I'm having trouble simply posting a response to this list. This is my 3rd
attempt so if anyone is being spammed, I'm sorry, but I'm just not seeing the
replies and I keep getting rejection notices from the list manager…
Here we go again:
Hi Lukas,
Sorry it has taken me so long to join this party, I have been away and I'm just
catching up.
On 29 Aug 2011, at 09:05, Lukas Schulze wrote:
> A friend of mine found out how it could work: I have to delete the entry
> first and after storing it in the database I've to check the result.
> It's not the prettiest code I've written before, but without the while-loop
> it will work for nearly 97% of my tuples. With the while-loop everything
> works fine.
>
> ======================================
> RiakObject riakIndex = new RiakObject(attrName, attrValue,
> indexString.getBytes());
> riakIndex.setContentType("text/plain; charset=UTF-8");
> try{
> //have to be deleted because of cache (?)
No, there is no cache.
> riakPBCClient.delete(attrName, attrValue);
> riakPBCClient.store(riakIndex);
> RiakObject[] fetched = riakPBCClient.fetch(attrName, attrValue);
> //check whether the entry is correctly stored in the database
> while(fetched.length == 0) {//try it until it works...
> riakPBCClient.store(riakIndex);
> fetched = riakPBCClient.fetch(attrName, attrValue);
> }
>
I don't understand what you're doing here? If you want the object you stored,
why not just returnBody=true for the store operation?
> //fetched entry doesn't match our stored one
> if(!riakIndex.getValue().equals(fetched[0].getValue())) {
> System.err.println("index match: failed -> " + attrName + "." +
> attrValue);
> }
You really need to do this with n_val, r, w, dw all = 1 and allow_mult=false
and no other clients? Something is wrong. Please let me know what version of
the RJC you are using and what version of Riak on what erlang/OS/arch etc. I'd
like to try this at home as storing data and retrieving is what we are all
about and this should *just work* (we have integration tests like this and they
*DO* work.)
Forgive me if I am teaching you to suck eggs here, but right at the start
there, when you store the "riakIndex" object, is there a chance it already
exists?
Does the bucket have allow_mult set to false?
Do you fetch before your store (if you use the new RJC it does a fetch before a
store to handle the vector clock for you)?
Are you attempting to overwrite an existing value but providing a stale vclock?
If you have allow_mult set to false and try and write your object with a stale
vclock your write will be silently dropped. Likewise, if you provide *no*
vclock but a clientId that already has a write on that key, your write will be
dropped. I realise this can be confusing at first, but does it explain the
behaviour you're seeing?
For fun, try this:
curl -v -X GET http://127.0.0.1:8098/riak/b/k
(404)
curl -v -X PUT http://127.0.0.1:8098/riak/b/k -d"a"
(204)
curl -v -X GET http://127.0.0.1:8098/riak/b/k
(200) a
curl -v -X PUT http://127.0.0.1:8098/riak/b/k -d"b"
curl -v -X GET http://127.0.0.1:8098/riak/b/k
(200) b
BUT do the same thing with a clientId header set
curl -v -X GET http://127.0.0.1:8098/riak/c/k -H"X-Riak-ClientId: pete"
(404)
curl -v -X PUT http://127.0.0.1:8098/riak/c/k -d"a" -H"X-Riak-ClientId: pete"
(204)
curl -v -X GET http://127.0.0.1:8098/riak/c/k -H"X-Riak-ClientId: pete"
(200) a
curl -v -X PUT http://127.0.0.1:8098/riak/c/k -d"b" -H"X-Riak-ClientId: pete"
curl -v -X GET http://127.0.0.1:8098/riak/c/k
(200) a (HUH?)
Does that explain any of what you see?
A well behaved client will always fetch before store, and will use the
vlcock/clientId. The new RJC does this for you behind the scenes. See
http://blog.basho.com/2011/07/14/The-All-New-Riak-Java-Client/ and
https://github.com/basho/riak-java-client/blob/master/README.org for more
details.
What is your use case? When you go into production will you have multiple
nodes? Will you have allow_mult set to true? Let me know what I can do to help,
'cos it is great to see someone else using the Java client and I want to make
it easy for you to do so.
It would be far simpler to start defining you strategy for resolving
conflicting writes/sibling values than it would be to try and acheive 100%
consistency in a distributed, fault tolerant database.
Cheers
Russell
>
> }
> ======================================
>
> Best regards
> Lukas
>
>
> On Mon, Aug 29, 2011 at 9:20 AM, Lukas Schulze <[email protected]> wrote:
> Hi,
>
> thank you for your answers.
> I know that Riak is designed for running on distributed servers.
> But what's about adding lots of data and every tuple depends on another one?
> I thought that having only 1 node and disabling replications could solve my
> problems of getting always the latest data from Riak.
>
> Is there another way to achieve 100% consistency in a riak database after a
> very short time?
>
> Best regards
> Lukas
>
>
>
> On Sat, Aug 27, 2011 at 5:43 PM, Ian Plosker <[email protected]> wrote:
> Jonathan,
>
> Excuse me, that last message should have been addressed to you.
>
> Ian Plosker
> Developer Advocate
> Basho Technologies
>
>
> On Aug 27, 2011, at 11:39 AM, Ian Plosker wrote:
>
>> Lukas,
>>
>> Yes, even for dev you'd be best advised to develop and test your application
>> with the same or similar number of nodes and n, r, and w settings as you
>> would in production. It's good practice to develop applications in a
>> dev/test environment that mirrors the production environment as much as is
>> reasonable/feasible. You can run a single node cluster, but note that this
>> isn't a configuration you'll see in a production.
>>
>> Ian Plosker
>> Developer Advocate
>> Basho Technologies
>>
>>
>>
>> On Aug 27, 2011, at 5:33 AM, Jonathan Langevin wrote:
>>
>>> Even for development-purposes only? Otherwise it seems data would be
>>> written n times to the same machine, which is needless in a dev environment
>>> with low storage specs...
>>>
>>>
>>> Jonathan Langevin
>>> Systems Administrator
>>> Loom Inc.
>>> Wilmington, NC: (910) 241-0433 - [email protected] -
>>> www.loomlearning.com - Skype: intel352
>>>
>>>
>>>
>>> On Fri, Aug 26, 2011 at 5:01 PM, Ian Plosker <[email protected]> wrote:
>>> Lukas,
>>>
>>> Also, we don't advise that you run single node clusters. Riak is designed
>>> to be used in clusters of at least 3 nodes. You can run a multi-node
>>> cluster on a single development machine by downloading the Riak source, and
>>> running "make devrel". Take a look at the Riak Fast Track
>>> (http://wiki.basho.com/The-Riak-Fast-Track.html) for more details.
>>>
>>> Ian Plosker
>>> Developer Advocate
>>> Basho Technologies
>>>
>>> On Aug 26, 2011, at 3:17 PM, Lukas Schulze wrote:
>>>
>>>> I'm doing some simple tests with Riak and tried to build something like an
>>>> index.
>>>> Therefore I created new buckets for some attributes like "name", "street"
>>>> and "city".
>>>> One entry in the index-bucket "name" is for example "Mueller" and the
>>>> value contains all user ids, formatted as an JSON string:
>>>> "{id:[1,5,8,13,2,7]}"
>>>> The java objects are saved as JSON strings in a separate bucket "users",
>>>> the keys in this bucket are the user-ids, the values are the JSON strings.
>>>>
>>>> If I add 200 users via Java and the RiakPBC client every loop I fetch the
>>>> index, add the new user id and store it again in Riak.
>>>> But java is too fast, so I receive an old version of the bucket.
>>>>
>>>> Because I've only one node I set the n-value to 1, r = 1, w = 1 and dw = 1.
>>>> But I have to wait nearly 2 seconds to be mostly sure to get the correct
>>>> response. (the computer isn't an high-end machine ;-) )
>>>>
>>>> Is it possible to be sure that the data will be saved permanently and I
>>>> can continue adding users?
>>>> Are there any caching methods I can configure?
>>>> Can I set the default n-value to 1 so that every newly created bucket will
>>>> have this value?
>>>> Does Riak have any kind of indexes or is it possible to implement it a
>>>> better way?
>>>>
>>>> In my first version I saved all users in one bucket and iterated over all
>>>> of them to find the correct one. But for every single request from the
>>>> Java Service to Riak it took nearly 200ms. For a huge amount of entries
>>>> (10,000) this isn't practible. Therefore I tried to implement my own
>>>> indexes.
>>>>
>>>> The main focus of my question is getting rid of the inconsistent reads.
>>>>
>>>> Thank you.
>>>>
>>>> Best Regards
>>>> Lukas
>>>> _______________________________________________
>>>> riak-users mailing list
>>>> [email protected]
>>>> http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com
>>>
>>>
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