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From Ralph Goers <ralph.go...@dslextreme.com>
Subject Re: Flume-NG Channels
Date Thu, 12 Jan 2012 05:24:25 GMT
One thing I've learned from working on Log4j 2.0 is that for loops are actually a lot slower
than you might think. In a configuration that desires a single channel there should be no
for loop. Instead, it should go directly to the channel. In the case of multiple channels
then the "channel" that is selected should be a multiplexing channel that is configured with
other channels. The for loop (or while loop) is in the multiplexing channel.

Thus, your ChannelSelector could (and should) in fact, be a Channel that can select any or
all of its configured channels.

FWIW, in Log4j 2 in the XML configuration you would specify

<RollingFileAppender name="MainAppender" ...>
  <MarkerFilter marker="MyMarker"/>
</RollingFileAppender>

or 

<RollingFileAppender" name="MainAppender" ...>
  <filters>
    <MarkerFilter marker="MyMarker"/>
    <ThresholdFilter level="DEBUG"/>
  <filters>
</RollingFileAppender>

The filters element is actually a CompositeFilter that invokes each of its configured filters
in turn.

Ralph

On Jan 11, 2012, at 5:55 PM, Arvind Prabhakar wrote:

> Hi Praveen,
> 
> Here is what I could muster up after some thought on this use-case:
> 
> We modify the source interface to accept a "Channel Processor", a new component that
is responsible for putting the event into one or more channels. 
> A channel processor will delegate the selection of the channel to place the event on
via another component called "Channel Selector" which is responsible for selecting the appropriate
channel from the list of channels the source is configured with.
> The default implementation of channel selector in the channel processor will be a "replicating
channel selector" which will result in the event being copied over to all configured channels.
> Another implementation of the channel selector will be "Mapping Channel Selector" which
will allow events to be mapped to different channel(s) based on the value of a specified header.
> 
> With this facility, you will be able to inject headers into events at the point of origination
and then configure the mapping channel selector at each source in the pipeline to place the
event on separate channels as desired based on the value of the header.
> 
> Do you think this will adequately address your use case? If not, what do you think is
missing here.
> 
> Thanks,
> Arvind
> 
> 
> On Tue, Jan 10, 2012 at 8:03 PM, Praveen Ramachandra <praveen_ramachandra@yahoo.com>
wrote:
> Hi
> 
> Security is not the reason for isolation.
> 
> Isolation could be used to realize quite a few quality attributes of the system, e.g.,
many aspects of QoS.
> 
> Regardless, if we have specific event handling requirement that are different for each
"kind" of data the question is how do one realize it using flume-ng.
> 
> As it stands currently, sources/sinks & channels are tied to the hip, which is fine.
Only issue is requiring to allocate dedicated host/port to achieve. 
> 
> 
> As I had mentioned in my first email, one could develop custom sources/sinks and configuration
that goes along with to mux/demux events that are flowing through the system. 
> 
> Question to ask ourself is, why is there a need to have a change in deployment to accommodate
a new "flow" in the system.
> 
> 
> 
> --
> Regards,
> Praveen Ramachandra
> 
> From: Ralph Goers <ralph.goers@dslextreme.com>
> To: flume-user@incubator.apache.org 
> Sent: Tuesday, January 10, 2012 6:01 PM
> Subject: Re: Flume-NG Channels
> 
> When you speak of flow isolation are you doing that for security, failure protection
or for some other reason?  From a failure protection case you would need physically different
Flume agents, not just channels. I'm not sure what the security gains are in isolation, if
any.
> 
> I guess to give you a proper response I would want to know what your actual requirements
are and possibly why. 
> 
> For what its worth, I also work in a multi-tenant environment and this has never been
a requirement. 
> 
> Ralph
> 
> 
> 
> On Jan 10, 2012, at 12:42 AM, Praveen Ramachandra wrote:
> 
>> Hi arvind,
>> 
>> Thanks for responding.
>> 
>> if we want to model separation not only in transit but also at rest i.e., if channel
has a filechannel/jdbcchannel/memorychannel backing separation is required when data resides
in those channels before they are shipped to the next hop.
>> 
>> on multi-tenant, I was trying to figure out from isolation perspective. Flow isolation
is required from one collecting agent tier, to aggregating agent-tier and a tier that is going
to deposit/deliver the events.
>> 
>> "How do you propose the platform be modified in order to support this use-case?"
you ask, Thinking out loud now :-).
>> One option is to have a notion of a flow that is visible at flume-ng level, applications
will map channels to flows and sources/sinks across agent tiers, can mux/demux it appropriately.
>> 
>> This will also decouple mapping across agent tiers i.e., 
>> 
>> If you smell scribe in my above description, I wouldn't hold it against you :-).
Honestly the simplicity of scribe let us prototype for our use case in a matter of hour or
two, compared to many days that it took to get almost similar thing prototyped with flume.
We even struggle today to model the use cases seamlessly in flume (og or ng).
>> 
>> 
>> --
>> Regards,
>> Praveen Ramachandra
>> 
>> 
>> 
>> 
>> From: Arvind Prabhakar <arvind@apache.org>
>> To: flume-user@incubator.apache.org; Praveen Ramachandra <praveen_ramachandra@yahoo.com>

>> Sent: Monday, January 9, 2012 11:15 PM
>> Subject: Re: Flume-NG Channels
>> 
>> Hi Praveen,
>> 
>> First to your question:
>> 
>> > Did I get the modeling right with flume-ng
>> 
>> More-or-less yes. The one distinction that I would like to point out
>> is that having separate source-sink end points for individual channels
>> is stemming more from your requirement than by design of flume. A
>> channel in flume implementation does not care how many sources write
>> to it or how many sink's read from it.
>> 
>> > 2. Is there a better way to do it at a platform level
>> >             2.1 I know if I can write a bunch of custom sinks/sources and
>> > embed a notion of channel to which each events belong to in the message, I
>> > can effectively mux and demux the events at either ends.
>> 
>> The key issue here is the layering of a multi-tenant semantic on top
>> of flows. Since fundamentally flume is not aware of the contents of
>> the events in a flow, and does not expose any client auth/id model -
>> there is no inherent support of doing this out of the box.
>> 
>> Moreover, from your description it seems that the channels that
>> logically separate out the flows will operate within the same agent.
>> If that is the case, then it may be a better option to use a single
>> channel and have a multiplexing terminal sink that can route the
>> messages to the correct destination.
>> 
>> >             2.2 Which means the default support for channel is also not of
>> > much use
>> 
>> How do you propose the platform be modified in order to support this use-case?
>> 
>> Thanks,
>> Arvind
>> 
>> 
>> 
>> On Mon, Jan 9, 2012 at 9:36 PM, Praveen Ramachandra
>> <praveen_ramachandra@yahoo.com> wrote:
>> > They are in low 100's in the best case scenario, and could be in 1000 in the
>> > worst case scenario.
>> >
>> > I believe this aspect can be pretty much shielded from application if the
>> > underlying platform has the right set of responsibilities.
>> >
>> >
>> > --
>> > Regards,
>> > Praveen Ramachandra
>> >
>> >
>> >
>> > ________________________________
>> > From: Ralph Goers <ralph.goers@dslextreme.com>
>> > To: flume-user@incubator.apache.org
>> > Sent: Monday, January 9, 2012 6:53 PM
>> > Subject: Re: Flume-NG Channels
>> >
>> >
>> > On Jan 9, 2012, at 2:28 AM, Praveen Ramachandra wrote:
>> >
>> > Hi,
>> >
>> > We were trying to design a multi-tenanted system using flume-ng, where each
>> > logically independent data set is modelled through a channel going through
>> > the system of collectors, aggregators and delivery agents (to end
>> > destination). Each channel will carry data that logically belong together.
>> > The requirement is that we should be able to bring up and tear down a
>> > channel with ease.
>> >
>> >
>> > When we completed the exercise, it turned out that we have to run a separate
>> > Source/Sink, at a designated host/port combination for each channel. The
>> > issue with this is that, it is an operational overhead that we have work
>> > with net-ops to punch holes in the firewall to let tcp traffic flow on
>> > non-standard ports. I would imagine that it would be the case in many
>> > organizations as well.
>> >
>> > Two questions.
>> >
>> > 1. Did I get the modeling right with flume-ng
>> > 2. Is there a better way to do it at a platform level
>> >             2.1 I know if I can write a bunch of custom sinks/sources and
>> > embed a notion of channel to which each events belong to in the message, I
>> > can effectively mux and demux the events at either ends.
>> >             2.2 Which means the default support for channel is also not of
>> > much use
>> >
>> >
>> > What is your target destination(s) for the tenants?  Can they all flow
>> > through a single channel in Flume and then be delivered to the correct
>> > destination by a smarter sink at the end?
>> >
>> > Ralph
>> >
>> >
>> 
>> 
> 
> 
> 
> 


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