[chord] infinite retries on KEYHASH blocks

[Benjie Chen]

i fixed this on a check-in earlier today (a few hours ago)... give it
another try.

thanks

benjie


On Mon, Jul 21, 2003 at 09:27:35PM -0400, Michael Walfish wrote:
> 
> Hello,
> 
> 1) It appears, from the code in dhash/client.C, that the intended behavior 
> on a DHASH_KEYHASH retrieve() request when the block is not found on 
> the correct node is:
>    
>    --look for the block on each successor
>    --if that fails, repeat looking for the block on each successor 
> 'retries' number of times (hardcoded to 5 in the code below, marked with 
> **).
> 
> 2) However, the code never checks the number of retries. I marked -------
> below where it looks like this check should happen.
> 
> 3) The current behavior is that the retries decrement ad infinitum. The 
> parameter goes to -2, -3, etc. Confirmed in gdb. And of course doing  
> 
>    dhashclient->retrieve(non_existent_chordid, DHASH_KEYHASH, wrap(&cb))
> 
> inside 'typetest' results in the code never returning (you can see the
> retries happening every 5 seconds forever in the output from lsd). This is
> all with the stock code.
> 
> 
> Was wondering:
> a) if infinite retrying is intended behavior
> b) if not, whether this will be fixed soon. I'd be happy to mail in a
> patch. It's just a tiny code modification, of course:
> 
>  if (options & DHASHCLIENT_NO_RETRY_ON_LOOKUP) { 
>                -->
>  if (retries == 0 || options & DHASHCLIENT_NO_RETRY_ON_LOOKUP) {
> 
> 
> Thanks,
> Mike
> 
> 
> --------------------------------------------------------------------
> from dhash/client.C
> 
> void
> dhashcli::retrieve (blockID blockID, cb_ret cb, int options, 
> 		    ptr<chordID> guess)
> {
>   . . . .
>   if (blockID.ctype == DHASH_KEYHASH) {
>     ci->first_hop (wrap (this, &dhashcli::retrieve_block_hop_cb, rs, ci,
> 			 options, **5**, guess),
> 		   guess);
>   }
>   . . . .  
> }
> 
> void
> dhashcli::retrieve_block_hop_cb (ptr<rcv_state> rs, route_iterator *ci,
> 				 int options, int retries, ptr<chordID> guess,
> 				 bool done)
> {
>  . . . .
>   chord_node s = rs->succs.pop_front ();
>   dhash_download::execute (clntnode, s, rs->key, NULL, 0, 0, 0,
> 			   wrap (this, &dhashcli::retrieve_dl_or_walk_cb,
> 				 rs, status, options, retries, guess));
> }
> 
> void
> dhashcli::retrieve_dl_or_walk_cb (ptr<rcv_state> rs, dhash_stat status,
> 				  int options, int retries, ptr<chordID> guess,
> 				  ptr<dhash_block> blk)
> {
>   chordID myID = clntnode->my_ID ();
> 
>   if(!blk) {
>     if (options & DHASHCLIENT_NO_RETRY_ON_LOOKUP -------- ) {
>       rs->complete (DHASH_NOENT, NULL);
>       rs = NULL;
>     } else if (rs->succs.size() == 0) {
>       trace << myID << ": walk (" << rs->key << "): No luck walking successors, retrying..\n";
>       route_iterator *ci = r_factory->produce_iterator_ptr (rs->key.ID);
>       delaycb (5, wrap (ci, &route_iterator::first_hop, 
> 			wrap (this, &dhashcli::retrieve_block_hop_cb,
> 			      rs, ci, options, retries - 1, guess),
> 			guess));
>     } else {
>       chord_node s = rs->succs.pop_front ();
>       dhash_download::execute (clntnode, s, rs->key, NULL, 0, 0, 0,
> 			       wrap (this, &dhashcli::retrieve_dl_or_walk_cb,
> 				     rs, status, options, retries,
> 				     guess));
>     }
>   } else {
>     rs->timemark ();
> 
>     blk->ID = rs->key.ID;
>     blk->hops = rs->r.size ();
>     blk->errors = rs->nextsucc - dhash::num_dfrags ();
>     blk->retries = blk->errors;
> 
>     rs->complete (DHASH_OK, blk);
>     rs = NULL;
>   }
> }
> 
> 
> 
> _______________________________________________
> chord mailing list
> chord at amsterdam.lcs.mit.edu
> https://amsterdam.lcs.mit.edu/mailman/listinfo/chord

-- 
benjie chen
benjie at lcs.mit.edu