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From Steve Brewin <sbre...@synsys.com>
Subject Re: Notes on JAMES-1352 Commits
Date Sun, 18 Dec 2011 18:02:44 GMT
Hi Eric

It's probably better that you look at the code first and ask questions 
later. It will be quicker this way :)

Cheers
--Steve

On 18/12/2011 18:19, Eric Charles wrote:
> Hi Steve,
>
> Last time I connected to LDAP from JAVA code is ten years ago.
> I don't remember if we were using a connection pool or whatever...
>
> A timeout can occur on an overloaded LDAP server, and retrying gives a 
> risk to make things worst as the LDAP will keep on to be more and more 
> overloaded due to retrying clients.
>
> I will take some time in coming days to look at the Tomcat's JNDI 
> Realm as well as to your code (and see if you retry with incremental 
> period of time for example).
>
> Can you also further elaborate on your Q2 (the interfaces in util)?
>
> Thx again,
>
> Eric
>
>
> On 18/12/11 12:38, Steve Brewin wrote:
>> Hi Eric
>>
>> Even when deployed in highly resilient infrastructures with multiple
>> LDAP servers there is a need to retry in the case where the server
>> connected to fails. In this scenario, a single instantaneous retry is
>> sufficient.
>>
>> In less resilient infrastructures, retry provides a greater level of
>> resilience. Retrying over a defined duration offers an alternative to
>> having to recycle James should the LDAP server become temporarily
>> unavailable.
>>
>> The former is common, see Tomcat's JNDI Realm. The latter easy to
>> provide once support for the former is added. So why not?
>>
>> Cheers
>> --Steve
>>
>> On 18/12/2011 11:09, Eric Charles wrote:
>>> Hi Steve,
>>> I will take more time in the next days to comment on:
>>>
>>> - Why do we need some retry (I know you asked the question before and
>>> I didn't answer by lack of time - just curious to further discuss,
>>> won't ask for any revert :).
>>>
>>> - I saw util maven project more for utility classes, without any
>>> further structure.
>>>
>>> Stay tuned.
>>> Thx,
>>>
>>> Eric
>>>
>>>
>>> On 13/12/11 12:09, Steve Brewin wrote:
>>>> Hi
>>>> Yesterday I committed fixes for JAMES-1352 "Increase the robustness of
>>>> org.apache.james.userldap.ReadOnlyUsersLDAPRepository". A few design
>>>> questions arise from this.
>>>>
>>>> Aside from a little house-keeping, the only changes to the
>>>> org.apache.james.userldap package are:
>>>> - The introduction of a retryable LDAP context via a proxy class.
>>>> - Authorization uses a reconnect() on a new instance of the existing
>>>> LdapContext, thereby propagating all other Context related settings.
>>>> - All retry functionality is implemented in
>>>> org.apache.james.util.retry.* packages as this retry functionality is
>>>> generic and reusable. In fact, there are no references to other James
>>>> packages here.
>>>>
>>>> Q1: Are there any objections to factoring the generic behaviour into
>>>> org.apache.james.util. as done here? If so, we can repackage. Where 
>>>> else
>>>> should it live?
>>>>
>>>> Q2: I've introduced interfaces into the maven james-server-util 
>>>> project.
>>>> Some, but not all, other projects have been split to separate classes
>>>> from interfaces. Do we need to do this here? Or should we wait 
>>>> until the
>>>> interfaces are actually used outside of the james-server-util project?
>>>>
>>>> Cheers
>>>> Steve
>>>>
>>>>
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>>>
>>
>>
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>

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