Working with Rules

The Foglight for MongoDB cartridge includes a set of predefined rules summarized below. You can change default threshold values or scope them to specific settings, typically through registry variables. These rules can be copied, modified, disabled, or customized in various ways. For more information, refer to the Foglight documentation or contact Quest Software PSO.

This section covers the following rules:


MongoDB Asserts Count

Raises an alert if any warning or user asserts are raised. While assert errors are typically uncommon, if there are non-zero values for the asserts, you should check the log file for more information. In many cases, these errors are trivial, but are worth investigating.


MongoDB Availability

Raises an alert if the monitored mongod or mongos server is unreachable two or more times in a row.


MongoDB Cluster Mongos Availability

Alert when cluster is missing an active mongos.


MongoDB Collection Growth

Raises an alert if a collection has grown faster than usual. Collection size is compared to an historical average to determine if collection size growth/shrinkage is out of the ordinary.


MongoDB Connections UsedPercent

Raises an alert if the monitored instance is approaching its limit of available simultaneous connections.


MongoDB Cursors NoTimeout

Alert if there are open “no timeout” cursors.


MongoDB Database ExecutionTime Command

Alert if database command execution times are higher than usual.


MongoDB Database ExecutionTime Read

Alert if database read lock times are higher than usual.


MongoDB Database ExecutionTime Write

Alert if database write lock times are higher than usual.


MongoDB Flush Time

Raises an alert if the average amount of time the server has spent writing data to disk is high. Background flush information only appears for instances that use the MMAPv1 storage engine.


MongoDB Locks Deadlocks

Raises an alert if any deadlocks are encountered during lock acquisition.


MongoDB Locks Queue Length

Raises an alert if the combined global reader lock queue and global writer lock queue is getting long.


MongoDB Log Patterns

Alert if there are any log entries matching configured agent properties patterns.


MongoDB Memory DataFit

Alert if the total data size and index size on a server does not fit in physical memory. Must have the Infrastructure Cartridge enabled.


MongoDB Memory IndexFit

Alert if the total index size on a server does not fit in physical memory. Must have the Infrastructure Cartridge enabled.


MongoDB Memory Mapped Ratio

Raises an alert if mapped memory is too large with respect to non-mapped memory, the virtual memory used by a mongod process. With journaling enabled, non-mapped memory should be at least double the value of mapped memory. Three times larger or more may indicate a memory leak.


MongoDB Memory Page Faults

Raises an alert if the ratio of page faults to total database operations is too high.


MongoDB Profiling Operation Execution Time

Raises an alert if the average execution time for profiled operations is too high. Applicable when profiling is enabled for a given database.


MongoDB ReplicaMember PingMS

Alert if replica member pingMs is large.


MongoDB Replica Member Unreachable

Raises an alert if one or more members of a replica set are not running.


MongoDB Replica Set Not Stable

Raises an alert if a replica set member is unreachable two or more times in a row.


MongoDB Replication Buffer Ratio

Raises an alert if the replication buffer is filling up. MongoDB buffers oplog operations from the replication sync source buffer before applying oplog entries in a batch.


MongoDB Replication NoPrimary

Alert if a replica set has no primary.


MongoDB Replication Oplog Headroom

Alert if replication on a secondary is falling behind and may not have time to replicate the oldest oplog entries before they are recycled.


MongoDB Replication Oplog Lag

Alert if the replication oplog lag on a secondary server is too long.


MongoDB Replication Oplog Window

Alert if the replication oplog window is too small.


MongoDB Server State Change

Alert if a member of a replica set changes state.


MongoDB Slow Op Time

Alert if a slow operation time exceeds the threshold.


MongoDB SSL Certificate Expiration

Raises an alert if a MongoDB server using an SSL/TLS certificate is approaching its expiration date.


MongoDB WiredTiger Cache DirtyBytes

Alert if the tracked dirty bytes in the WiredTiger cache is high.


MongoDB WiredTiger Cache PagesEvictedClean

Alert if the percentage of unmodified pages evicted to the total pages currently held in the WiredTiger cache is high.


MongoDB WiredTiger ConcurrentTransaction ReadTicketsAvailable

Alert if the number of available WiredTiger concurrent transaction read tickets approaches zero.


MongoDB WiredTiger ConcurrentTransaction WriteTicketsAvailable

Alert if the number of available WiredTiger concurrent transaction write tickets approaches zero.


MongoDB WiredTiger Cursor CursorCount

Alert if there is a higher than average number of open WiredTiger cursors.


MongoDB WiredTiger Cursor SessionCount

Alert if there is a higher than average number of open WiredTiger sessions.


MongoDB WiredTiger Transaction Failures

Alert if there are any WiredTiger transaction failures due to cache overflow.