Scheduler Configuration

The Aurora scheduler can take a variety of configuration options through command-line arguments. Examples are available under examples/scheduler/. For a list of available Aurora flags and their documentation, see Scheduler Configuration Reference.

A Note on Configuration

Like Mesos, Aurora uses command-line flags for runtime configuration. As such the Aurora “configuration file” is typically a shell script of the form.


# Flags controlling the JVM.
  # GC tuning, etc.

# Flags controlling the scheduler.
  # Port for client RPCs and the web UI
  # Log configuration, etc.

# Environment variables controlling libmesos
export JAVA_HOME=...
export GLOG_v=1
# Port used to communicate with the Mesos master and for the replicated log

JAVA_OPTS="${JAVA_OPTS[*]}" exec "$AURORA_HOME/bin/aurora-scheduler" "${AURORA_FLAGS[@]}"

That way Aurora’s current flags are visible in ps and in the /vars admin endpoint.

Replicated Log Configuration

Aurora schedulers use ZooKeeper to discover log replicas and elect a leader. Only one scheduler is leader at a given time - the other schedulers follow log writes and prepare to take over as leader but do not communicate with the Mesos master. Either 3 or 5 schedulers are recommended in a production deployment depending on failure tolerance and they must have persistent storage.

Below is a summary of scheduler storage configuration flags that either don’t have default values or require attention before deploying in a production environment.


Defines the Mesos replicated log quorum size. In a cluster with N schedulers, the flag -native_log_quorum_size should be set to floor(N/2) + 1. So in a cluster with 1 scheduler it should be set to 1, in a cluster with 3 it should be set to 2, and in a cluster of 5 it should be set to 3.

Number of schedulers (N) -native_log_quorum_size setting (floor(N/2) + 1)
1 1
3 2
5 3
7 4

Incorrectly setting this flag will cause data corruption to occur!


Location of the Mesos replicated log files. Consider allocating a dedicated disk (preferably SSD) for Mesos replicated log files to ensure optimal storage performance.


ZooKeeper path used for Mesos replicated log quorum discovery.

See code for other available Mesos replicated log configuration options and default values.

Changing the Quorum Size

Special care needs to be taken when changing the size of the Aurora scheduler quorum. Since Aurora uses a Mesos replicated log, similar steps need to be followed as when changing the mesos quorum size.

As a preparation, increase -native_log_quorum_size on each existing scheduler and restart them. When updating from 3 to 5 schedulers, the quorum size would grow from 2 to 3.

When starting the new schedulers, use the -native_log_quorum_size set to the new value. Failing to first increase the quorum size on running schedulers can in some cases result in corruption or truncating of the replicated log used by Aurora. In that case, see the documentation on recovering from backup.

Backup Configuration

Configuration options for the Aurora scheduler backup manager.


The interval on which the scheduler writes local storage backups. The default is every hour.


Directory to write backups to.


Maximum number of backups to retain before deleting the oldest backup(s).

Process Logs

Log destination

By default, Thermos will write process stdout/stderr to log files in the sandbox. Process object configuration allows specifying alternate log file destinations like streamed stdout/stderr or suppression of all log output. Default behavior can be configured for the entire cluster with the following flag (through the -thermos_executor_flags argument to the Aurora scheduler):


both configuration will send logs to files and stream to parent stdout/stderr outputs.

See Configuration Reference for all destination options.

Log rotation

By default, Thermos will not rotate the stdout/stderr logs from child processes and they will grow without bound. An individual user may change this behavior via configuration on the Process object, but it may also be desirable to change the default configuration for the entire cluster. In order to enable rotation by default, the following flags can be applied to Thermos (through the -thermosexecutorflags argument to the Aurora scheduler):


In the above example, each instance of the Thermos runner will rotate stderr/stdout logs once they reach 100 MiB in size and keep a maximum of 10 backups. If a user has provided a custom setting for their process, it will override these default settings.

Thermos Executor Wrapper

If you need to do computation before starting the thermos executor (for example, setting a different --announcer-hostname parameter for every executor), then the thermos executor should be invoked inside a wrapper script. In such a case, the aurora scheduler should be started with -thermos_executor_path pointing to the wrapper script and -thermos_executor_resources set to a comma separated string of all the resources that should be copied into the sandbox (including the original thermos executor).

For example, to wrap the executor inside a simple wrapper, the scheduler will be started like this -thermos_executor_path=/path/to/ -thermos_executor_resources=/usr/share/aurora/bin/thermos_executor.pex

Docker containers

In order for Aurora to launch jobs using docker containers, a few extra configuration options must be set. The docker containerizer must be enabled on the mesos slaves by launching them with the --containerizers=docker,mesos option.

By default, Aurora will configure Mesos to copy the file specified in -thermos_executor_path into the container’s sandbox. If using a wrapper script to launch the thermos executor, specify the path to the wrapper in that argument. In addition, the path to the executor pex itself must be included in the -thermos_executor_resources option. Doing so will ensure that both the wrapper script and executor are correctly copied into the sandbox. Finally, ensure the wrapper script does not access resources outside of the sandbox, as when the script is run from within a docker container those resources will not exist.

A scheduler flag, -global_container_mounts allows mounting paths from the host (i.e., the slave) into all containers on that host. The format is a comma separated list of hostpath:containerpath[:mode] tuples. For example -global_container_mounts=/opt/secret_keys_dir:/mnt/secret_keys_dir:ro mounts /opt/secret_keys_dir from the slaves into all launched containers. Valid modes are ro and rw.

If you would like to run a container with a read-only filesystem, it may also be necessary to pass to use the scheduler flag -thermos_home_in_sandbox in order to set HOME to the sandbox before the executor runs. This will make sure that the executor/runner PEX extractions happens inside of the sandbox instead of the container filesystem root.

If you would like to supply your own parameters to docker run when launching jobs in docker containers, you may use the following flags:


-allow_docker_parameters controls whether or not users may pass their own configuration parameters through the job configuration files. If set to false (the default), the scheduler will reject jobs with custom parameters. NOTE: this setting should be used with caution as it allows any job owner to specify any parameters they wish, including those that may introduce security concerns (privileged=true, for example).

-default_docker_parameters allows a cluster operator to specify a universal set of parameters that should be used for every container that does not have parameters explicitly configured at the job level. The argument accepts a multimap format: