This document shows you how to install Heron on Kubernetes in a step-by-step, “by hand” fashion. An easier way to install Heron on Kubernetes is to use the Helm package manager. For instructions on doing so, see Heron on Kubernetes with Helm).

Heron supports deployment on Kubernetes (sometimes called k8s). Heron deployments on Kubernetes use Docker as the containerization format for Heron topologies and use the Kubernetes API for scheduling.

You can use Heron on Kubernetes in multiple environments:

Requirements

In order to run Heron on Kubernetes, you will need:

  • A Kubernetes cluster with at least 3 nodes (unless you’re running locally on Minikube)
  • The kubectl CLI tool installed and set up to communicate with your cluster
  • The heron CLI tool

Any additional requirements will depend on where you’re running Heron on Kubernetes.

How Heron on Kubernetes Works

When deploying to Kubernetes, each Heron container is deployed as a Kubernetes pod inside of a Docker container. If there are 20 containers that are going to be deployed with a topoology, for example, then there will be 20 pods deployed to your Kubernetes cluster for that topology.

Minikube

Minikube enables you to run a Kubernetes cluster locally on a single machine.

Requirements

To run Heron on Minikube you’ll need to install Minikube in addition to the other requirements listed above.

Starting Minikube

First you’ll need to start up Minikube using the minikube start command. We recommend starting Minikube with:

  • at least 7 GB of memory
  • 5 CPUs
  • 20 GB of storage

This command will accomplish precisely that:

$ minikube start \
  --memory=7168 \
  --cpus=5 \
  --disk-size=20G

Starting components

There are a variety of Heron components that you’ll need to start up separately and in order. Make sure that the necessary pods are up and in the RUNNING state before moving on to the next step. You can track the progress of the pods using this command:

$ kubectl get pods -w

ZooKeeper

Heron uses ZooKeeper for a variety of coordination- and configuration-related tasks. To start up ZooKeeper on Minikube:

$ kubectl create -f https://raw.githubusercontent.com/twitter/heron/master/deploy/kubernetes/minikube/zookeeper.yaml

BookKeeper

When running Heron on Kubernetes, Apache BookKeeper is used for things like topology artifact storage. You can start up BookKeeper using this command:

$ kubectl create -f https://raw.githubusercontent.com/twitter/heron/master/deploy/kubernetes/minikube/bookkeeper.yaml

Heron tools

The so-called “Heron tools” include the Heron UI and the Heron Tracker. To start up the Heron tools:

$ kubectl create -f https://raw.githubusercontent.com/twitter/heron/master/deploy/kubernetes/minikube/tools.yaml

Heron API server

The Heron API server is the endpoint that the Heron CLI client uses to interact with the other components of Heron. To start up the Heron API server on Minikube:

$ kubectl create -f https://raw.githubusercontent.com/twitter/heron/master/deploy/kubernetes/minikube/apiserver.yaml

Managing topologies

Once all of the components have been successfully started up, you need to open up a proxy port to your Minikube Kubernetes cluster using the kubectl proxy command:

$ kubectl proxy -p 8001

Now, verify that the Heron API server running on Minikube is available using curl:

$ curl http://localhost:8001/api/v1/proxy/namespaces/default/services/heron-apiserver:9000/api/v1/version

You should get a JSON response like this:

{
  "heron.build.git.revision" : "bf9fe93f76b895825d8852e010dffd5342e1f860",
  "heron.build.git.status" : "Clean",
  "heron.build.host" : "ci-server-01",
  "heron.build.time" : "Sun Oct  1 20:42:18 UTC 2017",
  "heron.build.timestamp" : "1506890538000",
  "heron.build.user" : "release-agent1",
  "heron.build.version" : "0.16.2"
}

Success! You can now manage Heron topologies on your Minikube Kubernetes installation. To submit an example topology to the cluster:

$ heron submit kubernetes \
  --service-url=http://localhost:8001/api/v1/proxy/namespaces/default/services/heron-apiserver:9000 \
  ~/.heron/examples/heron-api-examples.jar \
  com.twitter.heron.examples.api.AckingTopology acking

You can also track the progress of the Kubernetes pods that make up the topology. When you run kubectl get pods you should see pods with names like acking-0 and acking-1.

Another option is to set the service URL for Heron using the heron config command:

$ heron config kubernetes set service_url \
  http://localhost:8001/api/v1/proxy/namespaces/default/services/heron-apiserver:9000

That would enable you to manage topologies without setting the --service-url flag.

Heron UI

The Heron UI is an in-browser dashboard that you can use to monitor your Heron topologies. It should already be running in Minikube.

You can access Heron UI in your browser by navigating to http://localhost:8001/api/v1/proxy/namespaces/default/services/heron-ui:8889.

Google Container Engine

You can use Google Container Engine (GKE) to run Kubernetes clusters on Google Cloud Platform.

Requirements

To run Heron on GKE, you’ll need to create a Kubernetes cluster with at least three nodes. This command would create a three-node cluster in your default Google Cloud Platform zone and project:

$ gcloud container clusters create heron-gke-cluster \
  --machine-type=n1-standard-4 \
  --num-nodes=3

You can specify a non-default zone and/or project using the --zone and --project flags, respectively.

Once the cluster is up and running, enable your local kubectl to interact with the cluster by fetching your GKE cluster’s credentials:

$ gcloud container clusters get-credentials heron-gke-cluster
Fetching cluster endpoint and auth data.
kubeconfig entry generated for heron-gke-cluster.

Finally, you need to create a Kubernetes secret that specifies the Cloud Platform connection credentials for your service account. First, download your Cloud Platform credentials as a JSON file, say key.json. This command will download your credentials:

$ gcloud iam service-accounts create key.json \
  --iam-account=YOUR-ACCOUNT

Topology artifact storage

Heron on Google Container Engine supports two static file storage options for topology artifacts:

Google Cloud Storage setup

If you’re running Heron on GKE, you can use either Google Cloud Storage or Apache BookKeeper for topology artifact storage.

If you’d like to use BookKeeper instead of Google Cloud Storage, skip to the BookKeeper section below.

To use Google Cloud Storage for artifact storage, you’ll need to create a Google Cloud Storage bucket. Here’s an example bucket creation command using gsutil:

$ gsutil mb gs://my-heron-bucket

Cloud Storage bucket names must be globally unique, so make sure to choose a bucket name carefully. Once you’ve created a bucket, you need to create a Kubernetes ConfigMap that specifies the bucket name. Here’s an example:

$ kubectl create configmap heron-apiserver-config \
  --from-literal=gcs.bucket=BUCKET-NAME

You can list your current service accounts using the gcloud iam service-accounts list command.

Then you can create the secret like this:

$ kubectl create secret generic heron-gcs-key \
  --from-file=key.json=key.json

Once you’ve created a bucket, a ConfigMap, and a secret, you can move on to starting up the various components of your Heron installation.

Starting components

There are a variety of Heron components that you’ll need to start up separately and in order. Make sure that the necessary pods are up and in the RUNNING state before moving on to the next step. You can track the progress of the pods using this command:

$ kubectl get pods -w

ZooKeeper

Heron uses ZooKeeper for a variety of coordination- and configuration-related tasks. To start up ZooKeeper on your GKE cluster:

$ kubectl create -f https://raw.githubusercontent.com/twitter/heron/master/deploy/kubernetes/gcp/zookeeper.yaml

BookKeeper setup

If you’re using Google Cloud Storage for topology artifact storage, skip to the Heron tools section below.

To start up an Apache BookKeeper cluster for Heron:

$ kubectl create -f https://raw.githubusercontent.com/twitter/heron/master/deploy/kubernetes/gcp/bookkeeper.yaml

Heron tools

The so-called “Heron tools” include the Heron UI and the Heron Tracker. To start up the Heron tools:

$ kubectl create -f https://raw.githubusercontent.com/twitter/heron/master/deploy/kubernetes/gcp/tools.yaml

Heron API server

The Heron API server is the endpoint that the Heron CLI client uses to interact with the other components of Heron. Heron on Google Container Engine has two separate versions of the Heron API server that you can run depending on which artifact storage system you’re using (Google Cloud Storage or Apache BookKeeper).

If you’re using Google Cloud Storage:

$ kubectl create -f https://raw.githubusercontent.com/twitter/heron/master/deploy/kubernetes/gcp/gcs-apiserver.yaml

If you’re using Apache BookKeeper:

$ kubectl create -f https://raw.githubusercontent.com/twitter/heron/master/deploy/kubernetes/gcp/bookkeeper-apiserver.yaml

Managing topologies

Once all of the components have been successfully started up, you need to open up a proxy port to your GKE Kubernetes cluster using the kubectl proxy command:

$ kubectl proxy -p 8001

Now, verify that the Heron API server running on GKE is available using curl:

$ curl http://localhost:8001/api/v1/proxy/namespaces/default/services/heron-apiserver:9000/api/v1/version

You should get a JSON response like this:

{
  "heron.build.git.revision" : "bf9fe93f76b895825d8852e010dffd5342e1f860",
  "heron.build.git.status" : "Clean",
  "heron.build.host" : "ci-server-01",
  "heron.build.time" : "Sun Oct  1 20:42:18 UTC 2017",
  "heron.build.timestamp" : "1506890538000",
  "heron.build.user" : "release-agent1",
  "heron.build.version" : "0.16.2"
}

Success! You can now manage Heron topologies on your GKE Kubernetes installation. To submit an example topology to the cluster:

$ heron submit kubernetes \
  --service-url=http://localhost:8001/api/v1/proxy/namespaces/default/services/heron-apiserver:9000 \
  ~/.heron/examples/heron-api-examples.jar \
  com.twitter.heron.examples.api.AckingTopology acking

You can also track the progress of the Kubernetes pods that make up the topology. When you run kubectl get pods you should see pods with names like acking-0 and acking-1.

Another option is to set the service URL for Heron using the heron config command:

$ heron config kubernetes set service_url \
  http://localhost:8001/api/v1/proxy/namespaces/default/services/heron-apiserver:9000

That would enable you to manage topologies without setting the --service-url flag.

Heron UI

The Heron UI is an in-browser dashboard that you can use to monitor your Heron topologies. It should already be running in your GKE cluster.

You can access Heron UI in your browser by navigating to http://localhost:8001/api/v1/proxy/namespaces/default/services/heron-ui:8889.

General Kubernetes clusters

Although Minikube and Google Container Engine provide two easy ways to get started running Heron on Kubernetes, you can also run Heron on any Kubernetes cluster. The instructions in this section are tailored to non-Minikube, non-GKE Kubernetes installations.

Requirements

To run Heron on a general Kubernetes installation, you’ll need to fulfill the requirements listed at the top of this doc. Once those requirements are met, you can begin starting up the various components that comprise a Heron on Kubernetes installation.

Starting components

There are a variety of Heron components that you’ll need to start up separately and in order. Make sure that the necessary pods are up and in the RUNNING state before moving on to the next step. You can track the progress of the pods using this command:

$ kubectl get pods -w

ZooKeeper

Heron uses ZooKeeper for a variety of coordination- and configuration-related tasks. To start up ZooKeeper on your Kubernetes cluster:

$ kubectl create -f https://raw.githubusercontent.com/twitter/heron/master/deploy/kubernetes/general/zookeeper.yaml

BookKeeper

When running Heron on Kubernetes, Apache BookKeeper is used for things like topology artifact storage (unless you’re running on GKE). You can start up BookKeeper using this command:

$ kubectl create -f https://raw.githubusercontent.com/twitter/heron/master/deploy/kubernetes/general/bookkeeper.yaml

Heron tools

The so-called “Heron tools” include the Heron UI and the Heron Tracker. To start up the Heron tools:

$ kubectl create -f https://raw.githubusercontent.com/twitter/heron/master/deploy/kubernetes/general/tools.yaml

Heron API server

The Heron API server is the endpoint that the Heron CLI client uses to interact with the other components of Heron. To start up the Heron API server on your Kubernetes cluster:

$ kubectl create -f https://raw.githubusercontent.com/twitter/heron/master/deploy/kubernetes/general/apiserver.yaml

Managing topologies

Once all of the components have been successfully started up, you need to open up a proxy port to your GKE Kubernetes cluster using the kubectl proxy command:

$ kubectl proxy -p 8001

Now, verify that the Heron API server running on GKE is available using curl:

$ curl http://localhost:8001/api/v1/proxy/namespaces/default/services/heron-apiserver:9000/api/v1/version

You should get a JSON response like this:

{
  "heron.build.git.revision" : "bf9fe93f76b895825d8852e010dffd5342e1f860",
  "heron.build.git.status" : "Clean",
  "heron.build.host" : "ci-server-01",
  "heron.build.time" : "Sun Oct  1 20:42:18 UTC 2017",
  "heron.build.timestamp" : "1506890538000",
  "heron.build.user" : "release-agent1",
  "heron.build.version" : "0.16.2"
}

Success! You can now manage Heron topologies on your GKE Kubernetes installation. To submit an example topology to the cluster:

$ heron submit kubernetes \
  --service-url=http://localhost:8001/api/v1/proxy/namespaces/default/services/heron-apiserver:9000 \
  ~/.heron/examples/heron-api-examples.jar \
  com.twitter.heron.examples.api.AckingTopology acking

You can also track the progress of the Kubernetes pods that make up the topology. When you run kubectl get pods you should see pods with names like acking-0 and acking-1.

Another option is to set the service URL for Heron using the heron config command:

$ heron config kubernetes set service_url \
  http://localhost:8001/api/v1/proxy/namespaces/default/services/heron-apiserver:9000

That would enable you to manage topologies without setting the --service-url flag.

Heron UI

The Heron UI is an in-browser dashboard that you can use to monitor your Heron topologies. It should already be running in your GKE cluster.

You can access Heron UI in your browser by navigating to http://localhost:8001/api/v1/proxy/namespaces/default/services/heron-ui:8889.

Heron on Kubernetes configuration

You can configure Heron on Kubernetes using a variety of YAML config files, listed in the sections below.

client.yaml

Configuration for the heron CLI tool.

Parameter Description Default
heron.package.core.uri Location of the core Heron package file:///vagrant/.herondata/dist/heron-core-release.tar.gz
heron.config.is.role.required Whether a role is required to submit a topology False
heron.config.is.env.required Whether an environment is required to submit a topology False

heron_internals.yaml

Configuration for a wide variety of Heron components, including logging, each topology’s stream manager and topology master, and more.

Parameter Description Default
heron.logging.directory The relative path to the logging directory log-files
heron.logging.maximum.size.mb The maximum log file size (in MB) 100
heron.logging.maximum.files The maximum number of log files 5
heron.check.tmaster.location.interval.sec The interval, in seconds, after which to check if the topology master location has been fetched or not 120
heron.logging.prune.interval.sec The interval, in seconds, at which to prune C++ log files 300
heron.logging.flush.interval.sec The interval, in seconds, at which to flush C++ log files 10
heron.logging.err.threshold The threshold level at which to log errors 3
heron.metrics.export.interval.sec The interval, in seconds, at which different components export metrics to the metrics manager 60
heron.metrics.max.exceptions.per.message.count The maximum count of exceptions in one MetricPublisherPublishMessage protobuf message 1024
heron.streammgr.cache.drain.frequency.ms The frequency, in milliseconds, at which to drain the tuple cache in the stream manager 10
heron.streammgr.stateful.buffer.size.mb The sized-based threshold (in MB) for buffering data tuples waiting for checkpoint markers before giving up 100
heron.streammgr.cache.drain.size.mb The sized-based threshold (in MB) for draining the tuple cache 100
heron.streammgr.xormgr.rotatingmap.nbuckets For efficient acknowledgements 3
heron.streammgr.mempool.max.message.number The max number of messages in the memory pool for each message type 512
heron.streammgr.client.reconnect.interval.sec The reconnect interval to other stream managers (in seconds) for the stream manager client 1
heron.streammgr.client.reconnect.tmaster.interval.sec The reconnect interval to the topology master (in seconds) for the stream manager client 10
heron.streammgr.client.reconnect.tmaster.max.attempts The max reconnect attempts to tmaster for stream manager client 30
heron.streammgr.network.options.maximum.packet.mb The maximum packet size (in MB) of the stream manager’s network options 10
heron.streammgr.tmaster.heartbeat.interval.sec The interval (in seconds) at which to send heartbeats 10
heron.streammgr.connection.read.batch.size.mb The maximum batch size (in MB) for the stream manager to read from socket 1
heron.streammgr.connection.write.batch.size.mb Maximum batch size (in MB) for the stream manager to write to socket 1
heron.streammgr.network.backpressure.threshold The number of times Heron should wait to see a buffer full while enqueueing data before declaring the start of backpressure 3
heron.streammgr.network.backpressure.highwatermark.mb The high-water mark on the number (in MB) that can be left outstanding on a connection 100
heron.streammgr.network.backpressure.lowwatermark.mb The low-water mark on the number (in MB) that can be left outstanding on a connection
heron.tmaster.metrics.collector.maximum.interval.min The maximum interval (in minutes) for metrics to be kept in the topology master 180
heron.tmaster.establish.retry.times The maximum number of times to retry establishing connection with the topology master 30
heron.tmaster.establish.retry.interval.sec The interval at which to retry establishing connection with the topology master 1
heron.tmaster.network.master.options.maximum.packet.mb Maximum packet size (in MB) of topology master’s network options to connect to stream managers 16
heron.tmaster.network.controller.options.maximum.packet.mb Maximum packet size (in MB) of the topology master’s network options to connect to scheduler 1
heron.tmaster.network.stats.options.maximum.packet.mb Maximum packet size (in MB) of the topology master’s network options for stat queries 1
heron.tmaster.metrics.collector.purge.interval.sec The interval (in seconds) at which the topology master purges metrics from socket 60
heron.tmaster.metrics.collector.maximum.exception The maximum number of exceptions to be stored in the topology metrics collector, to prevent out-of-memory errors 256
heron.tmaster.metrics.network.bindallinterfaces Whether the metrics reporter should bind on all interfaces False
heron.tmaster.stmgr.state.timeout.sec The timeout (in seconds) for the stream manager, compared with (current time - last heartbeat time) 60
heron.metricsmgr.network.read.batch.time.ms The maximum batch time (in milliseconds) for the metrics manager to read from socket 16
heron.metricsmgr.network.read.batch.size.bytes The maximum batch size (in bytes) to read from socket 32768
heron.metricsmgr.network.write.batch.time.ms The maximum batch time (in milliseconds) for the metrics manager to write to socket 32768
heron.metricsmgr.network.options.socket.send.buffer.size.bytes The maximum socket send buffer size (in bytes) 6553600
heron.metricsmgr.network.options.socket.received.buffer.size.bytes The maximum socket received buffer size (in bytes) for the metrics manager’s network options 8738000
heron.metricsmgr.network.options.maximum.packetsize.bytes The maximum packet size that the metrics manager can read 1048576
heron.instance.network.options.maximum.packetsize.bytes The maximum size of packets that Heron instances can read 10485760
heron.instance.internal.bolt.read.queue.capacity The queue capacity (num of items) in bolt for buffer packets to read from stream manager 128
heron.instance.internal.bolt.write.queue.capacity The queue capacity (num of items) in bolt for buffer packets to write to stream manager 128
heron.instance.internal.spout.read.queue.capacity The queue capacity (num of items) in spout for buffer packets to read from stream manager 1024
heron.instance.internal.spout.write.queue.capacity The queue capacity (num of items) in spout for buffer packets to write to stream manager 128
heron.instance.internal.metrics.write.queue.capacity The queue capacity (num of items) for metrics packets to write to metrics manager 128
heron.instance.network.read.batch.time.ms Time based, the maximum batch time in ms for instance to read from stream manager per attempt 16
heron.instance.network.read.batch.size.bytes Size based, the maximum batch size in bytes to read from stream manager 32768
heron.instance.network.write.batch.time.ms Time based, the maximum batch time (in milliseconds) for the instance to write to the stream manager per attempt 16
heron.instance.network.write.batch.size.bytes Size based, the maximum batch size in bytes to write to stream manager 32768
heron.instance.network.options.socket.send.buffer.size.bytes The maximum socket’s send buffer size in bytes 6553600
heron.instance.network.options.socket.received.buffer.size.bytes The maximum socket’s received buffer size in bytes of instance’s network options 8738000
heron.instance.set.data.tuple.capacity The maximum number of data tuple to batch in a HeronDataTupleSet protobuf 1024
heron.instance.set.data.tuple.size.bytes The maximum size in bytes of data tuple to batch in a HeronDataTupleSet protobuf 8388608
heron.instance.set.control.tuple.capacity The maximum number of control tuple to batch in a HeronControlTupleSet protobuf 1024
heron.instance.ack.batch.time.ms The maximum time in ms for a spout to do acknowledgement per attempt, the ack batch could also break if there are no more ack tuples to process 128
heron.instance.emit.batch.time.ms The maximum time in ms for an spout instance to emit tuples per attempt 16
heron.instance.emit.batch.size.bytes The maximum batch size in bytes for an spout to emit tuples per attempt 32768
heron.instance.execute.batch.time.ms The maximum time in ms for an bolt instance to execute tuples per attempt 16
heron.instance.execute.batch.size.bytes The maximum batch size in bytes for an bolt instance to execute tuples per attempt 32768
heron.instance.state.check.interval.sec The time interval for an instance to check the state change, for example, the interval a spout uses to check whether activate/deactivate is invoked 5
heron.instance.force.exit.timeout.ms The time to wait before the instance exits forcibly when uncaught exception happens 2000
heron.instance.reconnect.streammgr.interval.sec Interval in seconds to reconnect to the stream manager, including the request timeout in connecting 5
heron.instance.reconnect.streammgr.interval.sec Interval in seconds to reconnect to the stream manager, including the request timeout in connecting 60
heron.instance.reconnect.metricsmgr.interval.sec Interval in seconds to reconnect to the metrics manager, including the request timeout in connecting 5
heron.instance.reconnect.metricsmgr.times Interval in seconds to reconnect to the metrics manager, including the request timeout in connecting 60
heron.instance.metrics.system.sample.interval.sec The interval in second for an instance to sample its system metrics, for instance, cpu load. 10
heron.instance.slave.fetch.pplan.interval.sec The time interval (in seconds) at which Heron instances fetch the physical plan from slaves 1
heron.instance.acknowledgement.nbuckets For efficient acknowledgement 10
heron.instance.tuning.expected.bolt.read.queue.size The expected size on read queue in bolt 8
heron.instance.tuning.expected.bolt.write.queue.size The expected size on write queue in bolt 8
heron.instance.tuning.expected.spout.read.queue.size The expected size on read queue in spout 512
heron.instance.tuning.expected.spout.write.queue.size The exepected size on write queue in spout 8
heron.instance.tuning.expected.metrics.write.queue.size The expected size on metrics write queue 8
heron.instance.tuning.current.sample.weight 0.8
heron.instance.tuning.interval.ms Interval in ms to tune the size of in & out data queue in instance 100

packing.yaml

Parameter Description Default
heron.class.packing.algorithm Packing algorithm for packing instances into containers com.twitter.heron.packing.roundrobin.RoundRobinPacking

scheduler.yaml

Parameter Description Default
heron.class.scheduler scheduler class for distributing the topology for execution com.twitter.heron.scheduler.kubernetes.KubernetesScheduler
heron.class.launcher launcher class for submitting and launching the topology com.twitter.heron.scheduler.kubernetes.KubernetesLauncher
heron.directory.sandbox.java.home location of java - pick it up from shell environment $JAVA_HOME
heron.kubernetes.scheduler.uri The URI of the Kubernetes API
heron.scheduler.is.service Invoke the IScheduler as a library directly
heron.executor.docker.image docker repo for executor heron/heron:latest

stateful.yaml

Parameter Description Default
heron.statefulstorage.classname The type of storage to be used for state checkpointing com.twitter.heron.statefulstorage.localfs.LocalFileSystemStorage

statemgr.yaml

Parameter Description Default
heron.class.state.manager local state manager class for managing state in a persistent fashion com.twitter.heron.statemgr.zookeeper.curator.CuratorStateManager
heron.statemgr.connection.string local state manager connection string
heron.statemgr.root.path path of the root address to store the state in a local file system /heron
heron.statemgr.zookeeper.is.initialize.tree create the zookeeper nodes, if they do not exist True
heron.statemgr.zookeeper.session.timeout.ms timeout in ms to wait before considering zookeeper session is dead 30000
heron.statemgr.zookeeper.connection.timeout.ms timeout in ms to wait before considering zookeeper connection is dead 30000
heron.statemgr.zookeeper.retry.count timeout in ms to wait before considering zookeeper connection is dead 10
heron.statemgr.zookeeper.retry.interval.ms duration of time to wait until the next retry 10000

uploader.yaml

Parameter Description Default
heron.class.uploader uploader class for transferring the topology files (jars, tars, PEXes, etc.) to storage com.twitter.heron.uploader.s3.S3Uploader
heron.uploader.s3.bucket S3 bucket in which topology assets will be stored (if AWS S3 is being used)
heron.uploader.s3.access_key AWS access key (if AWS S3 is being used)
heron.uploader.s3.secret_key AWS secret access key (if AWS S3 is being used)