Oplog does not record operations within a transaction - MongoDb
Question
If you run the below code, outside a transaction object will appear in the oplog as an insert operation but oplog will have no record of inside a transaction but they will be both saved properly to the collection.
I tried to look up the problem with no luck, although I was able to get a confirmation that in my mongodb server version, oplog will create a separate entry for each operation , although I don't get either the 4.0 style, nor the 4.2 !
The Code
const { MongoClient } = require('mongodb');
const dbName = "db-name";
const collectionName = "collection-name";
const dbUri = "mongodb+srv://<user>:<pass>@<cluster-url>/<db-name>?retryWrites=true&w=majority";
const client = await new MongoClient(dbUri, { useUnifiedTopology: true }).connect();
const db = client.db(dbName);
const collection = db.collection(collectionName);
const session = client.startSession();
const transactionOptions = {
readConcern: { level: 'snapshot' },
writeConcern: { w: 'majority' }
};
await collection.insertOne({ name: "outside a transaction" });
await session.withTransaction(async () => {
await collection.insertOne({ name: "inside a transaction" }, { session: session});
}, transactionOptions);
await session.endSession();
await client.close();
Oplog Result
Query: db.oplog.rs.find({}).sort({$natural: -1}) Actual Count: 1 Expected Count: 2
{
"lsid":{
"id":{
"$binary":"IwdZfNnGTvGDoABb0gjxXQ==",
"$type":"4"
},
"uid":{
"$binary":"ddqot68vLpBUPnOuqFj2cdClv/dv/vF9ZVSwknYHEsE=",
"$type":"0"
}
},
"txnNumber":{
"$numberLong":"1"
},
"op":"i",
"ns":"testDb.tests",
"ui":{
"$binary":"2a1ZJWDySfGuvtgMK2G2gQ==",
"$type":"4"
},
"o":{
"_id":{
"$oid":"60f6feb12a662ec3fc985400"
},
"name":"outside a transaction"
},
"ts":{
"$timestamp":{
}
},
"t":{
"$numberLong":"73"
},
"wall":{
"$date":"2021-07-20T16:49:53.226Z"
},
"v":{
"$numberLong":"2"
},
"stmtId":0,
"prevOpTime":{
"ts":{
"$timestamp":{
}
},
"t":{
"$numberLong":"-1"
}
}
}
- Mongo Database Version: 4.2
- Mongo Database Setup: 3 Member Replica Set (Hosted on Atlas)
- Mongo Driver: Tried both V3.6 and V4 ( both are compatible with the database version )
1 answers
solution1
0 ACCPTED 2021-07-20 22:30:00
When I run this test on a MongoDB 5.0 (3-node replicaset) I see the two oplog entries...
use local
db.oplog.rs.find({ns: {$ne: ''}}).sort({ts: -1})
{
lsid: {
id: UUID("74450c89-04ca-441c-93b4-24472c833e98"),
uid: Binary(Buffer.from("92e7f3b655ee46a4a10212cc1146f3a783e6f4266bef6b5699dbc5528be5177c", "hex"), 0)
},
txnNumber: Long("1"),
op: 'c',
ns: 'admin.$cmd',
o: {
applyOps: [
{
op: 'i',
ns: 'nodetest.mycollection',
ui: UUID("b6079273-b2de-49a4-b148-837b4ac2c95f"),
o: {
_id: ObjectId("60f74ca3601963e6c5ca02f2"),
name: 'inside a transaction'
}
}
]
},
ts: Timestamp(3, 1626819747),
t: Long("95"),
v: Long("2"),
wall: ISODate("2021-07-20T22:22:27.714Z"),
prevOpTime: { ts: Timestamp(0, 0), t: Long("-1") }
},
{
lsid: {
id: UUID("92372b8e-89fd-48ff-ab2a-780520e97c39"),
uid: Binary(Buffer.from("92e7f3b655ee46a4a10212cc1146f3a783e6f4266bef6b5699dbc5528be5177c", "hex"), 0)
},
txnNumber: Long("1"),
op: 'i',
ns: 'nodetest.mycollection',
ui: UUID("b6079273-b2de-49a4-b148-837b4ac2c95f"),
o: {
_id: ObjectId("60f74ca3601963e6c5ca02f1"),
name: 'outside a transaction'
},
ts: Timestamp(2, 1626819747),
t: Long("95"),
v: Long("2"),
wall: ISODate("2021-07-20T22:22:27.367Z"),
stmtId: 0,
prevOpTime: { ts: Timestamp(0, 0), t: Long("-1") }
}
Same thing in MongoDB 4.4 ....
{
"lsid" : {
"id" : UUID("8d72b35a-a8d7-4ffd-a56a-1f2f02b944a5"),
"uid" : BinData(0,"kufztlXuRqShAhLMEUbzp4Pm9CZr72tWmdvFUovlF3w=")
},
"txnNumber" : NumberLong(1),
"op" : "c",
"ns" : "admin.$cmd",
"o" : {
"applyOps" : [
{
"op" : "i",
"ns" : "nodetest.mycollection",
"ui" : UUID("52fcd28a-9de8-45b0-966a-d1b869976d11"),
"o" : {
"_id" : ObjectId("60f74ead58cd50e7b5ec7e1c"),
"name" : "inside a transaction"
}
}
]
},
"ts" : Timestamp(1626820269, 1),
"t" : NumberLong(185),
"wall" : ISODate("2021-07-20T22:31:09.111Z"),
"v" : NumberLong(2),
"prevOpTime" : {
"ts" : Timestamp(0, 0),
"t" : NumberLong(-1)
}
}
{
"lsid" : {
"id" : UUID("3985c2b0-1863-4718-8851-747ff8160045"),
"uid" : BinData(0,"kufztlXuRqShAhLMEUbzp4Pm9CZr72tWmdvFUovlF3w=")
},
"txnNumber" : NumberLong(1),
"op" : "i",
"ns" : "nodetest.mycollection",
"ui" : UUID("52fcd28a-9de8-45b0-966a-d1b869976d11"),
"o" : {
"_id" : ObjectId("60f74eac58cd50e7b5ec7e1b"),
"name" : "outside a transaction"
},
"ts" : Timestamp(1626820268, 2),
"t" : NumberLong(185),
"wall" : ISODate("2021-07-20T22:31:08.912Z"),
"v" : NumberLong(2),
"stmtId" : 0,
"prevOpTime" : {
"ts" : Timestamp(0, 0),
"t" : NumberLong(-1)
}
}
MongoDB 4.2
{
"ts" : Timestamp(1626820723, 2),
"t" : NumberLong(501),
"h" : NumberLong(0),
"v" : 2,
"op" : "c",
"ns" : "admin.$cmd",
"wall" : ISODate("2021-07-20T22:38:43.304Z"),
"lsid" : {
"id" : UUID("0df8170a-6700-4751-9c14-88651ec54f9b"),
"uid" : BinData(0,"kufztlXuRqShAhLMEUbzp4Pm9CZr72tWmdvFUovlF3w=")
},
"txnNumber" : NumberLong(1),
"prevOpTime" : {
"ts" : Timestamp(0, 0),
"t" : NumberLong(-1)
},
"o" : {
"applyOps" : [
{
"op" : "i",
"ns" : "nodetest.mycollection",
"ui" : UUID("4c0507b2-8018-48d4-9f80-f2bb6bd227dd"),
"o" : {
"_id" : ObjectId("60f75073abc759e7f6d53ba6"),
"name" : "inside a transaction"
}
}
]
}
}
{
"ts" : Timestamp(1626820723, 1),
"t" : NumberLong(501),
"h" : NumberLong(0),
"v" : 2,
"op" : "i",
"ns" : "nodetest.mycollection",
"ui" : UUID("4c0507b2-8018-48d4-9f80-f2bb6bd227dd"),
"wall" : ISODate("2021-07-20T22:38:43.016Z"),
"lsid" : {
"id" : UUID("4983da87-0c9c-448b-8d54-50f3885ce9ce"),
"uid" : BinData(0,"kufztlXuRqShAhLMEUbzp4Pm9CZr72tWmdvFUovlF3w=")
},
"txnNumber" : NumberLong(1),
"stmtId" : 0,
"prevOpTime" : {
"ts" : Timestamp(0, 0),
"t" : NumberLong(-1)
},
"o" : {
"_id" : ObjectId("60f75072abc759e7f6d53ba5"),
"name" : "outside a transaction"
}
}
MongoDB 4.0
{
"ts" : Timestamp(1626821049, 3),
"t" : NumberLong(2),
"h" : NumberLong("-7247099881451421420"),
"v" : 2,
"op" : "c",
"ns" : "admin.$cmd",
"wall" : ISODate("2021-07-20T22:44:09.560Z"),
"lsid" : {
"id" : UUID("984168e5-c1fd-47cd-9981-acae8585e3e9"),
"uid" : BinData(0,"kufztlXuRqShAhLMEUbzp4Pm9CZr72tWmdvFUovlF3w=")
},
"txnNumber" : NumberLong(1),
"stmtId" : 0,
"prevOpTime" : {
"ts" : Timestamp(0, 0),
"t" : NumberLong(-1)
},
"o" : {
"applyOps" : [
{
"op" : "i",
"ns" : "nodetest.mycollection",
"ui" : UUID("60acd457-0d98-4e06-8921-bf10d1bb63c7"),
"o" : {
"_id" : ObjectId("60f751b926f38ce856f9b08d"),
"name" : "inside a transaction"
}
}
]
}
}
{
"ts" : Timestamp(1626821049, 2),
"t" : NumberLong(2),
"h" : NumberLong("6159503664626025226"),
"v" : 2,
"op" : "i",
"ns" : "nodetest.mycollection",
"ui" : UUID("60acd457-0d98-4e06-8921-bf10d1bb63c7"),
"wall" : ISODate("2021-07-20T22:44:09.266Z"),
"lsid" : {
"id" : UUID("8f7d6590-8c7c-4819-9ce7-f69b92725c26"),
"uid" : BinData(0,"kufztlXuRqShAhLMEUbzp4Pm9CZr72tWmdvFUovlF3w=")
},
"txnNumber" : NumberLong(1),
"stmtId" : 0,
"prevOpTime" : {
"ts" : Timestamp(0, 0),
"t" : NumberLong(-1)
},
"o" : {
"_id" : ObjectId("60f751b926f38ce856f9b08c"),
"name" : "outside a transaction"
}
}
Not testing with 3.6 since it is no longer a supported version and never supported transactions anyways.
I had to modify your example program to make it work, here is what I ran for a test...
Modified Test Program
const { MongoClient } = require('mongodb');
const dbName = "nodetest";
const collectionName = "mycollection";
const dbUri = "mongodb://barry:????????@localhost:44011,localhost:44012,localhost:44013/nodetest?replicaSet=replSet&authSource=admin&retryWrites=true&w=majority";
async function run() {
const client = await new MongoClient(dbUri, { useUnifiedTopology: true }).connect();
const db = client.db(dbName);
const collection = db.collection(collectionName);
const session = client.startSession();
const transactionOptions = {
readConcern: { level: 'snapshot' },
writeConcern: { w: 'majority' }
};
await collection.insertOne({ name: "outside a transaction" });
await session.withTransaction(async () => {
await collection.insertOne({ name: "inside a transaction" }, { session: session});
}, transactionOptions);
await session.endSession();
await client.close();
}
run().catch(console.dir);
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