The snap object provides access to Snap-level runtime information and metadata in expressions. These properties are available within any Snap and provide context about the current Snap execution, including identification, view statistics, and document counts.

Snap Identification

snap.label

The label (name) of the Snap.

Syntax:

snap.label

Example:

snap.label
// Returns: "Mapper+%28Data%29" for Mapper (Data)
// Note: Special characters are URL-encoded

snap.instanceId

The UUID (Universally Unique Identifier) of the Snap. Note that this is different from the runtime UUID of the Pipeline.

Syntax:

snap.instanceId

Example:

snap.instanceId
// Returns: "a1b2c3d4-e5f6-7890-abcd-ef1234567890"

Input View Statistics

snap.inputViews

The input view names and number of documents that have been read from these views.

Syntax:

snap.inputViews

Returns:

• If no view is defined, returns {}
• For each view defined, returns an object with view statistics

Example:

snap.inputViews
// Returns:
{
  "Target": {
    "input0": {
      "count": 42,
      "name": "input0"
    }
  }
}

// Where:
// - "Target" is the name of the target path this expression is mapping to
// - "input0" is the name of the input view
// - 42 is the number of documents that have been read

snap.in.totalCount

The total number of documents that have passed through all of the Snap's input views.

Syntax:

snap.in.totalCount

Example:

snap.in.totalCount
// Returns: 150 (total documents from all input views)

Output View Statistics

snap.outputViews

The output view names and number of documents that have been written to these views.

Syntax:

snap.outputViews

Returns:

• If no view is defined, returns {}
• For each view defined, returns an object with view statistics

Example:

snap.outputViews
// Returns:
{
  "Target": {
    "output0": {
      "count": 38,
      "name": "output0"
    }
  }
}

// Where:
// - "Target" is the name of the target path this expression is mapping to
// - "output0" is the name of the output view
// - 38 is the number of documents that have been written

snap.out.totalCount

The total number of documents that have passed through all of the Snap's output views.

Syntax:

snap.out.totalCount

Example:

snap.out.totalCount
// Returns: 145 (total documents from all output views)

Error View Statistics

snap.errorViews

The error view and number of documents that have been written to this view.

Syntax:

snap.errorViews

Example:

snap.errorViews
// Returns:
{
  "Target": {
    "error0": {
      "count": 5,
      "name": "error0"
    }
  }
}

// Where:
// - "Target" is the name of the target path this expression is mapping to
// - "error0" is the name of the error view
// - 5 is the number of documents that have been written to error

snap.error.totalCount

The total number of documents that have passed through all of the Snap's error views.

Syntax:

snap.error.totalCount

Example:

snap.error.totalCount
// Returns: 5 (total error documents)

Ultra Pipeline Properties

snap.original.load()

Loads the original message (document) coming to the FeedMaster when using an Ultra pipeline.

Syntax:

snap.original.load()

Returns: The original content of the document, along with the entire request sent to the feedmaster.

Example:

snap.original.load()
// Returns: Complete original request including headers, body, and metadata

snap.original.id

The unique ID associated with the message (document) coming into the Ultra pipeline.

Syntax:

snap.original.id

Returns: Unique ID of the message as a string.

Example:

snap.original.id
// Returns: "msg-12345-abcde-67890"

Common Use Cases

Conditional Processing Based on Document Count:

// Process only if there are documents
snap.in.totalCount > 0 ? $processData : null

Error Rate Monitoring:

// Calculate error rate
{
  "totalInput": snap.in.totalCount,
  "totalOutput": snap.out.totalCount,
  "totalErrors": snap.error.totalCount,
  "errorRate": snap.error.totalCount / snap.in.totalCount,
  "successRate": snap.out.totalCount / snap.in.totalCount
}

Audit Logging:

// Create audit record with Snap metadata
{
  "snapId": snap.instanceId,
  "snapName": snap.label,
  "documentsProcessed": snap.in.totalCount,
  "documentsOutput": snap.out.totalCount,
  "errors": snap.error.totalCount,
  "timestamp": Date.now()
}

Progress Tracking:

// Track processing progress
{
  "snap": snap.label,
  "processed": snap.in.totalCount,
  "successful": snap.out.totalCount,
  "failed": snap.error.totalCount,
  "status": snap.error.totalCount > 0 ? "Partial Success" : "Success"
}

Ultra Pipeline Request Tracking:

// Track original request in Ultra pipeline
{
  "requestId": snap.original.id,
  "originalRequest": snap.original.load(),
  "processedBy": snap.label,
  "timestamp": Date.now()
}

Data Quality Validation:

// Validate data quality based on error ratio
snap.error.totalCount / snap.in.totalCount > 0.1
  ? "Quality Check Failed: Error rate exceeds 10%"
  : "Quality Check Passed"

Dynamic Routing Based on View Counts:

// Route based on document count
snap.in.totalCount > 1000
  ? "high_volume_processing"
  : "standard_processing"

Best Practices

• Unique Identification: Use snap.instanceId for unique Snap identification in logs and tracking.
• Error Monitoring: Use snap.error.totalCount to monitor error rates and data quality.
• Performance Tracking: Compare snap.in.totalCount and snap.out.totalCount to track document processing efficiency.
• Audit Trails: Include snap.label and snap.instanceId in audit logs for traceability.
• Ultra Pipelines: Use snap.original.id for request correlation in Ultra pipelines.
• Conditional Logic: Use document counts for conditional processing logic (e.g., only process if data exists).
• Quality Checks: Calculate error rates to implement data quality thresholds.
• View Statistics: Use inputViews, outputViews, and errorViews for detailed view-level analysis.

Property Reference

Differences Between snap and pipe Objects

Calculating Document Processing Metrics

Success Rate:

// Calculate percentage of successful documents
(snap.out.totalCount / snap.in.totalCount) * 100

Error Rate:

// Calculate percentage of error documents
(snap.error.totalCount / snap.in.totalCount) * 100

Processing Efficiency:

// Documents lost in processing (neither output nor error)
snap.in.totalCount - (snap.out.totalCount + snap.error.totalCount)

Complete Processing Summary:

{
  "snapId": snap.instanceId,
  "snapName": snap.label,
  "input": snap.in.totalCount,
  "output": snap.out.totalCount,
  "errors": snap.error.totalCount,
  "successRate": ((snap.out.totalCount / snap.in.totalCount) * 100).toFixed(2) + "%",
  "errorRate": ((snap.error.totalCount / snap.in.totalCount) * 100).toFixed(2) + "%",
  "processed": snap.out.totalCount + snap.error.totalCount,
  "status": snap.error.totalCount === 0 ? "Clean" : "Has Errors"
}