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From <Manoj.Agraw...@cognizant.com>
Subject Re: Kafka topic partition distributing evenly on disks
Date Fri, 07 Aug 2020 18:38:54 GMT
Or manually you can move data dir  . I'm assuming you have  replica >1
Stop the kafka process on broker 1
Move 1 or 2  dir log from Disk 1 to disk 2
And start the kafka process

Wait for ISR sync

Then you can repeate this step again .

On 8/7/20, 6:45 AM, "William Reynolds" <william.reynolds@instaclustr.com> wrote:

    [External]


    Hmm, that's odd, I am sure it was in the docs previously. Here is the
    KIP on it https://apc01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fcwiki.apache.org%2Fconfluence%2Fdisplay%2FKAFKA%2FKIP-113%253A%2BSupport%2Breplicas%2Bmovement%2Bbetween%2Blog%2Bdirectories&amp;data=02%7C01%7CManoj.Agrawal2%40cognizant.com%7C3c313758d6c44da817ac08d83ad8262f%7Cde08c40719b9427d9fe8edf254300ca7%7C0%7C0%7C637324047321152477&amp;sdata=tTYPxMp%2FmZ9ufSXQqY%2FbDwAIAG4ZNxRrc7fFq3EEvSg%3D&amp;reserved=0
    Basically the reassignment json that you get looks like this from the
    initial generation and if you already have a realignment file you can
    just add the log dirs section to each partition entry

    {
      "version" : int,
      "partitions" : [
        {
          "topic" : str,
          "partition" : int,
          "replicas" : [int],
          "log_dirs" : [str]    <-- NEW. A log directory can be either
    "any", or a valid absolute path that begins with '/'. This is an
    optional filed. It is treated as an array of "any" if this field is
    not explicitly specified in the json file.
        },
        ...
      ]
    }

    Hope that helps
    William

    On 07/08/2020, Péter Nagykátai <st4r.f1sch@gmail.com> wrote:
    > Thank you William,
    >
    > I checked the doc and don't see any instructions regarding disks. Should I
    > simply "move around" the topics and Kafka will assign the topics evenly on
    > the two disks (per broker)? The current setup looks like this (for the
    > topic in question, 15 primary, replica partitions):
    >
    > Broker 1 - disk 1: 8 partition
    > Broker 1 - disk 2: 2 partition
    >
    > Broker 2 - disk 1: 8 partition
    > Broker 2 - disk 2: 2 partition
    >
    > Broker 3 - disk 1: 8 partition
    > Broker 3 - disk 2: 2 partition
    >
    > Thanks!
    >
    > On Fri, Aug 7, 2020 at 1:01 PM William Reynolds <
    > william.reynolds@instaclustr.com> wrote:
    >
    >> Hi Péter,
    >> Sounds like time to reassign the partitions you have across all the
    >> brokers/data dirs using the instructions from here
    >> https://apc01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fkafka.apache.org%2Fdocumentation%2F%23basic_ops_automigrate&amp;data=02%7C01%7CManoj.Agrawal2%40cognizant.com%7C3c313758d6c44da817ac08d83ad8262f%7Cde08c40719b9427d9fe8edf254300ca7%7C0%7C0%7C637324047321162468&amp;sdata=yWH5xhV8GXsTAOubFU1QmkuMlChpx6DVNe%2BKPpe5bwk%3D&amp;reserved=0.
That
    >> assumes that your partition strategy has somewhat evenly filled your
    >> partitions and given it may move all the partitions it could be a bit
    >> intensive so be sure to use the throttle option.
    >> Cheers
    >> William
    >>
    >> On 07/08/2020, Péter Nagykátai <st4r.f1sch@gmail.com> wrote:
    >> > Hello everybody,
    >> >
    >> > Thank you for the detailed answers. My issue is partly answered here:
    >> >
    >> >
    >> >
    >> >
    >> > *This rule also applies to disk-level, which means that when a set
    >> > ofpartitions assigned to a specific broker, each of the disks will get
    >> > thesame number of partitions without considering the load of disks at
    >> > thattime.*
    >> >
    >> >  I admit, I didn't provide enough info either.
    >> >
    >> > So my problem is that an existing topic got a huge surge of events for
    >> this
    >> > week. I knew that'll happen and I modified the partition count.
    >> > Unfortunately, it occurred to me a bit later, that I'll likely need
    >> > some
    >> > extra disk space. So I added an extra disk to each broker. The thing I
    >> > didn't know, that Kafka won't evenly distribute the partitions on the
    >> > disks.
    >> > So the question still remains:
    >> >  Is there any way to have Kafka evenly distribute data on its disks?
    >> > Also, what options do I have *after *I'm in the situation I described
    >> > above? (preferably without deleting the topic)
    >> >
    >> > Thanks!
    >> >
    >> > On Fri, Aug 7, 2020 at 12:00 PM Yingshuan Song
    >> > <songyingshuan@gmail.com>
    >> > wrote:
    >> >
    >> >> Hi Peter,
    >> >> Agreed with Manoj and Vinicius, i think those rules led to this result
    >> >> :
    >> >>
    >> >> 1)the partitions of a topic - N and replication number - R determine
    >> >> the
    >> >> real partition-replica count of this topic, which is N * R;
    >> >> 2)   kafka can distribute partitions evenly among brokers, but it is
    >> >> based
    >> >> on the broker count when the topic was created, this is important.
    >> >> If we create a topic (N - 4, R - 3) in a kafka cluster which contains
    >> >> 3
    >> >> kafka brokers, then 4 * 3 / 3 = 4 partitions will be assigned to each
    >> >> broker.
    >> >> But if a new broker was added into this cluster and another topic (N
-
    >> 4,
    >> >> R
    >> >> - 3) need to be created, then 4 * 3 / 4 = 3 partitions will be
    >> >> assigned
    >> >> to
    >> >> each broker.
    >> >> Kafka will not assign all those partitions to the new added broker
    >> >> even
    >> >> though it is idle and i think this is a shortcoming of kafka.
    >> >> This rule also applies to disk-level, which means that when a set of
    >> >> partitions assigned to a specific broker, each of the disks will get
    >> >> the
    >> >> same number of partitions without considering the load of disks at
    >> >> that
    >> >> time.
    >> >> 3) when producer send records to topics, how to chose partiton : 3-1)
    >> >> if
    >> >> a
    >> >> record has a key, then the partition number calculate according to the
    >> >> key;
    >> >> 3-2) if  records have no keys, then those records will be sent to each
    >> >> partition in turns. So, if there are lots of records with the same
    >> >> key,
    >> >> and
    >> >> those records will be sent to the same partition, and may take up a
    >> >> lot
    >> >> of
    >> >> disk space.
    >> >>
    >> >>
    >> >> hope this helps
    >> >>
    >> >> Vinicius Scheidegger <vinicius.scheidegger@gmail.com> 于2020年8月7日周五
    >> >> 上午6:10写道:
    >> >>
    >> >> > Hi Peter,
    >> >> >
    >> >> > AFAIK, everything depends on:
    >> >> >
    >> >> > 1) How you have configured your topic
    >> >> >   a) number of partitions (here I understand you have 15 partitions)
    >> >> >   b) partition replication configuration (each partition necessarily
    >> >> > has
    >> >> a
    >> >> > leader - primary responsible to hold the data - and for reads and
    >> >> > writes)
    >> >> > you can configure the topic to have a number of replicas
    >> >> > 2) How you publish messages to the topic
    >> >> >   a) The publisher is responsible to choose the partition. This
can
    >> >> > be
    >> >> done
    >> >> > consciously (by setting the partition id while sending the message
    >> >> > to
    >> >> > the
    >> >> > topic) or unconsciously (by using the DefaultPartitioner or any
    >> >> > other
    >> >> > partitioner scheme).
    >> >> >
    >> >> > All messages sent to a specific partition will be written first
to
    >> >> > the
    >> >> > leader (meaning that the disk configured for the partition leader
    >> >> > will
    >> >> > receive the load) and then replicated to the replica (followers).
    >> >> > Kafka does not automatically distribute the data equally to the
    >> >> > different
    >> >> > brokers - you need to think about your architecture having that
in
    >> >> > mind.
    >> >> >
    >> >> > I hope it helps
    >> >> >
    >> >> > On Thu, Aug 6, 2020 at 10:23 PM Péter Nagykátai
    >> >> > <st4r.f1sch@gmail.com
    >> >
    >> >> > wrote:
    >> >> >
    >> >> > > I initially started with one data disk (mounted solely to
hold
    >> >> > > Kafka
    >> >> > data)
    >> >> > > and recently added a new one.
    >> >> > >
    >> >> > > On Thu, Aug 6, 2020 at 10:13 PM <Manoj.Agrawal2@cognizant.com>
    >> wrote:
    >> >> > >
    >> >> > > > What do you mean older disk ?
    >> >> > > >
    >> >> > > > On 8/6/20, 12:05 PM, "Péter Nagykátai" <st4r.f1sch@gmail.com>
    >> >> wrote:
    >> >> > > >
    >> >> > > >     [External]
    >> >> > > >
    >> >> > > >
    >> >> > > >     Yeah, but it doesn't do that. My "older" disks have
~70
    >> >> partitions,
    >> >> > > the
    >> >> > > >     newer ones ~5 partitions. That's why I'm asking what
went
    >> >> > > > wrong.
    >> >> > > >
    >> >> > > >     On Thu, Aug 6, 2020 at 8:35 PM
    >> >> > > > <Manoj.Agrawal2@cognizant.com>
    >> >> > wrote:
    >> >> > > >
    >> >> > > >     > Kafka  evenly distributed number of partition
on each disk
    >> so
    >> >> in
    >> >> > > > your case
    >> >> > > >     > every disk should have 3/2 topic partitions
.
    >> >> > > >     > It is producer job to evenly produce data by
partition key
    >> >> > > > to
    >> >> > > topic
    >> >> > > >     > partition .
    >> >> > > >     > How it partition key , it is auto generated
or producer
    >> >> > > > sending
    >> >> > key
    >> >> > > > along
    >> >> > > >     > with message .
    >> >> > > >     >
    >> >> > > >     >
    >> >> > > >     > On 8/6/20, 7:29 AM, "Péter Nagykátai"
    >> >> > > > <st4r.f1sch@gmail.com
    >> >
    >> >> > > wrote:
    >> >> > > >     >
    >> >> > > >     >     [External]
    >> >> > > >     >
    >> >> > > >     >
    >> >> > > >     >     Hello,
    >> >> > > >     >
    >> >> > > >     >     I have a Kafka cluster with 3 brokers (v2.3.0)
and
    >> >> > > > each
    >> >> > broker
    >> >> > > > has 2
    >> >> > > >     > disks
    >> >> > > >     >     attached. I added a new topic (heavyweight)
and was
    >> >> surprised
    >> >> > > > that
    >> >> > > >     > even if
    >> >> > > >     >     the topic has 15 partitions, those weren't
distributed
    >> >> evenly
    >> >> > > on
    >> >> > > > the
    >> >> > > >     > disks.
    >> >> > > >     >     Thus I got one disk that's almost empty
and the other
    >> >> almost
    >> >> > > > filled
    >> >> > > >     > up. Is
    >> >> > > >     >     there any way to have Kafka evenly distribute
data on
    >> its
    >> >> > > disks?
    >> >> > > >     >
    >> >> > > >     >     Thank you!
    >> >> > > >     >
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    >>
    >>
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