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Posted to user@zookeeper.apache.org by ibrahim El-sanosi <ib...@gmail.com> on 2016/03/18 17:05:38 UTC
Dealing with old delivered requests in memory
Hi all,
Assume the Zookeeper have been running for about one year (from 1/1/2015
until now), how does ZooKeeper deal with old delivered write requests (To
optimize a memory used) (say from 1/1/2015 to 03/04/2015). I am assuming
the old delivered request are no longer used.
On the other words, what strategy ZK does to find and delete unused Znodes?
Ibrahim
Re: Dealing with old delivered requests in memory
Posted by ibrahim El-sanosi <ib...@gmail.com>.
Thank you Patrick,
Ibrahim
On Wed, Mar 23, 2016 at 4:44 PM, Patrick Hunt <ph...@apache.org> wrote:
> On Tue, Mar 22, 2016 at 7:53 AM, ibrahim El-sanosi
> <ib...@gmail.com> wrote:
> > Thank you Patrick,
> >
> >
> >
> >>That's correct. ZK is an in-memory store. As such all znodes
> >
> >>representing the current state are held in memory.
> >
> >>
> >
> >>> 2. If the leader crashes or lost a quorum, recovery mechanism applies
> >
> >>> latest snapshots. In this scenario, it is possible to eliminate the old
> > ZK
> >
> >>> states and could save memory space.
> >
> >>>
> >
> >>
> >
> >>This won't affect the in-memory state. It will be the same as prior to
> >
> >>the recovery.
> >
> >
> >
> > Observation (2), I assume the worst scenario when all ZK servers want
> down
> > and start recovery phase (No ZK states persent in memory at the moment).
> > Does ZK servers reapply all snapshot in memory or just takes the latest
> one?
> >
>
> The most recent valid snapshot is read and any transactions written to
> the logs subsequent to that snapshot are replayed.
>
> Patrick
>
> >
> >
> > Ibrahim
> >
> > On Tue, Mar 22, 2016 at 2:43 PM, Patrick Hunt <ph...@apache.org> wrote:
> >
> >> On Fri, Mar 18, 2016 at 10:10 AM, ibrahim El-sanosi
> >> <ib...@gmail.com> wrote:
> >> > Ok, Thank you for answering the question.
> >> >
> >> > So, what I understand from this thread is as following:
> >> >
> >> > 1. When the crash does occur (Leader does not crash and majority of
> >> > servers is always up), the state from Time T0 (ZK start of ZK) and
> until
> >> > time Tn (ZK state of now) will be in memory (even the size of ZK state
> >> > reaches to the memory size).
> >> >
> >>
> >> That's correct. ZK is an in-memory store. As such all znodes
> >> representing the current state are held in memory.
> >>
> >> > 2. If the leader crashes or lost a quorum, recovery mechanism applies
> >> > latest snapshots. In this scenario, it is possible to eliminate the
> old
> >> ZK
> >> > states and could save memory space.
> >> >
> >>
> >> This won't affect the in-memory state. It will be the same as prior to
> >> the recovery.
> >>
> >> Patrick
> >>
> >> >
> >> > Is that right?
> >> >
> >> >
> >> >
> >> > Regards,
> >> >
> >> > Ibrahim
> >> >
> >> > On Fri, Mar 18, 2016 at 4:49 PM, Flavio Junqueira <fp...@apache.org>
> >> wrote:
> >> >
> >> >> It is currently as Jordan says, although it is not entirely
> unreasonable
> >> >> to think of memory as cache and keep in memory only the current
> working
> >> >> set, possibly using say an SSD to store the remaining part of the
> state
> >> >> that you don't want to keep in memory. One key issue here is that if
> you
> >> >> have a pretty large state (that you don't want to keep all in
> memory),
> >> then
> >> >> you'll end up increasing worst-case recovery time.
> >> >>
> >> >> We certainly do not have any kind of expiration mechanism for znodes
> >> other
> >> >> than the ephemeral flag, which is associated to sessions.
> >> >>
> >> >> -Flavio
> >> >>
> >> >> > On 18 Mar 2016, at 16:38, ibrahim El-sanosi <
> ibrahimsabattt@gmail.com
> >> >
> >> >> wrote:
> >> >> >
> >> >> > Thank you for replaying.
> >> >> >
> >> >> >
> >> >> > Take this example, Zookeeper started on 1/1/2015, and assume ZK
> >> servers
> >> >> are
> >> >> > never crashed. Also, the ZK are very busy, reciveing continusly
> write
> >> >> > requests from clients and accordingly snapshots are generated
> >> overtime.
> >> >> On
> >> >> > 1/3/2015, what Znodes will be in memory data tree? do all Znodes
> >> still
> >> >> > store in memory (from 1/1/2015 to 1/3/2015) as there is no crashed
> >> occur.
> >> >> > Or Dsnapshhot is taken the data tree is
> >> >> >
> >> >> >
> >> >> > Note that I am not asking about data in log or snapshoot. I am
> asking
> >> >> > about the current data in memory.
> >> >> >
> >> >> > On Fri, Mar 18, 2016 at 4:12 PM, Flavio Junqueira <fp...@apache.org>
> >> >> wrote:
> >> >> >
> >> >> >> Hi Ibrahim,
> >> >> >>
> >> >> >> Are you asking about how we compact old logs? We do it by taking
> >> >> snapshots
> >> >> >> so that upon recovery, we only load the latest snapshot and replay
> >> the
> >> >> txn
> >> >> >> log from the snapshot tag. The snapshot tag is the last zxid
> >> committed
> >> >> when
> >> >> >> we start producing the snapshot.
> >> >> >>
> >> >> >> We don't actually delete anything, though, unless you
> intentionally
> >> turn
> >> >> >> on auto purge:
> >> >> >>
> >> >> >>
> >> >>
> >>
> https://zookeeper.apache.org/doc/trunk/zookeeperAdmin.html#sc_administering
> >> >> >> <
> >> >> >>
> >> >>
> >>
> https://zookeeper.apache.org/doc/trunk/zookeeperAdmin.html#sc_administering
> >> >> >>>
> >> >> >>
> >> >> >> -Flavio
> >> >> >>
> >> >> >>> On 18 Mar 2016, at 16:05, ibrahim El-sanosi <
> >> ibrahimsabattt@gmail.com>
> >> >> >> wrote:
> >> >> >>>
> >> >> >>> Hi all,
> >> >> >>>
> >> >> >>> Assume the Zookeeper have been running for about one year (from
> >> >> 1/1/2015
> >> >> >>> until now), how does ZooKeeper deal with old delivered write
> >> requests
> >> >> (To
> >> >> >>> optimize a memory used) (say from 1/1/2015 to 03/04/2015). I am
> >> >> assuming
> >> >> >>> the old delivered request are no longer used.
> >> >> >>>
> >> >> >>> On the other words, what strategy ZK does to find and delete
> unused
> >> >> >> Znodes?
> >> >> >>>
> >> >> >>> Ibrahim
> >> >> >>
> >> >> >>
> >> >>
> >> >>
> >>
>
Re: Dealing with old delivered requests in memory
Posted by Patrick Hunt <ph...@apache.org>.
On Tue, Mar 22, 2016 at 7:53 AM, ibrahim El-sanosi
<ib...@gmail.com> wrote:
> Thank you Patrick,
>
>
>
>>That's correct. ZK is an in-memory store. As such all znodes
>
>>representing the current state are held in memory.
>
>>
>
>>> 2. If the leader crashes or lost a quorum, recovery mechanism applies
>
>>> latest snapshots. In this scenario, it is possible to eliminate the old
> ZK
>
>>> states and could save memory space.
>
>>>
>
>>
>
>>This won't affect the in-memory state. It will be the same as prior to
>
>>the recovery.
>
>
>
> Observation (2), I assume the worst scenario when all ZK servers want down
> and start recovery phase (No ZK states persent in memory at the moment).
> Does ZK servers reapply all snapshot in memory or just takes the latest one?
>
The most recent valid snapshot is read and any transactions written to
the logs subsequent to that snapshot are replayed.
Patrick
>
>
> Ibrahim
>
> On Tue, Mar 22, 2016 at 2:43 PM, Patrick Hunt <ph...@apache.org> wrote:
>
>> On Fri, Mar 18, 2016 at 10:10 AM, ibrahim El-sanosi
>> <ib...@gmail.com> wrote:
>> > Ok, Thank you for answering the question.
>> >
>> > So, what I understand from this thread is as following:
>> >
>> > 1. When the crash does occur (Leader does not crash and majority of
>> > servers is always up), the state from Time T0 (ZK start of ZK) and until
>> > time Tn (ZK state of now) will be in memory (even the size of ZK state
>> > reaches to the memory size).
>> >
>>
>> That's correct. ZK is an in-memory store. As such all znodes
>> representing the current state are held in memory.
>>
>> > 2. If the leader crashes or lost a quorum, recovery mechanism applies
>> > latest snapshots. In this scenario, it is possible to eliminate the old
>> ZK
>> > states and could save memory space.
>> >
>>
>> This won't affect the in-memory state. It will be the same as prior to
>> the recovery.
>>
>> Patrick
>>
>> >
>> > Is that right?
>> >
>> >
>> >
>> > Regards,
>> >
>> > Ibrahim
>> >
>> > On Fri, Mar 18, 2016 at 4:49 PM, Flavio Junqueira <fp...@apache.org>
>> wrote:
>> >
>> >> It is currently as Jordan says, although it is not entirely unreasonable
>> >> to think of memory as cache and keep in memory only the current working
>> >> set, possibly using say an SSD to store the remaining part of the state
>> >> that you don't want to keep in memory. One key issue here is that if you
>> >> have a pretty large state (that you don't want to keep all in memory),
>> then
>> >> you'll end up increasing worst-case recovery time.
>> >>
>> >> We certainly do not have any kind of expiration mechanism for znodes
>> other
>> >> than the ephemeral flag, which is associated to sessions.
>> >>
>> >> -Flavio
>> >>
>> >> > On 18 Mar 2016, at 16:38, ibrahim El-sanosi <ibrahimsabattt@gmail.com
>> >
>> >> wrote:
>> >> >
>> >> > Thank you for replaying.
>> >> >
>> >> >
>> >> > Take this example, Zookeeper started on 1/1/2015, and assume ZK
>> servers
>> >> are
>> >> > never crashed. Also, the ZK are very busy, reciveing continusly write
>> >> > requests from clients and accordingly snapshots are generated
>> overtime.
>> >> On
>> >> > 1/3/2015, what Znodes will be in memory data tree? do all Znodes
>> still
>> >> > store in memory (from 1/1/2015 to 1/3/2015) as there is no crashed
>> occur.
>> >> > Or Dsnapshhot is taken the data tree is
>> >> >
>> >> >
>> >> > Note that I am not asking about data in log or snapshoot. I am asking
>> >> > about the current data in memory.
>> >> >
>> >> > On Fri, Mar 18, 2016 at 4:12 PM, Flavio Junqueira <fp...@apache.org>
>> >> wrote:
>> >> >
>> >> >> Hi Ibrahim,
>> >> >>
>> >> >> Are you asking about how we compact old logs? We do it by taking
>> >> snapshots
>> >> >> so that upon recovery, we only load the latest snapshot and replay
>> the
>> >> txn
>> >> >> log from the snapshot tag. The snapshot tag is the last zxid
>> committed
>> >> when
>> >> >> we start producing the snapshot.
>> >> >>
>> >> >> We don't actually delete anything, though, unless you intentionally
>> turn
>> >> >> on auto purge:
>> >> >>
>> >> >>
>> >>
>> https://zookeeper.apache.org/doc/trunk/zookeeperAdmin.html#sc_administering
>> >> >> <
>> >> >>
>> >>
>> https://zookeeper.apache.org/doc/trunk/zookeeperAdmin.html#sc_administering
>> >> >>>
>> >> >>
>> >> >> -Flavio
>> >> >>
>> >> >>> On 18 Mar 2016, at 16:05, ibrahim El-sanosi <
>> ibrahimsabattt@gmail.com>
>> >> >> wrote:
>> >> >>>
>> >> >>> Hi all,
>> >> >>>
>> >> >>> Assume the Zookeeper have been running for about one year (from
>> >> 1/1/2015
>> >> >>> until now), how does ZooKeeper deal with old delivered write
>> requests
>> >> (To
>> >> >>> optimize a memory used) (say from 1/1/2015 to 03/04/2015). I am
>> >> assuming
>> >> >>> the old delivered request are no longer used.
>> >> >>>
>> >> >>> On the other words, what strategy ZK does to find and delete unused
>> >> >> Znodes?
>> >> >>>
>> >> >>> Ibrahim
>> >> >>
>> >> >>
>> >>
>> >>
>>
Re: Dealing with old delivered requests in memory
Posted by ibrahim El-sanosi <ib...@gmail.com>.
Thank you Patrick,
>That's correct. ZK is an in-memory store. As such all znodes
>representing the current state are held in memory.
>
>> 2. If the leader crashes or lost a quorum, recovery mechanism applies
>> latest snapshots. In this scenario, it is possible to eliminate the old
ZK
>> states and could save memory space.
>>
>
>This won't affect the in-memory state. It will be the same as prior to
>the recovery.
Observation (2), I assume the worst scenario when all ZK servers want down
and start recovery phase (No ZK states persent in memory at the moment).
Does ZK servers reapply all snapshot in memory or just takes the latest one?
Ibrahim
On Tue, Mar 22, 2016 at 2:43 PM, Patrick Hunt <ph...@apache.org> wrote:
> On Fri, Mar 18, 2016 at 10:10 AM, ibrahim El-sanosi
> <ib...@gmail.com> wrote:
> > Ok, Thank you for answering the question.
> >
> > So, what I understand from this thread is as following:
> >
> > 1. When the crash does occur (Leader does not crash and majority of
> > servers is always up), the state from Time T0 (ZK start of ZK) and until
> > time Tn (ZK state of now) will be in memory (even the size of ZK state
> > reaches to the memory size).
> >
>
> That's correct. ZK is an in-memory store. As such all znodes
> representing the current state are held in memory.
>
> > 2. If the leader crashes or lost a quorum, recovery mechanism applies
> > latest snapshots. In this scenario, it is possible to eliminate the old
> ZK
> > states and could save memory space.
> >
>
> This won't affect the in-memory state. It will be the same as prior to
> the recovery.
>
> Patrick
>
> >
> > Is that right?
> >
> >
> >
> > Regards,
> >
> > Ibrahim
> >
> > On Fri, Mar 18, 2016 at 4:49 PM, Flavio Junqueira <fp...@apache.org>
> wrote:
> >
> >> It is currently as Jordan says, although it is not entirely unreasonable
> >> to think of memory as cache and keep in memory only the current working
> >> set, possibly using say an SSD to store the remaining part of the state
> >> that you don't want to keep in memory. One key issue here is that if you
> >> have a pretty large state (that you don't want to keep all in memory),
> then
> >> you'll end up increasing worst-case recovery time.
> >>
> >> We certainly do not have any kind of expiration mechanism for znodes
> other
> >> than the ephemeral flag, which is associated to sessions.
> >>
> >> -Flavio
> >>
> >> > On 18 Mar 2016, at 16:38, ibrahim El-sanosi <ibrahimsabattt@gmail.com
> >
> >> wrote:
> >> >
> >> > Thank you for replaying.
> >> >
> >> >
> >> > Take this example, Zookeeper started on 1/1/2015, and assume ZK
> servers
> >> are
> >> > never crashed. Also, the ZK are very busy, reciveing continusly write
> >> > requests from clients and accordingly snapshots are generated
> overtime.
> >> On
> >> > 1/3/2015, what Znodes will be in memory data tree? do all Znodes
> still
> >> > store in memory (from 1/1/2015 to 1/3/2015) as there is no crashed
> occur.
> >> > Or Dsnapshhot is taken the data tree is
> >> >
> >> >
> >> > Note that I am not asking about data in log or snapshoot. I am asking
> >> > about the current data in memory.
> >> >
> >> > On Fri, Mar 18, 2016 at 4:12 PM, Flavio Junqueira <fp...@apache.org>
> >> wrote:
> >> >
> >> >> Hi Ibrahim,
> >> >>
> >> >> Are you asking about how we compact old logs? We do it by taking
> >> snapshots
> >> >> so that upon recovery, we only load the latest snapshot and replay
> the
> >> txn
> >> >> log from the snapshot tag. The snapshot tag is the last zxid
> committed
> >> when
> >> >> we start producing the snapshot.
> >> >>
> >> >> We don't actually delete anything, though, unless you intentionally
> turn
> >> >> on auto purge:
> >> >>
> >> >>
> >>
> https://zookeeper.apache.org/doc/trunk/zookeeperAdmin.html#sc_administering
> >> >> <
> >> >>
> >>
> https://zookeeper.apache.org/doc/trunk/zookeeperAdmin.html#sc_administering
> >> >>>
> >> >>
> >> >> -Flavio
> >> >>
> >> >>> On 18 Mar 2016, at 16:05, ibrahim El-sanosi <
> ibrahimsabattt@gmail.com>
> >> >> wrote:
> >> >>>
> >> >>> Hi all,
> >> >>>
> >> >>> Assume the Zookeeper have been running for about one year (from
> >> 1/1/2015
> >> >>> until now), how does ZooKeeper deal with old delivered write
> requests
> >> (To
> >> >>> optimize a memory used) (say from 1/1/2015 to 03/04/2015). I am
> >> assuming
> >> >>> the old delivered request are no longer used.
> >> >>>
> >> >>> On the other words, what strategy ZK does to find and delete unused
> >> >> Znodes?
> >> >>>
> >> >>> Ibrahim
> >> >>
> >> >>
> >>
> >>
>
Re: Dealing with old delivered requests in memory
Posted by Patrick Hunt <ph...@apache.org>.
On Fri, Mar 18, 2016 at 10:10 AM, ibrahim El-sanosi
<ib...@gmail.com> wrote:
> Ok, Thank you for answering the question.
>
> So, what I understand from this thread is as following:
>
> 1. When the crash does occur (Leader does not crash and majority of
> servers is always up), the state from Time T0 (ZK start of ZK) and until
> time Tn (ZK state of now) will be in memory (even the size of ZK state
> reaches to the memory size).
>
That's correct. ZK is an in-memory store. As such all znodes
representing the current state are held in memory.
> 2. If the leader crashes or lost a quorum, recovery mechanism applies
> latest snapshots. In this scenario, it is possible to eliminate the old ZK
> states and could save memory space.
>
This won't affect the in-memory state. It will be the same as prior to
the recovery.
Patrick
>
> Is that right?
>
>
>
> Regards,
>
> Ibrahim
>
> On Fri, Mar 18, 2016 at 4:49 PM, Flavio Junqueira <fp...@apache.org> wrote:
>
>> It is currently as Jordan says, although it is not entirely unreasonable
>> to think of memory as cache and keep in memory only the current working
>> set, possibly using say an SSD to store the remaining part of the state
>> that you don't want to keep in memory. One key issue here is that if you
>> have a pretty large state (that you don't want to keep all in memory), then
>> you'll end up increasing worst-case recovery time.
>>
>> We certainly do not have any kind of expiration mechanism for znodes other
>> than the ephemeral flag, which is associated to sessions.
>>
>> -Flavio
>>
>> > On 18 Mar 2016, at 16:38, ibrahim El-sanosi <ib...@gmail.com>
>> wrote:
>> >
>> > Thank you for replaying.
>> >
>> >
>> > Take this example, Zookeeper started on 1/1/2015, and assume ZK servers
>> are
>> > never crashed. Also, the ZK are very busy, reciveing continusly write
>> > requests from clients and accordingly snapshots are generated overtime.
>> On
>> > 1/3/2015, what Znodes will be in memory data tree? do all Znodes still
>> > store in memory (from 1/1/2015 to 1/3/2015) as there is no crashed occur.
>> > Or Dsnapshhot is taken the data tree is
>> >
>> >
>> > Note that I am not asking about data in log or snapshoot. I am asking
>> > about the current data in memory.
>> >
>> > On Fri, Mar 18, 2016 at 4:12 PM, Flavio Junqueira <fp...@apache.org>
>> wrote:
>> >
>> >> Hi Ibrahim,
>> >>
>> >> Are you asking about how we compact old logs? We do it by taking
>> snapshots
>> >> so that upon recovery, we only load the latest snapshot and replay the
>> txn
>> >> log from the snapshot tag. The snapshot tag is the last zxid committed
>> when
>> >> we start producing the snapshot.
>> >>
>> >> We don't actually delete anything, though, unless you intentionally turn
>> >> on auto purge:
>> >>
>> >>
>> https://zookeeper.apache.org/doc/trunk/zookeeperAdmin.html#sc_administering
>> >> <
>> >>
>> https://zookeeper.apache.org/doc/trunk/zookeeperAdmin.html#sc_administering
>> >>>
>> >>
>> >> -Flavio
>> >>
>> >>> On 18 Mar 2016, at 16:05, ibrahim El-sanosi <ib...@gmail.com>
>> >> wrote:
>> >>>
>> >>> Hi all,
>> >>>
>> >>> Assume the Zookeeper have been running for about one year (from
>> 1/1/2015
>> >>> until now), how does ZooKeeper deal with old delivered write requests
>> (To
>> >>> optimize a memory used) (say from 1/1/2015 to 03/04/2015). I am
>> assuming
>> >>> the old delivered request are no longer used.
>> >>>
>> >>> On the other words, what strategy ZK does to find and delete unused
>> >> Znodes?
>> >>>
>> >>> Ibrahim
>> >>
>> >>
>>
>>
Re: Dealing with old delivered requests in memory
Posted by ibrahim El-sanosi <ib...@gmail.com>.
Ok, Thank you for answering the question.
So, what I understand from this thread is as following:
1. When the crash does occur (Leader does not crash and majority of
servers is always up), the state from Time T0 (ZK start of ZK) and until
time Tn (ZK state of now) will be in memory (even the size of ZK state
reaches to the memory size).
2. If the leader crashes or lost a quorum, recovery mechanism applies
latest snapshots. In this scenario, it is possible to eliminate the old ZK
states and could save memory space.
Is that right?
Regards,
Ibrahim
On Fri, Mar 18, 2016 at 4:49 PM, Flavio Junqueira <fp...@apache.org> wrote:
> It is currently as Jordan says, although it is not entirely unreasonable
> to think of memory as cache and keep in memory only the current working
> set, possibly using say an SSD to store the remaining part of the state
> that you don't want to keep in memory. One key issue here is that if you
> have a pretty large state (that you don't want to keep all in memory), then
> you'll end up increasing worst-case recovery time.
>
> We certainly do not have any kind of expiration mechanism for znodes other
> than the ephemeral flag, which is associated to sessions.
>
> -Flavio
>
> > On 18 Mar 2016, at 16:38, ibrahim El-sanosi <ib...@gmail.com>
> wrote:
> >
> > Thank you for replaying.
> >
> >
> > Take this example, Zookeeper started on 1/1/2015, and assume ZK servers
> are
> > never crashed. Also, the ZK are very busy, reciveing continusly write
> > requests from clients and accordingly snapshots are generated overtime.
> On
> > 1/3/2015, what Znodes will be in memory data tree? do all Znodes still
> > store in memory (from 1/1/2015 to 1/3/2015) as there is no crashed occur.
> > Or Dsnapshhot is taken the data tree is
> >
> >
> > Note that I am not asking about data in log or snapshoot. I am asking
> > about the current data in memory.
> >
> > On Fri, Mar 18, 2016 at 4:12 PM, Flavio Junqueira <fp...@apache.org>
> wrote:
> >
> >> Hi Ibrahim,
> >>
> >> Are you asking about how we compact old logs? We do it by taking
> snapshots
> >> so that upon recovery, we only load the latest snapshot and replay the
> txn
> >> log from the snapshot tag. The snapshot tag is the last zxid committed
> when
> >> we start producing the snapshot.
> >>
> >> We don't actually delete anything, though, unless you intentionally turn
> >> on auto purge:
> >>
> >>
> https://zookeeper.apache.org/doc/trunk/zookeeperAdmin.html#sc_administering
> >> <
> >>
> https://zookeeper.apache.org/doc/trunk/zookeeperAdmin.html#sc_administering
> >>>
> >>
> >> -Flavio
> >>
> >>> On 18 Mar 2016, at 16:05, ibrahim El-sanosi <ib...@gmail.com>
> >> wrote:
> >>>
> >>> Hi all,
> >>>
> >>> Assume the Zookeeper have been running for about one year (from
> 1/1/2015
> >>> until now), how does ZooKeeper deal with old delivered write requests
> (To
> >>> optimize a memory used) (say from 1/1/2015 to 03/04/2015). I am
> assuming
> >>> the old delivered request are no longer used.
> >>>
> >>> On the other words, what strategy ZK does to find and delete unused
> >> Znodes?
> >>>
> >>> Ibrahim
> >>
> >>
>
>
Re: Dealing with old delivered requests in memory
Posted by Jordan Zimmerman <jo...@jordanzimmerman.com>.
Also, since 3.5, there are “container” nodes that auto-delete once emptied of children.
-JZ
> On Mar 18, 2016, at 11:49 AM, Flavio Junqueira <fp...@apache.org> wrote:
>
> It is currently as Jordan says, although it is not entirely unreasonable to think of memory as cache and keep in memory only the current working set, possibly using say an SSD to store the remaining part of the state that you don't want to keep in memory. One key issue here is that if you have a pretty large state (that you don't want to keep all in memory), then you'll end up increasing worst-case recovery time.
>
> We certainly do not have any kind of expiration mechanism for znodes other than the ephemeral flag, which is associated to sessions.
>
> -Flavio
>
>> On 18 Mar 2016, at 16:38, ibrahim El-sanosi <ib...@gmail.com> wrote:
>>
>> Thank you for replaying.
>>
>>
>> Take this example, Zookeeper started on 1/1/2015, and assume ZK servers are
>> never crashed. Also, the ZK are very busy, reciveing continusly write
>> requests from clients and accordingly snapshots are generated overtime. On
>> 1/3/2015, what Znodes will be in memory data tree? do all Znodes still
>> store in memory (from 1/1/2015 to 1/3/2015) as there is no crashed occur.
>> Or Dsnapshhot is taken the data tree is
>>
>>
>> Note that I am not asking about data in log or snapshoot. I am asking
>> about the current data in memory.
>>
>> On Fri, Mar 18, 2016 at 4:12 PM, Flavio Junqueira <fp...@apache.org> wrote:
>>
>>> Hi Ibrahim,
>>>
>>> Are you asking about how we compact old logs? We do it by taking snapshots
>>> so that upon recovery, we only load the latest snapshot and replay the txn
>>> log from the snapshot tag. The snapshot tag is the last zxid committed when
>>> we start producing the snapshot.
>>>
>>> We don't actually delete anything, though, unless you intentionally turn
>>> on auto purge:
>>>
>>> https://zookeeper.apache.org/doc/trunk/zookeeperAdmin.html#sc_administering
>>> <
>>> https://zookeeper.apache.org/doc/trunk/zookeeperAdmin.html#sc_administering
>>>>
>>>
>>> -Flavio
>>>
>>>> On 18 Mar 2016, at 16:05, ibrahim El-sanosi <ib...@gmail.com>
>>> wrote:
>>>>
>>>> Hi all,
>>>>
>>>> Assume the Zookeeper have been running for about one year (from 1/1/2015
>>>> until now), how does ZooKeeper deal with old delivered write requests (To
>>>> optimize a memory used) (say from 1/1/2015 to 03/04/2015). I am assuming
>>>> the old delivered request are no longer used.
>>>>
>>>> On the other words, what strategy ZK does to find and delete unused
>>> Znodes?
>>>>
>>>> Ibrahim
>>>
>>>
>
Re: Dealing with old delivered requests in memory
Posted by Flavio Junqueira <fp...@apache.org>.
It is currently as Jordan says, although it is not entirely unreasonable to think of memory as cache and keep in memory only the current working set, possibly using say an SSD to store the remaining part of the state that you don't want to keep in memory. One key issue here is that if you have a pretty large state (that you don't want to keep all in memory), then you'll end up increasing worst-case recovery time.
We certainly do not have any kind of expiration mechanism for znodes other than the ephemeral flag, which is associated to sessions.
-Flavio
> On 18 Mar 2016, at 16:38, ibrahim El-sanosi <ib...@gmail.com> wrote:
>
> Thank you for replaying.
>
>
> Take this example, Zookeeper started on 1/1/2015, and assume ZK servers are
> never crashed. Also, the ZK are very busy, reciveing continusly write
> requests from clients and accordingly snapshots are generated overtime. On
> 1/3/2015, what Znodes will be in memory data tree? do all Znodes still
> store in memory (from 1/1/2015 to 1/3/2015) as there is no crashed occur.
> Or Dsnapshhot is taken the data tree is
>
>
> Note that I am not asking about data in log or snapshoot. I am asking
> about the current data in memory.
>
> On Fri, Mar 18, 2016 at 4:12 PM, Flavio Junqueira <fp...@apache.org> wrote:
>
>> Hi Ibrahim,
>>
>> Are you asking about how we compact old logs? We do it by taking snapshots
>> so that upon recovery, we only load the latest snapshot and replay the txn
>> log from the snapshot tag. The snapshot tag is the last zxid committed when
>> we start producing the snapshot.
>>
>> We don't actually delete anything, though, unless you intentionally turn
>> on auto purge:
>>
>> https://zookeeper.apache.org/doc/trunk/zookeeperAdmin.html#sc_administering
>> <
>> https://zookeeper.apache.org/doc/trunk/zookeeperAdmin.html#sc_administering
>>>
>>
>> -Flavio
>>
>>> On 18 Mar 2016, at 16:05, ibrahim El-sanosi <ib...@gmail.com>
>> wrote:
>>>
>>> Hi all,
>>>
>>> Assume the Zookeeper have been running for about one year (from 1/1/2015
>>> until now), how does ZooKeeper deal with old delivered write requests (To
>>> optimize a memory used) (say from 1/1/2015 to 03/04/2015). I am assuming
>>> the old delivered request are no longer used.
>>>
>>> On the other words, what strategy ZK does to find and delete unused
>> Znodes?
>>>
>>> Ibrahim
>>
>>
Re: Dealing with old delivered requests in memory
Posted by ibrahim El-sanosi <ib...@gmail.com>.
Thank you Jordan,
So as "ZooKeeper stores the entire database in memory. ZNodes exist until
deleted.". As we know the memory size is limited, we expect the
OutOfMemoryError
excption could occur even we set the Max heap size as maxumim value as
possible?
Ibrahim
On Fri, Mar 18, 2016 at 4:40 PM, Jordan Zimmerman <
jordan@jordanzimmerman.com> wrote:
> ZooKeeper stores the entire database in memory. Logs are for durability
> only. ZNodes exist until deleted.
>
> -Jordan
>
> > On Mar 18, 2016, at 11:38 AM, ibrahim El-sanosi <
> ibrahimsabattt@gmail.com> wrote:
> >
> > Thank you for replaying.
> >
> >
> > Take this example, Zookeeper started on 1/1/2015, and assume ZK servers
> are
> > never crashed. Also, the ZK are very busy, reciveing continusly write
> > requests from clients and accordingly snapshots are generated overtime.
> On
> > 1/3/2015, what Znodes will be in memory data tree? do all Znodes still
> > store in memory (from 1/1/2015 to 1/3/2015) as there is no crashed occur.
> > Or Dsnapshhot is taken the data tree is
> >
> >
> > Note that I am not asking about data in log or snapshoot. I am asking
> > about the current data in memory.
> >
> > On Fri, Mar 18, 2016 at 4:12 PM, Flavio Junqueira <fp...@apache.org>
> wrote:
> >
> >> Hi Ibrahim,
> >>
> >> Are you asking about how we compact old logs? We do it by taking
> snapshots
> >> so that upon recovery, we only load the latest snapshot and replay the
> txn
> >> log from the snapshot tag. The snapshot tag is the last zxid committed
> when
> >> we start producing the snapshot.
> >>
> >> We don't actually delete anything, though, unless you intentionally turn
> >> on auto purge:
> >>
> >>
> https://zookeeper.apache.org/doc/trunk/zookeeperAdmin.html#sc_administering
> >> <
> >>
> https://zookeeper.apache.org/doc/trunk/zookeeperAdmin.html#sc_administering
> >>>
> >>
> >> -Flavio
> >>
> >>> On 18 Mar 2016, at 16:05, ibrahim El-sanosi <ib...@gmail.com>
> >> wrote:
> >>>
> >>> Hi all,
> >>>
> >>> Assume the Zookeeper have been running for about one year (from
> 1/1/2015
> >>> until now), how does ZooKeeper deal with old delivered write requests
> (To
> >>> optimize a memory used) (say from 1/1/2015 to 03/04/2015). I am
> assuming
> >>> the old delivered request are no longer used.
> >>>
> >>> On the other words, what strategy ZK does to find and delete unused
> >> Znodes?
> >>>
> >>> Ibrahim
> >>
> >>
>
>
Re: Dealing with old delivered requests in memory
Posted by Jordan Zimmerman <jo...@jordanzimmerman.com>.
ZooKeeper stores the entire database in memory. Logs are for durability only. ZNodes exist until deleted.
-Jordan
> On Mar 18, 2016, at 11:38 AM, ibrahim El-sanosi <ib...@gmail.com> wrote:
>
> Thank you for replaying.
>
>
> Take this example, Zookeeper started on 1/1/2015, and assume ZK servers are
> never crashed. Also, the ZK are very busy, reciveing continusly write
> requests from clients and accordingly snapshots are generated overtime. On
> 1/3/2015, what Znodes will be in memory data tree? do all Znodes still
> store in memory (from 1/1/2015 to 1/3/2015) as there is no crashed occur.
> Or Dsnapshhot is taken the data tree is
>
>
> Note that I am not asking about data in log or snapshoot. I am asking
> about the current data in memory.
>
> On Fri, Mar 18, 2016 at 4:12 PM, Flavio Junqueira <fp...@apache.org> wrote:
>
>> Hi Ibrahim,
>>
>> Are you asking about how we compact old logs? We do it by taking snapshots
>> so that upon recovery, we only load the latest snapshot and replay the txn
>> log from the snapshot tag. The snapshot tag is the last zxid committed when
>> we start producing the snapshot.
>>
>> We don't actually delete anything, though, unless you intentionally turn
>> on auto purge:
>>
>> https://zookeeper.apache.org/doc/trunk/zookeeperAdmin.html#sc_administering
>> <
>> https://zookeeper.apache.org/doc/trunk/zookeeperAdmin.html#sc_administering
>>>
>>
>> -Flavio
>>
>>> On 18 Mar 2016, at 16:05, ibrahim El-sanosi <ib...@gmail.com>
>> wrote:
>>>
>>> Hi all,
>>>
>>> Assume the Zookeeper have been running for about one year (from 1/1/2015
>>> until now), how does ZooKeeper deal with old delivered write requests (To
>>> optimize a memory used) (say from 1/1/2015 to 03/04/2015). I am assuming
>>> the old delivered request are no longer used.
>>>
>>> On the other words, what strategy ZK does to find and delete unused
>> Znodes?
>>>
>>> Ibrahim
>>
>>
Re: Dealing with old delivered requests in memory
Posted by ibrahim El-sanosi <ib...@gmail.com>.
Thank you for replaying.
Take this example, Zookeeper started on 1/1/2015, and assume ZK servers are
never crashed. Also, the ZK are very busy, reciveing continusly write
requests from clients and accordingly snapshots are generated overtime. On
1/3/2015, what Znodes will be in memory data tree? do all Znodes still
store in memory (from 1/1/2015 to 1/3/2015) as there is no crashed occur.
Or Dsnapshhot is taken the data tree is
Note that I am not asking about data in log or snapshoot. I am asking
about the current data in memory.
On Fri, Mar 18, 2016 at 4:12 PM, Flavio Junqueira <fp...@apache.org> wrote:
> Hi Ibrahim,
>
> Are you asking about how we compact old logs? We do it by taking snapshots
> so that upon recovery, we only load the latest snapshot and replay the txn
> log from the snapshot tag. The snapshot tag is the last zxid committed when
> we start producing the snapshot.
>
> We don't actually delete anything, though, unless you intentionally turn
> on auto purge:
>
> https://zookeeper.apache.org/doc/trunk/zookeeperAdmin.html#sc_administering
> <
> https://zookeeper.apache.org/doc/trunk/zookeeperAdmin.html#sc_administering
> >
>
> -Flavio
>
> > On 18 Mar 2016, at 16:05, ibrahim El-sanosi <ib...@gmail.com>
> wrote:
> >
> > Hi all,
> >
> > Assume the Zookeeper have been running for about one year (from 1/1/2015
> > until now), how does ZooKeeper deal with old delivered write requests (To
> > optimize a memory used) (say from 1/1/2015 to 03/04/2015). I am assuming
> > the old delivered request are no longer used.
> >
> > On the other words, what strategy ZK does to find and delete unused
> Znodes?
> >
> > Ibrahim
>
>
Re: Dealing with old delivered requests in memory
Posted by ibrahim El-sanosi <ib...@gmail.com>.
Thank you for replaying.
Take this example, Zookeeper started on 1/1/2015, and assume ZK servers are
never crashed. Also, the ZK are very busy, reciveing continusly write
requests from clients and accordingly snapshots are generated overtime. On
1/3/2015, what Znodes will be in memory data tree? do all Znodes still
store in memory (from 1/1/2015 to 1/3/2015) as there is no crashed occur.
Or Does snapshhot free the memory (When Snapshoot is taken, does the data
tree become empty)?
Note that I am not asking about data in log or snapshoot. I am asking
about the current data in memory.
Thank you indeed
Ibrahim
On Fri, Mar 18, 2016 at 4:12 PM, Flavio Junqueira <fp...@apache.org> wrote:
> Hi Ibrahim,
>
> Are you asking about how we compact old logs? We do it by taking snapshots
> so that upon recovery, we only load the latest snapshot and replay the txn
> log from the snapshot tag. The snapshot tag is the last zxid committed when
> we start producing the snapshot.
>
> We don't actually delete anything, though, unless you intentionally turn
> on auto purge:
>
> https://zookeeper.apache.org/doc/trunk/zookeeperAdmin.html#sc_administering
> <
> https://zookeeper.apache.org/doc/trunk/zookeeperAdmin.html#sc_administering
> >
>
> -Flavio
>
> > On 18 Mar 2016, at 16:05, ibrahim El-sanosi <ib...@gmail.com>
> wrote:
> >
> > Hi all,
> >
> > Assume the Zookeeper have been running for about one year (from 1/1/2015
> > until now), how does ZooKeeper deal with old delivered write requests (To
> > optimize a memory used) (say from 1/1/2015 to 03/04/2015). I am assuming
> > the old delivered request are no longer used.
> >
> > On the other words, what strategy ZK does to find and delete unused
> Znodes?
> >
> > Ibrahim
>
>
Re: Dealing with old delivered requests in memory
Posted by Flavio Junqueira <fp...@apache.org>.
Hi Ibrahim,
Are you asking about how we compact old logs? We do it by taking snapshots so that upon recovery, we only load the latest snapshot and replay the txn log from the snapshot tag. The snapshot tag is the last zxid committed when we start producing the snapshot.
We don't actually delete anything, though, unless you intentionally turn on auto purge:
https://zookeeper.apache.org/doc/trunk/zookeeperAdmin.html#sc_administering <https://zookeeper.apache.org/doc/trunk/zookeeperAdmin.html#sc_administering>
-Flavio
> On 18 Mar 2016, at 16:05, ibrahim El-sanosi <ib...@gmail.com> wrote:
>
> Hi all,
>
> Assume the Zookeeper have been running for about one year (from 1/1/2015
> until now), how does ZooKeeper deal with old delivered write requests (To
> optimize a memory used) (say from 1/1/2015 to 03/04/2015). I am assuming
> the old delivered request are no longer used.
>
> On the other words, what strategy ZK does to find and delete unused Znodes?
>
> Ibrahim