Memory and disk alarms in RabbitMQ - Step-by-Step Execution

Process Flow - Memory and disk alarms

Start RabbitMQ Node

↓

Monitor Memory Usage

↓

Memory > Threshold?

No→Continue Normal Operation

Yes↓

Trigger Memory Alarm

↓

Block Producers to Prevent Overload

↓

Monitor Disk Space

↓

Disk Space < Threshold?

No→Continue Normal Operation

Yes↓

Trigger Disk Alarm

↓

Block Producers to Prevent Disk Full

↓

Wait for Resources to Free

↓

Alarms Cleared?

No→Keep Blocking Producers

Yes↓

Resume Normal Operation

RabbitMQ monitors memory and disk space continuously. If usage crosses set limits, it triggers alarms and blocks message producers to protect the system until resources are freed.

Execution Sample

RabbitMQ

rabbitmqctl set_vm_memory_high_watermark 0.4
rabbitmqctl set_disk_free_limit 50000000
rabbitmqctl status

Set memory alarm at 40% usage, disk free space limit at 50MB, then check RabbitMQ status.

Process Table

Step	Check	Condition	Action	Result
1	Memory usage	30% < 40%	No alarm	Normal operation
2	Memory usage	45% > 40%	Trigger memory alarm	Block producers
3	Disk free space	100MB > 50MB	No alarm	Normal operation
4	Disk free space	40MB < 50MB	Trigger disk alarm	Block producers
5	Resources freed	Memory 35%, Disk 60MB	Clear alarms	Resume operation
6	Memory usage	35% < 40%	No alarm	Normal operation

💡 Alarms cleared when memory and disk usage return below thresholds

Status Tracker

Variable	Start	After Step 2	After Step 4	After Step 5	Final
Memory Usage	30%	45%	45%	35%	35%
Disk Free Space	100MB	100MB	40MB	60MB	60MB
Producers Blocked	No	Yes	Yes	No	No
Alarms Active	No	Memory Alarm	Memory & Disk Alarm	No	No

Key Moments - 3 Insights

Why does RabbitMQ block producers when memory or disk alarms trigger?

Blocking producers prevents the system from running out of memory or disk space, protecting RabbitMQ from crashing. See execution_table steps 2 and 4 where alarms trigger and producers are blocked.

What happens if memory usage goes back below the threshold but disk space is still low?

RabbitMQ keeps producers blocked until all alarms clear. In execution_table step 4, both alarms are active, so blocking continues until both conditions improve (step 5).

How does RabbitMQ know when to clear alarms and resume normal operation?

It continuously monitors resource usage. When memory and disk usage return below thresholds (step 5), alarms clear and producers resume (step 6).

Visual Quiz - 3 Questions

Look at the execution table, what is the state of producers at step 4?

A Producers are paused temporarily

B Producers are blocked

C Producers are allowed

D Producers are restarted

💡 Hint

Check the 'Action' and 'Result' columns at step 4 in the execution_table

At which step does RabbitMQ clear all alarms and resume normal operation?

A Step 2

B Step 4

C Step 5

D Step 6

💡 Hint

Look for 'Clear alarms' and 'Resume operation' in the 'Action' and 'Result' columns

If the disk free space threshold was set lower, how would the execution table change?

A Disk alarm triggers later or not at all

B Disk alarm triggers earlier

C Memory alarm triggers earlier

D No change in alarms

💡 Hint

Consider how changing thresholds affects when alarms trigger, see 'Condition' column for disk space

Concept Snapshot

RabbitMQ monitors memory and disk space continuously.
If memory usage exceeds the high watermark or disk free space falls below the limit, RabbitMQ triggers alarms.
When alarms trigger, RabbitMQ blocks message producers to protect stability.
Alarms clear only when resource usage returns below thresholds.
Use rabbitmqctl commands to set thresholds and check status.

Full Transcript

RabbitMQ watches its memory and disk space all the time. When memory usage goes above a set limit, it triggers a memory alarm and blocks producers from sending more messages. Similarly, if disk free space drops below a set limit, it triggers a disk alarm and blocks producers. RabbitMQ keeps blocking producers until memory and disk usage return to safe levels. This protects RabbitMQ from crashing due to resource exhaustion. You can set these limits using rabbitmqctl commands and check the status to see if alarms are active. The execution table shows how memory and disk checks happen step by step, when alarms trigger, and when they clear to resume normal operation.