SERVER-44117 early stacktrace processInfo

4 files changed, 77 insertions, 20 deletions

diff --git a/src/mongo/util/stacktrace_posix.cpp b/src/mongo/util/stacktrace_posix.cpp
index a975f869feb..c24fb71e092 100644
--- a/src/mongo/util/stacktrace_posix.cpp
+++ b/src/mongo/util/stacktrace_posix.cpp
@@ -253,10 +253,7 @@ void appendJsonProcessInfo(IterationIface& source,
                            const StackTraceOptions& options) {
     if (!options.withProcessInfo)
         return;
-    auto bsonSoMap = globalSharedObjectMapInfo();
-    if (!bsonSoMap)
-        return;
-    const BSONObj& bsonProcInfo = bsonSoMap->obj();
+    const BSONObj& bsonProcInfo = globalSharedObjectMapInfo().obj();
     CheapJson::Value jsonProcInfo = jsonRoot.appendKey("processInfo").appendObj();
     if (options.trimSoMap) {
         printJsonProcessInfoTrimmed(source, bsonProcInfo, jsonProcInfo);
diff --git a/src/mongo/util/stacktrace_somap.cpp b/src/mongo/util/stacktrace_somap.cpp
index 75ccf94eb63..893df5b7744 100644
--- a/src/mongo/util/stacktrace_somap.cpp
+++ b/src/mongo/util/stacktrace_somap.cpp
@@ -306,32 +306,54 @@ void addOSComponentsToSoMap(BSONObjBuilder* soMap) {}
 
 #endif  // unknown OS
 
-SharedObjectMapInfo* _globalSharedObjectMapInfo = nullptr;
-
 /**
- * Builds the "soMapJson" string, which is a JSON encoding of various pieces of information
- * about a running process, including the map from load addresses to shared objects loaded at
- * those addresses.
+ * Used to build the "processInfo" field of the stacktrace JSON object. It's loaded with
+ * information about a running process, including the map from load addresses to shared
+ * objects loaded at those addresses.
  */
-MONGO_INITIALIZER(ExtractSOMap)(InitializerContext*) {
+BSONObj buildObj() {
     BSONObjBuilder soMap;
-
     auto&& vii = VersionInfoInterface::instance(VersionInfoInterface::NotEnabledAction::kFallback);
     soMap << "mongodbVersion" << vii.version();
     soMap << "gitVersion" << vii.gitVersion();
     soMap << "compiledModules" << vii.modules();
-
     addOSComponentsToSoMap(&soMap);
-    _globalSharedObjectMapInfo = new SharedObjectMapInfo(soMap.obj());
+    return soMap.obj();
+}
+
+SharedObjectMapInfo& mutableGlobalSharedObjectMapInfo() {
+    auto& p = *new SharedObjectMapInfo(buildObj());
+    return p;
+}
+
+MONGO_INITIALIZER(ExtractSOMap)(InitializerContext*) {
+    // Call buildObj() again now that there is better VersionInfo.
+    mutableGlobalSharedObjectMapInfo().setObj(buildObj());
     return Status::OK();
 }
 
+const bool dummyToForceEarlyInitializationOfSharedObjectMapInfo = [] {
+    mutableGlobalSharedObjectMapInfo();
+    return true;
+}();
+
 }  // namespace
 
 SharedObjectMapInfo::SharedObjectMapInfo(BSONObj obj) : _obj(std::move(obj)) {}
 
-SharedObjectMapInfo* globalSharedObjectMapInfo() {
-    return _globalSharedObjectMapInfo;
+const BSONObj& SharedObjectMapInfo::obj() const {
+    return _obj;
+}
+
+void SharedObjectMapInfo::setObj(BSONObj obj) {
+    _obj = std::move(obj);
+}
+
+const SharedObjectMapInfo& globalSharedObjectMapInfo() {
+    // This file internally has a non-const object, but only exposes a const reference
+    // to it to the public API. We do this to support stacktraces that might occur
+    // before the "ExtractSOMap" MONGO_INITIALIZER above.
+    return mutableGlobalSharedObjectMapInfo();
 }
 
 }  // namespace mongo
diff --git a/src/mongo/util/stacktrace_somap.h b/src/mongo/util/stacktrace_somap.h
index 9e2db532cc8..a689fef4714 100644
--- a/src/mongo/util/stacktrace_somap.h
+++ b/src/mongo/util/stacktrace_somap.h
@@ -37,15 +37,17 @@ namespace mongo {
 class SharedObjectMapInfo {
 public:
     explicit SharedObjectMapInfo(BSONObj obj);
-    const BSONObj& obj() const {
-        return _obj;
-    }
+
+    const BSONObj& obj() const;
+
+    void setObj(BSONObj obj);
 
 private:
     BSONObj _obj;
 };
 
-// Available after the MONGO_INITIALIZER has run.
-SharedObjectMapInfo* globalSharedObjectMapInfo();
+// Can always be called, but more information is populated
+// after the MONGO_INITIALIZER has run.
+const SharedObjectMapInfo& globalSharedObjectMapInfo();
 
 }  // namespace mongo
diff --git a/src/mongo/util/stacktrace_test.cpp b/src/mongo/util/stacktrace_test.cpp
index ee8d510cdec..3e1c47d3ade 100644
--- a/src/mongo/util/stacktrace_test.cpp
+++ b/src/mongo/util/stacktrace_test.cpp
@@ -358,6 +358,42 @@ TEST(StackTrace, WindowsFormat) {
         << "of trace: `" << trace << "`";
 }
 
+std::string traceString() {
+    std::ostringstream os;
+    printStackTrace(os);
+    return os.str();
+}
+
+/** Emit a stack trace before main() runs, for use in the EarlyTraceSanity test. */
+std::string earlyTrace = traceString();
+
+/**
+ * Verify that the JSON object emitted as part of a stack trace contains a "processInfo"
+ * field, and that it, in turn, contains the fields expected by mongosymb.py. Verify in
+ * particular that a stack trace emitted before main() and before the MONGO_INITIALIZERS
+ * have run will be valid according to mongosymb.py.
+ */
+TEST(StackTrace, EarlyTraceSanity) {
+    if (kIsWindows) {
+        return;
+    }
+
+    const std::string trace = traceString();
+    const std::string substrings[] = {
+        R"("processInfo":)",
+        R"("gitVersion":)",
+        R"("compiledModules":)",
+        R"("uname":)",
+        R"("somap":)",
+    };
+    for (const auto& sub : substrings) {
+        ASSERT_STRING_CONTAINS(earlyTrace, sub);
+    }
+    for (const auto& sub : substrings) {
+        ASSERT_STRING_CONTAINS(trace, sub);
+    }
+}
+
 class StringSink : public StackTraceSink {
 public:
     StringSink(std::string& s) : _s{s} {}