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176 lines
3.7 KiB
Markdown
176 lines
3.7 KiB
Markdown
# NATS
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Messaging system.
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1. [TL;DR](#tldr)
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1. [Troubleshooting](#troubleshooting)
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1. [Context deadline exceeded](#context-deadline-exceeded)
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1. [No responders available for request](#no-responders-available-for-request)
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1. [Further readings](#further-readings)
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1. [Sources](#sources)
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## TL;DR
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<details>
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<summary>Setup</summary>
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<details style="padding: 0 0 0 1em">
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<summary>Server</summary>
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```sh
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# Install.
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brew install 'nats-server'
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choco install 'nats-server'
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docker pull 'nats'
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go install 'github.com/nats-io/nats-server/v2@latest'
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yay 'nats-server'
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# Validate the configuration file.
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nats-server -c '/etc/nats/nats-server.conf' -t
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docker run --rm --name 'pg_flo_nats' -v "$PWD/config/nats-server.conf:/etc/nats/nats-server.conf" 'nats' \
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-c '/etc/nats/nats-server.conf' -t
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```
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</details>
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<details style="padding: 0 0 0 1em">
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<summary>Client</summary>
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```sh
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# Install.
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brew install 'nats-io/nats-tools/nats'
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```
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</details>
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</details>
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<details>
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<summary>Usage</summary>
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<details style="padding: 0 0 0 1em">
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<summary>Server</summary>
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```sh
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# Get help.
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docker run --rm --name 'pg_flo_nats' 'nats' --help
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# Run.
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nats-server -V
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nats-server -config 'nats-server.conf'
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docker run --name 'nats' -p '4222:4222' -ti 'nats:latest' -js
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# Run as cluster.
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docker run --name 'nats-0' --network 'nats' -p '4222:4222' -p '8222:8222' \
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'nats' --http_port '8222' --cluster_name 'NATS' --cluster 'nats://0.0.0.0:6222' \
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&& docker run --name 'nats-1' --network 'nats' \
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'nats' --cluster_name 'NATS' --cluster 'nats://0.0.0.0:6222' --routes='nats://ruser:T0pS3cr3t@nats:6222' \
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&& curl -fs 'http://localhost:8222/routez'
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# Reload the configuration.
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nats-server --signal 'reload'
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```
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</details>
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<details style="padding: 0 0 0 1em">
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<summary>Client</summary>
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```sh
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# Get help.
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nats cheat server
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# Check connection to the server.
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nats server check connection --server 'nats://0.0.0.0:4222'
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nats server check connection -s 'nats://localhost:4222'
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# Request a configuration reload.
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nats --user 'sys' --password 'sys' request '$SYS.REQ.SERVER.<server-id>.RELOAD' ""
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# Start subscribers.
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nats subscribe '>' -s '0.0.0.0:4222'
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nats subscribe -s 'nats://demo.nats.io' '>'
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# Publish messages.
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nats pub 'hello' 'world' -s '0.0.0.0:4222'
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# Start listeners for Request-Reply patterns.
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nats reply 'subject' 'message'
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# Send requests for Request-Reply patterns.
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nats request 'help.please' 'I need help!'
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# List configuration contexts
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nats context ls
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nats context ls --all
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# List available JetStream streams.
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nats stream ls
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nats stream ls --all
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# List available JetStream consumer.
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nats consumer ls
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nats consumer ls --all
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```
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</details>
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</details>
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<details>
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<summary>Real world use cases</summary>
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```sh
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# Try out the Request-Reply pattern.
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# The listener will hang waiting, run the second in another shell session.
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nats reply 'help.please' 'OK, I CAN HELP!!!'
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nats request 'help.please' 'I need help!'
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```
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</details>
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## Troubleshooting
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### Context deadline exceeded
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Error message example:
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```plaintext
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FTL Failed to create NATS client error="failed to create main stream: context deadline exceeded"
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```
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Root cause: the client cannot reach the server.
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### No responders available for request
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Error message example:
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```plaintext
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FTL Failed to create NATS client error="failed to create main stream: nats: no responders available for request"
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```
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Root cause: a request is sent to a subject that has no subscribers.
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## Further readings
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- [Website]
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- [Codebase]
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- [Documentation]
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### Sources
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<!--
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Reference
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═╬═Time══
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-->
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<!-- In-article sections -->
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<!-- Knowledge base -->
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<!-- Files -->
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<!-- Upstream -->
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[codebase]: https://github.com/nats-io
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[documentation]: https://docs.nats.io
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[website]: https://nats.io/
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<!-- Others -->
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