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Date: Tue, 31 May 2011 15:45:38 +0800
Message-ID: <BANLkTi=2booee_D_=nkXHh7MJSF7PXJXKA@mail.gmail.com>
Subject: sync commitlog in batch mode lose data
From: Preston Chang <zhangyf2007@gmail.com>
To: user@cassandra.apache.org
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Hi,

I have a cluster with two nodes (node A and node B) and make a test as
follows:

1). set commitlog sync in batch mode and the sync batch window in 0 ms
2). one client wrote random keys in infinite loop with consistency level
QUORUM and record the keys in file after the insert() method return normally
3). unplug one server (node A) power cord
4). restart the server and cassandra service
5). read the key list generated in step 2) with consistency level ONE

I thought the result of test is all the key in list can be read normally,
but actually there are some NotFound keys.

My question is why there are NotFound keys. In my opinion server would not
ack the client before finishing syncing the commitlog if I set commitlog
sync in batch mode and the sync batch window in 0 ms. So if the insert()
method return normally it means the mutation had been written in commitlog
and the commitlog had been synced to the disk. Am I right?

My Cassandra version is 0.7.3.

Thanks for your help very much.

-- 
by Preston Chang

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<div>Hi,</div><div><br></div><div>I have a cluster with two nodes (node A a=
nd node B) and make a test as follows:</div><div><br></div><div>1). set com=
mitlog sync in batch mode and the sync batch window in 0 ms</div><div>2). o=
ne client wrote random keys in infinite loop with consistency level QUORUM =
and record the keys in file after the insert()=A0method return normally</di=
v>
<div>3). unplug one server (node A) power cord</div><div>4). restart the se=
rver and cassandra service</div><div>5). read the key list generated in ste=
p 2) with consistency level ONE</div><div><br></div><div>I thought the resu=
lt of test is all the key in list can be read normally, but actually there =
are some NotFound keys.</div>
<div><br></div><div>My question is why there are NotFound keys. In my opini=
on server would not ack the client before finishing syncing the commitlog i=
f=A0I set commitlog sync in batch mode and the sync batch window in 0 ms. S=
o if the insert() method return normally it means the=A0mutation had been w=
ritten in commitlog and the commitlog had been synced to the disk. Am I rig=
ht?</div>
<div><br></div><div>My Cassandra version is 0.7.3.</div><div><br></div><div=
>Thanks for your help very much.</div><br>-- <br>by Preston Chang<br><br>

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