Nats Jet Strem, Hello World

Download and install from the release form this web site.

bash

go get github.com/nats-io/nats-server/v2

for install Nats-cli follow below link:

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https://github.com/nats-io/natscli

Run Nats server

bash

nats server run

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[54726] [INF] Starting nats-server[54726] [INF]   Version:  2.9.6[54726] [INF]   Git:      [not
set][54726] [INF]   Name:     nats_development[54726] [INF]   ID:
NCT7AV2WQ5UUD3EXWS3WJ6RBFP5GRQQ7D6UWK345VGXDQ24PQI3PPN4O[54726] [INF] Using configuration file:
/tmp/nats-server-run-1900677043.cfg[54726] [INF] Listening for client connections on
0.0.0.0:36275[54726] [INF] Server is ready

Select the Context

bash

nats context select nats_development

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NATS Configuration Context "nats_development"      Description: Local user access for NATS
Development instance      Server URLs: nats://0.0.0.0:36275         Username: local
Password: *********             Path: /home/usr/.config/nats/context/nats_development.json

Mechanism Request Reply

Reply data from the topic

bash

nats reply hello.jermy "hi"

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11:16:55 Listening on "hello.jermy" in group "NATS-RPLY-22"11:22:33 [#0] Received on subject
"hello.jermy":11:22:36 [#1] Received on subject "hello.jermy":11:22:41 [#2] Received on subject
"hello.jermy":11:22:44 [#3] Received on subject "hello.jermy":

Request Data into the topic

bash

nats req hello.jermy ""

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11:22:44 Sending request on "hello.jermy"11:22:44 Received with rtt 403.218µshi

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nats req hello.jermy "{ "hi" : "bye" }"11:26:33 Sending request on "hello.jermy"11:26:33 Received
with rtt 399.847µshi

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Recive :11:26:33 [#6] Received on subject "hello.jermy":{ hi : bye }

Mechanism Pub Sub

sub receive data from the topic

bash

nats sub hello.world[#2] Received on "hello.world"hi?

Publish data to the topic

bash

nats pub hello.world "hi?"11:46:50 Published 3 bytes to "hello.world"

Mechanism many Pub and 1 Sub

sub receive data from the topic

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nats sub hello.world[#483] Received on "hello.world"hi, guys[#484] Received on "hello.world"group 2

Publish data to the topic

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nats pub hello.world "hi, guys" --count=-1 --sleep=1s

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nats pub hello.world "group 2" --count=-1 --sleep=1s

Mechanism 1 Pub and many Sub

Fan out Design pattern

2 subs receive data from the topic

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nats sub hello.world04:32:15 Subscribing on hello.world [#1] Received on "hello.world"message

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nats sub hello.world04:33:03 Subscribing on hello.world [#1] Received on "hello.world"message

Publish data to the topic

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nats pub hello.world "message"04:33:20 Published 7 bytes to "hello.world"

Mechanism 1 Pub and many Sub with queue

In this Mechanim only one of the sub will get the data

2 subs receive data from the topic

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nats sub hello.world --queue greeter04:34:26 Subscribing on hello.world [#1] Received on
"hello.world"message

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nats sub hello.world --queue greeter04:34:42 Subscribing on hello.world

Publish data to the topic

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nats pub hello.world "message"04:34:56 Published 7 bytes to "hello.world"

If sending 1000 messages in this method, we will get as unique distributed in all of each pub services.

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nats pub hello.world "message" --count 10001000 / 1000
[========================================================================================================================================]    0s

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[#501] Received on "hello.world"message

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[#499] Received on "hello.world"message[#500] Received on "hello.world"message

Nats JetsStream

bash

nats server run --jetstream

Context selected

bash

nats context select nats_developmentNATS Configuration Context "nats_development"      Description:
Local user access for NATS Development instance      Server URLs: nats://0.0.0.0:36275
Username: local         Password: *********             Path:
/home/user/.config/nats/context/nats_development.json

List of Nats Jetstream exist

bash

nats stream lsNo Streams defined

Watch Nats Stream lists

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watch nats stream ls

Make Nats Stream

bash

nats stream add

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? Stream Name orders? Subjects orders.*? Storage file? Replication 1? Retention Policy Limits?
Discard Policy Old? Stream Messages Limit -1? Per Subject Messages Limit -1? Total Stream Size -1?
Message TTL -1? Max Message Size -1? Duplicate tracking time window 2m0s? Allow message Roll-ups No?
Allow message deletion Yes? Allow purging subjects or the entire stream YesStream orders was created

send Message into orders

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nats pub orders.us "{{.Count}}" --count 1000010000 / 10000
[========================================================================================================================================]    1s

Read from stream

bash

nats sub --stream orders

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[#19999] Received JetStream message: stream: orders seq 19999 / subject: orders.eu / time:
2022-12-28T05:03:48+03:309999[#20000] Received JetStream message: stream: orders seq 20000 /
subject: orders.eu / time: 2022-12-28T05:03:48+03:3010000[#20001] Received JetStream message:
stream: orders seq 20001 / subject: orders.us / time: 2022-12-28T05:05:36+03:301[#21999] Received
JetStream message: stream: orders seq 21999 / subject: orders.eu / time:
2022-12-28T05:05:40+03:30999[#22000] Received JetStream message: stream: orders seq 22000 / subject:
orders.eu / time: 2022-12-28T05:05:40+03:301000

Reading all messages from the topics again

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nats sub --stream orders --all

Reading new messages from the topic

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nats sub --stream orders --new05:08:21 Subscribing to JetStream Stream holding messages with subject
orders.* delivering any new messages received

Reading only last message

bash

nats sub --stream orders --last

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05:09:19 Subscribing to JetStream Stream holding messages with subject orders.* starting with the
last message received [#1] Received JetStream message: stream: orders seq 22000 / subject: orders.eu
/ time: 2022-12-28T05:05:40+03:301000

Get last message from specific subject

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nats sub --stream orders --last-per-subject orders.us05:10:44 Subscribing to JetStream Stream
holding messages with subject orders.us for the last messages for each subject in the Stream [#1]
Received JetStream message: stream: orders seq 21000 / subject: orders.us / time:
2022-12-28T05:05:37+03:301000

Get messages from specific sequence

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nats sub --stream orders --start-sequence=21900

Reading messages and clean up the queue

bash

nats sub  "orders.*" --durable my_consumer

Create Consumer

bash

nats consumer create? Consumer name pull_consumer? Delivery target (empty for Pull Consumers) ?
Start policy (all, new, last, subject, 1h, msg sequence) all? Acknowledgement policy explicit?
Replay policy instant? Filter Stream by subject (blank for all) ? Maximum Allowed Deliveries -1?
Maximum Acknowledgements Pending 0? Deliver headers only without bodies No? Add a Retry Backoff
Policy No? Select a Stream ordersInformation for Consumer orders > pull_consumer created
2022-12-28T05:22:57+03:30

Pull messages

bash

nats consumer next orders pull_consumer --count=10[05:24:09] subj: orders.us / tries: 1 / cons seq:
1 / str seq: 1 / pending: 21,9991Acknowledged message[05:24:09] subj: orders.us / tries: 1 / cons
seq: 2 / str seq: 2 / pending: 21,9982Acknowledged message[05:24:09] subj: orders.us / tries: 1 /
cons seq: 3 / str seq: 3 / pending: 21,9973Acknowledged message[05:24:09] subj: orders.us / tries: 1
/ cons seq: 4 / str seq: 4 / pending: 21,9964Acknowledged message[05:24:09] subj: orders.us / tries:
1 / cons seq: 5 / str seq: 5 / pending: 21,9955Acknowledged message[05:24:09] subj: orders.us /
tries: 1 / cons seq: 6 / str seq: 6 / pending: 21,9946Acknowledged message[05:24:09] subj: orders.us
/ tries: 1 / cons seq: 7 / str seq: 7 / pending: 21,9937Acknowledged message[05:24:09] subj:
orders.us / tries: 1 / cons seq: 8 / str seq: 8 / pending: 21,9928Acknowledged message[05:24:09]
subj: orders.us / tries: 1 / cons seq: 9 / str seq: 9 / pending: 21,9919Acknowledged
message[05:24:09] subj: orders.us / tries: 1 / cons seq: 10 / str seq: 10 / pending:
21,99010Acknowledged message

Check consumer

bash

nats consumer info? Select a Stream orders? Select a Consumer pull_consumerInformation for Consumer
orders > pull_consumer created 2022-12-28T05:22:57+03:30Configuration:        Durable Name:
pull_consumer           Pull Mode: true      Deliver Policy: All          Ack Policy: Explicit
Ack Wait: 30s       Replay Policy: Instant     Max Ack Pending: 1,000   Max Waiting Pulls: 512State:
Last Delivered Message: Consumer sequence: 10 Stream sequence: 10 Last delivery: 1m8s ago
Acknowledgment floor: Consumer sequence: 10 Stream sequence: 10 Last Ack: 1m8s ago
Outstanding Acks: 0 out of maximum 1,000     Redelivered Messages: 0     Unprocessed Messages:
21,990            Waiting Pulls: 0 of maximum 512

Nats Key value store

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nats kverror: a subcommand from the list below is required, use --help for full help including flags
and argumentsusage: nats kv <command> [<args> ...]Interacts with a JetStream based Key-Value
storeThe JetStream Key-Value store uses streams to store key-value pairs for an indefinite period or
a per-bucket configured TTL.Subcommands:  kv add      Adds a new KV Store Bucket  kv put      Puts a
value into a key  kv get      Gets a value for a key  kv create   Puts a value into a key only if
the key is new or
it's last operation was a delete  kv update   Updates a key with a new value if the previous value matches the given revision  kv del      Deletes a key or the entire bucket  kv purge    Deletes a key from the bucket, clearing history before creating a delete marker  kv history  Shows the full history for a key  kv revert   Reverts a value to a previous revision using put  kv info     View the status of a KV store  kv watch    Watch the bucket or a specific key for updated  kv ls       List available buckets or the keys in a bucket  kv compact  Removes all historic values from the store where the last value is a delete

Create key value buket

bash

nats kv add oneInformation for Key-Value Store Bucket one created
2022-12-28T05:30:54+03:30Configuration:          Bucket Name: one         History Kept: 1
Values Stored: 0   Backing Store Kind: JetStream          Bucket Size: 0 B  Maximum Bucket Size:
unlimited   Maximum Value Size: unlimited     JetStream Stream: KV_one              Storage: File

Set key and value

bash

nats kv put one hello world

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nats kv watch one[2022-12-28 05:33:17] PUT one > hello: world

mix stream with key value store

Delete the stream and see the list of data in stream

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watch nats stream lsnats stream purge NAMEOFSTREAMnats sub --stream CALLBACKS

Limits-based Stream in JetStream

Delivery reliability

Nats Jet Strem, Hello World