hadoop loadBalance源码分析

// Wait for region servers to report in.
this.serverManager.waitForRegionServers(status);
// Check zk for regionservers that are up but didn't register
for (ServerName sn: this.regionServerTracker.getOnlineServers()) {
    if (!this.serverManager.isServerOnline(sn)) {
    // Not registered; add it.
       LOG.info("Registering server found up in zk but who has not yet " +
　　　　"reported in: " + sn);
　　　　this.serverManager.recordNewServer(sn, HServerLoad.EMPTY_HSERVERLOAD);
　　}
}

      // Try and register with the Master; tell it we are here.  Break if
      // server is stopped or the clusterup flag is down or hdfs went wacky.
      while (keepLooping()) {
        MapWritable w = reportForDuty();
        if (w == null) {
          LOG.warn("reportForDuty failed; sleeping and then retrying.");
          this.sleeper.sleep();
        } else {
          handleReportForDutyResponse(w);
          break;
        }
      }

 // The main run loop.
 while (!this.stopped && isHealthy()) {
　　long now = System.currentTimeMillis();

 void regionServerReport(ServerName sn, HServerLoad hsl)
  throws YouAreDeadException, PleaseHoldException {
    checkIsDead(sn, "REPORT");
    if (!this.onlineServers.containsKey(sn)) {
      // Already have this host+port combo and its just different start code?
      checkAlreadySameHostPort(sn);
      // Just let the server in. Presume master joining a running cluster.
      // recordNewServer is what happens at the end of reportServerStartup.
      // The only thing we are skipping is passing back to the regionserver
      // the ServerName to use. Here we presume a master has already done
      // that so we'll press on with whatever it gave us for ServerName.
      recordNewServer(sn, hsl);
    } else {
      this.onlineServers.put(sn, hsl);
    }
  }

this.startcode = System.currentTimeMillis();

...

result = this.hbaseMaster.regionServerStartup(port, this.startcode, now);

...

this.serverNameFromMasterPOV = new ServerName(hostnameFromMasterPOV,
this.isa.getPort(), this.startcode);

...

this.hbaseMaster.regionServerReport(this.serverNameFromMasterPOV.getVersionedBytes(), hsl);