Memory Resolver Tutorial

The MEMORY resolver is a server built-in resolver for account JWTs. If there are a small number of accounts, or they do not change too often this can be a simpler configuration that does not require an external account resolver. Server configuration reload is supported, meaning the preloads can be updated in the server configuration and reloaded without a server restart.

The basic configuration for the server requires:

  • The operator JWT
  • resolver set to MEMORY
  • resolver_preload set to an object where account public keys are mapped to account JWTs.

Create Required Entities

Let’s create the setup:

  1. nsc add operator -n memory
  1. Generated operator key - private key stored "~/.nkeys/memory/memory.nk"
  2. Success! - added operator "memory"

Add an account ‘A’

  1. nsc add account --name A
  1. Generated account key - private key stored "~/.nkeys/memory/accounts/A/A.nk"
  2. Success! - added account "A"

Describe the account

  1. nsc describe account -W
  1. ╭──────────────────────────────────────────────────────────────────────────────────────╮
  2. │                                   Account Details                                    │
  3. ├───────────────────────────┬──────────────────────────────────────────────────────────┤
  4. │ Name                      │ A                                                        │
  5. │ Account ID                │ ACSU3Q6LTLBVLGAQUONAGXJHVNWGSKKAUA7IY5TB4Z7PLEKSR5O6JTGR │
  6. │ Issuer ID                 │ ODWZJ2KAPF76WOWMPCJF6BY4QIPLTUIY4JIBLU4K3YDG3GHIWBVWBHUZ │
  7. │ Issued                    │ 2019-04-30 20:21:34 UTC                                  │
  8. │ Expires                   │                                                          │
  9. ├───────────────────────────┼──────────────────────────────────────────────────────────┤
  10. │ Max Connections           │ Unlimited                                                │
  11. │ Max Leaf Node Connections │ Unlimited                                                │
  12. │ Max Data                  │ Unlimited                                                │
  13. │ Max Exports               │ Unlimited                                                │
  14. │ Max Imports               │ Unlimited                                                │
  15. │ Max Msg Payload           │ Unlimited                                                │
  16. │ Max Subscriptions         │ Unlimited                                                │
  17. │ Exports Allows Wildcards  │ True                                                     │
  18. ├───────────────────────────┼──────────────────────────────────────────────────────────┤
  19. │ Imports                   │ None                                                     │
  20. │ Exports                   │ None                                                     │
  21. ╰───────────────────────────┴──────────────────────────────────────────────────────────╯

Create a new user ‘TA’

  1. nsc add user --name TA
  1. Generated user key - private key stored "~/.nkeys/memory/accounts/A/users/TA.nk"
  2. Generated user creds file "~/.nkeys/memory/accounts/A/users/TA.creds"
  3. Success! - added user "TA" to "A"

Create the Server Config

The nsc tool can generate a configuration file automatically. You provide a path to the server configuration. The nsc tool will generate the server config for you:

  1. nsc generate config --mem-resolver --config-file /tmp/server.conf

If you require additional settings, you may want to consider using include in your main configuration, to reference the generated files. Otherwise, you can start a server and reference the generated configuration:

  1. nats-server -c /tmp/server.conf

You can then test it.

Manual Server Config

While generating a configuration file is easy, you may want to craft one by hand to know the details. With the entities created, and a standard location for the .nsc directory. You can reference the operator JWT and the account JWT in a server configuration or the JWT string directly. Remember that your configuration will be in $NSC_HOME/nats/<operator_name>/<operator_name>.jwt for the operator. The account JWT will be in $NSC_HOME/nats/<operator_name>/accounts/<account_name>/<account_name>.jwt

For the configuration you’ll need:

  • The path to the operator JWT
  • A copy of the contents of the account JWT file

The format of the file is:

  1. operator: <path to the operator jwt or jwt itself>
  2. resolver: MEMORY
  3. resolver_preload: {
  4.     <public key for an account>: <contents of the account jwt>
  5.     ### add as many accounts as you want
  6.     ...
  7. }

In this example this translates to:

  1. operator: /Users/synadia/.nsc/nats/memory/memory.jwt
  2. resolver: MEMORY
  3. resolver_preload: {
  4. ACSU3Q6LTLBVLGAQUONAGXJHVNWGSKKAUA7IY5TB4Z7PLEKSR5O6JTGR: eyJ0eXAiOiJqd3QiLCJhbGciOiJlZDI1NTE5In0.eyJqdGkiOiJPRFhJSVI2Wlg1Q1AzMlFJTFczWFBENEtTSDYzUFNNSEZHUkpaT05DR1RLVVBISlRLQ0JBIiwiaWF0IjoxNTU2NjU1Njk0LCJpc3MiOiJPRFdaSjJLQVBGNzZXT1dNUENKRjZCWTRRSVBMVFVJWTRKSUJMVTRLM1lERzNHSElXQlZXQkhVWiIsIm5hbWUiOiJBIiwic3ViIjoiQUNTVTNRNkxUTEJWTEdBUVVPTkFHWEpIVk5XR1NLS0FVQTdJWTVUQjRaN1BMRUtTUjVPNkpUR1IiLCJ0eXBlIjoiYWNjb3VudCIsIm5hdHMiOnsibGltaXRzIjp7InN1YnMiOi0xLCJjb25uIjotMSwibGVhZiI6LTEsImltcG9ydHMiOi0xLCJleHBvcnRzIjotMSwiZGF0YSI6LTEsInBheWxvYWQiOi0xLCJ3aWxkY2FyZHMiOnRydWV9fX0._WW5C1triCh8a4jhyBxEZZP8RJ17pINS8qLzz-01o6zbz1uZfTOJGvwSTS6Yv2_849B9iUXSd-8kp1iMXHdoBA
  5. }

Save the config at server.conf and start the server:

  1. nats-server -c server.conf

You can then test it.

Testing the Configuration

To test the configuration, simply use one of the standard tools:

  1. nats pub --creds ~/.nkeys/creds/memory/A/TA.creds hello world