\u81ea\u9002\u5e94\u9650\u6d41<\/strong><\/div>\n
\u4e00\u822c\u7684\u9650\u6d41\u5e38\u5e38\u9700\u8981\u6307\u5b9a\u4e00\u4e2a\u56fa\u5b9a\u503c(qps)\u4f5c\u4e3a\u9650\u6d41\u5f00\u5173\u7684\u9608\u503c\uff0c\u8fd9\u4e2a\u503c\u4e00\u662f\u9760\u7ecf\u9a8c\u5224\u65ad\uff0c\u4e8c\u662f\u9760\u901a\u8fc7\u5927\u91cf\u7684\u6d4b\u8bd5\u6570\u636e\u5f97\u51fa\u3002\u4f46\u8fd9\u4e2a\u9608\u503c\uff0c\u5728\u6d41\u91cf\u6fc0\u589e\u3001\u7cfb\u7edf\u81ea\u52a8\u4f38\u7f29\u6216\u8005\u67d0\u67d0commit\u4e86\u4e00\u6bb5\u6709\u6bd2\u4ee3\u7801\u540e\u5c31\u6709\u53ef\u80fd\u53d8\u5f97\u4e0d\u90a3\u4e48\u5408\u9002\u4e86\u3002\u5e76\u4e14\u4e00\u822c\u4e1a\u52a1\u65b9\u4e5f\u4e0d\u592a\u80fd\u591f\u6b63\u786e\u8bc4\u4f30\u81ea\u5df1\u7684\u5bb9\u91cf\uff0c\u53bb\u8bbe\u7f6e\u4e00\u4e2a\u5408\u9002\u7684\u9650\u6d41\u9608\u503c\u3002<\/p>\n
\u800c\u6b64\u65f6\u81ea\u9002\u5e94\u9650\u6d41\u5c31\u662f\u89e3\u51b3\u8fd9\u6837\u7684\u95ee\u9898\u7684\uff0c\u9650\u6d41\u9608\u503c\u4e0d\u9700\u8981\u624b\u52a8\u6307\u5b9a\uff0c\u4e5f\u4e0d\u9700\u8981\u53bb\u9884\u4f30\u7cfb\u7edf\u7684\u5bb9\u91cf\uff0c\u5e76\u4e14\u9608\u503c\u80fd\u591f\u968f\u7740\u7cfb\u7edf\u76f8\u5173\u6307\u6807\u53d8\u5316\u800c\u53d8\u5316\u3002<\/p>\n
\u81ea\u9002\u5e94\u9650\u6d41\u7b97\u6cd5\u501f\u9274\u4e86TCP\u62e5\u585e\u7b97\u6cd5\uff0c\u6839\u636e\u5404\u79cd\u6307\u6807\u9884\u4f30\u9650\u6d41\u7684\u9608\u503c\uff0c\u5e76\u4e14\u4e0d\u65ad\u8c03\u6574\u3002\u5927\u81f4\u83b7\u5f97\u7684\u6548\u679c\u5982\u4e0b:<\/p>\n
$\"\"$ <\/p>\n
\u4ece\u56fe\u4e0a\u53ef\u4ee5\u770b\u5230\uff0c\u9996\u5148\u4ee5\u4e00\u4e2a\u964d\u4f4e\u7684\u521d\u59cb\u5e76\u53d1\u503c\u53d1\u9001\u8bf7\u6c42\uff0c\u540c\u65f6\u901a\u8fc7\u589e\u5927\u9650\u6d41\u7a97\u53e3\u6765\u63a2\u6d4b\u7cfb\u7edf\u66f4\u9ad8\u7684\u5e76\u53d1\u6027\u3002\u800c\u4e00\u65e6\u5ef6\u8fdf\u589e\u52a0\u5230\u4e00\u5b9a\u7a0b\u5ea6\u4e86\uff0c\u53c8\u4f1a\u9000\u56de\u5230\u8f83\u5c0f\u7684\u9650\u6d41\u7a97\u53e3\u3002\u5faa\u73af\u5f80\u590d\u6301\u7eed\u63a2\u6d4b\u5e76\u53d1\u6781\u9650\uff0c\u4ece\u800c\u4ea7\u751f\u7c7b\u4f3c\u952f\u9f7f\u72b6\u7684\u65f6\u95f4\u5173\u7cfb\u51fd\u6570\u3002<\/p>\n
TCP Vegas<\/strong><\/div>\n
vegas\u662f\u4e00\u79cd\u4e3b\u52a8\u8c03\u6574cwnd\u7684\u62e5\u585e\u63a7\u5236\u7b97\u6cd5\uff0c\u4e3b\u8981\u662f\u8bbe\u7f6e\u4e24\u4e2a\u9608\u503calpha \u548c beta\uff0c\u7136\u540e\u901a\u8fc7\u8ba1\u7b97\u76ee\u6807\u901f\u7387\u548c\u5b9e\u9645\u901f\u7387\u7684\u5deediff\uff0c\u518d\u6bd4\u8f83\u5deediff\u4e0ealpha\u548cbeta\u7684\u5173\u7cfb\uff0c\u5bf9cwnd\u8fdb\u884c\u8c03\u8282\u3002\u4f2a\u4ee3\u7801\u5982\u4e0b\uff1a<\/p>\n
diff = cwnd*(1-baseRTT\/RTT) \r\nif (diff < alpha) \r\nset: cwndcwnd = cwnd + 1 \r\nelse if (diff >= beta) \r\nset: cwndcwnd = cwnd - 1 \r\nelse \r\nset: cwndcwnd = cwnd <\/pre>\n
\u5176\u4e2dbaseRTT\u6307\u7684\u662f\u6d4b\u91cf\u7684\u6700\u5c0f\u5f80\u8fd4\u65f6\u95f4\uff0cRTT\u6307\u7684\u662f\u5f53\u524d\u6d4b\u91cf\u7684\u5f80\u8fd4\u65f6\u95f4\uff0ccwnd\u6307\u7684\u662f\u5f53\u524d\u7684TCP\u7a97\u53e3\u5927\u5c0f\u3002\u901a\u5e38\u5728tcp\u4e2dalpha\u4f1a\u88ab\u8bbe\u7f6e\u62102-3\uff0cbeta\u4f1a\u88ab\u8bbe\u7f6e\u62104-6\u3002\u8fd9\u6837\u5b50\uff0ccwnd\u5c31\u4fdd\u6301\u5728\u4e86\u4e00\u4e2a\u5e73\u8861\u7684\u72b6\u6001\u3002<\/p>\n
netflix-concuurency-limits<\/strong><\/div>\n
concuurency-limits\u662fnetflix\u63a8\u51fa\u7684\u81ea\u9002\u5e94\u9650\u6d41\u7ec4\u4ef6\uff0c\u501f\u9274\u4e86TCP\u76f8\u5173\u62e5\u585e\u63a7\u5236\u7b97\u6cd5\uff0c\u4e3b\u8981\u662f\u6839\u636e\u8bf7\u6c42\u5ef6\u65f6\uff0c\u53ca\u5176\u76f4\u63a5\u5f71\u54cd\u5230\u7684\u6392\u961f\u957f\u5ea6\u6765\u8fdb\u884c\u9650\u6d41\u7a97\u53e3\u7684\u52a8\u6001\u8c03\u6574\u3002<\/p>\n
alpha , beta & threshold<\/strong><\/span><\/div>\n
vegas\u7b97\u6cd5\u5b9e\u73b0\u5728\u4e86VegasLimit\u7c7b\u4e2d\u3002\u5148\u770b\u4e00\u4e0b\u521d\u59cb\u5316\u76f8\u5173\u4ee3\u7801:<\/p>\n
private int initialLimit = 20; \r\n private int maxConcurrency = 1000; \r\n private MetricRegistry registry = EmptyMetricRegistry.INSTANCE; \r\n private double smoothing = 1.0; \r\n private Function alphaFunc = (limit) -> 3 * LOG10.apply(limit.intValue()); \r\n private Function betaFunc = (limit) -> 6 * LOG10.apply(limit.intValue()); \r\n private Function thresholdFunc = (limit) -> LOG10.apply(limit.intValue()); \r\n private Function increaseFunc = (limit) -> limit + LOG10.apply(limit.intValue()); \r\n private Function decreaseFunc = (limit) -> limit - LOG10.apply(limit.intValue()); <\/pre>\n
\u8fd9\u91cc\u9996\u5148\u5b9a\u4e49\u4e86\u4e00\u4e2a\u521d\u59cb\u5316\u503cinitialLimit\u4e3a20\uff0c\u4ee5\u53ca\u6781\u5927\u503cmaxConcurrency1000\u3002\u5176\u6b21\u662f\u4e09\u4e2a\u9608\u503c\u51fd\u6570alphaFunc\uff0cbetaFunc\u4ee5\u53cathresholdFunc\u3002\u6700\u540e\u662f\u4e24\u4e2a\u589e\u51cf\u51fd\u6570increaseFunc\u548cdecreaseFunc\u3002<\/p>\n
\u51fd\u6570\u90fd\u662f\u57fa\u4e8e\u5f53\u524d\u7684\u5e76\u53d1\u503climit\u505a\u8fd0\u7b97\u7684\u3002<\/p>\n
alphaFunc\u53ef\u7c7b\u6bd4vegas\u7b97\u6cd5\u4e2d\u7684alpha\uff0c\u6b64\u5904\u7684\u5b9e\u73b0\u662f3*log limit\u3002limit\u503c\u4ece\u521d\u59cb20\u589e\u52a0\u5230\u6781\u59271000\u65f6\u5019\uff0c\u76f8\u5e94\u7684alpha\u4ece3.9\u589e\u52a0\u5230\u4e869\u3002<\/p>\n
betaFunc\u5219\u53ef\u7c7b\u6bd4\u4e3avegas\u7b97\u6cd5\u4e2d\u7684beta\uff0c\u6b64\u5904\u7684\u5b9e\u73b0\u662f6*log limit\u3002limit\u503c\u4ece\u521d\u59cb20\u589e\u52a0\u5230\u6781\u59271000\u65f6\u5019\uff0c\u76f8\u5e94\u7684alpha\u4ece7.8\u589e\u52a0\u5230\u4e8618\u3002<\/p>\n
thresholdFunc\u7b97\u662f\u65b0\u589e\u7684\u4e00\u4e2a\u51fd\u6570\uff0c\u8868\u793a\u4e00\u4e2a\u8f83\u4e3a\u521d\u59cb\u7684\u9608\u503c\uff0c\u5c0f\u4e8e\u8fd9\u4e2a\u503c\u7684\u65f6\u5019limit\u4f1a\u91c7\u53d6\u6fc0\u8fdb\u4e00\u4e9b\u7684\u589e\u91cf\u7b97\u6cd5\u3002\u8fd9\u91cc\u7684\u5b9e\u73b0\u662f1\u500d\u7684log limit\u3002mit\u503c\u4ece\u521d\u59cb20\u589e\u52a0\u5230\u6781\u59271000\u65f6\u5019\uff0c\u76f8\u5e94\u7684alpha\u4ece1.3\u589e\u52a0\u5230\u4e863\u3002<\/p>\n
\u8fd9\u4e09\u4e2a\u51fd\u6570\u503c\u53ef\u4ee5\u8ba4\u4e3a\u786e\u5b9a\u4e86\u52a8\u6001\u8c03\u6574\u51fd\u6570\u7684\u56db\u4e2a\u533a\u95f4\u8303\u56f4\u3002\u5f53\u53d8\u91cfqueueSize = limit \u00d7 (1 \u2212 RTTnoLoad\/RTTactual)\u843d\u5230\u8fd9\u56db\u4e2a\u533a\u95f4\u7684\u65f6\u5019\u5e94\u7528\u4e0d\u540c\u7684\u8c03\u6574\u51fd\u6570\u3002<\/p>\n
\u53d8\u91cfqueueSize<\/strong><\/span><\/div>\n
\u5176\u4e2d\u53d8\u91cf\u4e3aqueueSize\uff0c\u8ba1\u7b97\u65b9\u6cd5\u5373\u4e3alimit \u00d7 (1 \u2212 RTTnoLoad\/RTTactual)\uff0c\u4e3a\u4ec0\u4e48\u8fd9\u4e48\u8ba1\u7b97\u5176\u5b9e\u7a0d\u52a0\u9886\u609f\u4e00\u4e0b\u5373\u53ef\u3002<\/p>\n
$\"\"$ <\/p>\n
\u6211\u4eec\u628a\u7cfb\u7edf\u5904\u7406\u8bf7\u6c42\u7684\u8fc7\u7a0b\u60f3\u8c61\u4e3a\u4e00\u4e2a\u6c34\u7ba1\uff0c\u5230\u6765\u7684\u8bf7\u6c42\u662f\u5f80\u8fd9\u4e2a\u6c34\u7ba1\u704c\u6c34\uff0c\u5f53\u7cfb\u7edf\u5904\u7406\u987a\u7545\u7684\u65f6\u5019\uff0c\u8bf7\u6c42\u4e0d\u9700\u8981\u6392\u961f\uff0c\u76f4\u63a5\u4ece\u6c34\u7ba1\u4e2d\u7a7f\u8fc7\uff0c\u8fd9\u4e2a\u8bf7\u6c42\u7684RT\u662f\u6700\u77ed\u7684\uff0c\u5373RTTnoLoad\uff1b<\/p>\n
\u53cd\u4e4b\uff0c\u5f53\u8bf7\u6c42\u5806\u79ef\u7684\u65f6\u5019\uff0c\u90a3\u4e48\u5904\u7406\u8bf7\u6c42\u7684\u65f6\u95f4\u5219\u4f1a\u53d8\u4e3a\uff1a\u6392\u961f\u65f6\u95f4+\u6700\u77ed\u5904\u7406\u65f6\u95f4\uff0c\u5373RTTactual = inQueueTime + RTTnoLoad\u3002\u800c\u663e\u7136\u6392\u961f\u7684\u961f\u5217\u957f\u5ea6\u4e3a<\/p>\n
\u603b\u6392\u961f\u65f6\u95f4\/\u6bcf\u4e2a\u8bf7\u6c42\u7684\u5904\u7406\u65f6\u95f4\u53caqueueSize = (limit * inQueueTime) \/ (inQueueTime + RTTnoLoad) = limit \u00d7 (1 \u2212 RTTnoLoad\/RTTactual)\u3002<\/p>\n
\u518d\u4e3e\u4e2a\u6817\u5b50\uff0c\u56e0\u4e3a\u5047\u8bbe\u5f53\u524d\u5ef6\u65f6\u5373\u4e3a\u6700\u4f73\u5ef6\u65f6\uff0c\u90a3\u4e48\u81ea\u7136\u662f\u4e0d\u7528\u6392\u961f\u7684\uff0c\u5373queueSize=0\u3002\u800c\u5047\u8bbe\u5f53\u524d\u5ef6\u65f6\u4e3a\u6700\u4f73\u5ef6\u65f6\u7684\u4e00\u500d\u7684\u65f6\u5019\uff0c\u53ef\u4ee5\u8ba4\u4e3a\u5904\u7406\u80fd\u529b\u6298\u534a\uff0c100\u4e2a\u6d41\u91cf\u8fdb\u6765\u4f1a\u6709\u4e00\u534a\u537350\u4e2a\u8bf7\u6c42\u5728\u6392\u961f\uff0c\u53caqueueSize= 100 * (1 \u2212 1\/2)=50\u3002<\/p>\n
\u52a8\u6001\u8c03\u6574\u51fd\u6570<\/strong><\/div>\n
\u8c03\u6574\u51fd\u6570\u4e2d\u6700\u91cd\u8981\u7684\u5373\u589e\u51fd\u6570\u4e0e\u51cf\u51fd\u6570\u3002\u4ece\u521d\u59cb\u5316\u7684\u4ee3\u7801\u4e2d\u5f97\u77e5\uff0c\u589e\u51fd\u6570increaseFunc\u5b9e\u73b0\u4e3alimit+log limit\uff0c\u51cf\u51fd\u6570decreaseFunc\u5b9e\u73b0\u4e3alimit-log limit\uff0c\u76f8\u5bf9\u6765\u8bf4\u589e\u51cf\u90fd\u662f\u6bd4\u8f83\u4fdd\u5b88\u7684\u3002<\/p>\n
\u770b\u4e00\u4e0b\u5e94\u7528\u52a8\u6001\u8c03\u6574\u51fd\u6570\u7684\u76f8\u5173\u4ee3\u7801\uff1a<\/p>\n
private int updateEstimatedLimit(long rtt, int inflight, boolean didDrop) { \r\n final int queueSize = (int) Math.ceil(estimatedLimit * (1 - (double)rtt_noload \/ rtt)); \r\n double newLimit; \r\n \/\/ Treat any drop (i.e timeout) as needing to reduce the limit \r\n \/\/ \u53d1\u73b0\u9519\u8bef\u76f4\u63a5\u5e94\u7528\u51cf\u51fd\u6570decreaseFunc \r\n if (didDrop) { \r\n newLimit = decreaseFunc.apply(estimatedLimit); \r\n \/\/ Prevent upward drift if not close to the limit \r\n } else if (inflight * 2 < estimatedLimit) { \r\n return (int)estimatedLimit; \r\n } else { \r\n int alpha = alphaFunc.apply((int)estimatedLimit); \r\n int beta = betaFunc.apply((int)estimatedLimit); \r\n int threshold = this.thresholdFunc.apply((int)estimatedLimit); \r\n \/\/ Aggressive increase when no queuing \r\n if (queueSize <= threshold) { \r\n newLimit = estimatedLimit + beta; \r\n \/\/ Increase the limit if queue is still manageable \r\n } else if (queueSize < alpha) { \r\n newLimit = increaseFunc.apply(estimatedLimit); \r\n \/\/ Detecting latency so decrease \r\n } else if (queueSize > beta) { \r\n newLimit = decreaseFunc.apply(estimatedLimit); \r\n \/\/ We're within he sweet spot so nothing to do \r\n } else { \r\n return (int)estimatedLimit; \r\n } \r\n } \r\n newLimit = Math.max(1, Math.min(maxLimit, newLimit)); \r\n newLimit = (1 - smoothing) * estimatedLimit + smoothing * newLimit; \r\n if ((int)newLimit != (int)estimatedLimit && LOG.isDebugEnabled()) { \r\n LOG.debug(\"New limit={} minRtt={} ms winRtt={} ms queueSize={}\", \r\n (int)newLimit, \r\n TimeUnit.NANOSECONDS.toMicros(rtt_noload) \/ 1000.0, \r\n TimeUnit.NANOSECONDS.toMicros(rtt) \/ 1000.0, \r\n queueSize); \r\n } \r\n estimatedLimit = newLimit; \r\n return (int)estimatedLimit; \r\n } <\/pre>\n
\u52a8\u6001\u8c03\u6574\u51fd\u6570\u89c4\u5219\u5982\u4e0b\uff1a<\/p>\n
\u5f53\u53d8\u91cfqueueSize < threshold\u65f6\uff0c\u9009\u53d6\u8f83\u6fc0\u8fdb\u7684\u589e\u91cf\u51fd\u6570\uff0cnewLimit = limit+beta\n\n\u5f53\u53d8\u91cfqueueSize < alpha\u65f6\uff0c\u9700\u8981\u589e\u5927\u9650\u6d41\u7a97\u53e3\uff0c\u9009\u62e9\u589e\u51fd\u6570increaseFunc\uff0c\u5373newLimit = limit + log limit\n\n\u5f53\u53d8\u91cfqueueSize\u5904\u4e8ealpha\uff0cbeta\u4e4b\u95f4\u65f6\u5019\uff0climit\u4e0d\u53d8\n\n\u5f53\u53d8\u91cfqueueSize\u5927\u4e8ebeta\u65f6\u5019\uff0c\u9700\u8981\u6536\u62e2\u9650\u6d41\u7a97\u53e3\uff0c\u9009\u62e9\u51cf\u51fd\u6570decreaseFunc\uff0c\u5373newLimit = limit - log limit\n\n[yiji]\u5e73\u6ed1\u9012\u51cf smoothingDecrease[\/yiji]\n\n\u6ce8\u610f\u5230\u53ef\u4ee5\u8bbe\u7f6e\u53d8\u91cfsmoothing\uff0c\u8fd9\u91cc\u521d\u59cb\u503c\u4e3a1\uff0c\u8868\u793a\u5e73\u6ed1\u9012\u51cf\u4e0d\u8d77\u4f5c\u7528\u3002\u5982\u679c\u6709\u9700\u8981\u7684\u8bdd\u53ef\u4ee5\u6309\u9700\u8bbe\u7f6e\uff0c\u6bd4\u5982\u8bbe\u7f6esmoothing\u4e3a0.5\u65f6\u5019\uff0c\u90a3\u4e48\u6548\u679c\u5c31\u662f\u91c7\u7528\u51cf\u51fd\u6570decreaseFunc\u65f6\u5019\u6548\u679c\u51cf\u534a\uff0c\u5b9e\u73b0\u65b9\u5f0f\u4e3anewLimitAfterSmoothing = 0.5 newLimit + 0.5 limit\u3002\n<\/p>\n","protected":false},"excerpt":{"rendered":"
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