MongoDB Monitoring Technical Reference

Overview

MongoDB monitoring is a Gateway configuration file that enables monitoring of MongoDB through the Toolkit plug-in.

MongoDB can monitor the database environment in a measurable way to spot any potential discrepancies and issues.

Some key areas to track when using MongoDB monitoring:

Key Area	Description
Metrics	Determine the crucial alerts to be set in the metrics to avoid any performance issues or errors.
Database performance	Monitor the database's current state.
Resource utilisation	Monitor the number of client connections to avoid abnormal traffic loads that can lead to performance issues.
Asserts	Show errors raised during the selected time period.

Intended audience

This technical reference is intended for users who will be using Active Console to monitor data from MongoDB. If you are setting up the integration for the first time, see MongoDB Monitoring User Guide.

Metrics and dataviews

MongoDB asserts

This view reports the number of asserts on the database:

Column Name	Description
msg	Number of message assertions raised since the server process started.
regular	Number of regular assertions raised since the server process started.
user	Number of user-asserts that have occurred since the last time the server process started.
warning	Number of warnings raised since the server process started.

MongoDB background flushing

The information on this view appears only for instances that use the MMAPv1 storage engine. Mongod periodically flushes and writes to disk.

In the default configuration, this happens every 60 seconds. This view contains data regarding these operations.

These metrics are important for write performance and journaling.

MongoDB concurrent transactions

The information on this view appears only for instances that use the wiredTiger storage engine.

This contains ticket details that the wiredTiger uses for its thread management.

MongoDB cursors

This view contains data regarding cursor state and use:

Column Name	Description
openNoTimeout	Number of open cursors with timeout disabled.
openTotal	Number of cursors that MongoDB is maintaining for clients. Since MongoDB exhausts unused cursors, this value is usually small or zero.
timedOut	Provides a counter of the total number of cursors that have timed out since the server process started. If this number is larger or growing at a regular rate, this may indicate an application error.

MongoDB dbStats

This view contains storage statistics for a given database. You can pass their database to the provided script:

Column Name	Description
dataSize	Total size in bytes of the data held in this database including the padding factor.
indexSize	Total size in bytes of all indexes created on this database.
objects	Contains a count of the number of objects like documents in the database across all collections.
storageSize	Total amount of space in bytes allocated to the collections in this database for document storage.

MongoDB instance

This view contains a build summary for the MongoDB server instance:

Column Name	Description
host	Configured host in the system.
localTime	Current time based on the server.
ok	Status of the server instance.
pid	Process ID number.
process	Current MongoDB process: mongod or mongos.
storageEngine	Type of storage engine.
uptime	Number of seconds that the MongoDB process has been active.
uptimeEstimate	Number in seconds based from MongoDB’s internal time keeping system.
uptimeMs	Number of milliseconds that the MongoDB process has been active.
version	Version of the current MongoDB process.

MongoDB locks

This view provides a granular report on MongoDB database-level lock use:

Column Name	Description
acquireCount	Number of times the lock has been acquired. Possible lock modes: (r) - intent shared lock (R) - shared lock (w) - intent exclusive lock (W) - exclusive lock
acquireWaitCount	Number of times when lock acquisitions waits because locks have encountered conflicts. Possible lock modes: (r) - intent shared lock (w) - intent exclusive lock (W) - exclusive lock
timeAcquiringMicros	Cumulative waiting time in microseconds for the lock acquisition. Possible lock modes: (r) - intent shared lock (w) - intent exclusive lock (W) - exclusive lock

MongoDB memory

This view contains the MongoDB memory metrics:

Column Name	Description
mapped	Provides the amount of mapped memory (in MB) by the database. Because MongoDB uses memory-mapped files, this value is likely to be roughly equivalent to the total size of your database(s).
nonMapped	Virtual memory collected by connections.
page_faults	Number of times MongoDB has requested to connect from disk per second.
resident	Equivalent to the amount of RAM (in MB) currently used by the database process. In normal use this value tends to grow, approaching total amount of system memory in dedicated servers.
virtual	Displays the quantity (in MB) of virtual memory used by the mongod process. If virtual value is significantly larger than mapped (e.g. 3 or more times), this may indicate a memory leak.

MongoDB opcounters

This view provides an overview of database operations by type. These numbers will grow over time and in response to database use:

Column Name	Description
getmore	Provides a counter of the total number of "getmore" operations since the mongod instance last started. This counter can be high even if the query count is low.
insert	Total number of "insert" operations since the mongod instance last started.
query	Total number of queries since the mongod instance last started.
readers	Number of clients with read operations.
update	Total number of "update" operations since the mongod instance last started.
writers	Number of clients with write operations.

MongoDB replication

This information appears only if the replica set is used and it contains metrics related to replication:

Column Name	Description
id	Unique identifier for each replication.
state	Value of state between 0 and 10 that represents the replica state.
stateStr	Describes the state string.
replicationLag	Shows the delay between a write operation on the primary and to its secondary. If the replication lag is set to zero, that means that there is no load issues yet.