ArangoSync Workers

The ArangoSync Worker is responsible for executing synchronization tasks.

For optimal performance at least 1 worker instance must be placed onevery machine that has an ArangoDB DBserver running. This ensures that taskscan be executed with minimal network traffic outside of the machine.

Since sync workers will automatically stop once their TLS server certificate expires(which is set to 2 years by default), it is recommended to run at least 2 instancesof a worker on every machine in the datacenter. That way, tasks can still beassigned in the most optimal way, even when a worker is temporarily down for arestart.

To start an ArangoSync Worker using a systemd service, use a unit like this:

  1. [Unit]
  2. Description=Run ArangoSync in worker mode
  3. After=network.target
  5. [Service]
  6. Restart=on-failure
  7. EnvironmentFile=/etc/arangodb.env
  8. EnvironmentFile=/etc/arangodb.env.local
  9. Environment=PORT=8729
  10. LimitNOFILE=1000000
  11. ExecStart=/usr/sbin/arangosync run worker \
  12.     --log.level=debug \
  13.     --server.port=${PORT} \
  14.     --server.endpoint=https://${PRIVATEIP}:${PORT} \
  15.     --master.endpoint=${MASTERENDPOINTS} \
  16.     --master.jwtSecret=${MASTERSECRET}
  17. TimeoutStopSec=60
  19. [Install]
  20. WantedBy=multi-user.target

The ArangoSync Worker must be reachable on a TCP port ${PORT} (used with —server.portoption). This port must be reachable from inside the datacenter (by sync masters).

Note the large file descriptor limit. The sync worker requires about 30 file descriptors pershard. If you use hardware with huge resources, and still run out of file descriptors,you can decide to run multiple sync workers on each machine in order to spread the tasks across them.

The sync workers should be run on all machines that also contain an ArangoDB DBServer.The sync worker can be memory intensive when running lots of databases & collections.

Consider these machines “cattle”.