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12 | 12 | {-# OPTIONS_GHC -Wno-unticked-promoted-constructors #-} |
13 | 13 |
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14 | 14 | -- | Node IPC protocols |
| 15 | +-- |
| 16 | +-- This module provides the client side of the node-to-client IPC protocol |
| 17 | +-- used to communicate with a local Cardano node. This can be used to |
| 18 | +-- query the node for information, to submit transactions, and even to |
| 19 | +-- get historical information aobut the chain by using the |
| 20 | +-- 'ChainSync' protocol. |
15 | 21 | module Cardano.Api.Internal.IPC |
16 | | - ( -- * Node interaction |
| 22 | + ( -- * Examples |
| 23 | + |
| 24 | + -- | In this section, we show two examples: one for querying the node |
| 25 | + -- and obtain some basic information, and another one for submitting a |
| 26 | + -- transaction to the node. |
| 27 | + -- |
| 28 | + -- To find out about how to create a transaction, see the documentation |
| 29 | + -- in "Cardano.Api.Internal.Tx.Body". |
| 30 | + -- |
| 31 | + -- For the following examples we will use the following qualified imports |
| 32 | + -- from @cardano-api@: |
| 33 | + -- |
| 34 | + -- @ |
| 35 | + -- import qualified Cardano.Api as Api |
| 36 | + -- import qualified Cardano.Api.Consensus as Consensus |
| 37 | + -- import qualified Cardano.Api.Network as Network |
| 38 | + -- import qualified Cardano.Api.Shelley as Shelley |
| 39 | + -- @ |
| 40 | + -- |
| 41 | + -- We will also use the following explicit import from @base@: |
| 42 | + -- |
| 43 | + -- @ |
| 44 | + -- import Control.Monad.Except (runExceptT) |
| 45 | + -- @ |
| 46 | + -- |
| 47 | + -- And we will assume we are working on top of the @IO@ monad and that |
| 48 | + -- we have unqualified access to the @Prelude@ module. |
| 49 | + |
| 50 | + -- ** Constructing connection information |
| 51 | + |
| 52 | + -- | Independently of whether we want to query the node or submit transactions, |
| 53 | + -- the first thing we need to do is to gather the connection information. |
| 54 | + -- |
| 55 | + -- We need three pieces of information: |
| 56 | + -- |
| 57 | + -- * The number of slots per epoch for the network the node is connected to. |
| 58 | + -- We can obtain this information by looking for the @epochLength@ key in |
| 59 | + -- the @shelley-genesis.json@ file that the node is using to connect to the |
| 60 | + -- network. For the preview network, this is currently @86_400@. |
| 61 | + -- * In the case we are connecting to a testnet, we also need to find out |
| 62 | + -- the magic number for the network the node is connected to. This can be |
| 63 | + -- obtained by looking for the @networkMagic@ key in the @shelley-genesis.json@ |
| 64 | + -- file that the node is using to connect to the network. For the preview |
| 65 | + -- network, the magic number is currently @2@. |
| 66 | + -- * The path to the socket file of the node. This can be set when starting the |
| 67 | + -- node by using the @--socket-path@ parameter. By default it can usually be |
| 68 | + -- found in the @db@ subfolder of the node's working directory. |
| 69 | + -- |
| 70 | + -- Then, we gather all the information into a 'LocalNodeConnectInfo' value. |
| 71 | + -- |
| 72 | + -- For example, let's assume we are connecting to the preview network, and that the |
| 73 | + -- socket file is located at @\/home\/user\/cardano-node\/db\/node.socket@. We could |
| 74 | + -- then create the 'LocalNodeConnectInfo' value as follows: |
| 75 | + -- |
| 76 | + -- @ |
| 77 | + -- let connectionInfo = |
| 78 | + -- Api.LocalNodeConnectInfo |
| 79 | + -- { Api.localConsensusModeParams = Api.CardanoModeParams (Api.EpochSlots 86_400) |
| 80 | + -- , Api.localNodeNetworkId = Api.Testnet (Api.NetworkMagic 2) |
| 81 | + -- , Api.localNodeSocketPath = Api.File "\/home\/user\/cardano-node\/db\/node.socket" |
| 82 | + -- } |
| 83 | + -- @ |
| 84 | + |
| 85 | + -- ** Querying the node for the UTxO set |
| 86 | + |
| 87 | + -- | Let's imagine we want to obtain the set of transaction outputs that |
| 88 | + -- are currently unspent in the network (UTxO set). |
| 89 | + |
| 90 | + -- *** Obtaining the current era |
| 91 | + |
| 92 | + -- | Depending on the type of query we want to perform, we usually need |
| 93 | + -- to know what era the node is currently in. We can hardcode this |
| 94 | + -- information by using one of the constructors of the 'ShelleyBasedEra' type. |
| 95 | + -- But we can also obtain this information from the node, as follows: |
| 96 | + -- |
| 97 | + -- @ |
| 98 | + -- eEra <- runExceptT $ Api.queryNodeLocalState connectionInfo Network.VolatileTip Api.QueryCurrentEra |
| 99 | + -- @ |
| 100 | + -- |
| 101 | + -- Here, 'VolatileTip' means we want to get the information out of the most recent node that the |
| 102 | + -- node is aware of. The disadvantage is that the information we get may potentially be rolled back |
| 103 | + -- and stop being valid. We need to account for this. Alternatively, we can use 'ImmutableTip' to |
| 104 | + -- obtain the information from the most recent block that is assumed by the consensus algorithm |
| 105 | + -- to be final, and that won't be rolled back. But this information is not so recent, in mainnet |
| 106 | + -- this is about 36 hours in the past. |
| 107 | + -- |
| 108 | + -- 'QueryCurrentEra' is the constructor of the query we want to run. In this case, we want to |
| 109 | + -- obtain the current era of the node. |
| 110 | + -- |
| 111 | + -- The result of the query is an 'ExceptT' monad, which we can run by using the 'runExceptT' |
| 112 | + -- function, which in turn gives us a @eEra@ value of type @Either AcquiringFailure AnyCardanoEra@. |
| 113 | + -- |
| 114 | + -- This is an example of how to unwrap this value into a 'ShelleyBasedEra' based era, assuming the node |
| 115 | + -- is not still running Byron: |
| 116 | + -- |
| 117 | + -- @ |
| 118 | + -- Api.AnyShelleyBasedEra sbe :: Api.AnyShelleyBasedEra <- case eEra of |
| 119 | + -- Right (Api.AnyCardanoEra era) -> |
| 120 | + -- Api.caseByronOrShelleyBasedEra |
| 121 | + -- (error "Error, we are in Byron era") |
| 122 | + -- (return . Api.AnyShelleyBasedEra) |
| 123 | + -- era |
| 124 | + -- Left Shelley.AFPointTooOld -> error "Error, point queried in the chain is too old!" |
| 125 | + -- Left Shelley.AFPointNotOnChain -> error "Error, point queried is not on chain!" |
| 126 | + -- @ |
| 127 | + -- |
| 128 | + -- 'AFPointToolOld' and 'AFPointNotOnChain' should not happen either with 'VolatileTip' or 'ImmutableTip'. |
| 129 | + |
| 130 | + -- *** Obtaining the UTxO set |
| 131 | + |
| 132 | + -- | Now that we know the current era, we can query the node for the UTxO set similarly |
| 133 | + -- by using the 'QueryUTxO' query as follow: |
| 134 | + -- |
| 135 | + -- @ |
| 136 | + -- eUtxo <- |
| 137 | + -- runExceptT $ |
| 138 | + -- Api.queryNodeLocalState |
| 139 | + -- connectionInfo |
| 140 | + -- Network.VolatileTip |
| 141 | + -- (Api.QueryInEra (Api.QueryInShelleyBasedEra sbe (Api.QueryUTxO Api.QueryUTxOWhole))) |
| 142 | + -- @ |
| 143 | + -- |
| 144 | + -- This time, @eUtxo@ has a nested type of @Either AcquiringFailure (Either EraMismatch (UTxO era))@. |
| 145 | + -- So we can unwrap it as follows: |
| 146 | + -- |
| 147 | + -- @ |
| 148 | + -- utxo <- case eUtxo of |
| 149 | + -- Right (Right (Api.UTxO utxo)) -> do |
| 150 | + -- return utxo |
| 151 | + -- Right (Left (Consensus.EraMismatch{Consensus.ledgerEraName, Consensus.otherEraName})) -> |
| 152 | + -- error |
| 153 | + -- ( "Error, we assumed era was " |
| 154 | + -- ++ show otherEraName |
| 155 | + -- ++ " but it was " |
| 156 | + -- ++ show ledgerEraName |
| 157 | + -- ) |
| 158 | + -- Left Shelley.AFPointTooOld -> error "Error, point queried in the chain is too old!" |
| 159 | + -- Left Shelley.AFPointNotOnChain -> error "Error, point queried is not on chain!" |
| 160 | + -- @ |
| 161 | + -- |
| 162 | + -- The obtained @utxo@ is a standard @Map@ of type @Map TxIn (TxOut CtxUTxO era)@. |
| 163 | + |
| 164 | + -- ** Submitting a transaction |
| 165 | + |
| 166 | + -- | Let's assume we have a signed transaction of the right era that we want to submit to the node, |
| 167 | + -- and that it is in the variable @signedTx@ of type @Tx era@. |
| 168 | + -- |
| 169 | + -- You can find out how to make such a transaction by looking at the documentation of the |
| 170 | + -- "Cardano.Api.Internal.Tx.Body" module. |
| 171 | + -- |
| 172 | + -- We can send it to the node by using the 'submitTxToNodeLocal' function as follows: |
| 173 | + -- |
| 174 | + -- @ |
| 175 | + -- result <- Api.submitTxToNodeLocal connectionInfo (Api.TxInMode sbe signedTx) |
| 176 | + -- @ |
| 177 | + -- |
| 178 | + -- The result of the submission is a 'SubmitResult' value, which can be inspected as follows: |
| 179 | + -- |
| 180 | + -- @ |
| 181 | + -- case result of |
| 182 | + -- Api.SubmitSuccess -> putStrLn "Transaction submitted successfully!" |
| 183 | + -- Api.SubmitFail reason -> error $ "Error submitting transaction: " ++ show reason |
| 184 | + -- @ |
| 185 | + -- |
| 186 | + -- If the command succeeds, then the transaction will be on the node's mempool ready |
| 187 | + -- to be included in a block. |
| 188 | + |
| 189 | + -- * Node interaction |
17 | 190 |
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18 | 191 | -- | Operations that involve talking to a local Cardano node. |
19 | 192 | connectToLocalNode |
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