Robert, I'll see what I can do. No promises on an ETA. It isn't in one of the white papers?
http://labs.google.com/papers/bigtable.html Oh what the heck ... the link is broken. Let me see what's up. -- Ikai Lan Developer Programs Engineer, Google App Engine plus.ikailan.com On Thu, Feb 2, 2012 at 1:56 PM, Robert Kluin <[email protected]> wrote: > Yeah Ikai is completely correct. I should have noted more clearly > that this is not something I even waste time worrying about until I > think I'm actually hitting it, which is not often. In the few cases > where I do think I've bumped into it, it is a writing thousands of > entities per second type of thing -- which is not very common. > > It is interesting that sharding is determined by access patterns. Is > that something you can elaborate on at all? ;) > > > Robert > > > > On Thu, Feb 2, 2012 at 16:14, Ikai Lan (Google) <[email protected]> wrote: > > Thanks for the answers, Robert. > > > > Shard size isn't determined by amount of data, but by access patterns. An > > example of an anti-pattern that will cause a shard size imbalance would > be > > an entity write every time a user takes an action - but you never do > > anything with this data. Since the data just kind of accumulates, the > shard > > never splits (unless it hits some hardware bound, which I've never really > > seen happen yet with GAE data). > > > > As a final note, it takes a LOT of writes before this sort of thing > happens, > > and I sometimes regret writing that blog post because anytime you write a > > blog post about scalability patterns, it invites people to prematurely > > implement them (Brett Slatkin's video generated an endless number of > > questions from people doing sub 1 QPS). We've done launches on the > > YouTube/Google homepage > > (http://blog.golang.org/2011/12/from-zero-to-go-launching-on-google.html > ) > > that haven't required us to make these changes because they did fine > under > > load testing. I'd invest more energy in figuring out the right way to > load > > test, then trying to figure out the bottlenecks when you hit limits with > > real data. > > > > -- > > Ikai Lan > > Developer Programs Engineer, Google App Engine > > plus.ikailan.com > > > > > > > > On Wed, Feb 1, 2012 at 9:19 PM, Robert Kluin <[email protected]> > wrote: > >> > >> So I'd say don't worry about it unless you actually hit this problem. > >> If you do know you'll hit it, see if you have a way to "shard" the > >> timestamp, by account, user, or region, etc..., to relieve some of the > >> pressure. If you must have a global timestamp, I'd say keep it as > >> simple as possible, until you hit the issue. At that point you can > >> figure out a fix. > >> > >> When I have timestamps on high write-rate entities that are > >> non-critical, for example "expiration" times that are used only for > >> cleanup, I'll sometimes add a random jitter of several hours to spread > >> the writes out a bit. I'd be surprised if changing it by a few > >> seconds helped much -- but it could. Keep in mind, there will already > >> be some degree of randomness since the instance clocks have some > >> slight variation. If you're hitting this issue, I'd give it a shot > >> though. If it works it could at least buy you some time to get a > >> better fix. > >> > >> I don't think there is a fixed number of rows per shard. I think it > >> is split up by data size, and I don't think the exact number is > >> publicly documented. Maybe you can roughly figure it out via > >> experimentation. > >> > >> > >> Robert > >> > >> > >> On Wed, Feb 1, 2012 at 02:28, WGuerlich <[email protected]> wrote: > >> > I know, I'm going to hit the write limit with a timestamp I need to > >> > update > >> > on every write and which needs to be indexed. > >> > > >> > As an alternative to sharding: What do you think about adding time > >> > jitter to > >> > the timestamp, that is, changing time randomly by a couple seconds? In > >> > my > >> > application the timestamp being off by a couple senconds wouldn't > pose a > >> > problem. > >> > > >> > Now what I need to know is: How many index entries can I expect to go > >> > into > >> > one tablet? This is needed to estimate the amount of jitter necessary > to > >> > avoid hitting the same tablet on every write. > >> > > >> > Any insights on this? > >> > > >> > Wolfram > >> > > >> > -- > >> > You received this message because you are subscribed to the Google > >> > Groups > >> > "Google App Engine" group. > >> > To view this discussion on the web visit > >> > https://groups.google.com/d/msg/google-appengine/-/r0SVTq6i4iEJ. > >> > > >> > To post to this group, send email to > [email protected]. > >> > To unsubscribe from this group, send email to > >> > [email protected]. > >> > For more options, visit this group at > >> > http://groups.google.com/group/google-appengine?hl=en. > >> > >> -- > >> You received this message because you are subscribed to the Google > Groups > >> "Google App Engine" group. > >> To post to this group, send email to [email protected]. > >> To unsubscribe from this group, send email to > >> [email protected]. > >> For more options, visit this group at > >> http://groups.google.com/group/google-appengine?hl=en. > >> > > > > -- > > You received this message because you are subscribed to the Google Groups > > "Google App Engine" group. > > To post to this group, send email to [email protected]. > > To unsubscribe from this group, send email to > > [email protected]. > > For more options, visit this group at > > http://groups.google.com/group/google-appengine?hl=en. > > -- > You received this message because you are subscribed to the Google Groups > "Google App Engine" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]. > For more options, visit this group at > http://groups.google.com/group/google-appengine?hl=en. > > -- You received this message because you are subscribed to the Google Groups "Google App Engine" group. 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