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本文主要研究一下sentinel的SystemSlot
SystemSlot
sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/system/SystemSlot.java
public class SystemSlot extends AbstractLinkedProcessorSlot<DefaultNode> {
@Override
public void entry(Context context, ResourceWrapper resourceWrapper, DefaultNode node, int count, Object... args)
throws Throwable {
SystemRuleManager.checkSystem(resourceWrapper);
fireEntry(context, resourceWrapper, node, count, args);
}
@Override
public void exit(Context context, ResourceWrapper resourceWrapper, int count, Object... args) {
fireExit(context, resourceWrapper, count, args);
}
}
- 这里是通过SystemRuleManager.checkSystem(resourceWrapper)进行系统限流判断
SystemRuleManager
public static void checkSystem(ResourceWrapper resourceWrapper) throws BlockException {
// 确定开关开了
if (checkSystemStatus.get() == false) {
return;
}
// for inbound traffic only
if (resourceWrapper.getType() != EntryType.IN) {
return;
}
// total qps
double currentQps = Constants.ENTRY_NODE == null ? 0.0 : Constants.ENTRY_NODE.successQps();
if (currentQps > qps) {
throw new SystemBlockException(resourceWrapper.getName(), "qps");
}
// total thread
int currentThread = Constants.ENTRY_NODE == null ? 0 : Constants.ENTRY_NODE.curThreadNum();
if (currentThread > maxThread) {
throw new SystemBlockException(resourceWrapper.getName(), "thread");
}
double rt = Constants.ENTRY_NODE == null ? 0 : Constants.ENTRY_NODE.avgRt();
if (rt > maxRt) {
throw new SystemBlockException(resourceWrapper.getName(), "rt");
}
// 完全按照RT,BBR算法来
if (highestSystemLoadIsSet && getCurrentSystemAvgLoad() > highestSystemLoad) {
if (currentThread > 1 &&
currentThread > Constants.ENTRY_NODE.maxSuccessQps() * Constants.ENTRY_NODE.minRt() / 1000) {
throw new SystemBlockException(resourceWrapper.getName(), "load");
}
}
}
public static double getCurrentSystemAvgLoad() {
return statusListener.getSystemAverageLoad();
}
- 先判断qps,在判断总线程数、之后判断rt,最后判断系统负载有没有超过限制
StatisticNode
sentinel-core/src/main/java/com/alibaba/csp/sentinel/node/StatisticNode.java
@Override
public long successQps() {
return rollingCounterInSecond.success() / IntervalProperty.INTERVAL;
}
@Override
public int curThreadNum() {
return curThreadNum.get();
}
@Override
public long avgRt() {
long successCount = rollingCounterInSecond.success();
if (successCount == 0) {
return 0;
}
return rollingCounterInSecond.rt() / successCount;
}
@Override
public long maxSuccessQps() {
return rollingCounterInSecond.maxSuccess() * SampleCountProperty.sampleCount;
}
@Override
public long minRt() {
return rollingCounterInSecond.minRt();
}
- successQps、curThreadNum、avgRt、maxSuccessQps、minRt指标在StatisticNode上进行维护
SystemStatusListener
sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/system/SystemStatusListener.java
public class SystemStatusListener implements Runnable {
volatile double currentLoad = -1;
volatile String reason = StringUtil.EMPTY;
static final int processor = ManagementFactory.getOperatingSystemMXBean().getAvailableProcessors();
public double getSystemAverageLoad() {
return currentLoad;
}
@Override
public void run() {
try {
if (!SystemRuleManager.getCheckSystemStatus()) {
return;
}
// system average load
OperatingSystemMXBean operatingSystemMXBean = ManagementFactory.getOperatingSystemMXBean();
currentLoad = operatingSystemMXBean.getSystemLoadAverage();
StringBuilder sb = new StringBuilder();
if (currentLoad > SystemRuleManager.getHighestSystemLoad()) {
sb.append("load:").append(currentLoad).append(";");
sb.append("qps:").append(Constants.ENTRY_NODE.passQps()).append(";");
sb.append("rt:").append(Constants.ENTRY_NODE.avgRt()).append(";");
sb.append("thread:").append(Constants.ENTRY_NODE.curThreadNum()).append(";");
sb.append("success:").append(Constants.ENTRY_NODE.successQps()).append(";");
sb.append("minRt:").append(Constants.ENTRY_NODE.minRt()).append(";");
sb.append("maxSuccess:").append(Constants.ENTRY_NODE.maxSuccessQps()).append(";");
RecordLog.info(sb.toString());
}
} catch (Throwable e) {
RecordLog.info("could not get system error ", e);
}
}
}
- 系统负载是通过SystemRuleManager定时调度SystemStatusListener,通过OperatingSystemMXBean去获取
static {
checkSystemStatus.set(false);
statusListener = new SystemStatusListener();
scheduler.scheduleAtFixedRate(statusListener, 5, 1, TimeUnit.SECONDS);
currentProperty.addListener(listener);
}
小结
sentinel的SystemSlot是通过判断系统相关指标来进行限流,主要的指标为qps、总线程数、rt、系统负载。
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