mgr: migrate from boost::variant to std::variant

Replace `boost::variant` with `std::variant` as part of our effort to reduce
third-party dependencies in favor of C++ standard library alternatives.

Benefits include:
- Improved code readability and maintainability
- Reduced external dependency surface
- More consistent API usage with other components

Signed-off-by: Kefu Chai <[email protected]>

Author: tchaikov

src/crimson/osd/osd.cc

@@ -192,7 +192,7 @@ seastar::future<> OSD::open_meta_coll()
 seastar::future<> OSD::set_perf_queries(const ConfigPayload &config_payload) {
   LOG_PREFIX(OSD::set_perf_queries);
   const OSDConfigPayload &osd_config_payload =
-    boost::get<OSDConfigPayload>(config_payload);
+    std::get<OSDConfigPayload>(config_payload);
   const std::map<OSDPerfMetricQuery, OSDPerfMetricLimits> &queries =
     osd_config_payload.config;
   DEBUG("setting {} queries", queries.size());

src/mds/MetricAggregator.cc

@@ -551,7 +551,7 @@ void MetricAggregator::notify_mdsmap(const MDSMap &mdsmap) {
 }
 
 void MetricAggregator::set_perf_queries(const ConfigPayload &config_payload) {
-  const MDSConfigPayload &mds_config_payload = boost::get<MDSConfigPayload>(config_payload);
+  const MDSConfigPayload &mds_config_payload = std::get<MDSConfigPayload>(config_payload);
   const std::map<MDSPerfMetricQuery, MDSPerfMetricLimits> &queries = mds_config_payload.config;
 
   dout(10) << ": setting " << queries.size() << " queries" << dendl;

src/mgr/DaemonServer.cc

@@ -812,7 +812,7 @@ bool DaemonServer::handle_report(const ref_t<MMgrReport>& m)
 
   if (m->metric_report_message) {
     const MetricReportMessage &message = *m->metric_report_message;
-    boost::apply_visitor(HandlePayloadVisitor(this), message.payload);
+    std::visit(HandlePayloadVisitor(this), message.payload);
   }
 
   return true;

src/mgr/MDSPerfMetricCollector.cc

@@ -21,7 +21,7 @@ MDSPerfMetricCollector::MDSPerfMetricCollector(MetricListener &listener)
 }
 
 void MDSPerfMetricCollector::process_reports(const MetricPayload &payload) {
-  const MDSPerfMetricReport &metric_report = boost::get<MDSMetricPayload>(payload).metric_report;
+  const MDSPerfMetricReport &metric_report = std::get<MDSMetricPayload>(payload).metric_report;
 
   std::lock_guard locker(lock);
   process_reports_generic(

src/mgr/MetricTypes.h

@@ -4,7 +4,7 @@
 #ifndef CEPH_MGR_METRIC_TYPES_H
 #define CEPH_MGR_METRIC_TYPES_H
 
-#include <boost/variant.hpp>
+#include <variant>
 #include "include/denc.h"
 #include "include/ceph_features.h"
 #include "mgr/OSDPerfMetricTypes.h"
@@ -89,9 +89,9 @@ WRITE_CLASS_DENC(OSDMetricPayload)
 WRITE_CLASS_DENC(MDSMetricPayload)
 WRITE_CLASS_DENC(UnknownMetricPayload)
 
-typedef boost::variant<OSDMetricPayload,
-                       MDSMetricPayload,
-                       UnknownMetricPayload> MetricPayload;
+typedef std::variant<OSDMetricPayload,
+		     MDSMetricPayload,
+		     UnknownMetricPayload> MetricPayload;
 
 class EncodeMetricPayloadVisitor : public boost::static_visitor<void> {
 public:
@@ -133,14 +133,14 @@ struct MetricReportMessage {
 
   bool should_encode(uint64_t features) const {
     if (!HAVE_FEATURE(features, SERVER_PACIFIC) &&
-	boost::get<MDSMetricPayload>(&payload)) {
+	std::get_if<MDSMetricPayload>(&payload)) {
       return false;
     }
     return true;
   }
 
   void encode(ceph::buffer::list &bl) const {
-    boost::apply_visitor(EncodeMetricPayloadVisitor(bl), payload);
+    std::visit(EncodeMetricPayloadVisitor(bl), payload);
   }
 
   void decode(ceph::buffer::list::const_iterator &iter) {
@@ -161,15 +161,15 @@ struct MetricReportMessage {
       break;
   }
 
-  boost::apply_visitor(DecodeMetricPayloadVisitor(iter), payload);
+  std::visit(DecodeMetricPayloadVisitor(iter), payload);
   }
   void dump(ceph::Formatter *f) const {
     f->open_object_section("payload");
-    if (const OSDMetricPayload* osdPayload = boost::get<OSDMetricPayload>(&payload)) {
+    if (const OSDMetricPayload* osdPayload = std::get_if<OSDMetricPayload>(&payload)) {
       osdPayload->dump(f);
-    } else if (const MDSMetricPayload* mdsPayload = boost::get<MDSMetricPayload>(&payload)) {
+    } else if (const MDSMetricPayload* mdsPayload = std::get_if<MDSMetricPayload>(&payload)) {
       mdsPayload->dump(f);
-    } else if (const UnknownMetricPayload* unknownPayload = boost::get<UnknownMetricPayload>(&payload)) {
+    } else if (const UnknownMetricPayload* unknownPayload = std::get_if<UnknownMetricPayload>(&payload)) {
       unknownPayload->dump(f);
     } else {
       ceph_abort();
@@ -255,9 +255,9 @@ WRITE_CLASS_DENC(OSDConfigPayload)
 WRITE_CLASS_DENC(MDSConfigPayload)
 WRITE_CLASS_DENC(UnknownConfigPayload)
 
-typedef boost::variant<OSDConfigPayload,
-                       MDSConfigPayload,
-                       UnknownConfigPayload> ConfigPayload;
+typedef std::variant<OSDConfigPayload,
+		     MDSConfigPayload,
+		     UnknownConfigPayload> ConfigPayload;
 
 class EncodeConfigPayloadVisitor : public boost::static_visitor<void> {
 public:
@@ -299,14 +299,14 @@ struct MetricConfigMessage {
 
   bool should_encode(uint64_t features) const {
     if (!HAVE_FEATURE(features, SERVER_PACIFIC) &&
-	boost::get<MDSConfigPayload>(&payload)) {
+	std::get_if<MDSConfigPayload>(&payload)) {
       return false;
     }
     return true;
   }
 
   void encode(ceph::buffer::list &bl) const {
-    boost::apply_visitor(EncodeConfigPayloadVisitor(bl), payload);
+    std::visit(EncodeConfigPayloadVisitor(bl), payload);
   }
 
   void decode(ceph::buffer::list::const_iterator &iter) {
@@ -327,7 +327,7 @@ struct MetricConfigMessage {
       break;
   }
 
-  boost::apply_visitor(DecodeConfigPayloadVisitor(iter), payload);
+  std::visit(DecodeConfigPayloadVisitor(iter), payload);
   }
 };
 

src/mgr/MgrClient.cc

@@ -465,7 +465,7 @@ bool MgrClient::handle_mgr_configure(ref_t<MMgrConfigure> m)
     handle_config_payload(m->osd_perf_metric_queries);
   } else if (m->metric_config_message) {
     const MetricConfigMessage &message = *m->metric_config_message;
-    boost::apply_visitor(HandlePayloadVisitor(this), message.payload);
+    std::visit(HandlePayloadVisitor(this), message.payload);
   }
 
   bool starting = (stats_period == 0) && (m->stats_period != 0);

src/mgr/OSDPerfMetricCollector.cc

@@ -21,7 +21,7 @@ OSDPerfMetricCollector::OSDPerfMetricCollector(MetricListener &listener)
 
 void OSDPerfMetricCollector::process_reports(const MetricPayload &payload) {
   const std::map<OSDPerfMetricQuery, OSDPerfMetricReport> &reports =
-    boost::get<OSDMetricPayload>(payload).report;
+    std::get<OSDMetricPayload>(payload).report;
 
   std::lock_guard locker(lock);
   process_reports_generic(

src/osd/OSD.cc

@@ -10586,7 +10586,7 @@ void OSD::get_latest_osdmap()
 // --------------------------------
 
 void OSD::set_perf_queries(const ConfigPayload &config_payload) {
-  const OSDConfigPayload &osd_config_payload = boost::get<OSDConfigPayload>(config_payload);
+  const OSDConfigPayload &osd_config_payload = std::get<OSDConfigPayload>(config_payload);
   const std::map<OSDPerfMetricQuery, OSDPerfMetricLimits> &queries = osd_config_payload.config;
   dout(10) << "setting " << queries.size() << " queries" << dendl;