Log Storage

Strøm stores job logs as structured JSONL files. Logs can be stored locally and optionally archived to a pluggable backend (S3 or local filesystem).

Configuration

Archive backend (recommended)

log_storage:
  local_dir: "/var/stroem/logs"
  archive:
    type: s3                         # "s3" or "local"
    bucket: "my-stroem-logs"         # S3 only
    region: "eu-west-1"              # S3 only
    prefix: "logs/"                  # optional key prefix, default ""
    endpoint: "http://minio:9000"    # optional — for S3-compatible storage
    # path: "/mnt/archive"           # local only — directory for archive files

Legacy S3 config (still supported)

log_storage:
  local_dir: "/var/stroem/logs"
  s3:                              # legacy format — use archive instead
    bucket: "my-stroem-logs"
    region: "eu-west-1"
    prefix: "logs/"
    endpoint: "http://minio:9000"

If both archive and s3 are set, archive takes precedence.

Fields

Field	Required	Description
local_dir	No	Directory for local JSONL log files (default: /tmp/stroem/logs)
archive.type	Archive only	Backend type: "s3" or "local"
archive.bucket	S3 only	S3 bucket name
archive.region	S3 only	AWS region
archive.prefix	No	Key prefix for archive objects (default: "")
archive.endpoint	No	Custom endpoint for S3-compatible storage (MinIO, LocalStack)
archive.path	Local only	Directory for local archive files

Log format

Each log line is a JSON object in JSONL format:

{"ts":"2025-02-12T10:56:45.123Z","stream":"stdout","step":"say-hello","line":"Hello World"}

Field	Description
ts	ISO 8601 timestamp
stream	"stdout" or "stderr"
step	Step name that produced this line
line	The log line content

Log archival

When an archive backend is configured, logs are uploaded when a job reaches a terminal state (completed/failed). The upload happens after hooks fire, so server events from hook execution are included in the archive.

Archive key structure

{prefix}{workspace}/{task}/YYYY/MM/DD/YYYY-MM-DDTHH-MM-SS_{job_id}.jsonl.gz

All timestamps in the key are UTC. Files are gzip-compressed.

For the local archive backend, this key maps to subdirectories under the configured path.

Read fallback

When reading logs, the server tries sources in order:

1. Local JSONL file (live buffer)
2. Legacy .log file (pre-JSONL format)
3. Archive backend (if configured)

S3 credentials

S3 credentials use the standard AWS credential chain: environment variables, IAM role, or ~/.aws/credentials.

Server events

Server-side errors (hook failures, orchestration errors, recovery timeouts) are written to the log file with step: "_server" and stream: "stderr". These are visible in the UI’s “Server Events” panel on the job detail page.

Retrieve server events via API:

curl -s http://localhost:8080/api/jobs/JOB_ID/steps/_server/logs | jq -r .logs

WebSocket streaming

Real-time log streaming is available via WebSocket:

GET /api/jobs/{id}/logs/stream

On connect, the server sends existing log content (backfill), then streams new log chunks as they arrive from workers.

websocat ws://localhost:8080/api/jobs/JOB_ID/logs/stream