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From "arvind@cloudera.com" <arv...@cloudera.com>
Subject Re: Flume-NG Channels
Date Thu, 12 Jan 2012 06:04:29 GMT
Point taken Ralph - avoiding a for-loop within the implementation of a
channel selector is important for performance. In this particular case
(that Praveen describes), the channel selector will be making a mapping
based decision. For example:

header value  --> channel
"stock" --> "ticker channel"
"temp" --> "weather channel"

All of this information will be statically configured for the agent and so
the selector will be able to configure itself during initialization and
create this mapping. Once setup, when an event arrives, the lookup will be
constant time to figure out which channel must be used (hashtable/hashmap).

Do you see any issues with such implementation?

Thanks,
Arvind


On Wed, Jan 11, 2012 at 9:24 PM, Ralph Goers <ralph.goers@dslextreme.com>wrote:

> 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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