Sleeping/pausing for a fixed amount of time between operations at best
is a hack to workaround an unknown issue, but it's almost always better
to be explicit about what you are waiting for. Where did you come up
with the 90 seconds number? What exactly are you waiting for by doing
that? If you want to wait for the node's state becomes normal (from
joining), be explicit about it, check the nodetool output or the
system.log file periodically instead of waiting for a fixed 90 seconds.
Streaming 600GB in a few hours sounds fairly reasonable. Since adding
nodes doesn't interfere with the client queries, the time it takes to
add a node shouldn't be a concern at all, as long as it's significantly
faster the data growth rate. Just leave it running in the background,
and get on with your life.
If you must speed up that process and don't care about data inconstancy
or potencial down time, there's faster ways to do it, but doing that
breaks the consistency and/or availability, which means it will
interfere with client read/write operations.
A few hundred GB to a few TB per node is pretty common in Cassandra
clusters. Big data is not about how much data on EACH node, it's about
how much data in TOTAL.
On 11/07/2022 09:01, Marc Hoppins wrote:
Well then…
I left this on Friday (still running) and came back to it today
(Monday) to find the service stopped. So, I blitzed this node from
the ring and began anew with a different new node.
I rather suspect the problem was with trying to use Ansible to add
these initially - despite the fact that I had a serial limit of 1 and
a pause of 90s for starting the service on each new node (based on the
time taken when setting up this Cassandra cluster).
So…moving forward…
It is recommended to only add one new node at a time from what I
read. This leads me to:
Although I see the new node LOAD is progressing far faster than the
previous failure, it is still going to take several hours to move from
UJ to UN, which means I’ll be at this all week for the 12 new nodes.
If our LOAD per node is around 400-600GB, is there any practical
method to speed up adding multiple new nodes which is unlikely to
cause problems? After all, in the modern world of big (how big is
big?) data, 600G per node is far less than the real BIG big-data.
Marc
*From:*Jeff Jirsa <jji...@gmail.com>
*Sent:* Friday, July 8, 2022 5:46 PM
*To:* cassandra <user@cassandra.apache.org>
*Cc:* Bowen Song <bo...@bso.ng>
*Subject:* Re: Adding nodes
EXTERNAL
Having a node UJ but not sending/receiving other streams is an invalid
state (unless 4.0 moved the streaming data out of netstats? I'm not
100% sure, but I'm 99% sure it should be there).
It likely stopped the bootstrap process long ago with an error (which
you may not have seen), and is running without being in the ring, but
also not trying to join the ring.
145GB vs 1.1T could be bits vs bytes (that's a factor of 8), or it
could be that you streamed data and compacted it away. Hard to say,
but less important - the fact that it's UJ but not streaming means
there's a different problem.
If it's me, I do this (not guaranteed to work, your mileage may vary,
etc):
1) Look for errors in the logs of ALL hosts. In the joining host, look
for an exception that stops bootstrap. In the others, look for
messages about errors streaming, and/or exceptions around file access.
In all of those hosts, check to see if any of them think they're
streaming ( nodetool netstats again)
2) Stop the joining host. It's almost certainly not going to finish
now. Remove data directories, commitlog directory, saved caches,
hints. Wait 2 minutes. Make sure every other host in the cluster sees
it disappear from the ring. Then, start it fresh and let it bootstrap
again. (you could alternatively try the resumable bootstrap option,
but I never use it).
On Fri, Jul 8, 2022 at 2:56 AM Marc Hoppins <marc.hopp...@eset.com> wrote:
Ifconfig shows RX of 1.1T. This doesn't seem to fit with the LOAD
of 145GiB (nodetool status), unless I am reading that wrong...and
the fact that this node still has a status of UJ.
Netstats on this node shows (other than :
Read Repair Statistics:
Attempted: 0
Mismatch (Blocking): 0
Mismatch (Background): 0
Pool Name Active Pending Completed Dropped
Large messages n/a 0 0 0
Small messages n/a 53 569755545 15740262
Gossip messages n/a 0 288878 2
None of this addresses the issue of not being able to add more nodes.
-----Original Message-----
From: Bowen Song via user <user@cassandra.apache.org>
Sent: Friday, July 8, 2022 11:47 AM
To: user@cassandra.apache.org
Subject: Re: Adding nodes
EXTERNAL
I would assume that's 85 GB (i.e. gigabytes) then. Which is
approximately 79 GiB (i.e. gibibytes). This still sounds awfully
slow - less than 1MB/s over a full day (24 hours).
You said CPU and network aren't the bottleneck. Have you checked
the disk IO? Also, be mindful with CPU usage. It can still be a
bottleneck if one thread uses 100% of a CPU core while all other
cores are idle.
On 08/07/2022 07:09, Marc Hoppins wrote:
> Thank you for pointing that out.
>
> 85 gigabytes/gibibytes/GIGABYTES/GIBIBYTES/whatever name you
care to
> give it
>
> CPU and bandwidth are not the problem.
>
> Version 4.0.3 but, as I stated, all nodes use the same version
so the version is not important either.
>
> Existing nodes have 350-400+(choose whatever you want to call a
> gigabyte)
>
> The problem appears to be that adding new nodes is a serial
process, which is fine when there is no data and each node is
added within 2minutes. It is hardly practical in production.
>
> -----Original Message-----
> From: Bowen Song via user <user@cassandra.apache.org>
> Sent: Thursday, July 7, 2022 8:43 PM
> To: user@cassandra.apache.org
> Subject: Re: Adding nodes
>
> EXTERNAL
>
>
> 86Gb (that's gigabits, which is 10.75GB, gigabytes) took an
entire day seems obviously too long. I would check the network
bandwidth, disk IO and CPU usage and find out what is the bottleneck.
>
> On 07/07/2022 15:48, Marc Hoppins wrote:
>> Hi all,
>>
>> Cluster of 2 DC and 24 nodes
>>
>> DC1 (RF3) = 12 nodes, 16 tokens each
>> DC2 (RF3) = 12 nodes, 16 tokens each
>>
>> Adding 12 more nodes to DC1: I installed Cassandra (version is
the same across all nodes) but, after the first node added, I
couldn't seem to add any further nodes.
>>
>> I check nodetool status and the newly added node is UJ. It
remains this way all day and only 86Gb of data is added to the
node over the entire day (probably not yet complete). This seems
a little slow and, more than a little inconvenient to only be able
to add one node at a time - or at least one node every 2 minutes.
When the cluster was created, I timed each node from service start
to status UJ (having a UUID) and it was around 120 seconds. Of
course there was no data.
>>
>> Is it possible I have some setting not correctly tuned?
>>
>> Thanks
>>
>> Marc
