i meant even if we were using hostnames for RS registration (which i think has lot of advantages - not necessarily in our environment though) - the master processing of the heartbeat (or whatever it's processing) shouldn't require a forward lookup. if it needs the ip address - it already has that via the connection object.
On Fri, Jan 29, 2010 at 11:19 AM, Karthik Ranganathan <kranganat...@facebook.com> wrote: > Yup totally - either name or ip would work. Not sure if there is a pro or a > con to choosing either one - but thought it better to use the ip as that > always remains the same (no resolve required) and used to open the sockets. > > @jd-cryans: Saw your JIRA update: "One example of weirdness is when the > region server is told which address to use according to the master:" > > Was meaning to ask about that too :) its all good now. > > Thanks > Karthik > > > -----Original Message----- > From: Joydeep Sarma [mailto:jsensa...@gmail.com] > Sent: Friday, January 29, 2010 11:01 AM > To: hbase-dev@hadoop.apache.org > Subject: Re: Cannot locate root region > > hmmm .. if the master doesn't need the RS ip address at this point - > seems like it should be able to use the hostname offered by the RS > directly? > > On Fri, Jan 29, 2010 at 10:44 AM, Karthik Ranganathan > <kranganat...@facebook.com> wrote: >> The master does another lookup independent of the region server using the >> hostname given by the region server: >> >> ServerManager.java, regionServerReport() does: >> HServerInfo storedInfo = serversToServerInfo.get(info.getServerName()); >> // info.getServerName() is hostname >> >> Which eventually does: >> HServerAddress.getHostname() >> >> HServerAddress' constructor creates the InetSocketAddress from the >> hostname:port, which involves mapping the hostname to the ip address using a >> lookup. >> >> Thanks >> Karthik >> >> >> -----Original Message----- >> From: Joydeep Sarma [mailto:jsensa...@gmail.com] >> Sent: Friday, January 29, 2010 9:46 AM >> To: hbase-dev@hadoop.apache.org >> Subject: Re: Cannot locate root region >> >> @Kannan - Karthik's mail said the reverse lookup happens in the RS >> (not the master). the master simply tried to match the offered >> hostname. >> >> i dont know whose reading is right - but if it's the RS - i didn't >> understand why that wasn't just the reverse lookup done once at >> bootstrap time (which wouldn't be affected by ongoing DNS badness). >> >> >> On Fri, Jan 29, 2010 at 9:39 AM, Jean-Daniel Cryans <jdcry...@apache.org> >> wrote: >>> I just created https://issues.apache.org/jira/browse/HBASE-2174 >>> >>> We handle addresses in different ways depending on which part of the >>> code you're in. We should correct that everywhere by implementing a >>> solution that also solves what you guys are seeing. >>> >>> J-D >>> >>> On Fri, Jan 29, 2010 at 8:33 AM, Kannan Muthukkaruppan >>> <kan...@facebook.com> wrote: >>>> @Joy: The info stored in .META. for various regions as well as in the >>>> ephemeral nodes for region servers in zookeeper are both already IP >>>> address based. So doesn't look like multi-homing and/or the other >>>> flexibilities you mention were a design goal as far as I can tell. >>>> >>>> Regarding: <<< doesn't the reverse ip lookup just once at RS startup >>>> time?>>>, what seems to be happening is this: >>>> >>>> A regionServer periodically sends a regionServerReport (RPC call) to the >>>> master. A HServerInfo argument is passed as an argument and it identifies >>>> the sending region server's identity in IP address format. >>>> >>>> The master, in ServerManager class, maintains a serversToServerInfo map >>>> which is hostname based. Every time a master receives a regionServerReport >>>> it converts the IP address based name to a hostname via the >>>> info.getServerName() call. Normally this call returns the hostname, but we >>>> suspect that during the DNS flakiness, it returned an IP address based >>>> string. And so, this caused ServerManager.java to think that it was >>>> hearing from a new server. And this lead to: >>>> >>>> HServerInfo storedInfo = serversToServerInfo.get(info.getServerName()); >>>> if (storedInfo == null) { >>>> if (LOG.isDebugEnabled()) { >>>> LOG.debug("Received report from unknown server -- telling it " + >>>> <<============ >>>> "to " + CALL_SERVER_STARTUP + ": " + info.getServerName()); >>>> <<============ >>>> } >>>> >>>> and bad things down the road. >>>> >>>> The above error message in our logs (example below) indeed identified the >>>> host in IP address syntax, even though normally the getServerName call >>>> would return the info in hostname format. >>>> >>>> 2010-01-28 11:21:34,539 DEBUG >>>> org.apache.hadoop.hbase.master.ServerManager: Received report from unknown >>>> server -- telling it to MSG_CALL_SERVER_STARTUP: >>>> 10.129.68.203,60020,1263605543210 >>>> >>>> This affected three of our test clusters at the same time! >>>> >>>> Perhaps all we need to do is to change the ServerManager's internal maps >>>> to all be IP based? That way we avoid/bypass the master having to look up >>>> the hostname on every heartbeat. >>>> >>>> regards, >>>> Kannan >>>> ________________________________________ >>>> From: Joydeep Sarma [jsensa...@gmail.com] >>>> Sent: Friday, January 29, 2010 1:20 AM >>>> To: hbase-dev@hadoop.apache.org >>>> Subject: Re: Cannot locate root region >>>> >>>> hadoop also uses the hostnames. if a host is multi-homed - it's >>>> hostname is a better identifier (which still allows it to use >>>> different nics/ips for actual traffic). it can help in the case the >>>> cluster is migrated for example (all the ips change). one could have >>>> the same hostname resolve to different ips depending on who's doing >>>> the lookup (this happens in AWS where the same elastic hostname >>>> resolves to private or public ip depending on where the peer is. so >>>> clients can talk from outside AWS via public ips and master etc. can >>>> talk over private ips). >>>> >>>> so lots of reasons i guess. doesn't the reverse ip lookup just once at >>>> RS startup time? (wondering how this reconciles with the DNS being >>>> flaky after the cluster was up and running). >>>> >>>> On Thu, Jan 28, 2010 at 9:30 PM, Karthik Ranganathan >>>> <kranganat...@facebook.com> wrote: >>>>> >>>>> We did some more digging into this and here is the theory. >>>>> >>>>> 1. The regionservers use their local ip to lookup their hostnames and >>>>> pass that to the HMaster. The HMaster finds the server info by using this >>>>> hostname as the key in the HashMap. >>>>> >>>>> HRegionServer.java >>>>> reinitialize() - >>>>> this.serverInfo = new HServerInfo(new HServerAddress( >>>>> new InetSocketAddress(address.getBindAddress(), >>>>> this.server.getListenerAddress().getPort())), >>>>> System.currentTimeMillis(), >>>>> this.conf.getInt("hbase.regionserver.info.port", 60030), >>>>> machineName); >>>>> >>>>> In run() - >>>>> HMsg msgs[] = hbaseMaster.regionServerReport( >>>>> serverInfo, outboundArray, getMostLoadedRegions()); >>>>> >>>>> >>>>> 2. I have observed in the past that there could be some DNS flakiness >>>>> which causes the IP address of the machines to be returned as their >>>>> hostnames. Guessing this is what happened. >>>>> >>>>> >>>>> 3. The HMaster looks in the map for the above IP address (masquerading as >>>>> the server name). It gets and does not find the entry in its map. So it >>>>> assumes that this is a new region server and issues a CALL_SERVER_STARTUP. >>>>> >>>>> >>>>> 4. The region server that receives it is in fact already running (under >>>>> its real hostname) and enters the "HMaster panic" mode and bad stuff >>>>> happens. >>>>> >>>>> ServerManager.java in regionServerReport() - >>>>> HServerInfo storedInfo = serversToServerInfo.get(info.getServerName()); >>>>> if (storedInfo == null) { >>>>> // snip... >>>>> return new HMsg[] {CALL_SERVER_STARTUP}; >>>>> } >>>>> >>>>> >>>>> Any reason why we use the hostname instead of the ip address in the map >>>>> that stores the regionserver info? >>>>> >>>>> Thanks >>>>> Karthik >>>>> >>>>> >>>>> -----Original Message----- >>>>> From: Karthik Ranganathan [mailto:kranganat...@facebook.com] >>>>> Sent: Thursday, January 28, 2010 3:58 PM >>>>> To: hbase-dev@hadoop.apache.org >>>>> Subject: Cannot locate root region >>>>> >>>>> Hey guys, >>>>> >>>>> Ran into some issues while testing and wanted to understand what has >>>>> happened better. Got the following exception when I went to the web UI >>>>> >>>>> Trying to contact region server 10.129.68.204:60020 for region .META.,,1, >>>>> row '', but failed after 3 attempts. >>>>> Exceptions: >>>>> org.apache.hadoop.hbase.NotServingRegionException: >>>>> org.apache.hadoop.hbase.NotServingRegionException: .META.,,1 >>>>> at >>>>> org.apache.hadoop.hbase.regionserver.HRegionServer.getRegion(HRegionServer.java:2254) >>>>> at >>>>> org.apache.hadoop.hbase.regionserver.HRegionServer.openScanner(HRegionServer.java:1837) >>>>> at sun.reflect.GeneratedMethodAccessor4.invoke(Unknown Source) >>>>> at >>>>> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) >>>>> at java.lang.reflect.Method.invoke(Method.java:597) >>>>> at >>>>> org.apache.hadoop.hbase.ipc.HBaseRPC$Server.call(HBaseRPC.java:648) >>>>> at >>>>> org.apache.hadoop.hbase.ipc.HBaseServer$Handler.run(HBaseServer.java:915) >>>>> >>>>> >>>>> From a program that reads from a HBase table: >>>>> java.lang.reflect.UndeclaredThrowableException >>>>> at $Proxy1.getRegionInfo(Unknown Source) >>>>> at >>>>> org.apache.hadoop.hbase.client.HConnectionManager$TableServers.locateRootRegion(HConnectionManager.java:985) >>>>> at >>>>> org.apache.hadoop.hbase.client.HConnectionManager$TableServers.locateRegion(HConnectionManager.java:625) >>>>> at >>>>> org.apache.hadoop.hbase.client.HConnectionManager$TableServers.locateRegion(HConnectionManager.java:601) >>>>> at >>>>> org.apache.hadoop.hbase.client.HConnectionManager$TableServers.locateRegionInMeta(HConnectionManager.java:675) >>>>> <snip> >>>>> >>>>> >>>>> Followed up on the hmaster's log: >>>>> >>>>> 2010-01-28 11:21:16,148 INFO org.apache.hadoop.hbase.master.BaseScanner: >>>>> RegionManager.metaScanner scan of 1 row(s) of meta region {server: >>>>> 10.129.68.204:60020, regionname: .META.,,1, startKey: <>} complete >>>>> 2010-01-28 11:21:16,148 INFO org.apache.hadoop.hbase.master.BaseScanner: >>>>> All 1 .META. region(s) scanned >>>>> 2010-01-28 11:21:34,539 DEBUG >>>>> org.apache.hadoop.hbase.master.ServerManager: Received report from >>>>> unknown server -- telling it to MSG_CALL_SERVER_STARTUP: >>>>> 10.129.68.203,60020,1263605543210 >>>>> 2010-01-28 11:21:35,622 INFO >>>>> org.apache.hadoop.hbase.master.ServerManager: Received start message >>>>> from: hbasetest004.ash1.facebook.com,60020,1264706494600 >>>>> 2010-01-28 11:21:36,649 DEBUG >>>>> org.apache.hadoop.hbase.zookeeper.ZooKeeperWrapper: Updated ZNode >>>>> /hbase/rs/1264706494600 with data 10.129.68.203:60020 >>>>> 2010-01-28 11:21:40,704 INFO org.apache.hadoop.ipc.HBaseServer: IPC >>>>> Server handler 39 on 60000, call createTable({NAME => 'test1', FAMILIES >>>>> => [{NAME => 'cf1', VERSIONS => '3', COMPRESSION => 'NONE', TTL => >>>>> '2147483647', BLOCKSIZE => '65536', IN_MEMORY => 'false', BLOCKCACHE => >>>>> 'true'}]}) from 10.131.29.183:63308: error: >>>>> org.apache.hadoop.hbase.TableExistsException: test1 >>>>> org.apache.hadoop.hbase.TableExistsException: test1 >>>>> at >>>>> org.apache.hadoop.hbase.master.HMaster.createTable(HMaster.java:792) >>>>> at >>>>> org.apache.hadoop.hbase.master.HMaster.createTable(HMaster.java:756) >>>>> at sun.reflect.GeneratedMethodAccessor6.invoke(Unknown Source) >>>>> at >>>>> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) >>>>> at java.lang.reflect.Method.invoke(Method.java:597) >>>>> at >>>>> org.apache.hadoop.hbase.ipc.HBaseRPC$Server.call(HBaseRPC.java:648) >>>>> at >>>>> org.apache.hadoop.hbase.ipc.HBaseServer$Handler.run(HBaseServer.java:915) >>>>> >>>>> From a hregionserver's logs: >>>>> >>>>> 2010-01-28 11:20:22,589 DEBUG >>>>> org.apache.hadoop.hbase.io.hfile.LruBlockCache: Cache Stats: Sizes: >>>>> Total=19.661453MB (20616528), Free=2377.0137MB (2492479408), >>>>> Max=2396.675MB (2513095936), Counts: Blocks=0, Access=0, Hit=0, Miss=0, >>>>> Evictions=0, Evicted=0, Ratios: Hit Ratio=NaN%, Miss Ratio=NaN%, >>>>> Evicted/Run=NaN >>>>> 2010-01-28 11:21:22,588 DEBUG >>>>> org.apache.hadoop.hbase.io.hfile.LruBlockCache: Cache Stats: Sizes: >>>>> Total=19.661453MB (20616528), Free=2377.0137MB (2492479408), >>>>> Max=2396.675MB (2513095936), Counts: Blocks=0, Access=0, Hit=0, Miss=0, >>>>> Evictions=0, Evicted=0, Ratios: Hit Ratio=NaN%, Miss Ratio=NaN%, >>>>> Evicted/Run=NaN >>>>> 2010-01-28 11:22:18,794 INFO >>>>> org.apache.hadoop.hbase.regionserver.HRegionServer: >>>>> MSG_CALL_SERVER_STARTUP >>>>> >>>>> >>>>> The code says the following: >>>>> case MSG_CALL_SERVER_STARTUP: >>>>> // We the MSG_CALL_SERVER_STARTUP on startup but we can >>>>> also >>>>> // get it when the master is panicking because for instance >>>>> // the HDFS has been yanked out from under it. Be wary of >>>>> // this message. >>>>> >>>>> Any ideas on what is going on? The best I can come up with is perhaps a >>>>> flaky DNS - would that explain this? This happened on three of our test >>>>> clusters at almost the same time. Also, what is the most >>>>> graceful/simplest way to recover from this? >>>>> >>>>> >>>>> Thanks >>>>> Karthik >>>>> >>>>> >>>> >>> >> >
