SERVER-27439 Large queries can omit comment in currentOp

1 files changed, 54 insertions, 13 deletions

diff --git a/src/mongo/db/curop.cpp b/src/mongo/db/curop.cpp
index 2af0907170d..f4c028879c3 100644
--- a/src/mongo/db/curop.cpp
+++ b/src/mongo/db/curop.cpp
@@ -296,23 +296,30 @@ Command::ReadWriteType CurOp::getReadWriteType() const {
 }
 
 namespace {
+
+/**
+ * Used by callers of appendAsObjOrString to indicate whether a comment parameter may be present and
+ * should be retained upon truncation.
+ */
+enum class TruncationMode { kNoComment, kIncludeComment };
+
 /**
- * Appends {name: obj} to the provided builder.  If obj is greater than maxSize, appends a
- * string summary of obj instead of the object itself.
+ * Appends {<name>: obj} to the provided builder.  If obj is greater than maxSize, appends a string
+ * summary of obj as { <name>: { $truncated: "obj" } }. If a comment parameter is present, add it to
+ * the truncation object.
  */
 void appendAsObjOrString(StringData name,
                          const BSONObj& obj,
                          size_t maxSize,
-                         BSONObjBuilder* builder) {
+                         BSONObjBuilder* builder,
+                         TruncationMode truncateBehavior = TruncationMode::kNoComment) {
     if (static_cast<size_t>(obj.objsize()) <= maxSize) {
         builder->append(name, obj);
     } else {
         // Generate an abbreviated serialization for the object, by passing false as the
         // "full" argument to obj.toString().
         std::string objToString = obj.toString();
-        if (objToString.size() <= maxSize) {
-            builder->append(name, objToString);
-        } else {
+        if (objToString.size() > maxSize) {
             // objToString is still too long, so we append to the builder a truncated form
             // of objToString concatenated with "...".  Instead of creating a new string
             // temporary, mutate objToString to do this (we know that we can mutate
@@ -320,8 +327,22 @@ void appendAsObjOrString(StringData name,
             objToString[maxSize - 3] = '.';
             objToString[maxSize - 2] = '.';
             objToString[maxSize - 1] = '.';
-            builder->append(name, StringData(objToString).substr(0, maxSize));
         }
+
+        StringData truncation = StringData(objToString).substr(0, maxSize);
+
+        // Append the truncated representation of the object to the builder. If this is an operation
+        // which supports a comment parameter and one is present, write it to the object alongside
+        // the truncated op. This object will appear as {$truncated: "{find: \"collection\", filter:
+        // {x: 1, ...", comment: "comment text" }
+        BSONObjBuilder truncatedBuilder(builder->subobjStart(name));
+        truncatedBuilder.append("$truncated", truncation);
+
+        if (truncateBehavior == TruncationMode::kIncludeComment && obj["comment"]) {
+            truncatedBuilder.append(obj["comment"]);
+        }
+
+        truncatedBuilder.doneFast();
     }
 }
 }  // namespace
@@ -354,9 +375,15 @@ void CurOp::reportState(BSONObjBuilder* builder) {
         appendAsObjOrString("query",
                             upconvertQueryEntry(_query, NamespaceString(_ns), ntoreturn, ntoskip),
                             maxQuerySize,
-                            builder);
+                            builder,
+                            TruncationMode::kIncludeComment);
     } else {
-        appendAsObjOrString("query", _query, maxQuerySize, builder);
+        appendAsObjOrString(
+            "query",
+            _query,
+            maxQuerySize,
+            builder,
+            (_isCommand ? TruncationMode::kIncludeComment : TruncationMode::kNoComment));
     }
 
     if (!_collation.isEmpty()) {
@@ -364,7 +391,11 @@ void CurOp::reportState(BSONObjBuilder* builder) {
     }
 
     if (!_originatingCommand.isEmpty()) {
-        appendAsObjOrString("originatingCommand", _originatingCommand, maxQuerySize, builder);
+        appendAsObjOrString("originatingCommand",
+                            _originatingCommand,
+                            maxQuerySize,
+                            builder,
+                            TruncationMode::kIncludeComment);
     }
 
     if (!_planSummary.empty()) {
@@ -557,15 +588,25 @@ void OpDebug::append(const CurOp& curop,
         appendAsObjOrString("query",
                             upconvertQueryEntry(curop.query(), nss, ntoreturn, ntoskip),
                             maxElementSize,
-                            &b);
+                            &b,
+                            TruncationMode::kIncludeComment);
     } else if (curop.haveQuery()) {
         const char* fieldName = (logicalOp == LogicalOp::opCommand) ? "command" : "query";
-        appendAsObjOrString(fieldName, curop.query(), maxElementSize, &b);
+        appendAsObjOrString(
+            fieldName,
+            curop.query(),
+            maxElementSize,
+            &b,
+            (iscommand ? TruncationMode::kIncludeComment : TruncationMode::kNoComment));
     }
 
     auto originatingCommand = curop.originatingCommand();
     if (!originatingCommand.isEmpty()) {
-        appendAsObjOrString("originatingCommand", originatingCommand, maxElementSize, &b);
+        appendAsObjOrString("originatingCommand",
+                            originatingCommand,
+                            maxElementSize,
+                            &b,
+                            TruncationMode::kIncludeComment);
     }
 
     if (!updateobj.isEmpty()) {