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nats input

Subscribe to a NATS subject.

# Common config fields, showing default values
input:
  label: ""
  nats:
    urls: [] # No default (required)
    subject: "" # No default (required)
    queue: "" # No default (optional)
    auto_replay_nacks: true
    send_ack: true

Metadata​

This input adds the following metadata fields to each message:

- nats_subject
- nats_reply_subject
- All message headers (when supported by the connection)

You can access these metadata fields using function interpolation.

Connection name​

When monitoring and managing a production NATS system, it is often useful to know which connection a message was send/received from. This can be achieved by setting the connection name option when creating a NATS connection.

Expanso Edge will automatically set the connection name based off the label of the given NATS component, so that monitoring tools between NATS and Expanso Edge can stay in sync.

Authentication​

There are several components within Expanso Edge which uses NATS services. You will find that each of these components support optional advanced authentication parameters for NKeys and User Credentials.

See an in-depth tutorial.

NKey file​

The NATS server can use these NKeys in several ways for authentication. The simplest is for the server to be configured with a list of known public keys and for the clients to respond to the challenge by signing it with its private NKey configured in the nkey_file or nkey field.

More details.

User credentials​

NATS server supports decentralized authentication based on JSON Web Tokens (JWT). Clients need an user JWT and a corresponding NKey secret when connecting to a server which is configured to use this authentication scheme.

The user_credentials_file field should point to a file containing both the private key and the JWT and can be generated with the nsc tool.

Alternatively, the user_jwt field can contain a plain text JWT and the user_nkey_seedcan contain the plain text NKey Seed.

More details.

Token​

The token field can contain a plain text token string for token-based authentication.

User and password​

The user and password fields can be used for username/password authentication.

Fields​

urls​

A list of URLs to connect to. If an item of the list contains commas it will be expanded into multiple URLs.

Type: array of string

max_reconnects​

The maximum number of times to attempt to reconnect to the server. If negative, it will never stop trying to reconnect.

Type: int

subject​

A subject to consume from. Supports wildcards for consuming multiple subjects. Either a subject or stream must be specified.

Type: string

queue​

An optional queue group to consume as.

Type: string

auto_replay_nacks​

Whether messages that are rejected (nacked) at the output level should be automatically replayed indefinitely, eventually resulting in back pressure if the cause of the rejections is persistent. If set to false these messages will instead be deleted. Disabling auto replays can greatly improve memory efficiency of high throughput streams as the original shape of the data can be discarded immediately upon consumption and mutation.

Type: bool
Default: true

send_ack​

Control whether ACKS are sent as a reply to each message. When enabled, these replies are sent only once the data has been delivered to all outputs.

Type: bool
Default: true

nak_delay​

An optional delay duration on redelivering a message when negatively acknowledged.

Type: string

prefetch_count​

The maximum number of messages to pull at a time.

Type: int
Default: 500000

tls​

Custom TLS settings can be used to override system defaults.

Type: object

tls.enabled​

Whether custom TLS settings are enabled.

Type: bool
Default: false

tls.skip_cert_verify​

Whether to skip server side certificate verification.

Type: bool
Default: false

tls.enable_renegotiation​

Whether to allow the remote server to repeatedly request renegotiation. Enable this option if you're seeing the error message local error: tls: no renegotiation.

Type: bool
Default: false

tls.root_cas​

An optional root certificate authority to use. This is a string, representing a certificate chain from the parent trusted root certificate, to possible intermediate signing certificates, to the host certificate.

Secret

This field contains sensitive information. Use a secret reference rather than a literal value.

Type: string
Default: ""

tls.root_cas_file​

An optional path of a root certificate authority file to use. This is a file, often with a .pem extension, containing a certificate chain from the parent trusted root certificate, to possible intermediate signing certificates, to the host certificate.

Type: string
Default: ""

tls.client_certs​

A list of client certificates to use. For each certificate either the fields cert and key, or cert_file and key_file should be specified, but not both.

Type: array of object
Default: []

tls.client_certs[].cert​

A plain text certificate to use.

Type: string
Default: ""

tls.client_certs[].key​

A plain text certificate key to use.

Secret

This field contains sensitive information. Use a secret reference rather than a literal value.

Type: string
Default: ""

tls.client_certs[].cert_file​

The path of a certificate to use.

Type: string
Default: ""

tls.client_certs[].key_file​

The path of a certificate key to use.

Type: string
Default: ""

tls.client_certs[].password​

A plain text password for when the private key is password encrypted in PKCS#1 or PKCS#8 format. The obsolete pbeWithMD5AndDES-CBC algorithm is not supported for the PKCS#8 format.

Because the obsolete pbeWithMD5AndDES-CBC algorithm does not authenticate the ciphertext, it is vulnerable to padding oracle attacks that can let an attacker recover the plaintext.

Secret

This field contains sensitive information. Use a secret reference rather than a literal value.

Type: string
Default: ""

tls_handshake_first​

Perform a TLS handshake before sending the INFO protocol message.

Type: bool
Default: false

auth​

Optional configuration of NATS authentication parameters.

Type: object

auth.nkey_file​

An optional file containing a NKey seed.

Type: string

auth.nkey​

The NKey seed.

Secret

This field contains sensitive information. Use a secret reference rather than a literal value.

Type: string

auth.user_credentials_file​

An optional file containing user credentials which consist of an user JWT and corresponding NKey seed.

Type: string

auth.user_jwt​

An optional plain text user JWT (given along with the corresponding user NKey Seed).

Secret

This field contains sensitive information. Use a secret reference rather than a literal value.

Type: string

auth.user_nkey_seed​

An optional plain text user NKey Seed (given along with the corresponding user JWT).

Secret

This field contains sensitive information. Use a secret reference rather than a literal value.

Type: string

auth.user​

An optional plain text user name (given along with the corresponding user password).

Type: string

auth.password​

An optional plain text password (given along with the corresponding user name).

Secret

This field contains sensitive information. Use a secret reference rather than a literal value.

Type: string

auth.token​

An optional plain text token.

Secret

This field contains sensitive information. Use a secret reference rather than a literal value.

Type: string

extract_tracing_map​

EXPERIMENTAL: A Bloblang mapping that attempts to extract an object containing tracing propagation information, which will then be used as the root tracing span for the message. The specification of the extracted fields must match the format used by the service wide tracer.

Type: string