I have ipc.client.tcpnodelay, ipc.server.tcpnodelay set to false and the hbase one - [hbase].ipc.client.tcpnodelay set to true. Do these induce network latency ?
On Fri, Feb 8, 2013 at 11:57 PM, lars hofhansl <la...@apache.org> wrote: > Sorry.. I meant set these two config parameters to true (not false as I > state below). > > > > ----- Original Message ----- > From: lars hofhansl <la...@apache.org> > To: "user@hbase.apache.org" <user@hbase.apache.org> > Cc: > Sent: Friday, February 8, 2013 11:41 PM > Subject: Re: Get on a row with multiple columns > > Only somewhat related. Seeing the magic 40ms random read time there. Did > you disable Nagle's? > (set hbase.ipc.client.tcpnodelay and ipc.server.tcpnodelay to false in > hbase-site.xml). > > ________________________________ > From: Varun Sharma <va...@pinterest.com> > To: user@hbase.apache.org; lars hofhansl <la...@apache.org> > Sent: Friday, February 8, 2013 10:45 PM > Subject: Re: Get on a row with multiple columns > > The use case is like your twitter feed. Tweets from people u follow. When > someone unfollows, you need to delete a bunch of his tweets from the > following feed. So, its frequent, and we are essentially running into some > extreme corner cases like the one above. We need high write throughput for > this, since when someone tweets, we need to fanout the tweet to all the > followers. We need the ability to do fast deletes (unfollow) and fast adds > (follow) and also be able to do fast random gets - when a real user loads > the feed. I doubt we will able to play much with the schema here since we > need to support a bunch of use cases. > > @lars: It does not take 30 seconds to place 300 delete markers. It takes 30 > seconds to first find which of those 300 pins are in the set of columns > present - this invokes 300 gets and then place the appropriate delete > markers. Note that we can have tens of thousands of columns in a single row > so a single get is not cheap. > > If we were to just place delete markers, that is very fast. But when > started doing that, our random read performance suffered because of too > many delete markers. The 90th percentile on random reads shot up from 40 > milliseconds to 150 milliseconds, which is not acceptable for our usecase. > > Thanks > Varun > > On Fri, Feb 8, 2013 at 10:33 PM, lars hofhansl <la...@apache.org> wrote: > > > Can you organize your columns and then delete by column family? > > > > deleteColumn without specifying a TS is expensive, since HBase first has > > to figure out what the latest TS is. > > > > Should be better in 0.94.1 or later since deletes are batched like Puts > > (still need to retrieve the latest version, though). > > > > In 0.94.3 or later you can also the BulkDeleteEndPoint, which basically > > let's specify a scan condition and then place specific delete marker for > > all KVs encountered. > > > > > > If you wanted to get really > > fancy, you could hook up a coprocessor to the compaction process and > > simply filter all KVs you no longer want (without ever placing any > > delete markers). > > > > > > Are you saying it takes 15 seconds to place 300 version delete markers?! > > > > > > -- Lars > > > > > > > > ________________________________ > > From: Varun Sharma <va...@pinterest.com> > > To: user@hbase.apache.org > > Sent: Friday, February 8, 2013 10:05 PM > > Subject: Re: Get on a row with multiple columns > > > > We are given a set of 300 columns to delete. I tested two cases: > > > > 1) deleteColumns() - with the 's' > > > > This function simply adds delete markers for 300 columns, in our case, > > typically only a fraction of these columns are actually present - 10. > After > > starting to use deleteColumns, we starting seeing a drop in cluster wide > > random read performance - 90th percentile latency worsened, so did 99th > > probably because of having to traverse delete markers. I attribute this > to > > profusion of delete markers in the cluster. Major compactions slowed down > > by almost 50 percent probably because of having to clean out > significantly > > more delete markers. > > > > 2) deleteColumn() > > > > Ended up with untolerable 15 second calls, which clogged all the > handlers. > > Making the cluster pretty much unresponsive. > > > > On Fri, Feb 8, 2013 at 9:55 PM, Ted Yu <yuzhih...@gmail.com> wrote: > > > > > For the 300 column deletes, can you show us how the Delete(s) are > > > constructed ? > > > > > > Do you use this method ? > > > > > > public Delete deleteColumns(byte [] family, byte [] qualifier) { > > > Thanks > > > > > > On Fri, Feb 8, 2013 at 9:44 PM, Varun Sharma <va...@pinterest.com> > > wrote: > > > > > > > So a Get call with multiple columns on a single row should be much > > faster > > > > than independent Get(s) on each of those columns for that row. I am > > > > basically seeing severely poor performance (~ 15 seconds) for certain > > > > deleteColumn() calls and I am seeing that there is a > > > > prepareDeleteTimestamps() function in HRegion.java which first tries > to > > > > locate the column by doing individual gets on each column you want to > > > > delete (I am doing 300 column deletes). Now, I think this should > ideall > > > by > > > > 1 get call with the batch of 300 columns so that one scan can > retrieve > > > the > > > > columns and the columns that are found, are indeed deleted. > > > > > > > > Before I try this fix, I wanted to get an opinion if it will make a > > > > difference to batch the get() and it seems from your answer, it > should. > > > > > > > > On Fri, Feb 8, 2013 at 9:34 PM, lars hofhansl <la...@apache.org> > > wrote: > > > > > > > > > Everything is stored as a KeyValue in HBase. > > > > > The Key part of a KeyValue contains the row key, column family, > > column > > > > > name, and timestamp in that order. > > > > > Each column family has it's own store and store files. > > > > > > > > > > So in a nutshell a get is executed by starting a scan at the row > key > > > > > (which is a prefix of the key) in each store (CF) and then scanning > > > > forward > > > > > in each store until the next row key is reached. (in reality it is > a > > > bit > > > > > more complicated due to multiple versions, skipping columns, etc) > > > > > > > > > > > > > > > -- Lars > > > > > ________________________________ > > > > > From: Varun Sharma <va...@pinterest.com> > > > > > To: user@hbase.apache.org > > > > > Sent: Friday, February 8, 2013 9:22 PM > > > > > Subject: Re: Get on a row with multiple columns > > > > > > > > > > Sorry, I was a little unclear with my question. > > > > > > > > > > Lets say you have > > > > > > > > > > Get get = new Get(row) > > > > > get.addColumn("1"); > > > > > get.addColumn("2"); > > > > > . > > > > > . > > > > > . > > > > > > > > > > When internally hbase executes the batch get, it will seek to > column > > > "1", > > > > > now since data is lexicographically sorted, it does not need to > seek > > > from > > > > > the beginning to get to "2", it can continue seeking, henceforth > > since > > > > > column "2" will always be after column "1". I want to know whether > > this > > > > is > > > > > how a multicolumn get on a row works or not. > > > > > > > > > > Thanks > > > > > Varun > > > > > > > > > > On Fri, Feb 8, 2013 at 9:08 PM, Marcos Ortiz <mlor...@uci.cu> > wrote: > > > > > > > > > > > Like Ishan said, a get give an instance of the Result class. > > > > > > All utility methods that you can use are: > > > > > > byte[] getValue(byte[] family, byte[] qualifier) > > > > > > byte[] value() > > > > > > byte[] getRow() > > > > > > int size() > > > > > > boolean isEmpty() > > > > > > KeyValue[] raw() # Like Ishan said, all data here is sorted > > > > > > List<KeyValue> list() > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > On 02/08/2013 11:29 PM, Ishan Chhabra wrote: > > > > > > > > > > > >> Based on what I read in Lars' book, a get will return a result a > > > > Result, > > > > > >> which is internally a KeyValue[]. This KeyValue[] is sorted by > the > > > key > > > > > and > > > > > >> you access this array using raw or list methods on the Result > > > object. > > > > > >> > > > > > >> > > > > > >> On Fri, Feb 8, 2013 at 5:40 PM, Varun Sharma < > va...@pinterest.com > > > > > > > > wrote: > > > > > >> > > > > > >> +user > > > > > >>> > > > > > >>> On Fri, Feb 8, 2013 at 5:38 PM, Varun Sharma < > > va...@pinterest.com> > > > > > >>> wrote: > > > > > >>> > > > > > >>> Hi, > > > > > >>>> > > > > > >>>> When I do a Get on a row with multiple column qualifiers. Do > we > > > sort > > > > > the > > > > > >>>> column qualifers and make use of the sorted order when we get > > the > > > > > >>>> > > > > > >>> results ? > > > > > >>> > > > > > >>>> Thanks > > > > > >>>> Varun > > > > > >>>> > > > > > >>>> > > > > > >> > > > > > >> > > > > > > -- > > > > > > Marcos Ortiz Valmaseda, > > > > > > Product Manager && Data Scientist at UCI > > > > > > Blog: http://marcosluis2186.**posterous.com< > > > > > http://marcosluis2186.posterous.com> > > > > > > Twitter: @marcosluis2186 <http://twitter.com/**marcosluis2186< > > > > > http://twitter.com/marcosluis2186> > > > > > > > > > > > > > > > > > > > > > > > > > > > > >