nats_kv processor

Perform operations on a NATS key-value bucket.

Common

# Common config fields, showing default values
pipeline:
  processors:
    - label: ""
      nats_kv:
        urls: [] # No default (required)
        bucket: "" # No default (required)
        operation: "" # No default (required)
        key: "" # No default (required)

Advanced

# All config fields, showing default values
pipeline:
  processors:
    - label: ""
      nats_kv:
        urls: [] # No default (required)
        max_reconnects: 0 # No default (optional)
        bucket: "" # No default (required)
        operation: "" # No default (required)
        key: "" # No default (required)
        revision: "" # No default (optional)
        timeout: "5s"
        tls:
          enabled: false
          skip_cert_verify: false
          enable_renegotiation: false
          root_cas: ""
          root_cas_file: ""
          client_certs: []
        tls_handshake_first: false
        auth:
          nkey_file: "" # No default (optional)
          nkey: "" # No default (optional)
          user_credentials_file: "" # No default (optional)
          user_jwt: "" # No default (optional)
          user_nkey_seed: "" # No default (optional)
          user: "" # No default (optional)
          password: "" # No default (optional)
          token: "" # No default (optional)

KV operations

The NATS KV processor supports a multitude of KV operations via the operation field. Along with get, put, and delete, this processor supports atomic operations like update and create, as well as utility operations like purge, history, and keys.

Metadata

This processor adds the following metadata fields to each message, depending on the chosen operation:

get, get_revision

- nats_kv_key
- nats_kv_bucket
- nats_kv_revision
- nats_kv_delta
- nats_kv_operation
- nats_kv_created

create, update, delete, purge

- nats_kv_key
- nats_kv_bucket
- nats_kv_revision
- nats_kv_operation

keys

- nats_kv_bucket

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

bucket

The name of the KV bucket.

Type: string

operation

The operation to perform on the KV bucket.

Type: string

Option	Summary
create	Adds the key/value pair if it does not exist. Returns an error if it already exists.
delete	Deletes the key/value pair, but keeps historical values.
get	Returns the latest value for key.
get_revision	Returns the value of key for the specified revision.
history	Returns historical values of key as an array of objects containing the following fields: key, value, bucket, revision, delta, operation, created.
keys	Returns the keys in the bucket which match the keys_filter as an array of strings.
purge	Deletes the key/value pair and all historical values.
put	Places a new value for the key into the store.
update	Updates the value for key only if the revision matches the latest revision.

key

The key for each message. Supports wildcards for the history and keys operations.

This field supports interpolation functions.

Type: string

revision

The revision of the key to operate on. Used for get_revision and update operations.

This field supports interpolation functions.

Type: string

timeout

The maximum period to wait on an operation before aborting and returning an error.

Type: string
Default: "5s"

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

Filtering the keys operation

The summary for the keys operation mentions a keys_filter. No such field exists: the filter is the key field, which supports NATS subject wildcards for the keys and history operations. Set key to the pattern you want to list, or to > for every key in the bucket:

pipeline:
  processors:
    - nats_kv:
        urls: [nats://localhost:4222]
        bucket: my_bucket
        operation: keys
        key: sensors.>

The operation returns the matching keys as an array of strings, so the message body is replaced rather than filtered.