b886c056bc
Motivation: Several issues were shown by various ticket (#2900 #2956). Also use the improvement on writability user management from #3036. And finally add a mixte handler, both for Global and Channels, with the advantages of being uniquely created and using less memory and less shaping. Issue #2900 When a huge amount of data are written, the current behavior of the TrafficShaping handler is to limit the delay to 15s, whatever the delay the previous write has. This is wrong, and when a huge amount of writes are done in a short time, the traffic is not correctly shapened. Moreover, there is a high risk of OOM if one is not using in his/her own handler for instance ChannelFuture.addListener() to handle the write bufferisation in the TrafficShapingHandler. This fix use the "user-defined writability flags" from #3036 to allow the TrafficShapingHandlers to "user-defined" managed writability directly, as for reading, thus using the default isWritable() and channelWritabilityChanged(). This allows for instance HttpChunkedInput to be fully compatible. The "bandwidth" compute on write is only on "acquired" write orders, not on "real" write orders, which is wrong from statistic point of view. Issue #2956 When using GlobalTrafficShaping, every write (and read) are synchronized, thus leading to a drop of performance. ChannelTrafficShaping is not touched by this issue since synchronized is then correct (handler is per channel, so the synchronized). Modifications: The current write delay computation takes into account the previous write delay and time to check is the 15s delay (maxTime) is really exceeded or not (using last scheduled write time). The algorithm is simplified and in the same time more accurate. This proposal uses the #3036 improvement on user-defined writability flags. When the real write occurs, the statistics are update accordingly on a new attribute (getRealWriteThroughput()). To limit the synchronisations, all synchronized on GlobalTrafficShapingHandler on submitWrite were removed. They are replaced with a lock per channel (since synchronization is still needed to prevent unordered write per channel), as in the sendAllValid method for the very same reason. Also all synchronized on TrafficCounter on read/writeTimeToWait() are removed as they are unnecessary since already locked before by the caller. Still the creation and remove operations on lock per channel (PerChannel object) are synchronized to prevent concurrency issue on this critical part, but then limited. Additionnal changes: 1) Use System.nanoTime() instead of System.currentTimeMillis() and minimize calls 2) Remove / 10 ° 10 since no more sleep usage 3) Use nanoTime instead of currentTime such that time spend is computed, not real time clock. Therefore the "now" relative time (nanoTime based) is passed on all sub methods. 4) Take care of removal of the handler to force write all pending writes and release read too 8) Review Javadoc to explicit: - recommandations to take into account isWritable - recommandations to provide reasonable message size according to traffic shaping limit - explicit "best effort" traffic shaping behavior when changing configuration dynamically Add a MixteGlobalChannelTrafficShapingHandler which allows to use only one handler for mixing Global and Channel TSH. I enables to save more memory and tries to optimize the traffic among various channels. Result: The traffic shaping is more stable, even with a huge number of writes in short time by taking into consideration last scheduled write time. The current implementation of TrafficShapingHandler using user-defined writability flags and default isWritable() and fireChannelWritabilityChanged works as expected. The statistics are more valuable (asked write vs real write). The Global TrafficShapingHandler should now have less "global" synchronization, hoping to the minimum, but still per Channel as needed. The GlobalChannel TrafficShapingHandler allows to have only one handler for all channels while still offering per channel in addition to global traffic shaping. And finally maintain backward compatibility. |
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