Thank you very much for the explanation. I am new to storm so I thought
the whole topology runs like a message broker. So I design the topology
accordingly. By the way, in most cases, we can not decide which bolt or
spout runs in which machine or thread right? Does that mean we have to
take care of such situation carefully? Thank you very much!!
On 01/04/2015 11:34 PM, Nathan Leung wrote:
Every time you send a tuple, it should be a new tuple. Secondly, when
you send a tuple within the same process, the data is passed by
reference, not serialized and deserialized. That means if you use
local cluster, or even a remote cluster you will see that some of your
data is sent by reference. So when you send a static variable by
reference and then change it, subsequent bolts will see this change.
Note that in remote cluster, localOrShuffleGrouping will send if at
all possible within the same process, and thereby avoid network /
serialization / deserialization costs. ShuffleGrouping will send in
process as well if there are any downstream bolts in the same process,
because it uses round robin. FieldsGrouping is the same if your key
has reasonable distribution. It's possible that you could avoid
passing by reference when using none grouping or direct grouping but
I'm not really sure why you would explicitly try to avoid this.
Also I would note that passing then changing a static variable can be
tricky; hopefully you have protected it against concurrent
modification from other bolt tasks within the same process.
On Sun, Jan 4, 2015 at 7:18 PM, hjh <[email protected]
<mailto:[email protected]>> wrote:
Hi, I am new to storm and I met a problem with tuple. In the local
mode does tuple between connected bolts share the same object? For
example BoltA emit a tuple to BoltB. If BoltB is processing the
tuple (this tuple is assigned to a private variable, say VAR, in
BoltB) and at the same time BoltA sends another tuple to BoltB,
then VAR changed immediately. Does that mean in local mode BoltA
and BoltB share the same tuple instance?? And how to deal with
such situation?
PS. I use java.
Any suggestion is warmly welcomed
Thank you very much!!!
