Patroni Fails to Start: 'TypeError: 'NoneType' object is not iterable' Error

[myugan]

I'm deploying a new cluster with a minor adjustment to the Ansible variable, specifically setting with_haproxy_load_balancing to true and updating the necessary instances in the inventory file. After making these changes, I executed the following command:

ansible-playbook deploy_pgcluster.yml

Additionally, I have ensured all firewalls are open. However, it appears the error occurs because Patroni is not functioning correctly. Upon checking the logs, I encountered the following error:

Traceback (most recent call last):
  File "/usr/bin/patroni", line 33, in <module>
    sys.exit(load_entry_point('patroni==3.3.0', 'console_scripts', 'patroni')())
  File "/usr/lib/python3/dist-packages/patroni/__main__.py", line 344, in main
    return patroni_main(args.configfile)
  File "/usr/lib/python3/dist-packages/patroni/__main__.py", line 232, in patroni_main
    abstract_main(Patroni, configfile)
  File "/usr/lib/python3/dist-packages/patroni/daemon.py", line 172, in abstract_main
    controller = cls(config)
  File "/usr/lib/python3/dist-packages/patroni/__main__.py", line 63, in __init__
    self.dcs = get_dcs(self.config)
  File "/usr/lib/python3/dist-packages/patroni/dcs/__init__.py", line 138, in get_dcs
    return dcs_class(config[name], get_mpp(config))
  File "/usr/lib/python3/dist-packages/patroni/dcs/etcd3.py", line 663, in __init__
    super(Etcd3, self).__init__(config, mpp, PatroniEtcd3Client,
  File "/usr/lib/python3/dist-packages/patroni/dcs/etcd.py", line 480, in __init__
    self._abstract_client = self.get_etcd_client(config, client_cls)
  File "/usr/lib/python3/dist-packages/patroni/dcs/etcd.py", line 559, in get_etcd_client
    for value in hosts:
TypeError: 'NoneType' object is not iterable

Here is the configuration of Patroni that is inside the instance:

---

scope: postgres-cluster
name: pgnode01
namespace: /service

restapi:
  listen: 0.0.0.0:8008
  connect_address: x.x.x.x:8008
#  certfile: /etc/ssl/certs/ssl-cert-snakeoil.pem
#  keyfile: /etc/ssl/private/ssl-cert-snakeoil.key
  authentication:
      username: patroni
      password: xxx

etcd3:
  hosts:

bootstrap:
  method: initdb
  dcs:
    ttl: 30
    loop_wait: 10
    retry_timeout: 10
    maximum_lag_on_failover: 1048576
    master_start_timeout: 300
    synchronous_mode: false
    synchronous_mode_strict: false
    synchronous_node_count: 1
    postgresql:
      use_pg_rewind: true
      use_slots: true
      parameters:
        max_connections: "1000"
        superuser_reserved_connections: "5"
        password_encryption: "scram-sha-256"
        max_locks_per_transaction: "512"
        max_prepared_transactions: "0"
        huge_pages: "try"
        shared_buffers: "479MB"
        effective_cache_size: "1439MB"
        work_mem: "128MB"
        maintenance_work_mem: "256MB"
        checkpoint_timeout: "15min"
        checkpoint_completion_target: "0.9"
        min_wal_size: "2GB"
        max_wal_size: "8GB"
        wal_buffers: "32MB"
        default_statistics_target: "1000"
        seq_page_cost: "1"
        random_page_cost: "1.1"
        effective_io_concurrency: "200"
        synchronous_commit: "on"
        autovacuum: "on"
        autovacuum_max_workers: "5"
        autovacuum_vacuum_scale_factor: "0.01"
        autovacuum_analyze_scale_factor: "0.01"
        autovacuum_vacuum_cost_limit: "500"
        autovacuum_vacuum_cost_delay: "2"
        autovacuum_naptime: "1s"
        max_files_per_process: "4096"
        archive_mode: "on"
        archive_timeout: "1800s"
        archive_command: "cd ."
        wal_level: "logical"
        wal_keep_size: "2GB"
        max_wal_senders: "10"
        max_replication_slots: "10"
        hot_standby: "on"
        wal_log_hints: "on"
        wal_compression: "on"
        shared_preload_libraries: "pg_stat_statements,auto_explain"
        pg_stat_statements.max: "10000"
        pg_stat_statements.track: "all"
        pg_stat_statements.track_utility: "false"
        pg_stat_statements.save: "true"
        auto_explain.log_min_duration: "10s"
        auto_explain.log_analyze: "true"
        auto_explain.log_buffers: "true"
        auto_explain.log_timing: "false"
        auto_explain.log_triggers: "true"
        auto_explain.log_verbose: "true"
        auto_explain.log_nested_statements: "true"
        auto_explain.sample_rate: "0.01"
        track_io_timing: "on"
        log_lock_waits: "on"
        log_temp_files: "0"
        track_activities: "on"
        track_activity_query_size: "4096"
        track_counts: "on"
        track_functions: "all"
        log_checkpoints: "on"
        logging_collector: "on"
        log_truncate_on_rotation: "on"
        log_rotation_age: "1d"
        log_rotation_size: "0"
        log_line_prefix: "%t [%p-%l] %r %q%u@%d "
        log_filename: "postgresql-%a.log"
        log_directory: "/var/log/postgresql"
        hot_standby_feedback: "on"
        max_standby_streaming_delay: "30s"
        wal_receiver_status_interval: "10s"
        idle_in_transaction_session_timeout: "10min"
        jit: "off"
        max_worker_processes: "24"
        max_parallel_workers: "8"
        max_parallel_workers_per_gather: "2"
        max_parallel_maintenance_workers: "2"
        tcp_keepalives_count: "10"
        tcp_keepalives_idle: "300"
        tcp_keepalives_interval: "30"

  initdb:  # List options to be passed on to initdb
    - encoding: UTF8
    - locale: en_US.UTF-8
    - data-checksums

  pg_hba:  # Add following lines to pg_hba.conf after running 'initdb'
    - host replication replicator 127.0.0.1/32 scram-sha-256
    - host all all 0.0.0.0/0 scram-sha-256

postgresql:
  listen: 0.0.0.0:5432
  connect_address: x.x.x.x:5432
  use_unix_socket: true
  data_dir: /var/lib/postgresql/16/main
  bin_dir: /usr/lib/postgresql/16/bin
  config_dir: /etc/postgresql/16/main
  pgpass: /var/lib/postgresql/.pgpass_patroni
  authentication:
    replication:
      username: replicator
      password: xxx
    superuser:
      username: postgres
      password: xxx
#    rewind:  # Has no effect on postgres 10 and lower
#      username: rewind_user
#      password: rewind_password
  parameters:
    unix_socket_directories: /var/run/postgresql

  remove_data_directory_on_rewind_failure: false
  remove_data_directory_on_diverged_timelines: false

  create_replica_methods:
    - basebackup
  basebackup:
    max-rate: '1000M'
    checkpoint: 'fast'

watchdog:
  mode: automatic  # Allowed values: off, automatic, required
  device: /dev/watchdog  # Path to the watchdog device
  safety_margin: 5

tags:
  nosync: false
  noloadbalance: false
  nofailover: false
  clonefrom: false

  # specify a node to replicate from (cascading replication)
#  replicatefrom: (node name)

[vitabaks]

The etcd cluster IP addresses are not specified here:

etcd3:
  hosts:

Specify the IP addresses of the servers in the etcd_cluster group (in the inventory file) to which the etcd cluster will be deployed. Or set the addresses of an existing cluster (if any) in the patroni_etcd_hosts variable (and dcs_exists: true in this case).