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diff --git a/src/crimson/common/config_proxy.h b/src/crimson/common/config_proxy.h
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+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+
+#pragma once
+
+#include <seastar/core/reactor.hh>
+#include <seastar/core/sharded.hh>
+#include "common/config.h"
+#include "common/config_obs.h"
+#include "common/config_obs_mgr.h"
+#include "common/errno.h"
+
+namespace ceph {
+class Formatter;
+}
+
+namespace crimson::common {
+
+// a facade for managing config. each shard has its own copy of ConfigProxy.
+//
+// In seastar-osd, there could be multiple instances of @c ConfigValues in a
+// single process, as we are using a variant of read-copy-update mechinary to
+// update the settings at runtime.
+class ConfigProxy : public seastar::peering_sharded_service<ConfigProxy>
+{
+ using LocalConfigValues = seastar::lw_shared_ptr<ConfigValues>;
+ seastar::foreign_ptr<LocalConfigValues> values;
+
+ md_config_t* remote_config = nullptr;
+ std::unique_ptr<md_config_t> local_config;
+
+ using ConfigObserver = ceph::md_config_obs_impl<ConfigProxy>;
+ ObserverMgr<ConfigObserver> obs_mgr;
+
+ const md_config_t& get_config() const {
+ return remote_config ? *remote_config : * local_config;
+ }
+ md_config_t& get_config() {
+ return remote_config ? *remote_config : * local_config;
+ }
+
+ // apply changes to all shards
+ // @param func a functor which accepts @c "ConfigValues&"
+ template<typename Func>
+ seastar::future<> do_change(Func&& func) {
+ return container().invoke_on(values.get_owner_shard(),
+ [func = std::move(func)](ConfigProxy& owner) {
+ // apply the changes to a copy of the values
+ auto new_values = seastar::make_lw_shared(*owner.values);
+ new_values->changed.clear();
+ func(*new_values);
+
+ // always apply the new settings synchronously on the owner shard, to
+ // avoid racings with other do_change() calls in parallel.
+ ObserverMgr<ConfigObserver>::rev_obs_map rev_obs;
+ owner.values.reset(new_values);
+ owner.obs_mgr.for_each_change(owner.values->changed, owner,
+ [&rev_obs](ConfigObserver *obs,
+ const std::string &key) {
+ rev_obs[obs].insert(key);
+ }, nullptr);
+ for (auto& [obs, keys] : rev_obs) {
+ obs->handle_conf_change(owner, keys);
+ }
+
+ return seastar::parallel_for_each(boost::irange(1u, seastar::smp::count),
+ [&owner, new_values] (auto cpu) {
+ return owner.container().invoke_on(cpu,
+ [foreign_values = seastar::make_foreign(new_values)](ConfigProxy& proxy) mutable {
+ proxy.values.reset();
+ proxy.values = std::move(foreign_values);
+
+ ObserverMgr<ConfigObserver>::rev_obs_map rev_obs;
+ proxy.obs_mgr.for_each_change(proxy.values->changed, proxy,
+ [&rev_obs](ConfigObserver *obs, const std::string& key) {
+ rev_obs[obs].insert(key);
+ }, nullptr);
+ for (auto& obs_keys : rev_obs) {
+ obs_keys.first->handle_conf_change(proxy, obs_keys.second);
+ }
+ });
+ }).finally([new_values] {
+ new_values->changed.clear();
+ });
+ });
+ }
+public:
+ ConfigProxy(const EntityName& name, std::string_view cluster);
+ const ConfigValues* operator->() const noexcept {
+ return values.get();
+ }
+ const ConfigValues get_config_values() {
+ return *values.get();
+ }
+ ConfigValues* operator->() noexcept {
+ return values.get();
+ }
+
+ // required by sharded<>
+ seastar::future<> start();
+ seastar::future<> stop() {
+ return seastar::make_ready_future<>();
+ }
+ void add_observer(ConfigObserver* obs) {
+ obs_mgr.add_observer(obs);
+ }
+ void remove_observer(ConfigObserver* obs) {
+ obs_mgr.remove_observer(obs);
+ }
+ seastar::future<> rm_val(const std::string& key) {
+ return do_change([key, this](ConfigValues& values) {
+ auto ret = get_config().rm_val(values, key);
+ if (ret < 0) {
+ throw std::invalid_argument(cpp_strerror(ret));
+ }
+ });
+ }
+ seastar::future<> set_val(const std::string& key,
+ const std::string& val) {
+ return do_change([key, val, this](ConfigValues& values) {
+ std::stringstream err;
+ auto ret = get_config().set_val(values, obs_mgr, key, val, &err);
+ if (ret < 0) {
+ throw std::invalid_argument(err.str());
+ }
+ });
+ }
+ int get_val(const std::string &key, std::string *val) const {
+ return get_config().get_val(*values, key, val);
+ }
+ template<typename T>
+ const T get_val(const std::string& key) const {
+ return get_config().template get_val<T>(*values, key);
+ }
+
+ int get_all_sections(std::vector<std::string>& sections) const {
+ return get_config().get_all_sections(sections);
+ }
+
+ int get_val_from_conf_file(const std::vector<std::string>& sections,
+ const std::string& key, std::string& out,
+ bool expand_meta) const {
+ return get_config().get_val_from_conf_file(*values, sections, key,
+ out, expand_meta);
+ }
+
+ unsigned get_osd_pool_default_min_size(uint8_t size) const {
+ return get_config().get_osd_pool_default_min_size(*values, size);
+ }
+
+ seastar::future<>
+ set_mon_vals(const std::map<std::string,std::string,std::less<>>& kv) {
+ return do_change([kv, this](ConfigValues& values) {
+ get_config().set_mon_vals(nullptr, values, obs_mgr, kv, nullptr);
+ });
+ }
+
+ seastar::future<> inject_args(const std::string& s) {
+ return do_change([s, this](ConfigValues& values) {
+ std::stringstream err;
+ if (get_config().injectargs(values, obs_mgr, s, &err)) {
+ throw std::invalid_argument(err.str());
+ }
+ });
+ }
+ void show_config(ceph::Formatter* f) const;
+
+ seastar::future<> parse_argv(std::vector<const char*>& argv) {
+ // we could pass whatever is unparsed to seastar, but seastar::app_template
+ // is used for driving the seastar application, and
+ // crimson::common::ConfigProxy is not available until seastar engine is up
+ // and running, so we have to feed the command line args to app_template
+ // first, then pass them to ConfigProxy.
+ return do_change([&argv, this](ConfigValues& values) {
+ get_config().parse_argv(values,
+ obs_mgr,
+ argv,
+ CONF_CMDLINE);
+ });
+ }
+
+ seastar::future<> parse_config_files(const std::string& conf_files);
+
+ using ShardedConfig = seastar::sharded<ConfigProxy>;
+
+private:
+ static ShardedConfig sharded_conf;
+ friend ConfigProxy& local_conf();
+ friend ShardedConfig& sharded_conf();
+};
+
+inline ConfigProxy& local_conf() {
+ return ConfigProxy::sharded_conf.local();
+}
+
+inline ConfigProxy::ShardedConfig& sharded_conf() {
+ return ConfigProxy::sharded_conf;
+}
+
+}