Karma

The karma module provides a way to limit Transactions. Users are limited in the number and timing of transactions by various karma parameters. There is one user called the Oracle who has unlimited access.

#Installation

To install, include the karma contract in the genesis.json file when starting the chain for the first time:

{
  "vm": "plugin",
  "format": "plugin",
  "name": "karma",
  "location": "karma:1.0.0",
  "init": {
  }
}

#Activation and zeknd.yaml

Activating the karma functionality is done from the zeknd.yaml configuration file.

  • KarmaEnabled bool Flag that sets the karma module on or off.

  • KarmaSessionDuration int64 A Time period in seconds. Karma restricts users to a configurable number of transactions during any interval of SessionDuration seconds.

  • KarmaMaxCallCount int64 Base value used to calculate the number of call Transaction permitted per SessionDuration. A KarmaMaxCallCount int64 of 0 indicates there is no limit imposed.

  • KarmaMaxDeployCount int64 Base value used to calculate the number of deploy Transaction permitted per SessionDuration. A KarmaMaxDeployCount int64 of 0 indicates there is no limit imposed.

Example zeknd.yaml fragment:

#Accessing karma methods

Public karma methods can either be run either directly in code using one of the SDKs or from the command line the using zeknd executable.

This will print the following output:

#Oracle

  • It is defined in the genesis file and can be updated by the UpdateOraclekarma method.

  • Note that the oracle is unaffected by karma restrictions.

  • To successfully call the following karma configuration transactions it is necessary to reference the oracle:

    • AppendSourcesForUser

    • DeleteSourcesForUser

    • ResetSources

    • UpdateOracle

  • If no oracle has been set yet then anyone can call UpdateOracle. If an oracle has been set, it is necessary to know the old oracle in order to update it using UpdateOracle.

Example genesis file entry.

#zeknd karma update-oracle

The oracle can be updated using the zeknd update-oracle command, which uses the UpdateOracle karma method:

The output should be similar to this:

As an example, let's say default:0xDeffe041cC978a193fCf0CE18b43b25B4592FC90 is the current oracle and ./cmd/zeknd/data/priv_key is the path to the oracle's private key . Then, we could update the oracle like this:

On success, it will print:

The old oracle can be omitted if no oracle has been set yet.

#Sources

Karma is generated by sources. Sources could correspond to different user types, privilege levels, promotions or temporary changes in status.

Nameis a descriptive name (string) used to identify a source. Reward is used to multiply karma associated with the source. A high Reward value means each point of karma generated by the source has more effect than a source with a lower Reward.

Sources can be configured in the genesis.json file or later by calling the karma GetSources and ResetSources methods.

#Sources: Genesis File

Sources can be set up in the karma init segment of the DAppChain genesis file. This allows sources to be available the first time the DAppChain is run. Let's take a look at an example:

This starts the DAppChain with three sources- "sms", "oauth" and "token". Each source has a different reward level.

#Sources: ResetSources

The karma method ResetSources is used to reset the karma parameters, including the sources, for a running DAppChain.

You might want to download the existing parameters with GetSourcesand amend that before using them to set the karma configuration with UpdateConfig.

#zeknd karma get-sources

To learn more about the available commands, type:

You should see something like this:

Here's an example:

will print

#zeknd karma reset-sources

The sources can be reset via the zeknd karma update-sources command.

If you want to add to the list of existing sources, you might want to get the list of existing sources first by running zeknd karma get-sources.

Let’s use the built-in help that to discover the available parameters and flags:

You should see something similar to this:

For example, if default:0xDeffe041cC978a193fCf0CE18b43b25B4592FC90 has previous been set as the oracle, you could reset sources by running:

You should see:

#go-zeknd update sources

The following Go code fragment gives an example of how you might do this in Go using go-zeknd.

Note: error checking is skipped for readability.

#Users

If karma has been enabled, each user will be restricted in the transactions they can call by their karma allocation. The following restrictions apply:

#Deploy transactions

Strictly positive karma is required to do any transactions.

If KarmaMaxDeployCount is zero then there is no limit imposed.

Otherwise, users will only be able to deploy a maximum of KarmaMaxDeployCount transactions within a period of SessionDurationseconds.

#Call transactions

Strictly positive karma is required to do any transactions.

If KarmaMaxCallCount is zero then there is no limit imposed.

Otherwise, users will only be able to make KarmaMaxCallCount + total karma call transactions in any period of SessionDuration seconds. The total karma is calculated from the count of sources held by the user as described below.

#User Karma

Each user will be associated with zero or more sources. This list may contain:

  • active sources (in karma's current list of sources) or

  • inactive sources (not currently in the list of current sources)

Name identifies a source and corresponds to the Name field in the KarmaSourceReward. Count the number of a particular source associated with the address. The amount of karma a source provides to a user is equal to KarmaSource.Count * KarmaSourceReward.Reward.

The total amount of karma is the sum of the karma from each active karma source associated with the user.

The sources associated with a user can be configured either in the genesis file or by the karma methods AppendSourcesForUser and DeleteSourcesForUser.

#Users: Genesis File

Users can be associated with sources in the genesis file. This allows users to have karma available as soon new DAppChain spins up. For example:

This genesis file fragment will create three sources and give the user with local address QjWhaN9qvpdI9MjS1YuL1GukwLc:

  • 10 rewards from oauth and

  • 3 rewards from token.

This user would then start with 10*3 + 3*4 = 42 karma.

#Users: AppendSourcesForUser and DeleteSourcesForUser

In a running DAppChain, we can add a source to a user with the karma method AppendSourcesForUser. In order to do so, we need a list of the names of the new sources, plus a count of the number of rewards. Note that sources can be removed by calling DeleteSourcesForUser.

#zeknd karma append-sources-for-user

New sources can be associated with a user by calling the karma method AppendSourcesForUser. You can also access it via the CLI:

For example, if default:0xDeffe041cC978a193fCf0CE18b43b25B4592FC90 is the oracle and default:0xAfaA41C81A316111fB0A4644B7a276c26bEA2C9F the user to which we want to add a new source, you would want to run something similar to this:

The output of the above command looks like:

#zeknd karma delete-sources-for-user

Existing sources can be disassociated with a user using the karma method DeleteSourcesForUser. To do the same, you can use the zeknd karma delete-sources-for-user.

To see the list of available command line parameters and flags, type:

This command displays the following output:

Say default:0xDeffe041cC978a193fCf0CE18b43b25B4592FC90 is the oracle and default:0xAfaA41C81A316111fB0A4644B7a276c26bEA2C9F the user from which we want to remove sources. We'll delete the sources by running:

Once the sources are deleted, the above command will print:

#zeknd karma get-user-state

To get the list of sources that have been associated with a user, you can use the zeknd karma get-user-state command.

First, let's take a look at the syntax:

Output:

For example, if default:0xDeffe041cC978a193fCf0CE18b43b25B4592FC90 is the user, you can get the list of the user's sources with the following command:

#Karma methods

The following methods can be called by anyone:

  • GetSources(ctx contract.StaticContext, ko *types.Address) (*ktypes.KarmaSources, error). Returns the current karma configuration details. This includes the current sources.

  • GetTotal(ctx contract.StaticContext, params *types.Address) (*karma.KarmaTotal, error) Returns the total amount of karma in the system. It sums up the karma for each user that has been associated with a source.

  • UpdateOracle(ctx contract.Context, params *ktypes.KarmaNewOracleValidator) error. This function can only be called by referencing the oracle unless there is no oracle yet.

The following methods can only be called by referencing the oracle:

  • ResetSources(ctx contract.Context, kpo *ktypes.KarmaSourcesValidator) error. Resets the list of possible sources.

  • AppendSourcesForUser(ctx contract.Context, ksu *karma.KarmaStateUser) error. Associate a collection of sources with counts for a user. See above for details.

  • DeleteSourcesForUser(ctx contract.Context, ksu *karma.KarmaStateKeyUser) error Disassociate a collection of sources for a user. See above for details.

Other methods:

  • Meta() (plugin.Meta, error)

  • Init(ctx contract.Context, req *InitRequest) error

#Genesis entries

An example genesis file entry is shown below:

A few things to note:

  • if the init block is left empty, it will just install the karma contact on the DAppChain.

  • You can define an Oracle in the genesis file. As an alternative, you can create an oracle later by calling the karma method UpdateOracle.

  • It is possible to initialize the karma contract with a list of karma sources. If you do this, you can also allocate a list of users to have allocated amounts of these sources.

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