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Why does MongoDB use so much memory in WiredTiger?
(As per documentation, WiredTiger uses at most ~60% of RAM for its cache, but considering the dataset size, does it even have enough data to be able to take 86GBs of RAM ?) Even if the memory usage is expected, why won’t mongo let go of its allocated memory in case another process starts requesting for more memory ?
How to automatically sync a member of a replica set in MongoDB?
MongoDB provides two options for performing an initial sync: Restart the mongod with an empty data directory and let MongoDB’s normal initial syncing feature restore the data. This is the more simple option but may take longer to replace the data. See Automatically Sync a Member.
When to sync MongoDB to empty DATA directory?
Schedule the synchronization during a time of low usage or during a maintenance window. MongoDB provides two options for performing an initial sync: Restart the mongod with an empty data directory and let MongoDB’s normal initial syncing feature restore the data. This is the more simple option but may take longer to replace the data.
Can a MongoDB backup be used to copy data?
If copying data files, ensure that your copy includes the content of the local database. You cannot use a mongodump backup for the data files: only a snapshot backup. For approaches to capturing a consistent snapshot of a running mongod instance, see the MongoDB Backup Methods documentation.
How can I limit the size of the MongoDB cache?
You can limit the MongoDB cache size by adding the cacheSizeGB argument to the /etc/mongod.conf configuration file, as shown below. But MongoDB uses both its internal cache and the system’s file system cache.
How to check virtual memory in MongoDB server?
To check your file system cache run free -k to show available virtual memory in kilobytes. Below is what my server looked like over 5 minute intervals when I ran the machine out of memory. The column to note is available . Divide the number shown by 1024*1024 to convert this number to gigabytes.
What are virt and Res in MongoDB?
VIRT and RES are virtual and resident memory. Below you see that mongod is using 91% of the system’s memory in this example. At that point the system became unresponsive. You can also get memory usage statistics from MongoDB in the shell: If you have even done C or C++ programming you will be familiar with malloc .
Is there a way to aggregate data in MongoDB?
Because MongoDB is document-based, we can shape our documents the way we need. However, there is often a requirement to use information from more than one collection. Using the $lookup (), here is an aggregate query that merges fields from two collections.
When to use useddisk indicator in MongoDB 4.2?
Starting in MongoDB 4.2, the profiler log messages and diagnostic log messages includes a usedDisk indicator if any aggregation stage wrote data to temporary files due to memory restrictions.