[erlang-questions] Is Erlang ideal for a global exchange?

[xu xiut]

https://github.com/LMAX-Exchange/disruptor/wiki/Introduction

Does the disruptor still sound like Riak?

On Tue, Jan 13, 2015 at 10:36 AM, T Ty <tty.erlang@REDACTED> wrote:

> Your comment is quite interesting. My take-away from reading the LMAX
> article wasn't the single threaded business logic process nor the shared
> memory communication.
>
> My take-aways were:
>
> 1. pipelining. Do all input validation and transformation before/after
> main business logic processing. This makes coding the 'happy-path' easier
> and keeps the business logic core small.
>
> 2. the business logic process is a master process that reacts to events
> and generate events. This allows scaling of the business logic process as
> it makes it easier to spawn processes to deal with the events.
> (gen_event/gen_fsm triggering supervisor in simple_one_for_one that starts
> other processes)
>
> 3. Event Sourcing. One added benefit is compliance. It is easier to
> demonstrate compliance when there are events to show how the system changed
> from one state to another. Compliance here can mean security compliance or
> regulatory compliance.
>
> 4. business logic processor deals with events in-memory. mnesia ram_tables
> fit this criteria easily as do ets tables.
>
> 5. Business Logic State Snapshot. Not only does this allow resilience
> between node restarts it also allows migrating the partial process to a
> different node entirely.
>
> 6. Avoiding external service calls in the Business Logic process.
> Transition to an event based model for interacting with external services.
> Have a middle layer of gen_fsm to determine where in the logic the current
> process is in.
>
> 7. Mention about session data being transient and can be discarded. Aka
> let process die and supervisor restart.
>
> The Disruptor sounds like Riak.
>
> Cheers
>
> On Tue, Jan 13, 2015 at 2:11 PM, Mihai Balea <mihai@REDACTED> wrote:
>
>>
>> > On Jan 12, 2015, at 4:10 AM, T Ty <tty.erlang@REDACTED> wrote:
>> >
>> > The LMAX architecture is an easy fit for Erlang and one which an
>> Erlanger would naturally arrive to.
>>
>> I beg to differ. LMAX uses a single threaded process to implement its
>> entire business logic, which makes it highly sensitive to sequential
>> performance. This is not one of Erlang’s strong points. Also, the
>> disruptors - which are essentially fancy circular buffers - depend on
>> preallocated memory and destructive updates to attain their performance.
>> Finally, the communication between various stages in the pipeline is done
>> through shared memory, and they do some clever tricks to avoid locking.
>>
>> Yes, you could emulate this architecture in Erlang, but you won’t get
>> anywhere near LMAX’s performance.
>>
>> Mihai
>>
>>
>
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