PeriodicMemstoreFlusher类 定时判断是否触发memflush，
判断间隔hbase.server.thread.wakefrequency 默认10S
@Override
protected void chore() {
for (HRegion r : this.server.onlineRegions.values()) {
if (r == null)
continue;
if (r.shouldFlush()) {
FlushRequester requester = server.getFlushRequester();
if (requester != null) {
long randomDelay = rand.nextInt(RANGE_OF_DELAY) + MIN_DELAY_TIME;
LOG.info(getName() + " requesting flush for region " + r.getRegionNameAsString() +
" after a delay of " + randomDelay);
//Throttle the flushes by putting a delay. If we don‘t throttle, and there
//is a balanced write-load on the regions in a table, we might end up
//overwhelming the filesystem with too many flushes at once.
requester.requestDelayedFlush(r, randomDelay);
}
}
}
}
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触发条件should Flush方法
boolean shouldFlush() {
if(this.completeSequenceId + this.flushPerChanges < this.sequenceId.get()) {//防止memstore变化太多
return true;
}
if (flushCheckInterval <= 0) { //disabled
return false;
}
long now = EnvironmentEdgeManager.currentTimeMillis();
//if we flushed in the recent past, we don‘t need to do again now
if ((now - getLastFlushTime() < flushCheckInterval)) {//每次flush间隔时间，hbase.regionserver.optionalcacheflushinterval默认为1小时
return false;
}
//since we didn‘t flush in the recent past, flush now if certain conditions
//are met. Return true on first such memstore hit.
for (Store s : this.getStores().values()) {
if (s.timeOfOldestEdit() < now - flushCheckInterval) { // oldest edit of store , one hour ago , now 有store在一小时钱修改过
// we have an old enough edit in the memstore, flush
return true;
}
}
return false;
}
?
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? 1.依照sequeceid，判断memstore没有太多flush，进行flush
? 2.比较每次flush的间隔时间，没到时间，不进行flush（单从时间上看，memstore够老）
? 3.超过间隔时间，并且有个store的edit超过间隔时间（从用户修改上看，memstore够老）
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hbase定时memflush PeriodicMemstoreFlusher
原文：http://blackproof.iteye.com/blog/2192110