use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again
I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again
I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again Agony
I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again I will never use distributed transactions again Agony and Pain lots of Pain
Locks break encapsulation • Taking too few locks • Taking too many locks • Taking the wrong locks • Taking locks in the wrong order • Error recovery is hard
to a DB: begin, commit, rollback (ACI) • Transactions are retried upon collision • Rolls back the memory on abort • Transactions can nest and compose • Use STM instead of abusing your database with temporary storage of “scratch” data • Examples: Haskell, Clojure & Scala STM
function to the Agent, which 1. adds it to an (ordered) queue, to be 2. applied to the Agent asynchronously • Reads are “free”, just dereferences the Ref • Cooperates with STM • Examples: Clojure & Akka Agents
If this thread blows up you are screwed • So you need to do all explicit error handling WITHIN this single thread • To make things worse - errors do not propagate between threads so there is NO WAY OF EVEN FINDING OUT that something have failed Failure Recovery in Java/C/C# etc.
If this thread blows up you are screwed • So you need to do all explicit error handling WITHIN this single thread • To make things worse - errors do not propagate between threads so there is NO WAY OF EVEN FINDING OUT that something have failed • This leads to DEFENSIVE programming with: Failure Recovery in Java/C/C# etc.
If this thread blows up you are screwed • So you need to do all explicit error handling WITHIN this single thread • To make things worse - errors do not propagate between threads so there is NO WAY OF EVEN FINDING OUT that something have failed • This leads to DEFENSIVE programming with: • Error handling TANGLED with business logic Failure Recovery in Java/C/C# etc.
If this thread blows up you are screwed • So you need to do all explicit error handling WITHIN this single thread • To make things worse - errors do not propagate between threads so there is NO WAY OF EVEN FINDING OUT that something have failed • This leads to DEFENSIVE programming with: • Error handling TANGLED with business logic • SCATTERED all over the code base Failure Recovery in Java/C/C# etc.
If this thread blows up you are screwed • So you need to do all explicit error handling WITHIN this single thread • To make things worse - errors do not propagate between threads so there is NO WAY OF EVEN FINDING OUT that something have failed • This leads to DEFENSIVE programming with: • Error handling TANGLED with business logic • SCATTERED all over the code base Failure Recovery in Java/C/C# etc. We can do better!!!
• Each running process has a supervising process • Errors are sent to the supervisor (asynchronously) • Supervisor manages the failure • Same semantics local as remote • For example the Actor Model solves it nicely
Transparency is the ultimate goal 2. Automatic object replication is desirable 3. All replicas are equal and deterministic Classic paper: A Note On Distributed Computing - Waldo et. al.
a distributed environment • Distributed Objects • “Sucks like an inverted hurricane” - Martin Fowler • Distributed Transactions • ...don’t get me started... Fallacy 1
across the network • Ignores: • Latency • Partial failures • General scalability concerns, caching etc. • “Convenience over Correctness” - Steve Vinoski
message is - sent out on the network? 2. The message is - received by the receiver host’s NIC? 3. The message is - put on the receiver’s queue? 4. The message is - applied to the receiver?
message is - sent out on the network? 2. The message is - received by the receiver host’s NIC? 3. The message is - put on the receiver’s queue? 4. The message is - applied to the receiver? 5. The message is - starting to be processed by the receiver?
message is - sent out on the network? 2. The message is - received by the receiver host’s NIC? 3. The message is - put on the receiver’s queue? 4. The message is - applied to the receiver? 5. The message is - starting to be processed by the receiver? 6. The message is - has completed processing by the receiver?
(0 additional cost) 2. Add the guarantees you need - one by one Different USE-CASES Different GUARANTEES Different COSTS For each additional guarantee you add you will either: • decrease performance, throughput or scalability • increase latency
Impedance Mismatch • We need functional processing, transformations etc. • Examples: Spark, Crunch/Scrunch, Cascading, Cascalog, Scalding, Scala Parallel Collections • Hadoop have been called the: • “Assembly language of MapReduce programming” • “EJB of our time”
• When is Eventual Consistency a better fit? • Different kinds of data has different needs • You need full consistency less than you think Then think again
and measure • Start by defining a baseline • Where are we now? • Define what is “good enough” - i.e. SLAs • Where do we want to go? • When are we done? • Beware of micro-benchmarks
defining a baseline • Where are we now? • Define what is “good enough” - i.e. SLAs • Where do we want to go? • When are we done? • Beware of micro-benchmarks ...or, when can we go for a beer?
others • Every strategic decision involves a trade-off • There's no "silver bullet" 2. Applying yesterday's best practices to the problems faced today will lead to: • Waste of resources • Performance and scalability bottlenecks • Unreliable systems