> ## Documentation Index
> Fetch the complete documentation index at: https://docs.mezmo.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Sudden Increase in Source Volume

> Configure an alert that triggers when a source's data volume rises 60% or more compared to a prior tumbling window, including the custom aggregation script.

This alert is triggered when there is a 60% increase in data volume compared to a prior window.

## General Configuration

| Field | Value |
| - | - |
| Name | Sudden increase in source volume. |
| Description | Triggers when a source volume increases by 60% compared to prior window. |

## Evaluation and Condition Configuration

| Field | Value |
| - | - |
| Operation | Custom |
| Window Type | Tumbling |
| Window Duration (minutes) | 30 |
| Group by Field Paths | `.source` |
| Operation | Custom |
| Window Type | Tumbling |
| Window Duration (minutes) | 30 |
| Conditional Statement | `if (.log_volume`percent\_change`_greater_or_equal 60)` |
| Event Timestamp | `.timestamp` |

## Custom Script

```bash theme={null}
// Receives the current event, metadata and an accumulator object. Logic can be performed
// on the event properties and added to the accumulator object for later analysis.
// The accumulator is persisted, and will become the emitted event when
// conditions are true, OR if the time window naturally expires. Those same conditions
// will also be evaluated against the emitted event to determine if the alert should
// be triggered.

function alertAggregation(accum, event, metadata) {
  let new_accum = accum
  if (!new_accum.message.log_volume) {
    const accum_str = JSON.stringify(accum)
    const accum_length = accum_str.length
    new_accum = {message: {log_volume: accum_length}}
  }
  
  const event_str = JSON.stringify(event)
  const event_length = event_str.length
  new_accum.message.log_volume = new_accum.message.log_volume + event_length
  
  return new_accum
}

```