Add book_changes rpc #4212
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| //------------------------------------------------------------------------------ | ||
| /* | ||
| This file is part of rippled: https://github.com/ripple/rippled | ||
| Copyright (c) 2019 Ripple Labs Inc. | ||
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| Permission to use, copy, modify, and/or distribute this software for any | ||
| purpose with or without fee is hereby granted, provided that the above | ||
| copyright notice and this permission notice appear in all copies. | ||
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| THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES | ||
| WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF | ||
| MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR | ||
| ANY SPECIAL , DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES | ||
| WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN | ||
| ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF | ||
| OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. | ||
| */ | ||
| //============================================================================== | ||
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| #ifndef RIPPLE_RPC_BOOKCHANGES_H_INCLUDED | ||
| #define RIPPLE_RPC_BOOKCAHNGES_H_INCLUDED | ||
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| namespace Json { | ||
| class Value; | ||
| } | ||
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| namespace ripple { | ||
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| class ReadView; | ||
| class Transaction; | ||
| class TxMeta; | ||
| class STTx; | ||
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| namespace RPC { | ||
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| template <class L> | ||
| Json::Value | ||
| computeBookChanges(std::shared_ptr<L const> const& lpAccepted) | ||
| { | ||
| std::map< | ||
| std::string, | ||
| std::tuple< | ||
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| STAmount, // side A volume | ||
| STAmount, // side B volume | ||
| STAmount, // high rate | ||
| STAmount, // low rate | ||
| STAmount, // open rate | ||
| STAmount // close rate | ||
| >> | ||
| tally; | ||
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| for (auto& tx : lpAccepted->txs) | ||
| { | ||
| if (!tx.first || !tx.second || | ||
| !tx.first->isFieldPresent(sfTransactionType)) | ||
| continue; | ||
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| std::optional<uint32_t> offerCancel; | ||
| uint16_t tt = tx.first->getFieldU16(sfTransactionType); | ||
| switch (tt) | ||
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| { | ||
| case ttOFFER_CANCEL: | ||
| case ttOFFER_CREATE: { | ||
| if (tx.first->isFieldPresent(sfOfferSequence)) | ||
| offerCancel = tx.first->getFieldU32(sfOfferSequence); | ||
| break; | ||
| } | ||
| // in future if any other ways emerge to cancel an offer | ||
| // this switch makes them easy to add | ||
| default: | ||
| break; | ||
| } | ||
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| for (auto const& node : tx.second->getFieldArray(sfAffectedNodes)) | ||
| { | ||
| SField const& metaType = node.getFName(); | ||
| uint16_t nodeType = node.getFieldU16(sfLedgerEntryType); | ||
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| // we only care about ltOFFER objects being modified or | ||
| // deleted | ||
| if (nodeType != ltOFFER || metaType == sfCreatedNode) | ||
| continue; | ||
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| // if either FF or PF are missing we can't compute | ||
| // but generally these are cancelled rather than crossed | ||
| // so skipping them is consistent | ||
| if (!node.isFieldPresent(sfFinalFields) || | ||
| !node.isFieldPresent(sfPreviousFields)) | ||
| continue; | ||
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| STObject& finalFields = (const_cast<STObject&>(node)) | ||
| .getField(sfFinalFields) | ||
| .downcast<STObject>(); | ||
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| STObject& previousFields = (const_cast<STObject&>(node)) | ||
| .getField(sfPreviousFields) | ||
| .downcast<STObject>(); | ||
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| // defensive case that should never be hit | ||
| if (!finalFields.isFieldPresent(sfTakerGets) || | ||
| !finalFields.isFieldPresent(sfTakerPays) || | ||
| !previousFields.isFieldPresent(sfTakerGets) || | ||
| !previousFields.isFieldPresent(sfTakerPays)) | ||
| continue; | ||
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| // filter out any offers deleted by explicit offer cancels | ||
| if (metaType == sfDeletedNode && offerCancel && | ||
| finalFields.getFieldU32(sfSequence) == *offerCancel) | ||
| continue; | ||
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| // compute the difference in gets and pays actually | ||
| // affected onto the offer | ||
| STAmount deltaGets = finalFields.getFieldAmount(sfTakerGets) - | ||
| previousFields.getFieldAmount(sfTakerGets); | ||
| STAmount deltaPays = finalFields.getFieldAmount(sfTakerPays) - | ||
| previousFields.getFieldAmount(sfTakerPays); | ||
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| std::string g{to_string(deltaGets.issue())}; | ||
| std::string p{to_string(deltaPays.issue())}; | ||
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| bool const noswap = | ||
| isXRP(deltaGets) ? true : (isXRP(deltaPays) ? false : (g < p)); | ||
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| STAmount first = noswap ? deltaGets : deltaPays; | ||
| STAmount second = noswap ? deltaPays : deltaGets; | ||
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| // defensively programmed, should (probably) never happen | ||
| if (second == beast::zero) | ||
| continue; | ||
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| STAmount rate = divide(first, second, noIssue()); | ||
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| if (first < beast::zero) | ||
| first = -first; | ||
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| if (second < beast::zero) | ||
| second = -second; | ||
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| std::stringstream ss; | ||
| if (noswap) | ||
| ss << g << "|" << p; | ||
| else | ||
| ss << p << "|" << g; | ||
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| std::string key{ss.str()}; | ||
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| if (tally.find(key) == tally.end()) | ||
| tally[key] = { | ||
| first, // side A vol | ||
| second, // side B vol | ||
| rate, // high | ||
| rate, // low | ||
| rate, // open | ||
| rate // close | ||
| }; | ||
| else | ||
| { | ||
| // increment volume | ||
| auto& entry = tally[key]; | ||
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| std::get<0>(entry) += first; // side A vol | ||
| std::get<1>(entry) += second; // side B vol | ||
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| if (std::get<2>(entry) < rate) // high | ||
| std::get<2>(entry) = rate; | ||
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| if (std::get<3>(entry) > rate) // low | ||
| std::get<3>(entry) = rate; | ||
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| std::get<5>(entry) = rate; // close | ||
| } | ||
| } | ||
| } | ||
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| Json::Value jvObj(Json::objectValue); | ||
| jvObj[jss::type] = "bookChanges"; | ||
| jvObj[jss::ledger_index] = lpAccepted->info().seq; | ||
| jvObj[jss::ledger_hash] = to_string(lpAccepted->info().hash); | ||
| jvObj[jss::ledger_time] = Json::Value::UInt( | ||
| lpAccepted->info().closeTime.time_since_epoch().count()); | ||
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| jvObj[jss::changes] = Json::arrayValue; | ||
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| for (auto const& entry : tally) | ||
| { | ||
| Json::Value& inner = jvObj[jss::changes].append(Json::objectValue); | ||
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| STAmount volA = std::get<0>(entry.second); | ||
| STAmount volB = std::get<1>(entry.second); | ||
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| inner[jss::currency_a] = | ||
| (isXRP(volA) ? "XRP_drops" : to_string(volA.issue())); | ||
| inner[jss::currency_b] = | ||
| (isXRP(volB) ? "XRP_drops" : to_string(volB.issue())); | ||
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| inner[jss::volume_a] = | ||
| (isXRP(volA) ? to_string(volA.xrp()) : to_string(volA.iou())); | ||
| inner[jss::volume_b] = | ||
| (isXRP(volB) ? to_string(volB.xrp()) : to_string(volB.iou())); | ||
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| inner[jss::high] = to_string(std::get<2>(entry.second).iou()); | ||
| inner[jss::low] = to_string(std::get<3>(entry.second).iou()); | ||
| inner[jss::open] = to_string(std::get<4>(entry.second).iou()); | ||
| inner[jss::close] = to_string(std::get<5>(entry.second).iou()); | ||
| } | ||
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| return jvObj; | ||
| } | ||
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| } // namespace RPC | ||
| } // namespace ripple | ||
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| #endif | ||
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Is it possible to compute these changes outside of rippled?
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It is possible to compute everything outside of rippled, given that it is a public ledger with a public mesh and well defined data formats.
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While theoretically true, that's not practically true. For instance, if I wanted to compute the state of each new ledger based on that ledgers transactions, outside of rippled, I'd have to copy the transaction application code and keep it up to date with amendments. While theoretically possible, this would be a huge lift, and I'd argue not practically possible. It would make sense to just rely on rippled for such a thing.
But this code just seems like parsing metadata. Is there a reason this can't be done in a simple Python script, outside of rippled?
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You would first need to request all the txn meta data for a given ledger from rippled then compute the result. This is a much heavier rpc call because you're pushing [potentially a lot] more data to an external service for aggregation, instead of just computing it in place where it already exists. It's equivalent to dumping every row in an SQL table because you want to find the
SUM()of a column.