[jira] [Commented] (NUTCH-207) Bandwidth target for fetcher rather than a thread count

["Sebastian Nagel (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/NUTCH-207?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13988655#comment-13988655 ] 

Sebastian Nagel commented on NUTCH-207:
---------------------------------------

Looks good.
- there are some collisions/overlaps with NUTCH-1182
- NPE if fetcher.bandwidth.target.check.everyNSecs set to 0
- conditions which disable the feature could be placed on top, e.g.:
{code}
if (targetBandwidth == -1 || maxNumThreads == -1) {
  // disabled
} else if (bandwidthTargetCheckCounter < bandwidthTargetCheckEveryNSecs) {
  bandwidthTargetCheckCounter++;
} ...
{code}
- in case "fetcher.maxNum.threads" is not set: could be initialized to number of threads. Would simplify configuration and code.
- log output should always use same unit: "averageBdwPerThread : 36721680" vs. "Exceeding target bandwidth (110 vs 1 Mbps)"
- missing space in log output: "Thread FetcherThreadhas no more work available"
- wouldn't be kbps not a more appropriate unit for configuration? Do we really need granularity and precision of bps? Would also avoid int overflows in the near future with GBit networks.
- line 1290-1: "check whether it is worth doing e.g. more queues than threads": shouldn't "fetcher.threads.per.host" be also taken into account? Then the bandwidth could be adjusted also when only one (local) server is crawled but with heavy load.


> Bandwidth target for fetcher rather than a thread count
> -------------------------------------------------------
>
>                 Key: NUTCH-207
>                 URL: https://issues.apache.org/jira/browse/NUTCH-207
>             Project: Nutch
>          Issue Type: New Feature
>          Components: fetcher
>    Affects Versions: 0.8
>            Reporter: Rod Taylor
>            Assignee: Julien Nioche
>             Fix For: 1.9
>
>         Attachments: NUTCH-207.trunk.patch, ratelimit.patch
>
>
> Increases or decreases the number of threads from the starting value (fetcher.threads.fetch) up to a maximum (fetcher.threads.maximum) to achieve a target bandwidth (fetcher.threads.bandwidth).
> It seems to be able to keep within 10% of the target bandwidth even when large numbers of errors are found or when a number of large pages is run across.
> To achieve more accurate tracking Nutch should keep track of protocol overhead as well as the volume of pages downloaded.



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