---
id: 90c94c9e-616e-11ee-8c99-0242ac120002
---

# Blocked Processes in Cassandra
---

Blocked Processes in Cassandra refers to an incident where certain operations or transactions in a Cassandra database are unable to proceed due to blocking caused by other processes. This can result in slow performance or even system crashes. Identifying and resolving blocked processes is critical for ensuring the smooth functioning of the Cassandra database.

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

export PATH_TO_LOG_FILE="PLACEHOLDER"

export PATH_TO_PERF_METRICS="PLACEHOLDER"

export PATH_TO_CASSANDRA_HOME_DIRECTORY="PLACEHOLDER"
```

## Debug

### Check if Cassandra service is running
```shell
systemctl status cassandra
```

### Check Cassandra node status
```shell
nodetool status
```

### Check the Cassandra system logs for any errors
```shell
tail -f /var/log/cassandra/system.log
```

### Check the Cassandra slow query logs for any slow queries
```shell
tail -f /var/log/cassandra/slowquery.log
```

### Check the system load and resource usage
```shell
top
```

### Check the disk space usage
```shell
df -h
```

### Check the network status and connections
```shell
netstat -an
```

### Check the JVM status and memory usage
```shell
jstat -gcutil ${CASSANDRA_PID}
```

### Check the open file descriptors
```shell
lsof -p ${CASSANDRA_PID}
```

### Check the Cassandra thread pool status
```shell
nodetool tpstats
```

### Check the active Java threads
```shell
jstack ${CASSANDRA_PID}
```

## Repair

### Identify the cause of the blocked processes by analyzing the system logs and monitoring performance metrics.
```shell


#!/bin/bash



# set variables

LOG_FILE=${PATH_TO_LOG_FILE}

PERF_METRICS=${PATH_TO_PERF_METRICS}



# analyze system logs

grep -i "blocked" $LOG_FILE



# monitor performance metrics

sar -u 1 10 > $PERF_METRICS


```

### Check for any long-running queries or transactions that may be causing the blocking and optimize them if possible.
```shell


#!/bin/bash



# Set the parameters

CASSANDRA_HOME=${PATH_TO_CASSANDRA_HOME_DIRECTORY}



# Check for long-running queries or transactions

echo "Checking for long-running queries or transactions..."

nodetool cfstats | grep "Pending flushes" > /dev/null 2>&1

if [ $? -eq 0 ]; then

    echo "Long-running queries or transactions detected"



    # Optimize the queries or transactions

    echo "Optimizing queries or transactions..."

    nodetool flush > /dev/null 2>&1

    echo "Queries or transactions optimized"

else

    echo "No long-running queries or transactions detected"

fi


```


Blocked Processes in Cassandra refers to an incident where certain operations or transactions in a Cassandra database are unable to proceed due to blocking caused by other processes. This can result in slow performance or even system crashes. Identifying and resolving blocked processes is critical for ensuring the smooth functioning of the Cassandra database.


This incident type involves a high number of processes being blocked in SQLServer. It may cause delays or errors in database operations and can impact the performance of the system.


High number of processes blocked in SQLServer

This incident type refers to a situation where there is a significant delay in the execution of queries on a Cassandra cluster. This delay can cause the system to become unresponsive and result in slower performance. It may be caused by a variety of factors such as an increase in traffic, inefficient queries, or hardware issues. The issue can impact the functionality of the system and requires immediate attention to prevent further disruption.


Slow Query Performance on Cassandra Cluster.

This incident type refers to a performance degradation issue in a Cassandra database caused by the new generation garbage collection (GC) process. Garbage collection is a process by which the unused memory occupied by objects in a program is cleared. In some cases, the new generation GC process may take longer than usual, causing performance issues in the Cassandra database. This could lead to slowness in queries or even crashing of the database.


Performance Degradation Due to New Generation Garbage Collection on Cassandra

This incident type describes a problem where the number of mutations in a Cassandra database has reached an excessive level. This is usually caused by full reads and writes, which can lead to an increased number of changes within the database. Excessive mutations can cause performance issues and impact the overall stability of the system. Therefore, it is important to resolve this issue as soon as possible to ensure the system is running smoothly.


Excessive Mutations in Cassandra Due to Full Reads and Writes

Excessive Memory Swap on Cassandra Cluster refers to an incident where the Cassandra database cluster is experiencing high levels of swapping between physical memory and disk space due to the unavailability of enough physical memory. This can lead to degraded performance and unresponsiveness of the database cluster, causing disruptions to the application or service that relies on it. This type of incident requires immediate attention from the operations team to identify the root cause and take necessary measures to mitigate the issue.


Excessive Memory Swap on Cassandra Cluster

```shell
export CASSANDRA_PID="PLACEHOLDER"

export PATH_TO_LOG_FILE="PLACEHOLDER"

export PATH_TO_PERF_METRICS="PLACEHOLDER"

export PATH_TO_CASSANDRA_HOME_DIRECTORY="PLACEHOLDER"
```


### Check if Cassandra service is running

```shell
systemctl status cassandra
```

### Check Cassandra node status

```shell
nodetool status
```

### Check the Cassandra system logs for any errors

```shell
tail -f /var/log/cassandra/system.log
```

### Check the Cassandra slow query logs for any slow queries

```shell
tail -f /var/log/cassandra/slowquery.log
```

### Check the system load and resource usage

```shell
top
```

### Check the disk space usage

```shell
df -h
```

### Check the network status and connections

```shell
netstat -an
```

### Check the JVM status and memory usage

```shell
jstat -gcutil ${CASSANDRA_PID}
```

### Check the open file descriptors

```shell
lsof -p ${CASSANDRA_PID}
```

### Check the Cassandra thread pool status

```shell
nodetool tpstats
```

### Check the active Java threads

```shell
jstack ${CASSANDRA_PID}
```


### Identify the cause of the blocked processes by analyzing the system logs and monitoring performance metrics.

```shell


#!/bin/bash



# set variables

LOG_FILE=${PATH_TO_LOG_FILE}

PERF_METRICS=${PATH_TO_PERF_METRICS}



# analyze system logs

grep -i "blocked" $LOG_FILE



# monitor performance metrics

sar -u 1 10 > $PERF_METRICS


```

### Check for any long-running queries or transactions that may be causing the blocking and optimize them if possible.

```shell


#!/bin/bash



# Set the parameters

CASSANDRA_HOME=${PATH_TO_CASSANDRA_HOME_DIRECTORY}



# Check for long-running queries or transactions

echo "Checking for long-running queries or transactions..."

nodetool cfstats | grep "Pending flushes" > /dev/null 2>&1

if [ $? -eq 0 ]; then

    echo "Long-running queries or transactions detected"



    # Optimize the queries or transactions

    echo "Optimizing queries or transactions..."

    nodetool flush > /dev/null 2>&1

    echo "Queries or transactions optimized"

else

    echo "No long-running queries or transactions detected"

fi


```


Blocked Processes in Cassandra

Overview

Parameters

Debug

Check if Cassandra service is running

Check Cassandra node status

Check the Cassandra system logs for any errors

Check the Cassandra slow query logs for any slow queries

Check the system load and resource usage

Check the disk space usage

Check the network status and connections

Check the JVM status and memory usage

Check the open file descriptors

Check the Cassandra thread pool status

Check the active Java threads

Repair

Identify the cause of the blocked processes by analyzing the system logs and monitoring performance metrics.

Check for any long-running queries or transactions that may be causing the blocking and optimize them if possible.

Learn more

Related Runbooks

High number of processes blocked in SQLServer

Slow Query Performance on Cassandra Cluster.

Performance Degradation Due to New Generation Garbage Collection on Cassandra

Excessive Mutations in Cassandra Due to Full Reads and Writes

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