Thanks, Alain.
Thanks for suggesting the use of "unchecked_tombstone_compaction". It was
suggested in my other related question "How to remove huge files with all
expired data sooner?"
(http://www.mail-archive.com/user%40cassandra.apache.org/msg44073.html), but I
had to wait until I upgrade C*.
Good to know that compaction is better in 2.1.x.
I will probably arrange to upgrade to 2.1.14 soon.
Thanks,
Dongfeng
On Thursday, June 2, 2016 4:53 AM, Alain RODRIGUEZ <arodr...@gmail.com>
wrote:
Hi Dongfeng,
3: Restarting the code does NOT remove those files. I stopped and restarted C*
many times and it did nothing.
Finally, my solution was to manually delete those old files. I actually deleted
them while C* is running and did not see any errors/warnings in system.log. My
guess is that those files are not in C* metadata so C* does not know their
existance.
This was a good move. If all the data is TTLed after 8 days, then any sstable
older than 8 days is no longer relevant, this is a guarantee. I would probably
have stopped the node though. Glad it worked.
Automatic compaction by C* does not work in a timely manner for me
You might want to give "unchecked_tombstone_compaction=true" a try on this
table options. This will allow a most aggressive tombstone eviction, and should
be quite safe. Not sure why this is not yet a Cassandra default. Single sstable
compactions will trigger, removing tombstones after 10 days (gc_grace_seconds).
So any data older than 8 days (TTL) + 10 days (gc_grace_seconds) = 18 days
should be eventually (and quite quickly) removed.
Major compaction (nodetool compaction) produces a very big sstables that will
no longer be compacted until there are 3 other files of the same size (using
default). I think running major comapction delay the issue (and might make it
worse) but does not solve it.
It is also good to know that compaction is doing a lot better in 2.1.X from my
own experience.
B: We have tested the procedure with 2.1.11 in our DEV environment quite some
time ago. Due to priority changes, we only started applying it to production
lately. By rule, I had to re-test it if I switch to 2.1.14, and I don't see
much benefits doing it.
As an example example, if you are planning to take profit of the incremental
repair features (new in 2.1) or DTCS, you probably want to jump to 2.1.14
because of:
"FIX 2.1.14 - DTCS repair both unrepaired / repaired sstables - incremental
onlyhttps://issues.apache.org/jira/browse/CASSANDRA-11113FIX 2.1.14 - Avoid
major compaction mixing repaired and unrepaired sstables in
DTCShttps://issues.apache.org/jira/browse/CASSANDRA-11113FIX 2.1.12 - A lot of
sstables using range repairs due to anticompaction - incremental
onlyhttps://issues.apache.org/jira/browse/CASSANDRA-10422FIX 2.1.12 - repair
hang when replica is down - incremental
onlyhttps://issues.apache.org/jira/browse/CASSANDRA-10288";
I would probably go through 2.1.11 --> 2.1.14 changes and see if it is worth
it. I am not saying you shouldn't test it, but, if migrating to 2.1.11 worked
for you, I guess 2.1.14 will work as well. I am quite confident, but as I won't
be responsible of it and of fixing any issue that might show up, it is up to
you :-). An other way is to do one more step from 2.1.11 to 2.1.14, but I see
no value in this as you would have to then test 2.1.11 --> 2.1.14 upgrade.
Since we are at 2.0.6, we have to migrate twice, from 2.0.6 to 2.0.17. then to
2.1.11.
Glad to see you did not miss that. I pointed it out, just in case :-).
Good luck with this all,
C*heers,
-----------------------Alain Rodriguez - alain@thelastpickle.comFrance
The Last Pickle - Apache Cassandra Consultinghttp://www.thelastpickle.com
2016-06-01 17:52 GMT+01:00 Dongfeng Lu <dlu66...@yahoo.com>:
Alain,
Thanks for responding to my question.
1 & 2: I think it is a bug, but as you said, maybe no one will dig it. I just
hope it has been fixed in the later versions.
3: Restarting the code does NOT remove those files. I stopped and restarted C*
many times and it did nothing.
4: Thanks for the links. I will probably try DTCS in the near future.
A: Automatic compaction by C* does not work in a timely manner for me. I set
TTL to 8 days, and hoped that I only have data files with timestamps like
within 2 weeks. However, I often saw files created 2 months ago with 50GB in
size.
In the final step of upgrade, I am suppose to run upgradesstables, which is
like a compaction. I know compaction takes a long time to run. In order to
reduce the amount of time during the actual upgrade, I ran a manual compaction
to cut down the size, by 80% in my case.
B: We have tested the procedure with 2.1.11 in our DEV environment quite some
time ago. Due to priority changes, we only started applying it to production
lately. By rule, I had to re-test it if I switch to 2.1.14, and I don't see
much benefits doing it.
C: Yes, I noticed the statement "When upgrading to Cassandra 2.1 all nodes must
be on at least Cassandra 2.0.7 to support rolling start." Since we are at
2.0.6, we have to migrate twice, from 2.0.6 to 2.0.17. then to 2.1.11.
Finally, my solution was to manually delete those old files. I actually deleted
them while C* is running and did not see any errors/warnings in system.log. My
guess is that those files are not in C* metadata so C* does not know their
existance.
Thanks,
Dongfeng
On Wednesday, June 1, 2016 6:36 AM, Alain RODRIGUEZ <arodr...@gmail.com>
wrote:
Hi,
About your main concern:
1. True those files should have been removed. Yet Cassandra 2.0 is no longer
supported, even more such an old version (2.0.6), so I think no one is going to
dig this issue. To fix it, upgrade will probably be enough.
I don't usually run manual compaction, and relied completely on Cassandra to
automatically do it. A couple of days ago in preparation for an upgrade to
Cassandra 2.1.11, I ran a manual, complete compaction
2. As you might know, sstables are immutable, meaning compacting, merging row
shards, has to be done somewhere else, not in place. Those -tmp- files are the
result of compactions ongoing basically. It is perfectly normal. Yet '-tmp-'
files are supposed to be removed once compaction is done.
3. Restarting the node will most probably solve your issue. To be sure to
indeed free disk space, make sure you have no snapshot of those old sstables.
4. The advantage of DTCS is that data is not mixed per age. Meaning Cassandra
can drop a full expired sstable, without compacting. It sounds like a good fit.
Yet this compaction strategy is the most recent one and some things are still
being fixed. I still think it is safe to use it. Make sure you read first:
https://labs.spotify.com/2014/12/18/date-tiered-compaction/ And/Or
http://www.datastax.com/dev/blog/datetieredcompactionstrategy
You also might want to have a look at https://github.com/jeffjirsa/twcs.
Some other off-topic, but maybe useful questions / info
A - Why do you need a manual compaction before upgrading? I really can't see
any reason for it.B - Why upgrading to Cassandra 2.1.14 when 2.1.14 is
available and brings some more bug fixes (compared to 2.1.11)?C - It is
recommended to move to 2.0.last before going to 2.1.X. You might run into some
issue. Either make sure to test it works or go incrementally 2.0.6 --> 2.0.17
--> 2.1.14. I would probably do both. Test it and go incrementally. I would not
go with 2.0.6 --> 2.1.14 without testing it first anyway.
Hope it is all clear and that a restart will solve your issue.
C*heers,
-----------------------Alain Rodriguez - alain@thelastpickle.comFrance
The Last Pickle - Apache Cassandra Consultinghttp://www.thelastpickle.com
2016-05-17 0:06 GMT+01:00 Dongfeng Lu <dlu66...@yahoo.com>:
Forgive me if that has been answered somewhere, but I could not find a concise
or clear answer.
I am using Cassandra 2.0.6 on a 3 node cluster. I don't usually run manual
compaction, and relied completely on Cassandra to automatically do it. A couple
of days ago in preparation for an upgrade to Cassandra 2.1.11, I ran a manual,
complete compaction. The compaction ran for many hours, but it did complete
successfully, and the "load" in "nodetool status" dropped 80%. However, I did
not see a big drop in disk usage, even after waiting for a couple of days.
There are still many old data files left on the disk. For instance, here is a
list of data files for one table.
-bash-4.1$ ls -ltr *-Data.db
-rw-r--r-- 1 cassandra cassandra 36441245112 Jan 19 05:42
keyspace-event_index-jb-620839-Data.db
-rw-r--r-- 1 cassandra cassandra 48117578123 Jan 25 05:17
keyspace-event_index-jb-649329-Data.db
-rw-r--r-- 1 cassandra cassandra 8731574747 Jan 27 18:30
keyspace-event_index-jb-662597-Data.db
-rw-r--r-- 1 cassandra cassandra 835204478 Feb 2 07:20
keyspace-event_index-jb-670851-Data.db
-rw-r--r-- 1 cassandra cassandra 39496133 Feb 2 15:29
keyspace-event_index-tmp-jb-672828-Data.db
... about 110 files listed here, removed for clarity ...
-rw-r--r-- 1 cassandra cassandra 149344563 May 9 20:53
keyspace-event_index-tmp-jb-827472-Data.db
-rw-r--r-- 11 cassandra cassandra 20149715779 May 15 04:18
keyspace-event_index-jb-829601-Data.db
-rw-r--r-- 11 cassandra cassandra 7153875910 May 15 11:15
keyspace-event_index-jb-830446-Data.db
-rw-r--r-- 11 cassandra cassandra 3051908121 May 16 03:08
keyspace-event_index-jb-831112-Data.db
-rw-r--r-- 11 cassandra cassandra 6109582092 May 16 06:11
keyspace-event_index-jb-831709-Data.db
-rw-r--r-- 11 cassandra cassandra 2922532233 May 16 07:14
keyspace-event_index-jb-831873-Data.db
-rw-r--r-- 11 cassandra cassandra 1766025989 May 16 08:31
keyspace-event_index-jb-832111-Data.db
-rw-r--r-- 8 cassandra cassandra 2922259593 May 16 11:39
keyspace-event_index-jb-832693-Data.db
-rw-r--r-- 8 cassandra cassandra 1224495235 May 16 11:50
keyspace-event_index-jb-832764-Data.db
-rw-r--r-- 7 cassandra cassandra 2051385733 May 16 12:57
keyspace-event_index-jb-832975-Data.db
-rw-r--r-- 6 cassandra cassandra 853824939 May 16 13:12
keyspace-event_index-jb-833100-Data.db
-rw-r--r-- 5 cassandra cassandra 763243638 May 16 14:58
keyspace-event_index-jb-833203-Data.db
-rw-r--r-- 3 cassandra cassandra 99076639 May 16 16:29
keyspace-event_index-jb-833222-Data.db
-rw-r--r-- 2 cassandra cassandra 254935385 May 16 17:21
keyspace-event_index-jb-833233-Data.db
-rw-r--r-- 2 cassandra cassandra 66006223 May 16 17:51
keyspace-event_index-jb-833238-Data.db
-rw-r--r-- 1 cassandra cassandra 50204322 May 16 18:18
keyspace-event_index-jb-833243-Data.db
-rw-r--r-- 2 cassandra cassandra 16078537 May 16 18:26
keyspace-event_index-jb-833244-Data.db
However, it looks to me that Cassandra knows that the first 115 files are old
and are not really used to create snapshot. Here is the newly created snapshot.
-bash-4.1$ ls -ltr snapshots/20160516-1800/*-Data.db
-rw-r--r-- 11 cassandra cassandra 20149715779 May 15 04:18
snapshots/20160516-1800/keyspace-event_index-jb-829601-Data.db
-rw-r--r-- 11 cassandra cassandra 7153875910 May 15 11:15
snapshots/20160516-1800/keyspace-event_index-jb-830446-Data.db
-rw-r--r-- 11 cassandra cassandra 3051908121 May 16 03:08
snapshots/20160516-1800/keyspace-event_index-jb-831112-Data.db
-rw-r--r-- 11 cassandra cassandra 6109582092 May 16 06:11
snapshots/20160516-1800/keyspace-event_index-jb-831709-Data.db
-rw-r--r-- 11 cassandra cassandra 2922532233 May 16 07:14
snapshots/20160516-1800/keyspace-event_index-jb-831873-Data.db
-rw-r--r-- 11 cassandra cassandra 1766025989 May 16 08:31
snapshots/20160516-1800/keyspace-event_index-jb-832111-Data.db
-rw-r--r-- 8 cassandra cassandra 2922259593 May 16 11:39
snapshots/20160516-1800/keyspace-event_index-jb-832693-Data.db
-rw-r--r-- 8 cassandra cassandra 1224495235 May 16 11:50
snapshots/20160516-1800/keyspace-event_index-jb-832764-Data.db
-rw-r--r-- 7 cassandra cassandra 2051385733 May 16 12:57
snapshots/20160516-1800/keyspace-event_index-jb-832975-Data.db
-rw-r--r-- 6 cassandra cassandra 853824939 May 16 13:12
snapshots/20160516-1800/keyspace-event_index-jb-833100-Data.db
-rw-r--r-- 5 cassandra cassandra 763243638 May 16 14:58
snapshots/20160516-1800/keyspace-event_index-jb-833203-Data.db
-rw-r--r-- 3 cassandra cassandra 99076639 May 16 16:29
snapshots/20160516-1800/keyspace-event_index-jb-833222-Data.db
-rw-r--r-- 2 cassandra cassandra 254935385 May 16 17:21
snapshots/20160516-1800/keyspace-event_index-jb-833233-Data.db
-rw-r--r-- 2 cassandra cassandra 66006223 May 16 17:51
snapshots/20160516-1800/keyspace-event_index-jb-833238-Data.db
-rw-r--r-- 2 cassandra cassandra 16336415 May 16 17:59
snapshots/20160516-1800/keyspace-event_index-jb-833239-Data.db
-rw-r--r-- 2 cassandra cassandra 1947026 May 16 18:00
snapshots/20160516-1800/keyspace-event_index-jb-833240-Data.db
-bash-4.1$
You can see that only files dated "May 15 04:18" or later exist in the snapshot
folder.
My questions:
1. I believe Cassandra should have deleted all old 115 data files. What could
have prevented those files being deleted? What can I do to make sure old files
will be deleted in future compactions?
2. What are those files with "-tmp-"? What is the implication of their
existance? Does it mean a compaction failed?
3. Since Cassandra knows what files are actually used, is there some utility
that I can use to delete those old files? I can delete them manually, but that
would be error-prone.
4. The table uses SizeTieredCompactionStrategy, and contains data with a TTL of
8 days. Will switching to DateTieredCompactionStrategy after upgrading to
2.1.11 offer much better compaction performance?
Thanks,Dongfeng
