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MapReduce >> mail # user >> HA for hadoop-0.20.2


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Re: HA for hadoop-0.20.2
Hi,

Why not just use the 2.x releases for HA-NNs? There is quite a wide
delta between 0.20.x and 2.x, especially around the edit log areas
after HDFS-1073.

In any case, I think your question suits [EMAIL PROTECTED]
more than the user lists, although I don't quite understand what
you're attempting to do (or point).

On Tue, Nov 13, 2012 at 2:18 PM, lei liu <[EMAIL PROTECTED]> wrote:
> I want to implement HA function for hadoop-0.20.2.
>
> When I learn the hadoop-2.0 code, I meet some question like this:
>
> Thera are below code in FSEditLogLoader.loadEditRecords method.
>
>    if (op.hasTransactionId()) {
>             if (op.getTransactionId() > expectedTxId) {
>               MetaRecoveryContext.editLogLoaderPrompt("There appears " +
>                   "to be a gap in the edit log.  We expected txid " +
>                   expectedTxId + ", but got txid " +
>                   op.getTransactionId() + ".", recovery, "ignoring missing "
> +
>                   " transaction IDs");
>             } else if (op.getTransactionId() < expectedTxId) {
>               MetaRecoveryContext.editLogLoaderPrompt("There appears " +
>                   "to be an out-of-order edit in the edit log.  We " +
>                   "expected txid " + expectedTxId + ", but got txid " +
>                   op.getTransactionId() + ".", recovery,
>                   "skipping the out-of-order edit");
>               continue;
>             }
>           }
>
> The method use transaction id to  guarantee same transaction log is not
> applied to namespace more than once.
>
> But in hadoop-0.20.2, FSEditLog don't store the transaction id into edits
> log file. So I want to know if  StandbyNN apply same transaction log  to
> namespace more than once, that will lead to the namespace of StandbyNN is
> corrupt?
>
> Please give me some advice,Thanks.
>
>
>
> Best Regards
>
> LiuLei

--
Harsh J