Configuration File

You can use a configuration file to configure the options specific to the NATS Streaming Server.

Use the -sc or --stan_config command line parameter to specify the file to use.

For the embedded NATS Server, you can use another configuration file and pass it to the Streaming Server using -c or --config command line parameters.

Since most options do not overlap, it is possible to combine all options into a single file and specify this file using either the -sc or -c command line parameter.

However, the option named tls is common to NATS Server and NATS Streaming Server. If you plan to use a single configuration file and configure TLS, you should have all the streaming configuration included in a streaming map. This is actually a good practice regardless if you use TLS or not, to protect against possible addition of new options in NATS Server that would conflict with the names of NATS Streaming options.

For instance, you could use a single configuration file with such content:

# Some NATS Server TLS Configuration
listen: localhost:5222
tls: {
    cert_file: "/path/to/server/cert_file"
    key_file: "/path/to/server/key_file"
    verify: true
    timeout: 2
}

# NATS Streaming Configuration
streaming: {
    cluster_id: my_cluster

    tls: {
        client_cert: "/path/to/client/cert_file"
        client_key: "/path/to/client/key_file"
    }
}

However, if you want to avoid any possible conflict, simply use two different configuration files.

Note the order in which options are applied during the start of a NATS Streaming server:

1. Start with some reasonable default options.

2. If a configuration file is specified, override those options

   with all options defined in the file. This includes options that are defined

   but have no value specified. In this case, the zero value for the type of the

   option will be used.

3. Any command line parameter override all of the previous set options.

In general the configuration parameters are the same as the command line arguments. Below is the list of NATS Streaming parameters:

Parameter	Meaning	Possible Values	Usage Example	Default Value
cluster_id	Cluster name	String, underscore possible	cluster_id: "my_cluster_name"	test-cluster
discover_prefix	Subject prefix for server discovery by clients	NATS Subject	discover_prefix: "_STAN.Discovery"	_STAN.discover
store	Store type	memory, file or sql	store: "file"	memory
dir	When using a file store, this is the root directory	File path	dir: "/path/to/storage	N/A
sd	Enable debug logging	true or false	sd: true	false
sv	Enable trace logging	true or false	sv: true	false
nats_server_url	If specified, connects to an external NATS Server, otherwise starts an embedded one	NATS URL	nats_server_url: "nats://localhost:4222"	N/A
secure	If true, creates a TLS connection to the server but without the need to use TLS configuration (no NATS Server certificate verification)	true or false	secure: true	false
tls	TLS Configuration	Map: tls: { ... }	See details below
store_limits	Store Limits	Map: store_limits: { ... }	See details below
file_options	File Store specific options	Map: file_options: { ... }	See details below
sql_options	SQL Store specific options	Map: sql_options: { ... }	See details below
hb_interval	Interval at which the server sends an heartbeat to a client	Duration	hb_interval: "10s"	30s
hb_timeout	How long the server waits for a heartbeat response from the client before considering it a failed heartbeat	Duration	hb_timeout: "10s"	10s
hb_fail_count	Count of failed heartbeats before server closes the client connection. The actual total wait is: (fail count + 1) * (hb interval + hb timeout)	Number	hb_fail_count: 2	10
ft_group	In Fault Tolerance mode, you can start a group of streaming servers with only one server being active while others are running in standby mode. This is the name of this FT group	String	ft_group: "my_ft_group"	N/A
partitioning	If set to true, a list of channels must be defined in store_limits/channels section. This section then serves two purposes, overriding limits for a given channel or adding it to the partition	true or false	partitioning: true	false
cluster	Cluster Configuration	Map: cluster: { ... }	See details below
encrypt	Specify if server should encrypt messages (only the payload) when storing them	true or false	encrypt: true	false
encryption_cipher	Cipher to use for encryption. Currently support AES and CHAHA (ChaChaPoly). Defaults to AES	AES or CHACHA	encryption_cipher: "AES"	Depends on platform
encryption_key	Encryption key. It is recommended to specify the key through the NATS_STREAMING_ENCRYPTION_KEY environment variable instead	String	encryption_key: "mykey"	N/A
credentials	Credentials file to connect to external NATS 2.0+ Server	String	credentials: "streaming_server.creds"	N/A

TLS Configuration

Note that the Streaming Server uses a connection to a NATS Server, and so the NATS Streaming TLS Configuration is in fact a client-side TLS configuration.

Parameter	Meaning	Possible Values	Usage Example	Default Value
client_cert	Client key for the streaming server	File path	client_cert: "/path/to/client/cert_file"	N/A
client_key	Client certificate for the streaming server	File path	client_key: "/path/to/client/key_file"	N/A
client_ca	Client certificate CA for the streaming server	File path	client_ca: "/path/to/client/ca_file"	N/A
server_name	Expected hostname returned in the NATS Server certificate	String	server_name: "theserverhostname"	N/A
insecure	Skips the NATS server's certificate chain and host name verification. Should not be used in production	true or false	insecure: true	false

Store Limits Configuration

Parameter	Meaning	Possible Values	Usage Example	Default Value
max_channels	Maximum number of channels, 0 means unlimited	Number >= 0	max_channels: 100	100
max_subs	Maximum number of subscriptions per channel, 0 means unlimited	Number >= 0	max_subs: 100	1000
max_msgs	Maximum number of messages per channel, 0 means unlimited	Number >= 0	max_msgs: 10000	1000000
max_bytes	Total size of messages per channel, 0 means unlimited	Number >= 0	max_bytes: 1GB	1GB
max_age	How long messages can stay in the log	Duration	max_age: "24h"	Unlimited
max_inactivity	How long without any subscription and any new message before a channel can be automatically deleted	Duration	max_inactivity: "24h"	Unlimited
channels	A map of channel names with specific limits	Map: channels: { ... }	See details below

Channels

The channels section is a map with the key being the channel name. For instance:

   channels: {
       "foo": {
           max_msgs: 100
       }
   }

For a given channel, the possible parameters are:

Parameter	Meaning	Possible Values	Usage Example	Default Value
max_subs	Maximum number of subscriptions per channel, 0 means unlimited	Number >= 0	max_subs: 100	Inherit from global settings
max_msgs	Maximum number of messages per channel, 0 means unlimited	Number >= 0	max_msgs: 10000	Inherit from global settings
max_bytes	Total size of messages per channel, 0 means unlimited	Bytes	max_bytes: 1GB	Inherit from global settings
max_age	How long messages can stay in the log	Duration	max_age: "24h"	Inherit from global settings
max_inactivity	How long without any subscription and any new message before a channel can be automatically deleted	Duration	max_inactivity: "24h"	Inherit from global settings

File Options Configuration

Parameter	Meaning	Possible Values	Usage Example	Default Value
compact	Enable/disable file compaction. Only some of the files (clients.dat and subs.dat) are subject to compaction	true or false	compact: true	true
compact_fragmentation	Compaction threshold (in percentage)	Number >= 0	compact_fragmentation: 50	50
compact_interval	Minimum interval between attempts to compact files	Expressed in seconds	compact_interval: 300	300
compact_min_size	Minimum size of a file before compaction can be attempted	Bytes	compact_min_size: 1GB	1MB
buffer_size	Size of buffers that can be used to buffer write operations	Bytes	buffer_size: 2MB	2MB
crc	Define if CRC of records should be computed on reads	true or false	crc: true	true
crc_poly	You can select the CRC polynomial. Note that changing the value after records have been persisted would result in server failing to start complaining about data corruption	Number >= 0	crc_poly: 3988292384	3988292384
sync_on_flush	Define if server should perform "file sync" operations during a flush	true or false	sync_on_flush: true	true
slice_max_msgs	Define the file slice maximum number of messages. If set to 0 and a channel count limit is set, then the server will set a slice count limit automatically	Number >= 0	slice_max_msgs: 10000	automatic
slice_max_bytes	Define the file slice maximum size (including the size of index file). If set to 0 and a channel size limit is set, then the server will set a slice bytes limit automatically	Bytes	slice_max_bytes: 64MB	64MB
slice_max_age	Define the period of time covered by a file slice, starting at when the first message is stored. If set to 0 and a channel age limit is set, then the server will set a slice age limit automatically	Duration	slice_max_age: "24h"	automatic
slice_archive_script	Define the location and name of a script to be invoked when the server discards a file slice due to limits. The script is invoked with the name of the channel, the name of data and index files. It is the responsibility of the script to then remove the unused files	File path	slice_archive_script: "/home/nats-streaming/archive/script.sh"	N/A
file_descriptors_limit	Channels translate to sub-directories under the file store's root directory. Each channel needs several files to maintain the state so the need for file descriptors increase with the number of channels. This option instructs the store to limit the concurrent use of file descriptors. Note that this is a soft limit and there may be cases when the store will use more than this number. A value of 0 means no limit. Setting a limit will probably have a performance impact	Number >= 0	file_descriptors_limit: 100	unlimited
parallel_recovery	When the server starts, the recovery of channels (directories) is done sequentially. However, when using SSDs, it may be worth setting this value to something higher than 1 to perform channels recovery in parallel	Number >= 1	parallel_recovery: 4	1
read_buffer_size	Size of buffers used to read ahead from message stores. This can significantly speed up sending messages to consumers after messages have been published. Default is 2MB. Set to 0 to disable	Bytes	read_buffer_size: 2MB	2MB
auto_sync	Interval at which the store should be automatically flushed and sync'ed on disk. Default is every minute. Set to <=0 to disable	Duration	auto_sync: "2m"	1m

Cluster Configuration

Parameter	Meaning	Possible Values	Usage Example	Default Value
node_id	ID of the node within the cluster if there is no stored ID	String (no whitespace)	node_id: "node-a"	N/A
bootstrap	Bootstrap the cluster if there is no existing state by electing self as leader	true or false	bootstrap: true	false
peers	List of cluster peer node IDs to bootstrap cluster state	List of node IDs	peers: ["node-b", "node-c"]	N/A
log_path	Directory to store log replication data	File path	log_path: "/path/to/storage"	N/A
log_cache_size	Number of log entries to cache in memory to reduce disk IO	Number >= 0	log_cache_size: 1024	512
log_snapshots	Number of log snapshots to retain	Number >= 0	log_snapshots: 1	2
trailing_logs	Number of log entries to leave after a snapshot and compaction	Number >= 0	trailing_logs: 256	10240
sync	Do a file sync after every write to the replication log and message store	true or false	sync: true	false
raft_logging	Enable logging from the Raft library (disabled by default)	true or false	raft_logging: true	false
raft_heartbeat_timeout	Specifies the time in follower state without a leader before attempting an election	Duration	raft_heartbeat_timeout: "2s"	2s
raft_election_timeout	Specifies the time in candidate state without a leader before attempting an election	Duration	raft_election_timeout: "2s"	2s
raft_lease_timeout	Specifies how long a leader waits without being able to contact a quorum of nodes before stepping down as leader	Duration	raft_lease_timeout: "1s"	1s
raft_commit_timeout	Specifies the time without an Apply() operation before sending an heartbeat to ensure timely commit. Due to random staggering, may be delayed as much as 2x this value	Duration	raft_commit_timeout: "100ms"	100ms

SQL Options Configuration

Parameter	Meaning	Possible Values	Usage Example	Default Value
driver	Name of the SQL driver to use	mysql or postgres	driver: "mysql"	N/A
source	How to connect to the database. This is driver specific	String	source: "ivan:pwd@/nss_db"	N/A
no_caching	Enable/Disable caching for messages and subscriptions operations.	true or false	no_caching: false	false (caching enabled)
max_open_conns	Maximum number of opened connections to the database. Value <= 0 means no limit.	Number	max_open_conns: 5	unlimited