wasmd/x/wasm

Wasm Module

This should be a brief overview of the functionality

Configuration

You can add the following section to config/app.toml:

[wasm]
# This is the maximum sdk gas (wasm and storage) that we allow for any x/wasm "smart" queries
query_gas_limit = 300000
# This defines the memory size for Wasm modules that we can keep cached to speed-up instantiation
# The value is in MiB not bytes
memory_cache_size = 300

The values can also be set via CLI flags on with the start command:

--wasm.memory_cache_size uint32     Sets the size in MiB (NOT bytes) of an in-memory cache for wasm modules. Set to 0 to disable. (default 100)
--wasm.query_gas_limit uint         Set the max gas that can be spent on executing a query with a Wasm contract (default 3000000)

Events

A number of events are returned to allow good indexing of the transactions from smart contracts.

Every call to Instantiate or Execute will be tagged with the info on the contract that was executed and who executed it. It should look something like this (with different addresses). The module is always wasm, and code_id is only present when Instantiating a contract, so you can subscribe to new instances, it is omitted on Execute. There is also an action tag which is auto-added by the Cosmos SDK and has a value of either store-code, instantiate or execute depending on which message was sent:

{
    "Type": "message",
    "Attr": [
        {
            "key": "module",
            "value": "wasm"
        },
        {
            "key": "action",
            "value": "instantiate"
        },
        {
            "key": "signer",
            "value": "cosmos1vx8knpllrj7n963p9ttd80w47kpacrhuts497x"
        },
        {
            "key": "code_id",
            "value": "1"
        },
        {
            "key": "_contract_address",
            "value": "cosmos14hj2tavq8fpesdwxxcu44rty3hh90vhuc53mp6"
        }
    ]
}

If any funds were transferred to the contract as part of the message, or if the contract released funds as part of it's executions, it will receive the typical events associated with sending tokens from bank. In this case, we instantiate the contract and provide a initial balance in the same MsgInstantiateContract. We see the following events in addition to the above one:

[
    {
        "Type": "transfer",
        "Attr": [
            {
                "key": "recipient",
                "value": "cosmos14hj2tavq8fpesdwxxcu44rty3hh90vhuc53mp6"
            },
            {
                "key": "sender",
                "value": "cosmos1ffnqn02ft2psvyv4dyr56nnv6plllf9pm2kpmv"
            },
            {
                "key": "amount",
                "value": "100000denom"
            }
        ]
    }
]

Finally, the contract itself can emit a "custom event" on Execute only (not on Init). There is one event per contract, so if one contract calls a second contract, you may receive one event for the original contract and one for the re-invoked contract. All attributes from the contract are passed through verbatim, and we add a _contract_address attribute that contains the actual contract that emitted that event. Here is an example from the escrow contract successfully releasing funds to the destination address:

{
    "Type": "wasm",
    "Attr": [
        {
            "key": "_contract_address",
            "value": "cosmos14hj2tavq8fpesdwxxcu44rty3hh90vhuc53mp6"
        },
        {
            "key": "action",
            "value": "release"
        },
        {
            "key": "destination",
            "value": "cosmos14k7v7ms4jxkk2etmg9gljxjm4ru3qjdugfsflq"
        }
    ]
}

Pulling this all together

We will invoke an escrow contract to release to the designated beneficiary. The escrow was previously loaded with 100000denom (from the above example). In this transaction, we send 5000denom along with the MsgExecuteContract and the contract releases the entire funds (105000denom) to the beneficiary.

We will see all the following events, where you should be able to reconstruct the actions (remember there are two events for each transfer). We see (1) the initial transfer of funds to the contract, (2) the contract custom event that it released funds (3) the transfer of funds from the contract to the beneficiary and (4) the generic x/wasm event stating that the contract was executed (which always appears, while 2 is optional and has information as reliable as the contract):

[
    {
        "Type": "transfer",
        "Attr": [
            {
                "key": "recipient",
                "value": "cosmos14hj2tavq8fpesdwxxcu44rty3hh90vhuc53mp6"
            },
            {
                "key": "sender",
                "value": "cosmos1zm074khx32hqy20hlshlsd423n07pwlu9cpt37"
            },
            {
                "key": "amount",
                "value": "5000denom"
            }
        ]
    },
    {
        "Type": "wasm",
        "Attr": [
            {
                "key": "_contract_address",
                "value": "cosmos14hj2tavq8fpesdwxxcu44rty3hh90vhuc53mp6"
            },
            {
                "key": "action",
                "value": "release"
            },
            {
                "key": "destination",
                "value": "cosmos14k7v7ms4jxkk2etmg9gljxjm4ru3qjdugfsflq"
            }
        ]
    },
    {
        "Type": "transfer",
        "Attr": [
            {
                "key": "recipient",
                "value": "cosmos14k7v7ms4jxkk2etmg9gljxjm4ru3qjdugfsflq"
            },
            {
                "key": "sender",
                "value": "cosmos14hj2tavq8fpesdwxxcu44rty3hh90vhuc53mp6"
            },
            {
                "key": "amount",
                "value": "105000denom"
            }
        ]
    },
    {
        "Type": "message",
        "Attr": [
            {
                "key": "module",
                "value": "wasm"
            },
            {
                "key": "action",
                "value": "execute"
            },
            {
                "key": "signer",
                "value": "cosmos1zm074khx32hqy20hlshlsd423n07pwlu9cpt37"
            },
            {
                "key": "_contract_address",
                "value": "cosmos14hj2tavq8fpesdwxxcu44rty3hh90vhuc53mp6"
            }
        ]
    }
]

A note on this format. This is what we return from our module. However, it seems to me that many events with the same Type get merged together somewhere along the stack, so in this case, you may end up with one "transfer" event with the info for both transfers. Double check when evaluating the event logs, I will document better with more experience, especially when I find out the entire path for the events.

Messages

TODO

CLI

TODO - working, but not the nicest interface (json + bash = bleh). Use to upload, but I suggest to focus on frontend / js tooling

Rest

TODO - main supported interface, under rapid change