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-- Denis On Tue, Mar 27, 2018 at 8:56 AM, Ilya Lantukh <ilant...@gridgain.com> wrote: > Unfortunately, I don't have permission to create page for IEP on wiki. > Denis, can you grant it? My username is ilantukh. > > On Mon, Mar 26, 2018 at 8:04 PM, Anton Vinogradov <a...@apache.org> wrote: > > > >> It is impossible to disable WAL only for certain partitions without > > >> completely overhauling design of Ignite storage mechanism. Right now > we > > can > > >> afford only to change WAL mode per cache group. > > > > Cache group rebalancing is a one cache rebalancing, and then this cache > > ("cache group") can be presented as a set of virtual caches. > > So, there is no issues for initial rebalancing. > > Lets disable WAL on initial rebalancing. > > > > 2018-03-26 16:46 GMT+03:00 Ilya Lantukh <ilant...@gridgain.com>: > > > > > Dmitry, > > > It is impossible to disable WAL only for certain partitions without > > > completely overhauling design of Ignite storage mechanism. Right now we > > can > > > afford only to change WAL mode per cache group. > > > > > > The idea is to disable WAL when node doesn't have any partition in > OWNING > > > state, which means it doesn't have any consistent data and won't be > able > > to > > > restore from WAL anyway. I don't see any potential use for WAL on such > > > node, but we can keep a configurable parameter indicating can we > > > automatically disable WAL in such case or not. > > > > > > On Fri, Mar 23, 2018 at 10:40 PM, Dmitry Pavlov <dpavlov....@gmail.com > > > > > wrote: > > > > > > > Denis, as I understood, there is and idea to exclude only rebalanced > > > > partition(s) data. All other data will go to the WAL. > > > > > > > > Ilya, please correct me if I'm wrong. > > > > > > > > пт, 23 мар. 2018 г. в 22:15, Denis Magda <dma...@apache.org>: > > > > > > > > > Ilya, > > > > > > > > > > That's a decent boost (5-20%) even having WAL enabled. Not sure > that > > we > > > > > should stake on the WAL "off" mode here because if the whole > cluster > > > goes > > > > > down, it's then the data consistency is questionable. As an > > architect, > > > I > > > > > wouldn't disable WAL for the sake of rebalancing; it's too risky. > > > > > > > > > > If you agree, then let's create the IEP. This way it will be easier > > to > > > > > track this endeavor. BTW, are you already ready to release any > > > > > optimizations in 2.5 that is being discussed in a separate thread? > > > > > > > > > > -- > > > > > Denis > > > > > > > > > > > > > > > > > > > > On Fri, Mar 23, 2018 at 6:37 AM, Ilya Lantukh < > ilant...@gridgain.com > > > > > > > > wrote: > > > > > > > > > > > Denis, > > > > > > > > > > > > > - Don't you want to aggregate the tickets under an IEP? > > > > > > Yes, I think so. > > > > > > > > > > > > > - Does it mean we're going to update our B+Tree implementation? > > Any > > > > > ideas > > > > > > how risky it is? > > > > > > One of tickets that I created ( > > > > > > https://issues.apache.org/jira/browse/IGNITE-7935) involves > B+Tree > > > > > > modification, but I am not planning to do it in the nearest > future. > > > It > > > > > > shouldn't affect existing tree operations, only introduce new > ones > > > > > (putAll, > > > > > > invokeAll, removeAll). > > > > > > > > > > > > > - Any chance you had a prototype that shows performance > > > optimizations > > > > > the > > > > > > approach you are suggesting to take? > > > > > > I have a prototype for simplest improvements ( > > > > https://issues.apache.org/ > > > > > > jira/browse/IGNITE-8019 & https://issues.apache.org/ > > > > > > jira/browse/IGNITE-8018) > > > > > > - together they increase throughput by 5-20%, depending on > > > > configuration > > > > > > and environment. Also, I've tested different WAL modes - > switching > > > from > > > > > > LOG_ONLY to NONE gives over 100% boost - this is what I expect > from > > > > > > https://issues.apache.org/jira/browse/IGNITE-8017. > > > > > > > > > > > > On Thu, Mar 22, 2018 at 9:48 PM, Denis Magda <dma...@apache.org> > > > > wrote: > > > > > > > > > > > > > Ilya, > > > > > > > > > > > > > > That's outstanding research and summary. Thanks for spending > your > > > > time > > > > > on > > > > > > > this. > > > > > > > > > > > > > > Not sure I have enough expertise to challenge your approach, > but > > it > > > > > > sounds > > > > > > > 100% reasonable to me. As side notes: > > > > > > > > > > > > > > - Don't you want to aggregate the tickets under an IEP? > > > > > > > - Does it mean we're going to update our B+Tree > > implementation? > > > > Any > > > > > > > ideas how risky it is? > > > > > > > - Any chance you had a prototype that shows performance > > > > > optimizations > > > > > > of > > > > > > > the approach you are suggesting to take? > > > > > > > > > > > > > > -- > > > > > > > Denis > > > > > > > > > > > > > > On Thu, Mar 22, 2018 at 8:38 AM, Ilya Lantukh < > > > ilant...@gridgain.com > > > > > > > > > > > > wrote: > > > > > > > > > > > > > > > Igniters, > > > > > > > > > > > > > > > > I've spent some time analyzing performance of rebalancing > > > process. > > > > > The > > > > > > > > initial goal was to understand, what limits it's throughput, > > > > because > > > > > it > > > > > > > is > > > > > > > > significantly slower than network and storage device can > > > > > theoretically > > > > > > > > handle. > > > > > > > > > > > > > > > > Turns out, our current implementation has a number of issues > > > caused > > > > > by > > > > > > a > > > > > > > > single fundamental problem. > > > > > > > > > > > > > > > > During rebalance data is sent in batches called > > > > > > > > GridDhtPartitionSupplyMessages. Batch size is configurable, > > > > default > > > > > > > value > > > > > > > > is 512KB, which could mean thousands of key-value pairs. > > However, > > > > we > > > > > > > don't > > > > > > > > take any advantage over this fact and process each entry > > > > > independently: > > > > > > > > - checkpointReadLock is acquired multiple times for every > > entry, > > > > > > leading > > > > > > > to > > > > > > > > unnecessary contention - this is clearly a bug; > > > > > > > > - for each entry we write (and fsync, if configuration > assumes > > > it) > > > > a > > > > > > > > separate WAL record - so, if batch contains N entries, we > might > > > end > > > > > up > > > > > > > > doing N fsyncs; > > > > > > > > - adding every entry into CacheDataStore also happens > > completely > > > > > > > > independently. It means, we will traverse and modify each > index > > > > tree > > > > > N > > > > > > > > times, we will allocate space in FreeList N times and we will > > > have > > > > to > > > > > > > > additionally store in WAL O(N*log(N)) page delta records. > > > > > > > > > > > > > > > > I've created a few tickets in JIRA with very different levels > > of > > > > > scale > > > > > > > and > > > > > > > > complexity. > > > > > > > > > > > > > > > > Ways to reduce impact of independent processing: > > > > > > > > - https://issues.apache.org/jira/browse/IGNITE-8019 - > > > > aforementioned > > > > > > > bug, > > > > > > > > causing contention on checkpointReadLock; > > > > > > > > - https://issues.apache.org/jira/browse/IGNITE-8018 - > > > inefficiency > > > > > in > > > > > > > > GridCacheMapEntry implementation; > > > > > > > > - https://issues.apache.org/jira/browse/IGNITE-8017 - > > > > automatically > > > > > > > > disable > > > > > > > > WAL during preloading. > > > > > > > > > > > > > > > > Ways to solve problem on more global level: > > > > > > > > - https://issues.apache.org/jira/browse/IGNITE-7935 - a > ticket > > > to > > > > > > > > introduce > > > > > > > > batch modification; > > > > > > > > - https://issues.apache.org/jira/browse/IGNITE-8020 - > complete > > > > > > redesign > > > > > > > of > > > > > > > > rebalancing process for persistent caches, based on file > > > transfer. > > > > > > > > > > > > > > > > Everyone is welcome to criticize above ideas, suggest new > ones > > or > > > > > > > > participate in implementation. > > > > > > > > > > > > > > > > -- > > > > > > > > Best regards, > > > > > > > > Ilya > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > -- > > > > > > Best regards, > > > > > > Ilya > > > > > > > > > > > > > > > > > > > > > > > > > > > -- > > > Best regards, > > > Ilya > > > > > > > > > -- > Best regards, > Ilya >