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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
cluster_id Cluster name String, underscore possible cluster_id: "my_cluster_name"
discover_prefix Subject prefix for server discovery by clients NATS Subject discover_prefix: "_STAN.Discovery"
store Store type memory, file or sql store: "file"
dir When using a file store, this is the root directory File path dir: "/path/to/storage
sd Enable debug logging true or false sd: true
sv Enable trace logging true or false sv: true
nats_server_url If specified, connects to an external NATS Server, otherwise starts an embedded one NATS URL nats_server_url: "nats://localhost:4222"
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
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"
hb_timeout How long the server waits for a heartbeat response from the client before considering it a failed heartbeat Duration hb_timeout: "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
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"
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
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
encryption_cipher Cipher to use for encryption. Currently support AES and CHAHA (ChaChaPoly). Defaults to AES AES or CHACHA encryption_cipher: "AES"
encryption_key Encryption key. It is recommended to specify the key through the NATS_STREAMING_ENCRYPTION_KEY environment variable instead String encryption_key: "mykey"

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
client_cert Client key for the streaming server File path client_cert: "/path/to/client/cert_file"
client_key Client certificate for the streaming server File path client_key: "/path/to/client/key_file"
client_ca Client certificate CA for the streaming server File path client_ca: "/path/to/client/ca_file"

Store Limits Configuration

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

File Options Configuration

Parameter Meaning Possible Values Usage Example
compact Enable/disable file compaction. Only some of the files (clients.dat and subs.dat) are subject to compaction true or false compact: true
compact_fragmentation Compaction threshold (in percentage) Number >= 0 compact_fragmentation: 50
compact_interval Minimum interval between attempts to compact files Expressed in seconds compact_interval: 300
compact_min_size Minimum size of a file before compaction can be attempted Bytes compact_min_size: 1GB
buffer_size Size of buffers that can be used to buffer write operations Bytes buffer_size: 2MB
crc Define if CRC of records should be computed on reads true or false crc: 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
sync_on_flush Define if server should perform "file sync" operations during a flush true or false sync_on_flush: 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
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
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"
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"
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
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
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
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"

Cluster Configuration

Parameter Meaning Possible Values Usage Example
node_id ID of the node within the cluster if there is no stored ID String (no whitespace) node_id: "node-a"
bootstrap Bootstrap the cluster if there is no existing state by electing self as leader true or false bootstrap: true
peers List of cluster peer node IDs to bootstrap cluster state List of node IDs peers: ["node-b", "node-c"]
log_path Directory to store log replication data File path log_path: "/path/to/storage"
log_cache_size Number of log entries to cache in memory to reduce disk IO Number >= 0 log_cache_size: 1024
log_snapshots Number of log snapshots to retain Number >= 0 log_snapshots: 1
trailing_logs Number of log entries to leave after a snapshot and compaction Number >= 0 trailing_logs: 256
sync Do a file sync after every write to the replication log and message store true or false sync: true
raft_logging Enable logging from the Raft library (disabled by default) true or false raft_logging: true
raft_heartbeat_timeout Specifies the time in follower state without a leader before attempting an election Duration raft_heartbeat_timeout: "2s"
raft_election_timeout Specifies the time in candidate state without a leader before attempting an election Duration raft_election_timeout: "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"
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"

SQL Options Configuration

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

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