Details
Description
The oplog starting in version 2.2.1 seemed to get a new format when updates are performed containing $set operations. This new format creates BSON documents in the rs.oplog collection where the $set key is included for each $set operation, whereas in versions prior to 2.2.1 there would only be a single $set key in the document and a subdocument would describe all the fields to be set. Since there are multiple $set keys, most drivers cannot parse these oplog documents, and will get exceptions while iterating through the oplog query results that contain any update operation with multiple $set updates.
Here is an example for creating the malformed oplog entries on a new 2.2.1 or 2.2.2 system:
rs0:PRIMARY> db.mycoll.save({_id:"unique-id-1234", "aaa":"0000", "bbb": "1111"})
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rs0:PRIMARY> db.mycoll.update({_id:"unique-id-1234"}, {$set:{"aaa":"1234","bbb":"7654"}})
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rs0:PRIMARY> use local
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rs0:PRIMARY> db.oplog.rs.find().pretty()
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{
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"ts" : Timestamp(1353099630000, 1),
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"h" : NumberLong(0),
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"v" : 2,
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"op" : "n",
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"ns" : "",
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"o" : {
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"msg" : "initiating set"
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}
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}
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{
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"ts" : Timestamp(1353099716000, 1),
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"h" : NumberLong("6562103115049336849"),
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"v" : 2,
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"op" : "i",
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"ns" : "sample.mycoll",
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"o" : {
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"_id" : "unique-id-1234",
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"aaa" : "0000",
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"bbb" : "1111"
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}
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}
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{
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"ts" : Timestamp(1353099904000, 1),
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"h" : NumberLong("-7902296395036453900"),
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"v" : 2,
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"op" : "u",
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"ns" : "sample.mycoll",
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"o2" : {
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"_id" : "unique-id-1234"
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},
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"o" : {
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"$set" : {
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"aaa" : "1234"
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},
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"$set" : {
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"aaa" : "1234"
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}
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}
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}
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You will notice the "o" subdocument contains two "$set" keys, and drivers can't handle this new format. In prior versions, including 2.2.0, I would see this type of oplog entry when performing a update on a document, setting multiple fields:
{
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"ts" : Timestamp(1353074108000, 3),
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"h" : NumberLong("-3950642131243057651"),
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"op" : "u",
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"ns" : "mydb.mycollection",
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"o2" : {
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"_id" : "my-unique-id-1234"
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},
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"o" : {
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"$set" : {
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"aaa" : "1234",
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"bbb" : "2345",
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"ccc" : "3456",
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"ddd" : "4567",
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"eee" : "5678",
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"fff" : "6789",
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"ggg" : "7890",
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"hhh" : "asdf"
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}
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}
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}
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If it is helpful, here is the entire conversation in context.
Attachments
Issue Links
- duplicates
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SERVER-1606 Oplog entries contain repeated fields ($set)
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- Closed
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- related to
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- Closed
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DOCS-923 Document driver support for duplicate BSON keys
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- Closed
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