to young generation heap. That is
helpful.
Mohammed
On Jun 25, 2013, at 1:28
No deletes. In my test, I am just writing and reading data.
There is a lot of GC, but only on the younger generation. Cassandra terminates
before the GC for old generation kicks in.
I know that our queries are reading an unusual amount of data. However, I
expected it to throw a timeout
We have a 3-node cassandra cluster on AWS. These nodes are running cassandra
1.2.2 and have 8GB memory. We didn't change any of the default heap or GC
settings. So each node is allocating 1.8GB of heap space. The rows are wide;
each row stores around 260,000 columns. We are reading the data
Hello Mohammed,
You should increase the heap space. You should also tune the garbage
collection so young generation objects are collected faster, relieving
pressure on heap We have been using jdk 7 and it uses G1 as the default
collector. It does a better job than me trying to optimise the JDK 6
Looks like you are putting lot of pressure on the heap by doing a slice
query on a large row.
Do you have lot of deletes/tombstone on the rows? That might be causing a
problem.
Also why are you returning so many columns as once, you can use auto
paginate feature in Astyanax.
Also do you see lot
