[chord] dhashclient question

[Yanyan Wang]

Hello chord authors,

I met a weird problem when I tried the robustness of chord network. Could you
please kindly help me explain it? I used the chord prototype to do the
experiment. I did the following:

1. I started two chord nodes each of which has 16 virtual nodes;
2. I inserted 32 strings into the chord network and got 32 corresponding keys;
3. I killed one of the lsd processes;
4. I retrieved the 32 keys.

>From the explanation in your sigcomm paper, I expected about half of the 32 key
retrievals should fail because of the key lost as the result of my killing one
lsd process. But my result is all the retrievals succeed in getting the
corresponding strings. I am very surprised at this result. The logs of the live
chord node for the retrieval of key 9f8ff2967cff70d7373cb304807e053a44d8a047
are:

...
lsd: will order successors 1
lsd: dhash_download failed: 9f8ff2967cff70d7373cb304807e053a44d8a047:0:1:
DHASH_NOENT at 3eb6ccaf98300a77989e0059cbe9a465bbc6f35d
lsd: dhash_download failed: 9f8ff2967cff70d7373cb304807e053a44d8a047:0:1:
DHASH_NOENT at 40f746245f6c3bb924ad6e5ddcf15811ea456e9a
lsd: dhash_download failed: 9f8ff2967cff70d7373cb304807e053a44d8a047:0:1:
DHASH_NOENT at 1ac46b2343075c88e9c0f601e96aa64b3651d8d7
lsd: dhash_download failed: 9f8ff2967cff70d7373cb304807e053a44d8a047:0:1:
DHASH_NOENT at 48896252b67623a835fb117b6559c70eeb583fc7
lsd: dhash_download failed: 9f8ff2967cff70d7373cb304807e053a44d8a047:0:1:
DHASH_NOENT at 15282e83543d99cbf76669c03b4d26b0e15b96da
lsd: dhash_download failed: 9f8ff2967cff70d7373cb304807e053a44d8a047:0:1:
DHASH_NOENT at 6793bc04e0c544d5c23e84c6c0605cd0998ee2b7
lsd: dhash_download failed: 9f8ff2967cff70d7373cb304807e053a44d8a047:0:1:
DHASH_NOENT at 766a83e4c5a2f0e76723006c6dad002de53aeaf9

It seems all dhash_download are failed. But why it still can get the correct
string of the key? I am very confused and I would be very appreciated for any
ideas. Thanks a lot!

Thanks!
Yanyan :)


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Yanyan Wang
Department of Computer Science
University of Colorado at Boulder
Boulder, CO, 80302
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