Mongo request calls BSONElement: bad type 65

Question

We are faced with a situation where the documents that exist in our MongoDB cannot be requested without leading to:

db.collection.find({"_id":ObjectId("50d393be70a580280b117ea5")}) Wed Jan 2 12:30:44 Assertion: 10320:BSONElement: bad type 65 0x6073f1 0x5d1aa9 0x4b0d98 0x5c17a6 0x6b3f35 0x6b6a2c 0x69be0a 0x6aa13f 0x668e46 0x668ec2 0x66a2ce 0x5cbcc4 0x4a4a14 0x4a67e6 0x7f2223434c4d 0x49f669 mongo(_ZN5mongo15printStackTraceERSo+0x21) [0x6073f1] mongo(_ZN5mongo11msgassertedEiPKc+0x99) [0x5d1aa9] mongo(_ZNK5mongo11BSONElement4sizeEv+0x1d8) [0x4b0d98] mongo(_ZN5mongo16resolveBSONFieldEP9JSContextP8JSObjectljPS3_+0x146) [0x5c17a6] mongo(js_LookupPropertyWithFlags+0x3f5) [0x6b3f35] mongo(js_GetProperty+0x7c) [0x6b6a2c] mongo(js_Interpret+0x10ea) [0x69be0a] mongo(js_Execute+0x36f) [0x6aa13f] mongo(JS_EvaluateUCScriptForPrincipals+0x66) [0x668e46] mongo(JS_EvaluateUCScript+0x22) [0x668ec2] mongo(JS_EvaluateScript+0x6e) [0x66a2ce] mongo(_ZN5mongo7SMScope4execERKNS_10StringDataERKSsbbbi+0x144) [0x5cbcc4] mongo(_Z5_mainiPPc+0x26c4) [0x4a4a14] mongo(main+0x26) [0x4a67e6] /lib/libc.so.6(__libc_start_main+0xfd) [0x7f2223434c4d] mongo(__gxx_personality_v0+0x2a1) [0x49f669] 

I can run mongodump of this particular entry, and then when I convert bson to json, I get:

 $ bsondump server1_collection.bson > server1_collection.json terminate called after throwing an instance of 'std::length_error' what():  basic_string::_S_create Aborted 

It looks like there might be a problem with UTF-8 characters and / or base64 encoded strings, which will lead to the preservation of the invalid BSON: - https://jira.mongodb.org/browse/SERVER-7769

It seems like moving forward, I can run mongod with --objcheck to ensure that invalid data cannot be inserted (uncertainty about performance penalties).

I don’t know how I can easily hide old data and delete these invalid records.

Answer 1

Here are related questions and answers . You should probably heal database corruption.

You can check if there are any errors (use mongo shell):

 db.getSiblingDB("your_base").oplog.rs.validate(true) 

Try using: db.repairDatabase() Note that this only affects the current database .

Or start mongod with mongod --repair .

The zero termination character in the data can also be a topic .

Sometimes it is impossible to restore db : how can you restore data from a replica or an earlier dump.