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Connection alerts typically occur when the maximum number of allowable connections to a MongoDB process has been exceeded. Once the limit is exceeded, no new connections can be opened until the number of open connections drops down below the limit.
You can configure the following alert conditions in the project-level alert settings page to trigger alerts.
Connections occurs if the number of active
connections to the host meets the specified average.
Connections % of configured limit occurs if the number of open
connections to the host exceeds the specified percentage.
Exceeding the connection limit for an Atlas cluster may occur for
a number of reasons. Different Atlas tiers have different
connection limits; clusters of size
M0/M2/M5, for example, are limited to 500 connections, and clusters
M10 are limited to 1500 connections. Larger cluster tiers
have higher connection limits. Different database
access applications have different ways of implementing
which affects how many open connections your application maintains at
any given time.
To resolve a connection alert condition, restart the application which is currently making connections to your Atlas cluster. Restarting the application terminates all existing connections opened by the application and allows the Atlas cluster to resume normal operations.
Atlas clusters of size
M10 and greater can utilize the
Test Primary Failover
option. The Test Primary Failover procedure steps down the current
primary node and triggers an
election, which drops all
connections to the primary node.
If your application connects exclusively to a secondary node, you may need to perform the Test Failover procedure several times to make sure the applicable secondary node rotates its position within the replica set and drops its connections.
Test Failover is usually the preferable solution, but another possible solution is to restart the application currently making connections to your Atlas cluster. Restarting the application terminates all existing connections and allows the Atlas cluster to resume normal operations.
Connection alerts are generally a symptom of a larger problem. Employing one of the strategies outlined above will fix the immediate problem, but a permanent solution usually requires either:
Examining your database applications for flawed connection code. Situations in which connections are opened but never closed can allow old connections to pile up and eventually exceed the connection limit. Additionally, you may need to implement some form of connection pooling.
Upgrading to a larger Atlas cluster tier which allows a greater number of connections, if your user base is too large for your current cluster tier.
View the Connections chart to monitor the total number of connections to the cluster.
Monitor connections to determine whether the current connection limits are sufficient. If necessary, upgrade the cluster tier.
To learn more, see View Cluster Metrics.