Favre

Favre is a wrapper around Csync2 for automatic, eventually-consistent file synchronization within a Docker Swarm.

Configuration

Many of the configuration options available for Csync2 are available for Favre.

FAVRE_TASKS_ENDPOINT: must be set to "tasks.{{.Service.Name}}." for discovery

CSYNC2_AUTO: defaults to younger

CSYNC2_DB_DIR: advised to persist with docker volume, default /var/lib/csync2; this is where Csync2 stores its state

CSYNC2_PSK_FILE: mandatory, no default, should be stored as a docker secret

CSYNC2_INCLUDE: globs to include in the sync; more than one line can be rendered by setting CSYNC2_INCLUDE_0, CSYNC2_INCLUDE_1, etc.

CSYNC2_EXCLUDE: patterns to exclude from sync; more than one line can be rendered in the same manner as CSYNC2_EXCLUDE_0, CSYNC2_EXCLUDE_1, etc.

CSYNC2_BACKUP_DIRECTORY: optional, no default

CSYNC2_BACKUP_GENERATIONS: optional, no default

CSYNC2_DB_DIR: optional, defaults to /var/lib/csync2

CSYNC2_SYSTEM_DIR: optional, defaults to /etc/csync2

CSYNC2_DAEMON_VERBOSITY: optional, defaults to -v

CSYNC2_CLIENT_VERBOSITY: optional, defaults to -v

CSYNC2_PORT: optional, defaults to 30865

CSYNC2_TEMPLATE_FILE: optional, defaults to a template in the image

FAVRE_DEBOUNCE_DELAY: optional; wait this long after a file change is detected before calling sync(); defaults to 100 milliseconds

FAVRE_START_DELAY: optional; waits some milliseconds after the daemon is spawned before the clients start; defaults to 5000 milliseconds

FAVRE_REMOVE_TIMEOUT: optional; timeout for removing unused hosts from the database; defaults to 7500 milliseconds

FAVRE_SYNC_TIMEOUT: optional; timeout for sync'ing files; defaults to 90000 milliseconds

FAVRE_LOOKUP_ATTEMPTS: optional; how many times should the client attempt to discover its swarm peers; defaults to 5

FAVRE_LOOKUP_TIMEOUT: optional; how long to wait between service discovery queries; defaults to 3000 milliseconds

FAVRE_TMP_SUBFOLDER: optional; where the healthcheck puts its test file; defaults to /favre

FAVRE_POLL_INTERVAL: optional; set an interval for regular sync'ing independent of the file watcher; defaults to undefined

Compose

It is imperative that hostname not be changed. The values from a reverse DNS lookup must be marshalled to match this hostname.

version: "3.8"

services:
  sync:
    image: coryaent/favre
    hostname: "{{.Task.ID}}"
    secrets:
      - favre_key
    environment:
      CSYNC2_PSK_FILE: /run/secrets/favre_key
      CSYNC2_INCLUDE: /sync
      FAVRE_TASKS_ENDPOINT: "tasks.{{.Service.Name}}."
    networks:
      - internal
    volumes:
      - state:/var/lib/csync2/
      - sync:/sync/
    deploy:
      mode: global
      endpoint_mode: dnsrr

secrets:
  favre_key:
    external: true

networks:
  internal:
    attachable: false
    driver: overlay
    driver_opts:
      encrypted: "true"

volumes:
  state:
    driver: local
  sync:
    driver: local