MongoDB Recipes: Change mongod’s log level

To view the current log verbosity levels, use the db.getLogComponents() method.
In the below mongod instance, the verbosity is 0 (default informational level). Here we can see that the verbosity of individual components are -1, this means the component inherits the log level of its parent.

We can configure log verbosity levels by

1. Method 1: Using mongod’s startup settings
2. Method 2: Using the logComponentVerbosity parameter
3. Method 3: Using the db.setLogLevel() method.

Method 1:

We can configure global verbosity level using: the systemLog.verbosity settings

Also we can change verbosity level of an individual log component using the systemLog.component.<name>.verbosity setting for that component.

For example we are changing the verbosity level of network component to 0.
systemLog.component.network.verbosity

Method 2:

To change log verbosity level using the logComponentVerbosity parameter, pass a document with the required verbosity settings.
Example, we are going to set the default verbosity level to 2, verbosity level of storage to 1, and the storage.journal to 0
> use admin
> db.runCommand( { setParameter: 1, logComponentVerbosity:
{
verbosity: 2,
storage: {
verbosity: 1,
journal:
{
verbosity: 0
}
}
}
} )

Method 3:

We can use the db.setLogLevel() method to update a single component’s log level.
Example:

• Change the default verbosity level to 0:
  
• Change the storage.journal log level to 4:
  

MongoDB Receipes: Change chunk size in a shared cluster

The default chunk size in a shared cluster is 64MB. If we want to change it to a smaller/larger size (the allowed range of the chunk size is between 1 and 1024 MB):

Method 1:

This method works before/after the shared cluster is initialized and is recommended method

• Login to any mongos of the shared cluster:
  
• To change the global chunk size, update the value field of chunksize in the config database, here we are changing the chunk size to 5MB:
  

Method 2:

This method works only when you initialize the cluster for the first time. After the cluster is initialized, this method will not change the chunk size of the cluster.
Start the mongos with sharding.chunkSize (using config file) or --chunkSize (command line option) and set this option to desired chunk size value.