Why fork is used?
fork is the right way to make sure your MongoDB runs as a daemon. In this case, fork should be defined as true in the configuration file. If you want to run it as an interactive process. just set it to false.
How to Perform Lookup?
db.classes.aggregate( [
{ $lookup: {
from: "members",
localField: "enrollmentlist",
foreignField: "name",
as: "enrollee_info"
}}
])
mongostat and mongotop
These two great tools are provided as part of the MongoDB installation and can be used to detect the queries types and collections that most heavily affect the MongoDB performance.
Simple Backup and Restore
mongodump --out /tmp/dump/
mongorestore mongodb://127.0.0.1 /tmp/dump/
mongorestore mongodb://127.0.0.1 /tmp/dump/
How to Reset Your MongoDB Instance?
Stop the service, remove all content from the /var/lib/mongodb directory, and start the service again:
sudo service mongod stop
sudo rm -rf /var/lib/mongodb
sudo service mongod start
Setting Custom Replication Source
MongoDB replication automatically balances between replication from the Primary (most updated values) and secondaries w/ a low networking latency to minimize WAN network usage and optimize network resources.
However, your can control this behavior and configure specific source rs.syncFrom() command. Please notice that this command result is temporary and will reset to default once mongod is restarted, connection closed between nodes or 30 sec timeout is reached.
Initiate Your Replicaset:
1. Set the replicaset name in the mongod.conf file
2. Change the bindIP to 0.0.0.0 in the config file
3. Run on the first node the rs.initiate command
rs.initiate(
{
_id: "rs",
version: 1,
members: [
{ _id: 0, host : "172.30.0.158:27017" },
{ _id: 1, host : "172.30.0.151:27017" },
{ _id: 2, host : "172.30.0.219:27017" }
]
}
)
Search for Delta in the Oplog
db.oplog.rs.find({"ts":{$gt : Timestamp(1640074543, 1)}})
