The Pinot Controller is responsible for a number of things

• Controllers maintain the global metadata (e.g. configs and schemas) of the system with the help of Zookeeper which is used as the persistent metadata store.

• Controllers host Helix Controller and is responsible for managing other pinot components (brokers, servers, minions)

• They maintain the mapping of which servers are responsible for which segments. This mapping is used by the servers, to download the portion of the segments that they are responsible for. This mapping is also used by the broker to decide which servers to route the queries to.

• Controller has admin endpoints for viewing, creating, updating and deleting configs which help us manage and operate the cluster.

• Controllers also have endpoints for segment uploads which are used in offline data pushes. They are responsible for initializing realtime consumption and coordination of persisting the realtime segments into the segment store periodically.

• They undertake other management activities such as managing retention of segments, validations.

There can be multiple instances of Pinot controller for redundancy. If there are multiple controllers, Pinot expects that all of them are configured with the same back-end storage system so that they have a common view of the segments (e.g. NFS). Pinot can use other storage systems such as HDFS or ADLS.

Starting a Controller

Make sure you've setup Zookeeper. If you're using docker, make sure to pull the pinot docker image. To start a controller

docker run \
    --network=pinot-demo \
    --name pinot-controller \
    -p 9000:9000 \
    -d ${PINOT_IMAGE} StartController \
    -zkAddress pinot-zookeeper:2181

bin/pinot-admin.sh StartController \
  -zkAddress localhost:2181 \
  -clusterName PinotCluster \
  -controllerPort 9000

Starting Minion

Cluster is a set a nodes comprising of servers, brokers, controllers and minions.

Cluster components

Briefly, Helix divides nodes into three logical components based on their responsibilities

Participant

The nodes that host distributed, partitioned resources

Spectator

The nodes that observe the current state of each Participant and use that information to access the resources. Spectators are notified of state changes in the cluster (state of a participant, or that of a partition in a participant).

Controller

The node that observes and controls the Participant nodes. It is responsible for coordinating all transitions in the cluster and ensuring that state constraints are satisfied while maintaining cluster stability.

Logical view

Setup a Pinot Cluster

To setup a Pinot cluster, we need to first start Zookeeper.

Once we've started Zookeeper, we can start other components to join this cluster. If you're using docker, pull the latest apachepinot/pinot image.

To start other components to join the cluster