SERVER-57326: Add bson data gdb pretty printer function.

2 files changed, 72 insertions, 0 deletions

diff --git a/buildscripts/gdb/mongo.py b/buildscripts/gdb/mongo.py
index 08a26df539b..caea23d7a02 100644
--- a/buildscripts/gdb/mongo.py
+++ b/buildscripts/gdb/mongo.py
@@ -24,6 +24,13 @@ except Exception as e:
     print("Failed to load the libstdc++ pretty printers: " + str(e))
 # pylint: enable=invalid-name,wildcard-import
 
+try:
+    import bson
+except ImportError as err:
+    print("Warning: Could not load bson library for Python '" + str(sys.version) + "'.")
+    print("Check with the pip command if pymongo 3.x is installed.")
+    bson = None
+
 if sys.version_info[0] < 3:
     raise gdb.GdbError(
         "MongoDB gdb extensions only support Python 3. Your GDB was compiled against Python 2")
@@ -748,6 +755,36 @@ class MongoDBJavaScriptStack(gdb.Command):
 MongoDBJavaScriptStack()
 
 
+class MongoDBPPrintBsonAtPointer(gdb.Command):
+    """Interprets a pointer into raw memory as the start of a bson object. Pretty print the results."""
+
+    def __init__(self):
+        """Init."""
+        RegisterMongoCommand.register(self, "mongodb-pprint-bson", gdb.COMMAND_STATUS)
+
+    def invoke(self, args, _from_tty):  # pylint: disable=no-self-use
+        """Invoke."""
+        args = args.split(' ')
+        if len(args) == 0 or (len(args) == 1 and len(args[0]) == 0):
+            print("Usage: mongodb-pprint-bson <ptr> <optional length>")
+            return
+
+        ptr = eval(args[0])  # pylint: disable=eval-used
+        size = 20 * 1024
+        if len(args) >= 2:
+            size = int(args[1])
+        print("Pretty printing bson object at %s (%d bytes)" % (ptr, size))
+
+        memory = gdb.selected_inferior().read_memory(ptr, size).tobytes()
+        bsonobj = next(bson.decode_iter(memory))
+
+        from pprint import pprint
+        pprint(bsonobj)
+
+
+MongoDBPPrintBsonAtPointer()
+
+
 class MongoDBHelp(gdb.Command):
     """Dump list of mongodb commands."""
 
diff --git a/buildscripts/gdb/mongo_printers.py b/buildscripts/gdb/mongo_printers.py
index 6adf0f3b3b0..c8a5790d305 100644
--- a/buildscripts/gdb/mongo_printers.py
+++ b/buildscripts/gdb/mongo_printers.py
@@ -566,6 +566,40 @@ class MongoPrettyPrinterCollection(gdb.printing.PrettyPrinter):
         return None
 
 
+class WtUpdateToBsonPrinter(object):
+    """Pretty printer for WT_UPDATE. Interpreting the `data` field as bson."""
+
+    def __init__(self, val):
+        """Initializer."""
+        self.val = val
+        self.size = self.val['size']
+        self.ptr = self.val['data']
+
+    @staticmethod
+    def display_hint():
+        """DisplayHint."""
+        return 'map'
+
+    # pylint: disable=R0201
+    def to_string(self):
+        """ToString."""
+        elems = []
+        for idx in range(len(self.val.type.fields())):
+            fld = self.val.type.fields()[idx]
+            val = self.val[fld.name]
+            elems.append(str((fld.name, str(val))))
+        return "WT_UPDATE: \n  %s" % ('\n  '.join(elems))
+
+    def children(self):
+        """children."""
+        memory = gdb.selected_inferior().read_memory(self.ptr, self.size).tobytes()
+        bsonobj = next(bson.decode_iter(memory))  # pylint: disable=stop-iteration-return
+
+        for key, value in list(bsonobj.items()):
+            yield 'key', key
+            yield 'value', bson.json_util.dumps(value)
+
+
 def build_pretty_printer():
     """Build a pretty printer."""
     pp = MongoPrettyPrinterCollection()
@@ -582,6 +616,7 @@ def build_pretty_printer():
     pp.add('__wt_cursor', '__wt_cursor', False, WtCursorPrinter)
     pp.add('__wt_session_impl', '__wt_session_impl', False, WtSessionImplPrinter)
     pp.add('__wt_txn', '__wt_txn', False, WtTxnPrinter)
+    pp.add('__wt_update', '__wt_update', False, WtUpdateToBsonPrinter)
     return pp