Merge #11099: [RPC][mempool]: Add savemempool RPC

1aa97ee08 Add savemempool RPC (Lawrence Nahum)
467cbbcbf Add return value to DumpMempool (Lawrence Nahum)

Pull request description:

  Adds a simple parameterless rpc command to dump the mempool.

  Rationale:

  Sometimes there can be a crash for whatever reason (bug, power loss, etc) causing the mempool.dat file to not be saved.

  This change allows to script/cron the rpc call to have more regular saves to the file as well as cli/ad-hoc.

  This should solve issue https://github.com/bitcoin/bitcoin/issues/11086

Tree-SHA512: e856ae9777425a4521279c9b58e69285d8e374790bebefd3284cf91931eac0e456f86224f427a087a01bf70440bf6e439fa02c8a34940eb1046ae473e98b6aaa

src/rpc/blockchain.cpp

@@ -1534,6 +1534,25 @@ UniValue getchaintxstats(const JSONRPCRequest& request)
     return ret;
 }
 
+UniValue savemempool(const JSONRPCRequest& request)
+{
+    if (request.fHelp || request.params.size() != 0) {
+        throw std::runtime_error(
+            "savemempool\n"
+            "\nDumps the mempool to disk.\n"
+            "\nExamples:\n"
+            + HelpExampleCli("savemempool", "")
+            + HelpExampleRpc("savemempool", "")
+        );
+    }
+
+    if (!DumpMempool()) {
+        throw JSONRPCError(RPC_MISC_ERROR, "Unable to dump mempool to disk");
+    }
+
+    return NullUniValue;
+}
+
 static const CRPCCommand commands[] =
 { //  category              name                      actor (function)         argNames
   //  --------------------- ------------------------  -----------------------  ----------
@@ -1554,6 +1573,7 @@ static const CRPCCommand commands[] =
     { "blockchain",         "gettxout",               &gettxout,               {"txid","n","include_mempool"} },
     { "blockchain",         "gettxoutsetinfo",        &gettxoutsetinfo,        {} },
     { "blockchain",         "pruneblockchain",        &pruneblockchain,        {"height"} },
+    { "blockchain",         "savemempool",            &savemempool,            {} },
     { "blockchain",         "verifychain",            &verifychain,            {"checklevel","nblocks"} },
 
     { "blockchain",         "preciousblock",          &preciousblock,          {"blockhash"} },