---
id: d8d547bc-2ea7-458d-b730-71e99f31742c
---

# Frequent primary node elections in a MongoDB replica set.
---

This incident type refers to a recurring problem in a MongoDB replica set where the primary node is frequently being elected, causing disruption to the database operations. This can occur due to various reasons such as network issues, hardware failures, or misconfiguration of MongoDB replica set. The frequent elections can lead to reduced performance, data inconsistency, and downtime of the database system. It requires prompt investigation and resolution to prevent further disruptions and ensure the stability of the database operations.

### Parameters
```shell
export HOSTNAME="PLACEHOLDER"

export PASSWORD="PLACEHOLDER"

export USERNAME="PLACEHOLDER"

export AUTH_DATABASE="PLACEHOLDER"

export NEW_ELECTION_TIMEOUT="PLACEHOLDER"

export CONFIG_FILE_PATH="PLACEHOLDER"
```

## Debug

### Check if all nodes in the replica set are running
```shell
echo "rs.status()" | mongo --host ${HOSTNAME} -u ${USERNAME} -p ${PASSWORD} --authenticationDatabase ${AUTH_DATABASE}
```

### Check the replica set configuration
```shell
echo "rs.conf()" | mongo --host ${HOSTNAME} -u ${USERNAME} -p ${PASSWORD} --authenticationDatabase ${AUTH_DATABASE}
```

### Check the replica set status
```shell
echo "rs.status()" | mongo --host ${HOSTNAME} -u ${USERNAME} -p ${PASSWORD} --authenticationDatabase ${AUTH_DATABASE}
```

### Check the replica set oplog size and usage
```shell
echo "db.getReplicationInfo()" | mongo --host ${HOSTNAME} -u ${USERNAME} -p ${PASSWORD} --authenticationDatabase ${AUTH_DATABASE}
```

### Check the replica set members' ping time
```shell
echo "rs.isMaster()" | mongo --host ${HOSTNAME} -u ${USERNAME} -p ${PASSWORD} --authenticationDatabase ${AUTH_DATABASE}
```

### Check the replica set members' log files for errors
```shell
tail -f /var/log/mongodb/mongod.log
```

## Repair

### Consider increasing the election timeout value to allow more time for a primary node to recover before triggering an election.
```shell


#!/bin/bash



# Set the parameters

ELECTION_TIMEOUT=${NEW_ELECTION_TIMEOUT}

CONFIG_FILE=${CONFIG_FILE_PATH}



# Update the election timeout value in the MongoDB configuration file

sed -i "s/electionTimeoutMillis:.*/electionTimeoutMillis: $ELECTION_TIMEOUT/" $CONFIG_FILE



# Restart the MongoDB service to apply the changes

systemctl restart mongodb.service


```

This incident type refers to a recurring problem in a MongoDB replica set where the primary node is frequently being elected, causing disruption to the database operations. This can occur due to various reasons such as network issues, hardware failures, or misconfiguration of MongoDB replica set. The frequent elections can lead to reduced performance, data inconsistency, and downtime of the database system. It requires prompt investigation and resolution to prevent further disruptions and ensure the stability of the database operations.


```shell
export HOSTNAME="PLACEHOLDER"

export PASSWORD="PLACEHOLDER"

export USERNAME="PLACEHOLDER"

export AUTH_DATABASE="PLACEHOLDER"

export NEW_ELECTION_TIMEOUT="PLACEHOLDER"

export CONFIG_FILE_PATH="PLACEHOLDER"
```


### Check if all nodes in the replica set are running

```shell
echo "rs.status()" | mongo --host ${HOSTNAME} -u ${USERNAME} -p ${PASSWORD} --authenticationDatabase ${AUTH_DATABASE}
```

### Check the replica set configuration

```shell
echo "rs.conf()" | mongo --host ${HOSTNAME} -u ${USERNAME} -p ${PASSWORD} --authenticationDatabase ${AUTH_DATABASE}
```

### Check the replica set status

```shell
echo "rs.status()" | mongo --host ${HOSTNAME} -u ${USERNAME} -p ${PASSWORD} --authenticationDatabase ${AUTH_DATABASE}
```

### Check the replica set oplog size and usage

```shell
echo "db.getReplicationInfo()" | mongo --host ${HOSTNAME} -u ${USERNAME} -p ${PASSWORD} --authenticationDatabase ${AUTH_DATABASE}
```

### Check the replica set members' ping time

```shell
echo "rs.isMaster()" | mongo --host ${HOSTNAME} -u ${USERNAME} -p ${PASSWORD} --authenticationDatabase ${AUTH_DATABASE}
```

### Check the replica set members' log files for errors

```shell
tail -f /var/log/mongodb/mongod.log
```


### Consider increasing the election timeout value to allow more time for a primary node to recover before triggering an election.

```shell


#!/bin/bash



# Set the parameters

ELECTION_TIMEOUT=${NEW_ELECTION_TIMEOUT}

CONFIG_FILE=${CONFIG_FILE_PATH}



# Update the election timeout value in the MongoDB configuration file

sed -i "s/electionTimeoutMillis:.*/electionTimeoutMillis: $ELECTION_TIMEOUT/" $CONFIG_FILE



# Restart the MongoDB service to apply the changes

systemctl restart mongodb.service


```


Frequent primary node elections in a MongoDB replica set.

Overview

Parameters

Debug

Check if all nodes in the replica set are running

Check the replica set configuration

Check the replica set status

Check the replica set oplog size and usage

Check the replica set members' ping time

Check the replica set members' log files for errors

Repair

Consider increasing the election timeout value to allow more time for a primary node to recover before triggering an election.

Learn more

Related Runbooks

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