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From: Till Rohrmann <trohrmann@apache.org>
Date: Thu, 23 Jun 2016 15:19:03 +0200
Message-ID: <CAC27z=MJVmBWq9mhkqVTNoQc+JR2Tu8aSstROqKPtnm2F+Z_6Q@mail.gmail.com>
Subject: Re: Initialization of static variables
To: user@flink.apache.org
Content-Type: multipart/alternative; boundary=001a1148e4d6ecfa5f0535f1e507
archived-at: Thu, 23 Jun 2016 13:19:08 -0000

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Yes this is normal Flink behaviour. The reason is that static variables are
not transferred to the cluster. What happens instead when you first load
the class on the cluster is that the static variables are created and
possible class initializer are executed. That is also the reason why your
second example works whereas the first fails.

Cheers,
Till

On Thu, Jun 23, 2016 at 3:12 PM, Flavio Pompermaier <pompermaier@okkam.it>
wrote:

> Hi all,
> I've a Flink job that initialize a static Map in the main program, before
> starting any Flink transformation. If I run the job locally that variable
> is not empty, running the job on the cluster reset that variable..is it a
> bug or am I doing something wrong?
> It only works if I initialize that variable in a static statement before
> the main, that is:
>
> ///////////////// KO EXAMPLE
> class ErrorMain {
>
>     private static final Map<String,String> ht = new HashMap<>();
>
>     publis static final main(String[]args){
>      ht.put("test","test");
>      env.readFile().map(
>         ...
>        //here ht.get("test") returns null
>   }
> }
>
> ///////////////// OK EXAMPLE
> class OkMain {
>
>     private static final Map<String,String> ht = new HashMap<>();
>     static{
>         ht.put("test","test");
>     }
>     publis static final main(String[] args){
>
>      env.readFile().map(
>         ...
>        //here ht.get("test") works
>   }
> }
>
>
> Best,
> Flavio
>
>

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<div dir=3D"ltr">Yes this is normal Flink behaviour. The reason is that sta=
tic variables are not transferred to the cluster. What happens instead when=
 you first load the class on the cluster is that the static variables are c=
reated and possible class initializer are executed. That is also the reason=
 why your second example works whereas the first fails.<div><br></div><div>=
Cheers,</div><div>Till</div></div><div class=3D"gmail_extra"><br><div class=
=3D"gmail_quote">On Thu, Jun 23, 2016 at 3:12 PM, Flavio Pompermaier <span =
dir=3D"ltr">&lt;<a href=3D"mailto:pompermaier@okkam.it" target=3D"_blank">p=
ompermaier@okkam.it</a>&gt;</span> wrote:<br><blockquote class=3D"gmail_quo=
te" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"=
><div dir=3D"ltr">Hi all,<div>I&#39;ve a Flink job that initialize a static=
 Map in the main program, before starting any Flink transformation. If I ru=
n the job locally that variable is not empty, running the job on the cluste=
r reset that variable..is it a bug or am I doing something wrong?</div><div=
>It only works if I initialize that variable in a static statement before t=
he main, that is:</div><div><br></div><div>///////////////// KO EXAMPLE</di=
v><div>class ErrorMain {</div><div><br></div><div>=C2=A0 =C2=A0 private sta=
tic final Map&lt;String,String&gt; ht =3D new HashMap&lt;&gt;();</div><div>=
<br></div><div>=C2=A0 =C2=A0 publis static final main(String[]args){</div><=
div>=C2=A0 =C2=A0 =C2=A0ht.put(&quot;test&quot;,&quot;test&quot;);</div><di=
v>=C2=A0 =C2=A0 =C2=A0env.readFile().map(</div><div>=C2=A0 =C2=A0 =C2=A0 =
=C2=A0 ...</div><div>=C2=A0 =C2=A0 =C2=A0 =C2=A0//here ht.get(&quot;test&qu=
ot;) returns null</div><div>=C2=A0 }</div><div>}</div><div><br></div><div>/=
//////////////// OK EXAMPLE<br></div><div><div>class OkMain {</div><div><br=
></div><div>=C2=A0 =C2=A0 private static final Map&lt;String,String&gt; ht =
=3D new HashMap&lt;&gt;();</div><div>=C2=A0 =C2=A0 static{</div><div>=C2=A0=
 =C2=A0 =C2=A0 =C2=A0 ht.put(&quot;test&quot;,&quot;test&quot;);<br></div><=
div>=C2=A0 =C2=A0 }</div><div>=C2=A0 =C2=A0 publis static final main(String=
[] args){</div><div>=C2=A0 =C2=A0=C2=A0</div><div>=C2=A0 =C2=A0 =C2=A0env.r=
eadFile().map(</div><div>=C2=A0 =C2=A0 =C2=A0 =C2=A0 ...</div><div>=C2=A0 =
=C2=A0 =C2=A0 =C2=A0//here ht.get(&quot;test&quot;) works</div><div>=C2=A0 =
}</div><div>}</div></div><div><br></div><div><br></div><div>Best,</div><div=
>Flavio</div><div><div data-smartmail=3D"gmail_signature"><div dir=3D"ltr">=
<p></p><p></p><p></p><p></p></div></div>
</div></div>
</blockquote></div><br></div>

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