How can I log actual queries to MongoDB with mongo java driver

Question

I want to see what queries mongo java driver produce, but I'm not able to do that.

Using information from the official documentation I'm able just see in the log that update operation executes, but I don't see the query of this operation.

Answer 1

You can set the logger level for org.mongodb to DEBUG and your Java driver will emit detailed logging like this:

2018-01-18 16:51:07|[main]|[NA]|INFO |org.mongodb.driver.connection|Opened connection [connectionId{localValue:2, serverValue:39}] to localhost:27017  
2018-01-18 16:51:07|[main]|[NA]|DEBUG|org.mongodb.driver.protocol.insert|Inserting 1 documents into namespace stackoverflow.sample on connection [connectionId{localValue:2, serverValue:39}] to server localhost:27017  
2018-01-18 16:51:07|[main]|[NA]|DEBUG|org.mongodb.driver.protocol.insert|Insert completed  
2018-01-18 16:51:07|[main]|[NA]|DEBUG|org.mongodb.driver.protocol.command|Sending command {find : BsonString{value='sample'}} to database stackoverflow on connection [connectionId{localValue:2, serverValue:39}] to server localhost:27017  
2018-01-18 16:51:07|[main]|[NA]|DEBUG|org.mongodb.driver.protocol.command|Command execution completed  
2018-01-18 16:51:07|[main]|[NA]|DEBUG|org.mongodb.driver.protocol.command|Sending command {findandmodify : BsonString{value='sample'}} to database stackoverflow on connection [connectionId{localValue:2, serverValue:39}] to server localhost:27017  
2018-01-18 16:51:07|[main]|[NA]|DEBUG|org.mongodb.driver.protocol.command|Command execution completed  

In the above log output you can see the details of a query submitted by the client:

org.mongodb.driver.protocol.command|Sending command {find : BsonString{value='sample'}}

Alternatively, you can enable profiling on the server side ...

db.setProfilingLevel(2)

... causes the MongoDB profiler to collect data for all operations against that database.

The profiler output (which includes the query submitted by the client) is written to the system.profile collection in whichever database profiling has been enabled.

More details in the docs but the short summary is:

// turn up the logging
db.setProfilingLevel(2)

// ... run some commands

// find all profiler documents, most recent first
db.system.profile.find().sort( { ts : -1 } )

// turn down the logging
db.setProfilingLevel(0)