# Copyright IBM Corp. All Rights Reserved.
#
# SPDX-License-Identifier: Apache-2.0
#

version: '2'

services:

  zookeeper:
    image: hyperledger/fabric-zookeeper
    environment:
      #
      # server.x=[hostname]:nnnnn[:nnnnn]
      # The list of servers that make up the ZK ensemble. The list that is used
      # by the clients must match the list of ZooKeeper servers that each ZK
      # server has. There are two port numbers `nnnnn`. The first is what
      # followers use to connect to the leader, while the second is for leader
      # election.
      - ZOO_SERVERS=server.1=zookeeper0.example.com:2888:3888 server.2=zookeeper1.example.com:2888:3888 server.3=zookeeper2.example.com:2888:3888
    restart: always

  kafka:
    image: hyperledger/fabric-kafka
    restart: always
    environment:
      # ========================================================================
      #     Reference: https://kafka.apache.org/documentation/#configuration
      # ========================================================================
      #
      # socket.request.max.bytes
      # The maximum number of bytes in a socket request. ATTN: If you set this
      # env var, you should make sure that the value assigned to
      # `brokerConfig.Producer.MaxMessageBytes` in `newBrokerConfig()` in
      # `fabric/orderer/kafka/util.go` matches it.
      #- KAFKA_SOCKET_REQUEST_MAX_BYTES=104857600 # 100 * 1024 * 1024 B
      #
      # message.max.bytes
      # The maximum size of envelope that the broker can receive.
      - KAFKA_MESSAGE_MAX_BYTES=103809024 # 99 * 1024 * 1024 B
      #
      # replica.fetch.max.bytes
      # The number of bytes of messages to attempt to fetch for each channel.
      # This is not an absolute maximum, if the fetched envelope is larger than
      # this value, the envelope will still be returned to ensure that progress
      # can be made. The maximum message size accepted by the broker is defined
      # via message.max.bytes above.
      - KAFKA_REPLICA_FETCH_MAX_BYTES=103809024 # 99 * 1024 * 1024 B
      #
      # unclean.leader.election.enable
      # Data consistency is key in a blockchain environment. We cannot have a
      # leader chosen outside of the in-sync replica set, or we run the risk of
      # overwriting the offsets that the previous leader produced, and --as a
      # result-- rewriting the blockchain that the orderers produce.
      - KAFKA_UNCLEAN_LEADER_ELECTION_ENABLE=false

      #
      # min.insync.replicas
      # Let the value of this setting be M. Data is considered committed when
      # it is written to at least M replicas (which are then considered in-sync
      # and belong to the in-sync replica set, or ISR). In any other case, the
      # write operation returns an error. Then:
      # 1. if just one replica out of the N (see default.replication.factor
      # below) that the channel data is written to becomes unavailable,
      # operations proceed normally.
      # 2. If N - M + 1 (or more) replicas become unavailable, Kafka cannot
      # maintain an ISR set of M, so it stops accepting writes. Reads work
      # without issues. The cluster becomes writeable again when M replicas get
      # in-sync.
      - KAFKA_MIN_INSYNC_REPLICAS=2
      #
      # default.replication.factor
      # Let the value of this setting be M. This means that:
      # 1. Each channel will have its data replicated to N brokers. These are
      # the candidates for the ISR set for a channel. As we've noted in the
      # min.insync.replicas section above, not all of these brokers have to be
      # available all the time. We choose a default.replication.factor of N so
      # as to have the largest possible candidate set for a channel's ISR.
      # 2. Channel creations cannot go forward if less than N brokers are up.
      - KAFKA_DEFAULT_REPLICATION_FACTOR=3
      #
      # zookeper.connect
      # Point to the set of Zookeeper nodes comprising a ZK ensemble.
      - KAFKA_ZOOKEEPER_CONNECT=zookeeper0.example.com:2181,zookeeper1.example.com:2181,zookeeper2.example.com:2181
      #
      # zookeeper.connection.timeout.ms
      # The max time that the client waits to establish a connection to
      # Zookeeper. If not set, the value in zookeeper.session.timeout.ms (below)
      # is used.
      #- KAFKA_ZOOKEEPER_CONNECTION_TIMEOUT_MS = 6000
      #
      # zookeeper.session.timeout.ms
      #- KAFKA_ZOOKEEPER_SESSION_TIMEOUT_MS = 6000
    #ports:
      #- '9092'