-Re: Accumulo Utilities
roshanp@... 2013-03-28, 16:15
Thanks! I like the idea of sending my own thread pool to the batch scanner, that would definitely be the better solution.
Yeah I thought about creating a batch scanner with only one thread, but I was not sure if that is making a separate thread (outside of the current one) or using the current one. At the time I did not want a new thread to be created at all. Though, didn't realize the Scanner was also spinning up a thread at all, thought that was in process.
To mitigate the separate RPC call per range, would it make more sense to do a "binRanges" based on the ranges at the tablets to reduce the number of ranges?
On Mar 28, 2013, at 11:55 AM, Keith Turner <[EMAIL PROTECTED]> wrote:
> I took a quick look at the code. Excluding the threading issue, a
> major conceptual difference is that BatchScannerWithScanners seems to
> do a RPC round trip for each range. The TabletServerBatchReader
> sends all of the ranges that a tablet server needs to lookup in one
> Instead of creating a BatchScannerWithScanners, maybe you could create
> a batch scanner with just one thread when resources are exceeded?
> This will be similar to what you are doing now, just one thread will
> be doing work fetching data. The client thread would just be waiting
> on this background thread. Although this does allow the processing
> of result to happen concurrently with fetching of data. Using
> BatchScannerWithScanners would not allow this.
> Something to be aware of, the regular scanner will spin up a read
> ahead thread if you read a lot of data through it. It does not do
> this immediately, only after fetching a few batches of key value pairs
> from the tablet server. If this happens you could have one thread
> fetching data while the client thread processes results.
> Do you think we should open a a ticket about giving users control over
> threads created by client code? Maybe users could pass in their own
> thread pool to a batch scanner?
> On Thu, Mar 28, 2013 at 11:00 AM, <[EMAIL PROTECTED]> wrote:
>> In some of my projects, we needed to control the number of threads spun up with the use of multiple batch scanners. We created a utility to control the number of threads, and if the max threads has been reached, return a batch scanner that is actually backed by Scanners. Wanted to get any feedback on the code. Seems like such a simple thing to do, I bet someone already has this. Thanks!