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configuration.md

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Configuration

Liftbridge provides limited configuration through command-line flags and full configuration using a configuration file. Flags will always take precedent over settings in the configuration file.

The configuration file is passed in using the --config flag:

$ liftbridge --config liftbridge.conf

To get a full list of the CLI flags, use the --help flag:

$ liftbridge --help
NAME:
   liftbridge - Lightweight, fault-tolerant message streams

USAGE:
   liftbridge [global options] command [command options] [arguments...]

VERSION:
   0.0.1

COMMANDS:
     help, h  Shows a list of commands or help for one command

GLOBAL OPTIONS:
   --config FILE, -c FILE         load configuration from FILE
   --server-id value, --id value  ID of the server in the cluster if there is no stored ID
   --namespace value, --ns value  cluster namespace (default: "liftbridge-default")
   --nats-server ADDR, -n ADDR    connect to NATS server at ADDR (default: "nats://localhost:4222")
   --data-dir DIR, -d DIR         store data in DIR (default: "/tmp/liftbridge/<namespace>")
   --port value, -p value         port to bind to (default: 9292)
   --level value, -l value        logging level [debug|info|warn|error] (default: "info")
   --raft-bootstrap-seed          bootstrap the Raft cluster by electing self as leader if there is no existing state
   --raft-bootstrap-peers value   bootstrap the Raft cluster with the provided list of peer IDs if there is no existing state
   --help, -h                     show help
   --version, -v                  print the version

Configuration File Format

The configuration file format borrows from the NATS configuration format. It is a flexible format that combines the best of traditional configuration formats and newer styles such as JSON and YAML.

The config file format supports the following syntax:

  • Mixed Arrays: [...]
  • Nested Maps: {...}
  • Multiple comment types: # and //
  • Key value assigments using:
    • Equals sign (foo = 2)
    • Colon (foo: 2)
    • Whitespace (foo 2)
  • Maps can be assigned with no key separator
  • Semicolons as value terminators in key/value assignments are optional

Example Configuration File

An example configuration file is shown below.

listen: localhost:9293
data.dir: /tmp/liftbridge/server-2
log.level: debug

# Define NATS cluster to connect to.
nats {
    servers: ["nats://localhost:4300", "nats://localhost:4301"]
}

# Specify message log settings.
log {
    segment.max.bytes: 1000000
    retention.max.bytes: 100000000000
}

# Specify cluster settings.
clustering {
    server.id: server-2
    raft.logging: true
    raft.bootstrap.seed: true
    replica.max.lag.time: "20s"
}

Configuration Settings

Below is the list of Liftbridge configuration settings, including the name of the setting in the configuration file and the CLI flag if it exists.

Name Flag Description Type Default Valid Values
listen The server host/port. string localhost:9292
host The server host. string localhost
port port The server port. int 9292
log.level level The logging level. string info [debug, info, warn, error]
data.dir data-dir The directory to store data in. string /tmp/liftbridge/namespace
batch.max.messages The maximum number of messages to batch when writing to disk. int 1024
batch.wait.time The time to wait to batch more messages when writing to disk. duration 0
metadata.cache.max.age The maximum age of cached broker metadata. duration 2m
nats NATS configuration. map See below
log Stream write-ahead log configuration. map See below
clustering Broker cluster configuration. map See below

NATS Configuration Settings

Below is the list of the configuration settings for the nats part of the configuration file.

Name Flag Description Type Default Valid Values
servers nats-server List of NATS hosts to connect to. list nats://localhost:4222

Log Configuration Settings

Below is the list of the configuration settings for the log part of the configuration file.

Name Flag Description Type Default Valid Values
retention.max.bytes The maximum size of the log before truncating it. int64 -1
segment.max.bytes The maximum size of a single log segment file. int64 10485760

Clustering Configuration Settings

Below is the list of the configuration settings for the clustering part of the configuration file.

Name Flag Description Type Default Valid Values
server.id server-id ID of the server in the cluster. string random id string with no spaces or periods
namespace namespace Cluster namespace. string liftbridge-default string with no spaces or periods
raft.snapshot.retain The number Raft log snapshots to retain on disk. int 2
raft.snapshot.threshold Controls how many outstanding logs there must be before taking a snapshot. This prevents excessive snapshots when a small set of logs can be replayed. int 8192
raft.cache.size The number of Raft logs to hold in memory for quick lookup. int 512
raft.bootstrap.seed raft-bootstrap-seed Bootstrap the Raft cluster by electing self as leader if there is no existing state. bool false
raft.bootstrap.peers raft-bootstrap-peers Bootstrap the Raft cluster with the provided list of peer IDs if there is no existing state. list
raft.logging Enables logging in the Raft subsystem. bool false
replica.max.lag.time If a follower hasn't sent any replication requests or hasn't caught up to the leader's log end offset for at least this time, the leader will remove the follower from ISR. duration 10s
replica.fetch.timeout Timeout duration for follower replication requests. duration 5s