Add <datadir>/settings.json persistent settings storage.

Persistent settings are used in followup PRs #15936 to unify gui settings
between bitcoin-qt and bitcoind, and #15937 to add a load_on_startup flag to
the loadwallet RPC and maintain a dynamic list of wallets that should be loaded
on startup that also can be shared between bitcoind and bitcoin-qt.

Author: ryanofsky

doc/files.md

@@ -50,14 +50,15 @@ Subdirectory       | File(s)               | Description
 `indexes/blockfilter/basic/`    | `fltrNNNNN.dat`<sup>[\[2\]](#note2)</sup> | Blockfilter index filters for the basic filtertype; *optional*, used if `-blockfilterindex=basic`
 `wallets/`         |                       | [Contains wallets](#multi-wallet-environment); can be specified by `-walletdir` option; if `wallets/` subdirectory does not exist, a wallet resides in the data directory
 `./`               | `banlist.dat`         | Stores the IPs/subnets of banned nodes
-`./`               | `bitcoin.conf`        | Contains [configuration settings](bitcoin-conf.md) for `bitcoind` or `bitcoin-qt`; can be specified by `-conf` option
+`./`               | `bitcoin.conf`        | User-defined [configuration settings](bitcoin-conf.md) for `bitcoind` or `bitcoin-qt`. File is not written to by the software and must be created manually. Path can be specified by `-conf` option
 `./`               | `bitcoind.pid`        | Stores the process ID (PID) of `bitcoind` or `bitcoin-qt` while running; created at start and deleted on shutdown; can be specified by `-pid` option
 `./`               | `debug.log`           | Contains debug information and general logging generated by `bitcoind` or `bitcoin-qt`; can be specified by `-debuglogfile` option
 `./`               | `fee_estimates.dat`   | Stores statistics used to estimate minimum transaction fees and priorities required for confirmation
 `./`               | `guisettings.ini.bak` | Backup of former [GUI settings](#gui-settings) after `-resetguisettings` option is used
 `./`               | `mempool.dat`         | Dump of the mempool's transactions
 `./`               | `onion_private_key`   | Cached Tor hidden service private key for `-listenonion` option
 `./`               | `peers.dat`           | Peer IP address database (custom format)
+`./`               | `settings.json`       | Read-write settings set through GUI or RPC interfaces, augmenting manual settings from [bitcoin.conf](bitcoin-conf.md). File is created automatically if read-write settings storage is not disabled with `-nosettings` option. Path can be specified with `-settings` option
 `./`               | `.cookie`             | Session RPC authentication cookie; if used, created at start and deleted on shutdown; can be specified by `-rpccookiefile` option
 `./`               | `.lock`               | Data directory lock file
 

src/bitcoind.cpp

@@ -101,6 +101,11 @@ static bool AppInit(int argc, char* argv[])
             }
         }
 
+        if (!gArgs.InitSettings(error)) {
+            InitError(Untranslated(error));
+            return false;
+        }
+
         // -server defaults to true for bitcoind but not for the GUI so do this here
         gArgs.SoftSetBoolArg("-server", true);
         // Set this early so that parameter interactions go to console

src/init.cpp

@@ -397,7 +397,7 @@ void SetupServerArgs(NodeContext& node)
 #endif
     gArgs.AddArg("-blockreconstructionextratxn=<n>", strprintf("Extra transactions to keep in memory for compact block reconstructions (default: %u)", DEFAULT_BLOCK_RECONSTRUCTION_EXTRA_TXN), ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
     gArgs.AddArg("-blocksonly", strprintf("Whether to reject transactions from network peers. Automatic broadcast and rebroadcast of any transactions from inbound peers is disabled, unless the peer has the 'forcerelay' permission. RPC transactions are not affected. (default: %u)", DEFAULT_BLOCKSONLY), ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
-    gArgs.AddArg("-conf=<file>", strprintf("Specify configuration file. Relative paths will be prefixed by datadir location. (default: %s)", BITCOIN_CONF_FILENAME), ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
+    gArgs.AddArg("-conf=<file>", strprintf("Specify path to read-only configuration file. Relative paths will be prefixed by datadir location. (default: %s)", BITCOIN_CONF_FILENAME), ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
     gArgs.AddArg("-datadir=<dir>", "Specify data directory", ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
     gArgs.AddArg("-dbbatchsize", strprintf("Maximum database write batch size in bytes (default: %u)", nDefaultDbBatchSize), ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::OPTIONS);
     gArgs.AddArg("-dbcache=<n>", strprintf("Maximum database cache size <n> MiB (%d to %d, default: %d). In addition, unused mempool memory is shared for this cache (see -maxmempool).", nMinDbCache, nMaxDbCache, nDefaultDbCache), ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
@@ -418,6 +418,7 @@ void SetupServerArgs(NodeContext& node)
             "(default: 0 = disable pruning blocks, 1 = allow manual pruning via RPC, >=%u = automatically prune block files to stay under the specified target size in MiB)", MIN_DISK_SPACE_FOR_BLOCK_FILES / 1024 / 1024), ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
     gArgs.AddArg("-reindex", "Rebuild chain state and block index from the blk*.dat files on disk", ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
     gArgs.AddArg("-reindex-chainstate", "Rebuild chain state from the currently indexed blocks. When in pruning mode or if blocks on disk might be corrupted, use full -reindex instead.", ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
+    gArgs.AddArg("-settings=<file>", strprintf("Specify path to dynamic settings data file. Can be disabled with -nosettings. File is written at runtime and not meant to be edited by users (use %s instead for custom settings). Relative paths will be prefixed by datadir location. (default: %s)", BITCOIN_CONF_FILENAME, BITCOIN_SETTINGS_FILENAME), ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
 #ifndef WIN32
     gArgs.AddArg("-sysperms", "Create new files with system default permissions, instead of umask 077 (only effective with disabled wallet functionality)", ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
 #else

src/interfaces/node.cpp

@@ -66,6 +66,7 @@ class NodeImpl : public Node
     bool softSetArg(const std::string& arg, const std::string& value) override { return gArgs.SoftSetArg(arg, value); }
     bool softSetBoolArg(const std::string& arg, bool value) override { return gArgs.SoftSetBoolArg(arg, value); }
     void selectParams(const std::string& network) override { SelectParams(network); }
+    bool initSettings(std::string& error) override { return gArgs.InitSettings(error); }
     uint64_t getAssumedBlockchainSize() override { return Params().AssumedBlockchainSize(); }
     uint64_t getAssumedChainStateSize() override { return Params().AssumedChainStateSize(); }
     std::string getNetwork() override { return Params().NetworkIDString(); }

src/interfaces/node.h

@@ -66,6 +66,11 @@ class Node
     //! Choose network parameters.
     virtual void selectParams(const std::string& network) = 0;
 
+    //! Read and update <datadir>/settings.json file with saved settings. This
+    //! needs to be called after selectParams() because the settings file
+    //! location is network-specific.
+    virtual bool initSettings(std::string& error) = 0;
+
     //! Get the (assumed) blockchain size.
     virtual uint64_t getAssumedBlockchainSize() = 0;
 

src/qt/bitcoin.cpp

@@ -528,6 +528,11 @@ int GuiMain(int argc, char* argv[])
     // Parse URIs on command line -- this can affect Params()
     PaymentServer::ipcParseCommandLine(*node, argc, argv);
 #endif
+    if (!node->initSettings(error)) {
+        node->initError(Untranslated(error));
+        QMessageBox::critical(nullptr, PACKAGE_NAME, QObject::tr("Error initializing settings: %1").arg(QString::fromStdString(error)));
+        return EXIT_FAILURE;
+    }
 
     QScopedPointer<const NetworkStyle> networkStyle(NetworkStyle::instantiate(Params().NetworkIDString()));
     assert(!networkStyle.isNull());

src/test/util_tests.cpp

@@ -9,6 +9,7 @@
 #include <key.h>  // For CKey
 #include <optional.h>
 #include <sync.h>
+#include <test/util/logging.h>
 #include <test/util/setup_common.h>
 #include <test/util/str.h>
 #include <uint256.h>
@@ -1128,6 +1129,28 @@ BOOST_FIXTURE_TEST_CASE(util_ChainMerge, ChainMergeTestingSetup)
     BOOST_CHECK_EQUAL(out_sha_hex, "f0b3a3c29869edc765d579c928f7f1690a71fbb673b49ccf39cbc4de18156a0d");
 }
 
+BOOST_AUTO_TEST_CASE(util_ReadWriteSettings)
+{
+    // Test writing setting.
+    TestArgsManager args1;
+    args1.LockSettings([&](util::Settings& settings) { settings.rw_settings["name"] = "value"; });
+    args1.WriteSettingsFile();
+
+    // Test reading setting.
+    TestArgsManager args2;
+    args2.ReadSettingsFile();
+    args2.LockSettings([&](util::Settings& settings) { BOOST_CHECK_EQUAL(settings.rw_settings["name"].get_str(), "value"); });
+
+    // Test error logging, and remove previously written setting.
+    {
+        ASSERT_DEBUG_LOG("Failed renaming settings file");
+        fs::remove(GetDataDir() / "settings.json");
+        fs::create_directory(GetDataDir() / "settings.json");
+        args2.WriteSettingsFile();
+        fs::remove(GetDataDir() / "settings.json");
+    }
+}
+
 BOOST_AUTO_TEST_CASE(util_FormatMoney)
 {
     BOOST_CHECK_EQUAL(FormatMoney(0), "0.00");

src/util/settings.cpp

@@ -13,12 +13,13 @@ namespace {
 enum class Source {
    FORCED,
    COMMAND_LINE,
+   RW_SETTINGS,
    CONFIG_FILE_NETWORK_SECTION,
    CONFIG_FILE_DEFAULT_SECTION
 };
 
 //! Merge settings from multiple sources in precedence order:
-//! Forced config > command line > config file network-specific section > config file default section
+//! Forced config > command line > read-write settings file > config file network-specific section > config file default section
 //!
 //! This function is provided with a callback function fn that contains
 //! specific logic for how to merge the sources.
@@ -33,6 +34,10 @@ static void MergeSettings(const Settings& settings, const std::string& section,
     if (auto* values = FindKey(settings.command_line_options, name)) {
         fn(SettingsSpan(*values), Source::COMMAND_LINE);
     }
+    // Merge in the read-write settings
+    if (const SettingsValue* value = FindKey(settings.rw_settings, name)) {
+        fn(SettingsSpan(*value), Source::RW_SETTINGS);
+    }
     // Merge in the network-specific section of the config file
     if (!section.empty()) {
         if (auto* map = FindKey(settings.ro_config, section)) {

src/util/settings.h

@@ -26,13 +26,15 @@ namespace util {
 //!       https://github.com/bitcoin/bitcoin/pull/15934/files#r337691812)
 using SettingsValue = UniValue;
 
-//! Stored bitcoin settings. This struct combines settings from the command line
-//! and a read-only configuration file.
+//! Stored settings. This struct combines settings from the command line, a
+//! read-only configuration file, and a read-write runtime settings file.
 struct Settings {
     //! Map of setting name to forced setting value.
     std::map<std::string, SettingsValue> forced_settings;
     //! Map of setting name to list of command line values.
     std::map<std::string, std::vector<SettingsValue>> command_line_options;
+    //! Map of setting name to read-write file setting value.
+    std::map<std::string, SettingsValue> rw_settings;
     //! Map of config section name and setting name to list of config file values.
     std::map<std::string, std::map<std::string, std::vector<SettingsValue>>> ro_config;
 };
@@ -48,7 +50,7 @@ bool WriteSettings(const fs::path& path,
     std::vector<std::string>& errors);
 
 //! Get settings value from combined sources: forced settings, command line
-//! arguments and the read-only config file.
+//! arguments, runtime read-write settings, and the read-only config file.
 //!
 //! @param ignore_default_section_config - ignore values in the default section
 //!                                        of the config file (part before any

src/util/system.cpp

@@ -73,6 +73,7 @@
 const int64_t nStartupTime = GetTime();
 
 const char * const BITCOIN_CONF_FILENAME = "bitcoin.conf";
+const char * const BITCOIN_SETTINGS_FILENAME = "settings.json";
 
 ArgsManager gArgs;
 
@@ -372,6 +373,84 @@ bool ArgsManager::IsArgSet(const std::string& strArg) const
     return !GetSetting(strArg).isNull();
 }
 
+bool ArgsManager::InitSettings(std::string& error)
+{
+    if (!GetSettingsPath()) {
+        return true; // Do nothing if settings file disabled.
+    }
+
+    std::vector<std::string> errors;
+    if (!ReadSettingsFile(&errors)) {
+        error = strprintf("Failed loading settings file:\n- %s\n", Join(errors, "\n- "));
+        return false;
+    }
+    if (!WriteSettingsFile(&errors)) {
+        error = strprintf("Failed saving settings file:\n- %s\n", Join(errors, "\n- "));
+        return false;
+    }
+    return true;
+}
+
+bool ArgsManager::GetSettingsPath(fs::path* filepath, bool temp) const
+{
+    if (IsArgNegated("-settings")) {
+        return false;
+    }
+    if (filepath) {
+        std::string settings = GetArg("-settings", BITCOIN_SETTINGS_FILENAME);
+        *filepath = fs::absolute(temp ? settings + ".tmp" : settings, GetDataDir(/* net_specific= */ true));
+    }
+    return true;
+}
+
+static void SaveErrors(const std::vector<std::string> errors, std::vector<std::string>* error_out)
+{
+    for (const auto& error : errors) {
+        if (error_out) {
+            error_out->emplace_back(error);
+        } else {
+            LogPrintf("%s\n", error);
+        }
+    }
+}
+
+bool ArgsManager::ReadSettingsFile(std::vector<std::string>* errors)
+{
+    fs::path path;
+    if (!GetSettingsPath(&path, /* temp= */ false)) {
+        return true; // Do nothing if settings file disabled.
+    }
+
+    LOCK(cs_args);
+    m_settings.rw_settings.clear();
+    std::vector<std::string> read_errors;
+    if (!util::ReadSettings(path, m_settings.rw_settings, read_errors)) {
+        SaveErrors(read_errors, errors);
+        return false;
+    }
+    return true;
+}
+
+bool ArgsManager::WriteSettingsFile(std::vector<std::string>* errors) const
+{
+    fs::path path, path_tmp;
+    if (!GetSettingsPath(&path, /* temp= */ false) || !GetSettingsPath(&path_tmp, /* temp= */ true)) {
+        throw std::logic_error("Attempt to write settings file when dynamic settings are disabled.");
+    }
+
+    LOCK(cs_args);
+    std::vector<std::string> write_errors;
+    if (!util::WriteSettings(path_tmp, m_settings.rw_settings, write_errors)) {
+        SaveErrors(write_errors, errors);
+        return false;
+    }
+    if (!RenameOver(path_tmp, path)) {
+        SaveErrors({strprintf("Failed renaming settings file %s to %s\n", path_tmp.string(), path.string())}, errors);
+        return false;
+    }
+    return true;
+}
+
 bool ArgsManager::IsArgNegated(const std::string& strArg) const
 {
     return GetSetting(strArg).isFalse();
@@ -893,6 +972,9 @@ void ArgsManager::LogArgs() const
     for (const auto& section : m_settings.ro_config) {
         logArgsPrefix("Config file arg:", section.first, section.second);
     }
+    for (const auto& setting : m_settings.rw_settings) {
+        LogPrintf("Setting file arg: %s = %s\n", setting.first, setting.second.write());
+    }
     logArgsPrefix("Command-line arg:", "", m_settings.command_line_options);
 }