Flux provides rich, structured logging to track every aspect of data synchronization — including timing, throughput, retries, file operations, and queue performance. This observability is delivered via two key log streams:

metricinfo.log: Captures metrics about operations (timing, size, IO).
metricevent.log: Captures lifecycle events (start, end, file state changes).

All logs follow a structured JSON format with embedded context to support downstream indexing, alerting, and visualization.

Log Overview

Log Name	Description	Path	Collected To	Configuration Source

Log Name	Description	Path	Collected To	Configuration Source
`metricevent.log`	Informative lifecycle events (start, end, failure, etc.)	`log/metricevent.log`	Shared configuration (per node)	`log4jXpolog.properties`
`metricinfo.log`	Detailed operational metrics	`log/metricinfo.log`	Shared configuration (per node)	`log4jXpolog.properties`

Standard Context Fields

Included in all events and metrics:

Field	Description

Field	Description
`scope`	Logical name of operation (`xplg.flux.data-sync`)
`appTags`	App tags associated with the task (if any)
`task.id`	Unique task ID from configuration
`task.name`	Task name from configuration
`job.id`	Runtime job instance ID
`job.name`	Human-readable job name
`nodes.source.id`	Source agent ID (account ID)
`nodes.source.name`	Source agent name (account name)

File-related events may include:

directory
filename
file.length

metricinfo Fields

Each metric provides structured insight into performance, behavior, and system usage.

Name	Metric Key	Extra Context	Unit	Relevant To	Description

Name	Metric Key	Extra Context	Unit	Relevant To	Description
Time of data sync	`process.time`	–	`milliseconds`	Target/Agent	Total time to complete a sync task - Full duration of the data sync task, measured from start to finish. This is the primary indicator of job duration and is essential for performance monitoring.
Time waiting in queue	`process.wait.time`	–	`milliseconds`	Target/Agent	Delay due to queue limitations - Time a sync task spent waiting in queue before execution. High values suggest delays or system backpressure.
Bytes received from network	`system.network.bytes.read`	`sessionId`	`bytes`	Target	Total bytes read from the remote connection
Read latency from network	`system.network.read.cpu.time`	`sessionId`	`milliseconds`	Target	Time spent waiting for a network packet
Bytes sent over network	`system.network.bytes.write`	`sessionId`	`bytes`	Target	Total bytes sent per request
Write latency to network	`system.network.write.cpu.time`	`sessionId`	`milliseconds`	Target	Time spent writing a packet to the network
File block received (write)	`system.io.bytes.write`	`start_pos`, `end_pos`	`bytes`	Target	Amount of data written to the repository per block - Summing this value gives the exact volume of data successfully transferred and stored.
File block read (source)	`system.io.bytes.read`	`start_pos`, `end_pos`	`bytes`	Agent	Amount read per file block
File read time (IO)	`system.io.read.cpu.time`	`start_pos`, `end_pos`, `data_length`	`milliseconds`	Agent	Time to read data block from disk
File write time (IO)	`system.io.write.cpu.time`	`start_pos`, `end_pos`, `data_length`	`milliseconds`	Target	Time to write data block to disk
Queue waiting time	`system.queue.cpu.waitingtime`	`sessionId`	`milliseconds`	Agent	Time task waited on an internal queue

Example: metricinfo Log Record

[2025-06-01 09:50:00,074] {"metric":"process.time","startTimeUnixNano":1750067400026000000,"timeUnixNano":1750067400074000000,"value":48,"attributes":{"scope":"xplg.flux.data-sync","task.id":"1749729871595","task.name":"data sync: manual test task","nodes.source.name":"agent1","nodes.source.id":"","job.name":"data sync: test task","job.id":"1749729871595_test_datasync-agent_1750067400026","appTags":""}}

metricevent Fields

Name	Log Event	Extra Context	Description

Name	Log Event	Extra Context	Description
Data Sync Start	`event.data-sync.start`	–	Emitted at the start of a data sync task
Data Sync End	`event.data-sync.end`	–	Emitted at the completion of a data sync task
File Sync	`event.data-sync.file`	`File Context`	Indicates the outcome of a file: `NEW`, `NOT_CHANGE`, `UPDATE`, `DELETE`, `FAIL`, `CHECKSUM`, `COMPLETED`
File Sync State Change	`event.data-sync.file.state`	`File Context`	Indicates the outcome of a file: `NEW`, `NOT_CHANGE`, `UPDATE`, `DELETE`, `FAIL`, `CHECKSUM`, `COMPLETED`

Example: metricevent Log Record

[2025-06-01 09:51:00,072] {"event":"event.data-sync.end","eventName":"Events","timeUnixNano":1750067460072000000,"attributes":{"scope":"xplg.flux.data-sync","task.id":"1749729871595","task.name":"data sync: test task","nodes.source.name":"agent1","nodes.source.id":"","job.name":"data sync: test task test_datasync-agent","job.id":"1749729871595_test_datasync-agent_1750067460022","appTags":""}}