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Date: Sat, 23 Mar 2013 16:18:51 +0900
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Subject: Connection threads sticking around
From: Brett Wooldridge <brett.wooldridge@gmail.com>
To: derby-dev@db.apache.org
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I'm trying to figure out how Derby's network server manages threads, maybe
someone with knowledge of that area can help.

I have a client-side connection pool with a minimum of 10 connections,
maximum of 100, and idle timeout of 300 seconds.  Using JMX, I can see that
the pool is indeed sitting at 10 connections.  However, when I perform a
thread dump on the server-side, I see that there are dozens of threads
waiting on socket read() like this one:

DRDAConnThread_19380
java.net.SocketInputStream.socketRead0(Native Method)
java.net.SocketInputStream.read(SocketInputStream.java:150)
java.net.SocketInputStream.read(SocketInputStream.java:121)
org.apache.derby.impl.drda.DDMReader.fill(Unknown Source)
org.apache.derby.impl.drda.DDMReader.ensureALayerDataInBuffer(Unknown Source)
org.apache.derby.impl.drda.DDMReader.readDssHeader(Unknown Source)
org.apache.derby.impl.drda.DRDAConnThread.processCommands(Unknown Source)
org.apache.derby.impl.drda.DRDAConnThread.run(Unknown Source)

Full dump of "DRDAConnThread" theads here:

http://dpaste.com/1032074/

I do not understand why Derby is keeping these around once the client-side
has closed the connection.  What controls server-side connection (thread)
retirement?  If it is pooling them for efficiency, it still seems there
must be a way to control how many/how long they live.

Looking at the thread dump, something else interesting is that
DRDAConnThread_0 thru 9 seemed to die off correctly.  DRDAConnThread_10
thru 19 are still around.  And then there is a jump in number to threads
numbers > ~19300.

Thanks in advance.

Brett

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<div dir=3D"ltr">I&#39;m trying to figure out how Derby&#39;s network serve=
r manages threads, maybe someone with knowledge of that area can help.<div>=
<br></div><div style>I have a client-side connection pool with a minimum of=
 10 connections, maximum of 100, and idle timeout of 300 seconds. =A0Using =
JMX, I can see that the pool is indeed sitting at 10 connections. =A0Howeve=
r, when I perform a thread dump on the server-side, I see that there are do=
zens of threads waiting on socket read() like this one:</div>
<div style><pre style=3D"font-family:&#39;Bitstream Vera Sans Mono&#39;,=
9;Courier New&#39;,Monaco,monospace;font-size:14px;color:rgb(0,0,0)">DRDACo=
nnThread_19380
java.net.SocketInputStream.socketRead0(Native Method)
java.net.SocketInputStream.read(SocketInputStream.java:150)
java.net.SocketInputStream.read(SocketInputStream.java:121)
org.apache.derby.impl.drda.DDMReader.fill(Unknown Source)
org.apache.derby.impl.drda.DDMReader.ensureALayerDataInBuffer(Unknown Sourc=
e)
org.apache.derby.impl.drda.DDMReader.readDssHeader(Unknown Source)
org.apache.derby.impl.drda.DRDAConnThread.processCommands(Unknown Source)
org.apache.derby.impl.drda.DRDAConnThread.run(Unknown Source)</pre></div><d=
iv style>Full dump of &quot;DRDAConnThread&quot; theads here:</div><div sty=
le><br></div><div style><a href=3D"http://dpaste.com/1032074/">http://dpast=
e.com/1032074/</a><br>
</div><div style><br></div><div style>I do not understand why Derby is keep=
ing these around once the client-side has closed the connection. =A0What co=
ntrols server-side connection (thread) retirement? =A0If it is pooling them=
 for efficiency, it still seems there must be a way to control how many/how=
 long they live.</div>
<div style><br></div><div style>Looking at the thread dump, something else =
interesting is that DRDAConnThread_0 thru 9 seemed to die off correctly. =
=A0DRDAConnThread_10 thru 19 are still around. =A0And then there is a jump =
in number to threads numbers &gt; ~19300<font color=3D"#000000" face=3D"Bit=
stream Vera Sans Mono, Courier New, Monaco, monospace"><span style=3D"font-=
size:14px">.</span></font></div>
<div style><font color=3D"#000000" face=3D"Bitstream Vera Sans Mono, Courie=
r New, Monaco, monospace"><span style=3D"font-size:14px"><br></span></font>=
</div><div style>Thanks in advance.</div><div style><br></div><div style>Br=
ett</div>
<div style><br></div></div>

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