Edge Delta Local Storage Destination

Overview

The Local Storage destination node sends items to local storage. It can accept log and other data types: custom, metric, cluster_pattern_and_sample, and signal. These items are raw archive bytes that are buffered with the archive buffer processor.

• incoming_data_types: log, custom, metric, cluster_pattern_and_sample, signal

This node requires Edge Delta agent version v0.1.59 or higher.

Example Configuration

nodes:
  - name: my_local
    type: localstorage_output
    mounted_path: "/var/archive_logs/my-local"
    compression: zstd
    ncoding: parquet
    use_native_compression: true
    path_prefix:
      order:
      - Year
      - Month
      - Day
      - Hour
      - 2 Minute
      - tag
      - host
      format: parquet/%s/%s/%s/%s/%s/%s/%s/

Required Parameters

name

A descriptive name for the node. This is the name that will appear in pipeline builder and you can reference this node in the YAML using the name. It must be unique across all nodes. It is a YAML list element so it begins with a - and a space followed by the string. It is a required parameter for all nodes.

nodes:
  - name: <node name>
    type: <node type>

type: localstorage_output

The type parameter specifies the type of node being configured. It is specified as a string from a closed list of node types. It is a required parameter.

nodes:
  - name: <node name>
    type: <node type>

mounted_path

The mounted_path parameter is the path in which to save archive files. It is specified as a string and is required.

nodes:
  - name: my_local
    type: localstorage_output
    mounted_path: "/var/archive_logs/my-local"

Optional Parameters

compression

The compression parameter specifies the compression format. It can be gzip, zstd, snappy or uncompressed. It is specified as a string, has a default of gzip, and it is optional.

nodes:
  - name: my_local
    type: localstorage_output
    mounted_path: "/var/archive_logs/my-local"
    compression: gzip | zstd | snappy | uncompressed

disable_compaction

This parameter configures whether to disable compaction by the Compactor Agent for data from this node before it is sent to the data destination. It is specified as a boolean, the default is false and it is optional.

nodes:
  - name: my_local
    type: localstorage_output
    mounted_path: "/var/archive_logs/my-local"
    disable_compaction: true

encoding

The encoding parameter specifies the encoding format. It can be json or parquet. It is specified as a string, has a default of json, and it is optional.

nodes:
  - name: my_local
    type: localstorage_output
    mounted_path: "/var/archive_logs/my-local"
    encoding: json | parquet

flush_interval

The flush_interval parameter specifies the duration to flush (or force) data to the destination, including buffered data. It is specified as a duration and is optional.

nodes:
  - name: my_local
    type: localstorage_output
    mounted_path: "/var/archive_logs/my-local"
    flush_interval: 10m

max_byte_limit

The max_byte_limit parameter specifies the maximum bytes before flushing buffered raw data to archive destination. It is specified with a data size and is optional. If not specified for this node the setting in the agent settings is used.

nodes:
  - name: my_local
    type: localstorage_output
    mounted_path: "/var/archive_logs/my-local"
    max_byte_limit: 32MB

path_prefix

The path_prefix parameter configures the path prefix using order and format child parameters. It is optional.

The order child parameter lists the formatting items that will define the path prefix:

• You can refer to Year, Month, Day, <any number that can divide 60> Minute, Hour, tag, host, OtherTags.<item related tags> and LogFields.<log related tags>.
• For ECS, ecs_cluster, ecs_container_name, ecs_task_family and ecs_task_version are available.
• For K8s, k8s_namespace, k8s_controller_kind, k8s_controller_logical_name, k8s_pod_name, k8s_container_name and k8s_container_image are available.
• For Docker, docker_container_name and docker_image_name are available

The format child parameter specifies a format string that has %s as placeholders per each order item.

nodes:
  - name: my_local
  type: localstorage_output
  mounted_path: "/var/archive_logs/my-local"
  path_prefix:
      order:
      - Year
      - Month
      - Day
      - Hour
      - 2 Minute
      - tag
      - host
    format: ver=parquet/year=%s/month=%s/day=%s/hour=%s/min=%s/tag=%s/host=%s/

use_native_compression

The archiver_enabled parameter configures whether archiver agents will be used for sending archive bytes. It is specified as a Boolean with the default of false and it is optional.

nodes:
  - name: my_local
    type: localstorage_output
    mounted_path: "/var/archive_logs/my-local"
    archiver_enabled: true

persistent_queue

The persistent_queue configuration enables disk-based buffering to prevent data loss during destination failures or slowdowns. When enabled, the agent stores data on disk and automatically retries delivery when the destination recovers.

Complete example:

persistent_queue:
  path: /var/lib/edgedelta/outputbuffer
  mode: error
  max_byte_size: 1GB
  drain_rate_limit: 1000

How it works:

1. Normal operation: Data flows directly to the destination (for error and backpressure modes) or through the disk buffer (for always mode)
2. Destination issue detected: Based on the configured mode, data is written to disk at the configured path
3. Recovery: When the destination recovers, buffered data drains at the configured drain_rate_limit while new data continues flowing
4. Completion: Buffer clears and normal operation resumes

Key benefits:

• Data durability: Logs preserved during destination outages and slowdowns
• Agent protection: Slow backends don’t cascade failures into the agent cluster
• Automatic recovery: No manual intervention required
• Configurable behavior: Choose when and how buffering occurs based on your needs

path

The path parameter specifies the directory where buffered data is stored on disk. This parameter is required when configuring a persistent queue.

Example:

persistent_queue:
  path: /var/lib/edgedelta/outputbuffer

Requirements:

• Required field - persistent queue will not function without a valid path
• The directory must have sufficient disk space for the configured max_byte_size
• The agent process must have read/write permissions to this location
• The path should be on a persistent volume (not tmpfs or memory-backed filesystem)

Best practices:

• Use dedicated storage for buffer data separate from logs
• Monitor disk usage to prevent buffer from filling available space
• Ensure the path persists across agent restarts to maintain buffered data

max_byte_size

The max_byte_size parameter defines the maximum disk space the persistent buffer is allowed to use. Once this limit is reached, any new incoming items are dropped, ensuring the buffer never grows beyond the configured maximum.

Example:

persistent_queue:
  path: /var/lib/edgedelta/outputbuffer
  max_byte_size: 1GB

Sizing guidance:

• Small deployments (1-10 logs/sec): 100MB - 500MB
• Medium deployments (10-100 logs/sec): 500MB - 2GB
• Large deployments (100+ logs/sec): 2GB - 10GB

Calculation example:

Average log size: 1KB
Expected outage duration: 1 hour
Log rate: 100 logs/sec

Buffer size = 1KB × 100 logs/sec × 3600 sec = 360MB
Recommended: 500MB - 1GB (with safety margin)

Important: Set this value based on your disk space availability and expected outage duration. The buffer will accumulate data during destination failures and drain when the destination recovers.

mode

The mode parameter determines when data is buffered to disk. Three modes are available:

• error (default) - Buffers data only when the destination returns errors (connection failures, HTTP 5xx errors, timeouts). During healthy operation, data flows directly to the destination without buffering.

• backpressure - Buffers data when the in-memory queue reaches 80% capacity OR when destination errors occur. This mode helps handle slow destinations that respond successfully but take longer than usual to process requests.

• always - Uses write-ahead-log behavior where all data is written to disk before being sent to the destination. This provides maximum durability but adds disk I/O overhead to every operation.

Example:

persistent_queue:
  path: /var/lib/edgedelta/outputbuffer
  mode: error
  max_byte_size: 1GB

Mode comparison:

Why choose error mode:

The error mode provides the minimal protection layer needed to prevent data loss when destinations temporarily fail. Without any persistent queue, a destination outage means data is lost. With error mode enabled, data is preserved on disk during failures and delivered automatically when the destination recovers.

Why choose backpressure mode:

The backpressure mode provides everything error mode offers, plus protection against slow destinations. When a destination is slow but not completely down:

• Without backpressure: Data delivery becomes unreliable, and the backend’s slowness propagates to the agent—the agent can get stuck waiting before sending subsequent payloads
• With backpressure: The agent spills data to disk and continues processing, isolating itself from the slow backend

This prevents a slow destination from cascading failures into your agent cluster. For most production environments, backpressure provides the best balance of protection and performance.

Why choose always mode:

The always mode is designed for customers with extremely strict durability requirements. It forces the agent to write every item to disk before attempting delivery, then reads from disk for transmission. This guarantees that data survives even sudden agent crashes or restarts.

Important: This mode introduces a measurable performance cost. Each agent performs additional disk I/O on every item, which reduces overall throughput. Most deployments do not require this level of durability—this feature addresses specialized needs that apply to a small minority of customers.

Only enable always mode if you have a specific, well-understood requirement where the durability guarantee outweighs the throughput reduction.

strict_ordering

The strict_ordering parameter controls how items are consumed from the persistent buffer.

When strict_ordering: true, the agent runs in strict ordering mode with a single processing thread. This mode always prioritizes draining buffered items first—new incoming data waits until all buffered items are processed in exact chronological order. When strict_ordering: false (default), multiple workers process data in parallel, and new data flows directly to the destination while buffered data drains in the background.

Example:

persistent_queue:
  path: /var/lib/edgedelta/outputbuffer
  mode: always
  strict_ordering: true
parallel_workers: 1

Default value: false

Important: Strict ordering is a specialized feature needed by a very small minority of deployments. Most users should keep the default value of false. Only enable strict ordering if you have a specific, well-understood requirement for exact event sequencing.

Required setting: When strict_ordering: true, you must set parallel_workers: 1. Pipeline validation will fail if parallel_workers is greater than 1 because parallel processing inherently breaks ordering guarantees.

Behavior:

Why the default is false:

In most observability use cases, data freshness is more valuable than strict ordering. When a destination recovers from an outage, operators typically want to see current system state on dashboards immediately, while historical data backfills in the background. The default behavior prioritizes this real-time visibility.

When to enable strict ordering:

Strict ordering is primarily needed by security-focused customers who build systems where events must arrive in the exact delivery order. These customers typically run stateful security streaming engines that depend on precise temporal sequencing.

Specific use cases:

• Stateful security streaming engines - Security systems that maintain state across events and detect patterns based on exact event order
• Audit and compliance logs - Regulatory requirements that mandate audit trails preserve exact temporal sequence
• State reconstruction - Systems that replay events to rebuild state require chronological order

When to keep default (false):

The vast majority of deployments should keep the default:

• Real-time monitoring dashboards - Current state visibility is more important than historical order
• High-volume log ingestion - Faster drain times reduce recovery period
• Stateless analytics - When each log is analyzed independently without temporal correlation

drain_rate_limit

The drain_rate_limit parameter controls the maximum items per second when draining the persistent buffer after a destination recovers from a failure.

Example:

persistent_queue:
  path: /var/lib/edgedelta/outputbuffer
  drain_rate_limit: 1000

Default value: 0 (no limit - drain as fast as the destination accepts)

Why rate limiting matters:

When a destination recovers from an outage, it may still be fragile. Immediately flooding it with hours of backlogged data can trigger another failure. The drain rate limit allows gradual, controlled recovery that protects destination stability.

Choosing the right rate:

Impact on recovery time:

Buffer size: 1GB
Average log size: 1KB
Total items: ~1,000,000 logs

At unlimited (0): Depends on destination capacity
At 5000:      ~3.5 minutes to drain
At 1000:      ~17 minutes to drain
At 100:       ~2.8 hours to drain