Json::Value doPathFind (RPC::Context& context)
{
auto lpLedger = context.ledgerMaster.getClosedLedger();
if (!context.params.isMember (jss::subcommand) ||
!context.params[jss::subcommand].isString ())
{
return rpcError (rpcINVALID_PARAMS);
}
if (!context.infoSub)
return rpcError (rpcNO_EVENTS);
auto sSubCommand = context.params[jss::subcommand].asString ();
if (sSubCommand == "create")
{
context.loadType = Resource::feeHighBurdenRPC;
context.infoSub->clearPathRequest ();
return context.app.getPathRequests().makePathRequest (
context.infoSub, lpLedger, context.params);
}
if (sSubCommand == "close")
{
PathRequest::pointer request = context.infoSub->getPathRequest ();
if (!request)
return rpcError (rpcNO_PF_REQUEST);
context.infoSub->clearPathRequest ();
return request->doClose (context.params);
}
if (sSubCommand == "status")
{
PathRequest::pointer request = context.infoSub->getPathRequest ();
if (!request)
return rpcError (rpcNO_PF_REQUEST);
return request->doStatus (context.params);
}
return rpcError (rpcINVALID_PARAMS);
}
// This interface is deprecated.
Json::Value doRipplePathFind (RPC::Context& context)
{
RPC::LegacyPathFind lpf (context.role == Role::ADMIN);
if (!lpf.isOk ())
return rpcError (rpcTOO_BUSY);
context.loadType = Resource::feeHighBurdenRPC;
AccountID raSrc;
AccountID raDst;
STAmount saDstAmount;
Ledger::pointer lpLedger;
Json::Value jvResult;
if (! context.suspend ||
getConfig().RUN_STANDALONE ||
context.params.isMember(jss::ledger) ||
context.params.isMember(jss::ledger_index) ||
context.params.isMember(jss::ledger_hash))
{
// The caller specified a ledger
jvResult = RPC::lookupLedgerDeprecated (lpLedger, context);
if (!lpLedger)
return jvResult;
}
else
{
if (getApp().getLedgerMaster().getValidatedLedgerAge() >
RPC::Tuning::maxValidatedLedgerAge)
{
return rpcError (rpcNO_NETWORK);
}
context.loadType = Resource::feeHighBurdenRPC;
lpLedger = context.ledgerMaster.getClosedLedger();
PathRequest::pointer request;
suspend(context,
[&request, &context, &jvResult, &lpLedger]
(RPC::Callback const& callback)
{
jvResult = getApp().getPathRequests().makeLegacyPathRequest (
request, callback, lpLedger, context.params);
assert(callback);
if (! request && callback)
callback();
});
if (request)
jvResult = request->doStatus (context.params);
return jvResult;
}
if (!context.params.isMember (jss::source_account))
{
jvResult = rpcError (rpcSRC_ACT_MISSING);
}
else if (! deprecatedParseBase58(raSrc,
context.params[jss::source_account]))
{
jvResult = rpcError (rpcSRC_ACT_MALFORMED);
}
else if (!context.params.isMember (jss::destination_account))
{
jvResult = rpcError (rpcDST_ACT_MISSING);
}
else if (! deprecatedParseBase58 (raDst,
context.params[jss::destination_account]))
{
jvResult = rpcError (rpcDST_ACT_MALFORMED);
}
else if (
// Parse saDstAmount.
!context.params.isMember (jss::destination_amount)
|| ! amountFromJsonNoThrow(saDstAmount, context.params[jss::destination_amount])
|| saDstAmount <= zero
|| (!isXRP(saDstAmount.getCurrency ())
&& (!saDstAmount.getIssuer () ||
noAccount() == saDstAmount.getIssuer ())))
{
WriteLog (lsINFO, RPCHandler) << "Bad destination_amount.";
jvResult = rpcError (rpcINVALID_PARAMS);
}
else if (
// Checks on source_currencies.
context.params.isMember (jss::source_currencies)
&& (!context.params[jss::source_currencies].isArray ()
|| !context.params[jss::source_currencies].size ())
// Don't allow empty currencies.
)
{
WriteLog (lsINFO, RPCHandler) << "Bad source_currencies.";
jvResult = rpcError (rpcINVALID_PARAMS);
}
else
{
context.loadType = Resource::feeHighBurdenRPC;
RippleLineCache::pointer cache;
if (lpLedger)
{
// The caller specified a ledger
lpLedger = std::make_shared<Ledger> (std::ref (*lpLedger), false);
cache = std::make_shared<RippleLineCache>(lpLedger);
}
else
{
// The closed ledger is recent and any nodes made resident
// have the best chance to persist
lpLedger = context.ledgerMaster.getClosedLedger();
cache = getApp().getPathRequests().getLineCache(lpLedger, false);
}
Json::Value jvSrcCurrencies;
if (context.params.isMember (jss::source_currencies))
{
jvSrcCurrencies = context.params[jss::source_currencies];
}
else
{
jvSrcCurrencies = buildSrcCurrencies(raSrc, cache);
}
// Fill in currencies destination will accept
Json::Value jvDestCur (Json::arrayValue);
// TODO(tom): this could be optimized the same way that
// PathRequest::doUpdate() is - if we don't obsolete this code first.
auto usDestCurrID = accountDestCurrencies (raDst, cache, true);
for (auto const& uCurrency: usDestCurrID)
jvDestCur.append (to_string (uCurrency));
jvResult[jss::destination_currencies] = jvDestCur;
jvResult[jss::destination_account] = getApp().accountIDCache().toBase58(raDst);
int level = getConfig().PATH_SEARCH_OLD;
if ((getConfig().PATH_SEARCH_MAX > level)
&& !getApp().getFeeTrack().isLoadedLocal())
{
++level;
}
if (context.params.isMember(jss::search_depth)
&& context.params[jss::search_depth].isIntegral())
{
int rLev = context.params[jss::search_depth].asInt ();
if ((rLev < level) || (context.role == Role::ADMIN))
level = rLev;
}
auto contextPaths = context.params.isMember(jss::paths) ?
boost::optional<Json::Value>(context.params[jss::paths]) :
boost::optional<Json::Value>(boost::none);
auto pathFindResult = ripplePathFind(cache, raSrc, raDst, saDstAmount,
jvSrcCurrencies, contextPaths, level);
if (!pathFindResult.first)
return pathFindResult.second;
// Each alternative differs by source currency.
jvResult[jss::alternatives] = pathFindResult.second;
}
WriteLog (lsDEBUG, RPCHandler)
<< "ripple_path_find< %s" << jvResult;
return jvResult;
}
// This interface is deprecated.
Json::Value doRipplePathFind (RPC::Context& context)
{
if (context.app.config().PATH_SEARCH_MAX == 0)
return rpcError (rpcNOT_SUPPORTED);
context.loadType = Resource::feeHighBurdenRPC;
std::shared_ptr <ReadView const> lpLedger;
Json::Value jvResult;
if (! context.app.config().standalone() &&
! context.params.isMember(jss::ledger) &&
! context.params.isMember(jss::ledger_index) &&
! context.params.isMember(jss::ledger_hash))
{
// No ledger specified, use pathfinding defaults
// and dispatch to pathfinding engine
if (context.app.getLedgerMaster().getValidatedLedgerAge() >
RPC::Tuning::maxValidatedLedgerAge)
{
return rpcError (rpcNO_NETWORK);
}
PathRequest::pointer request;
lpLedger = context.ledgerMaster.getClosedLedger();
// It doesn't look like there's much odd happening here, but you should
// be aware this code runs in a JobQueue::Coro, which is a coroutine.
// And we may be flipping around between threads. Here's an overview:
//
// 1. We're running doRipplePathFind() due to a call to
// ripple_path_find. doRipplePathFind() is currently running
// inside of a JobQueue::Coro using a JobQueue thread.
//
// 2. doRipplePathFind's call to makeLegacyPathRequest() enqueues the
// path-finding request. That request will (probably) run at some
// indeterminate future time on a (probably different) JobQueue
// thread.
//
// 3. As a continuation from that path-finding JobQueue thread, the
// coroutine we're currently running in (!) is posted to the
// JobQueue. Because it is a continuation, that post won't
// happen until the path-finding request completes.
//
// 4. Once the continuation is enqueued, and we have reason to think
// the path-finding job is likely to run, then the coroutine we're
// running in yield()s. That means it surrenders its thread in
// the JobQueue. The coroutine is suspended, but ready to run,
// because it is kept resident by a shared_ptr in the
// path-finding continuation.
//
// 5. If all goes well then path-finding runs on a JobQueue thread
// and executes its continuation. The continuation posts this
// same coroutine (!) to the JobQueue.
//
// 6. When the JobQueue calls this coroutine, this coroutine resumes
// from the line below the coro->yield() and returns the
// path-finding result.
//
// With so many moving parts, what could go wrong?
//
// Just in terms of the JobQueue refusing to add jobs at shutdown
// there are two specific things that can go wrong.
//
// 1. The path-finding Job queued by makeLegacyPathRequest() might be
// rejected (because we're shutting down).
//
// Fortunately this problem can be addressed by looking at the
// return value of makeLegacyPathRequest(). If
// makeLegacyPathRequest() cannot get a thread to run the path-find
// on, then it returns an empty request.
//
// 2. The path-finding job might run, but the Coro::post() might be
// rejected by the JobQueue (because we're shutting down).
//
// We handle this case by resuming (not posting) the Coro.
// By resuming the Coro, we allow the Coro to run to completion
// on the current thread instead of requiring that it run on a
// new thread from the JobQueue.
//
// Both of these failure modes are hard to recreate in a unit test
// because they are so dependent on inter-thread timing. However
// the failure modes can be observed by synchronously (inside the
// rippled source code) shutting down the application. The code to
// do so looks like this:
//
// context.app.signalStop();
// while (! context.app.getJobQueue().jobCounter().joined()) { }
//
// The first line starts the process of shutting down the app.
// The second line waits until no more jobs can be added to the
// JobQueue before letting the thread continue.
//
// May 2017
jvResult = context.app.getPathRequests().makeLegacyPathRequest (
request,
[&context] () {
// Copying the shared_ptr keeps the coroutine alive up
// through the return. Otherwise the storage under the
// captured reference could evaporate when we return from
// coroCopy->resume(). This is not strictly necessary, but
// will make maintenance easier.
std::shared_ptr<JobQueue::Coro> coroCopy {context.coro};
if (!coroCopy->post())
{
// The post() failed, so we won't get a thread to let
// the Coro finish. We'll call Coro::resume() so the
// Coro can finish on our thread. Otherwise the
// application will hang on shutdown.
coroCopy->resume();
}
},
context.consumer, lpLedger, context.params);
if (request)
{
context.coro->yield();
jvResult = request->doStatus (context.params);
}
return jvResult;
}
// The caller specified a ledger
jvResult = RPC::lookupLedger (lpLedger, context);
if (! lpLedger)
return jvResult;
RPC::LegacyPathFind lpf (isUnlimited (context.role), context.app);
if (! lpf.isOk ())
return rpcError (rpcTOO_BUSY);
auto result = context.app.getPathRequests().doLegacyPathRequest (
context.consumer, lpLedger, context.params);
for (auto &fieldName : jvResult.getMemberNames ())
result[fieldName] = std::move (jvResult[fieldName]);
return result;
}