Breakout session: cost model

April 2018 developer's conference

Regions and impact on costing

• If east costs more than central, and 

  • If there are more validators in a region, then it would cost more to operate in that region

  • IS there a concept of the number (min and max) of the validators in a region?

How do you split out rewards to the validators?

• PROPOSAL: Distribute rewards evenly (or even stake-weighted) to validators

  • Problem: Free-riding: 

• CONCERN: What if a validator turns on and off every 45 seconds, and then they get rewards (free-riding)

  • Free rider is a validator who watches the results of other validators and says they did it to get the reward

  • This problem is not unique to RChain. It is a problem that needs to be solved.

  • IDEA - TSA solution: To solve for an inattention problem, TSA inserts knives into bags that are not there. 

    • Insert a bogus transaction to force the network to ID, those who validate are free-riders
  • IDEA - The abusive boyfriend protocol
    • You know there are lies out there, if you sign something without checking it, then you are a free-rider
    • This is part of the consensus protocol
  • IDEA - Rewards are only distributed after the block is finalized. If you're block is not doing anything, then no rewards for you "Little Red Hen" concept

Ways to make REV

• Inflation
• Validation fees

How and when do fees change?

• Cost of storage 

When is the measure of the namespace determined? How is it established?

• ANSWER: It is determined by the region (the sum of measure of the regions) determined by the genesis block.
  • Regions establish the cost measures
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• Why can't it be the namespace?
  • Example: namespaces could come up with a costs model (A v B), but then C wants to join
  • ANSWER: This is prohibitive because it would require storage at the top
• It is important that the measures of the regions don't change frequently because it will impact trust
• You want namespaces that are in a federated, competitive market
  
  • You may decide to trade slowness for safety
  • You may decide to trade fastness for insecurity
  • What we want from the network is to have both extremes in the network

How is rent distributed?

• Costs increase as safety goes up
  • Ideal is to find a place in the middle where the least achievable amount of safety is allowed.
  • 

What's the difference between a region and a namespace?

• Nothing
• A region is the smallest version of a namespace
• This makes top-level transactions very expensive
• It's cheaper to interact with your trusted network
• Introduces competition based on cost (market economics)

Should validators decide costs by region?

• Should there be a default for the region?
• Regions determine costs, not namespaces

Contract mobility and region fee-setting

• How do you move a contract from region 1 to region 2?
• What if a region becomes a cartel?
  • Can validators in a region alter the price?
  • There is a dis-incentive because no one will want to join
  • But the ones stuck there will be held hostage
• The solution is that to become a validator you have to be approved at the top level.
  • Local price information is published globally
  • You need agreement globally to change the price regionally
• Are costs determined by humans?
  • Humans establish the region and standards and push for global consensus
  • Then the market can choose to participate in the region or not
• If a region can identify a region that is a cartel, you can set a standard not to process those transactions. You can set the stand
  • How much would Target spend to underprice Walmart?
  • You want everyone to lower the price as much as possible to encourage transaction volume (like multiple fast food locations at a single intersection)

If 2 '@foo' contracts are deployed simultaneously, how is it determined which contract points to which wallet 

• ANSWER  - When you deploy something there is a wallet in the same message, so you just pass the wallet

What happens when a contract runs out of Phlo?

• The block records what has happened so far and add a notice that it's out of phlo
• The network would store a record (a try) of contracts that ran out of phlo
  • Hash the computation and store the effect as a record in a log of contracts that ran out of phlo
  • Need to avoid replay attacks, where more than one person adds phlo to refuel the contract

OPTION A - Storage

• As time goes on the number of effects you have to keep track of more and more 
• You do have to keep track of what has been revived - this is the tricker part, trickier than reviving
  • What data structure would you use to track?
  • A complete try leaves a hole, which results in rewriting the try

Option B - Running to quiescence

•  
• Runs until there is nothing left to run
• Allows you to track when you're done
• It doesn't have to be sequential
• Kyle advocates to not run code that creates multiple races
  • The network will decide who wins what race
    • Could create slowness on the network
      • If you don't want to slowness due to resourcing for race designs, then don't write code like that. Suggestion is to write it differently.
      • Is it expensive and slow for the person writing it or for the validators?
• If running to quiescence then, one validator decides the race
  • Race winners are fair. They are just non-deterministic
  • If you want fair, write better code
• Example: Network has 100 validators, you opt for validation from three.
  • Transaction sent to 3 with a bunch of serial races, each validator calculates a trace and broadcasts to the network, the network decides the winner
  • No single actor knows which one will be selected as the winner (it's safe and not fair)
• You deploy and pay for all computation until it reaches quiescence
  • This disincentives others for writing on the platform (ex data feed will be expensive)
  • Nash, don't do this because no one will write an oracle if this is the case (required to run to quiescence)
  • Joe proposes deployer pays. If you invoke someone else's contract, you pay for it.
• This is Kyle's recommendation

Does phlo persist from block to block during a computation?

• Deploy (P) and Deploy (Q) exist and don't overlap overlap in the tuplespace.
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  • Henry needs to know this as it relates to storage
  • We want to be able to persist code is such a way that when someone runs it you continue paying
• What happens when the cost of running a contract fluctuates?
  • The phlo-balance-pointer solves for this
  • 
• Deployer pays until quiescence
  • Mike wants I want to send data and not pay for it
  • Think about each term of a contract being it's own tiny contract
• Would people have phlo wallets?
  • No. You don't get phlo back if it runs to quiescence
  • If there is any phlo let at the end of all your reductions, then you get change
    • Incentivizes running the contract to completion
    • Storage layer keeps a reference counter. If phlo not zero, then give change.
• If your code produces things in another namespace, your reference count remains 1 until you hear back from the other namespace that they've reached quiescense
  • Your phlo number would have to be synced across namespaces if contract is run across namespaces

How does rent work?

• Example, chess clock. Timed when contract is in the tuplespace, timed when contract is being executed. Rent is being charged when you're not running