The first step is to set up storage for our ORDERS related messages, these arrive on a wildcard of subjects all flowing into the same Stream and they are kept for 1 year.
Creating
nats str add ORDERS
? Subjects to consume ORDERS.*
? Storage backend file
? Retention Policy Limits
? Discard Policy Old
? Message count limit -1
? Message size limit -1
? Maximum message age limit 1y
? Maximum individual message size [? for help] (-1) -1
Stream ORDERS was created
Information for Stream ORDERS
Configuration:
Subjects: ORDERS.*
Acknowledgements: true
Retention: File - Limits
Replicas: 1
Maximum Messages: -1
Maximum Bytes: -1
Maximum Age: 8760h0m0s
Maximum Message Size: -1
Maximum Consumers: -1
Statistics:
Messages: 0
Bytes: 0 B
FirstSeq: 0
LastSeq: 0
Active Consumers: 0
You can get prompted interactively for missing information as above, or do it all on one command. Pressing ? in the CLI will help you map prompts to CLI options:
Additionally one can store the configuration in a JSON file, the format of this is the same as $ nats str info ORDERS -j | jq .config:
nats str add ORDERS --config orders.json
Listing
We can confirm our Stream was created:
nats str ls
Streams:
ORDERS
Querying
Information about the configuration of the Stream can be seen, and if you did not specify the Stream like below, it will prompt you based on all known ones:
nats str info ORDERS
Information for Stream ORDERS created 2021-02-27T16:49:36-07:00
Configuration:
Subjects: ORDERS.*
Acknowledgements: true
Retention: File - Limits
Replicas: 1
Discard Policy: Old
Duplicate Window: 2m0s
Maximum Messages: unlimited
Maximum Bytes: unlimited
Maximum Age: 1y0d0h0m0s
Maximum Message Size: unlimited
Maximum Consumers: unlimited
State:
Messages: 0
Bytes: 0 B
FirstSeq: 0
LastSeq: 0
Active Consumers: 0
Most commands that show data as above support -j to show the results as JSON:
This is the general pattern for the entire nats utility as it relates to JetStream - prompting for needed information but every action can be run non-interactively making it usable as a CLI API. All information output like seen above can be turned into JSON using -j.
Copying
A stream can be copied into another, which also allows the configuration of the new one to be adjusted via CLI flags:
Stream ORDERS was created
Information for Stream ORDERS created 2021-02-27T16:52:46-07:00
Configuration:
Subjects: ORDERS_ARCHIVE.*
Acknowledgements: true
Retention: File - Limits
Replicas: 1
Discard Policy: Old
Duplicate Window: 2m0s
Maximum Messages: unlimited
Maximum Bytes: unlimited
Maximum Age: 2y0d0h0m0s
Maximum Message Size: unlimited
Maximum Consumers: unlimited
State:
Messages: 0
Bytes: 0 B
FirstSeq: 0
LastSeq: 0
Active Consumers: 0
Editing
A stream configuration can be edited, which allows the configuration to be adjusted via CLI flags. Here I have an incorrectly created ORDERS stream that I fix:
nats str info ORDERS -j | jq .config.subjects
[
"ORDERS.new"
]
Change the subjects for the stream
nats str edit ORDERS --subjects "ORDERS.*"
Stream ORDERS was updated
Information for Stream ORDERS
Configuration:
Subjects: ORDERS.*
....
Additionally, one can store the configuration in a JSON file, the format of this is the same as $ nats str info ORDERS -j | jq .config:
nats str edit ORDERS --config orders.json
Publishing Into a Stream
Now let's add some messages to our Stream. You can use nats pub to add messages, pass the --wait flag to see the publish ack being returned.
You can publish without waiting for acknowledgement:
nats pub ORDERS.scratch hello
But if you want to be sure your messages got to JetStream and were persisted you can make a request:
nats req ORDERS.scratch hello
13:45:03 Sending request on [ORDERS.scratch]
13:45:03 Received on [_INBOX.M8drJkd8O5otORAo0sMNkg.scHnSafY]: '+OK'
Keep checking the status of the Stream while doing this and you'll see its stored messages increase.
nats str info ORDERS
Information for Stream ORDERS
...
Statistics:
Messages: 3
Bytes: 147 B
FirstSeq: 1
LastSeq: 3
Active Consumers: 0
After putting some throwaway data into the Stream, we can purge all the data out - while keeping the Stream active:
Deleting All Data
To delete all data in a stream use purge:
nats str purge ORDERS -f
...
State:
Messages: 0
Bytes: 0 B
FirstSeq: 1,000,001
LastSeq: 1,000,000
Active Consumers: 0
Deleting A Message
A single message can be securely removed from the stream:
nats str rmm ORDERS 1 -f
Deleting Sets
Finally, for demonstration purposes, you can also delete the whole Stream and recreate it. Then we're ready for creating the Consumers:
