Look at org.apache.accumulo.core.constraints.Constraint for a description and org.apache.accumulo.core.constraints.DefaultKeySizeConstraint as an example.
In short, Mutations which are live-ingested into a tablet server are validated against constraints you specify on the table. That means that all Mutations written to a table go through this bit of user-provided code at least once. You could use that fact to your advantage. However, this would be highly experimental and might have some caveats to consider. You can configure a constraint on a table with connector.tableOperations().addConstraint(...) On Sun, Dec 6, 2015 at 10:49 PM Thai Ngo <baothai...@gmail.com> wrote: > Christopher, > > This is interesting! Could you please give me more details about this? > > Thanks, > Thai > > On Thu, Dec 3, 2015 at 12:17 PM, Christopher <ctubb...@apache.org> wrote: > >> You could also implement a constraint to notify an external system when a >> row is updated. >> >> On Wed, Dec 2, 2015, 22:54 Josh Elser <josh.el...@gmail.com> wrote: >> >>> oops :) >>> >>> [1] http://fluo.io/ >>> >>> Josh Elser wrote: >>> > Hi Thai, >>> > >>> > There is no out-of-the-box feature provided with Accumulo that does >>> what >>> > you're asking for. Accumulo doesn't provide any functionality to push >>> > notifications to other systems. You could potentially maintain other >>> > tables/columns in which you maintain the last time a row was updated, >>> > but the onus is on your "other services" to read the table to find out >>> > when a change occurred (which is probably not scalable at "real time"). >>> > >>> > There are other systems you could likely leverage to solve this, >>> > depending on the durability and scalability that your application >>> needs. >>> > >>> > For a system "close" to Accumulo, you could take a look at Fluo [1] >>> > which is an implementation of Google's "Percolator" system. This is a >>> > system based on throughput rather than low-latency, so it may not be a >>> > good fit for your needs. There are probably other systems in the Apache >>> > ecosystem (Kafka, Storm, Flink or Spark Streaming maybe?) that are be >>> > helpful to your problem. I'm not an expert on these to recommend on >>> (nor >>> > do I think I understand your entire architecture well enough). >>> > >>> > Thai Ngo wrote: >>> >> Hi list, >>> >> >>> >> I have a use-case when existing rows in a table will be updated by an >>> >> internal service. Data in a row of this table is composed of 2 parts: >>> >> 1st part - immutable and the 2nd one - will be updated (filled in) a >>> >> little later. >>> >> >>> >> Currently, I have a need of knowing when and which rows will be >>> updated >>> >> in the table so that other services will be wisely start consuming the >>> >> data. It will make more sense when I need to consume the data in near >>> >> realtime. So developing a notification function or simpler - a trigger >>> >> is what I really want to do now. >>> >> >>> >> I am curious to know if someone has done similar job or there are >>> >> features or APIs or best practices available for Accumulo so far. I'm >>> >> thinking of letting the internal service which updates the data notify >>> >> us whenever it updates the data. >>> >> >>> >> What do you think? >>> >> >>> >> Thanks, >>> >> Thai >>> >> >
