nats bench

NATS is fast and lightweight and places a priority on performance. the nats CLI tool can, amongst many other things, be used for running benchmarks and measuring performance of your target NATS service infrastructure. In this tutorial you learn how to benchmark and tune NATS on your systems and environment.

Prerequisites

Start the NATS server with monitoring enabled

  1. nats-server -m 8222 -js

Verify that the NATS server starts successfully, as well as the HTTP monitor:

  1. [89075] 2021/10/05 23:26:35.342816 [INF] Starting nats-server
  2. [89075] 2021/10/05 23:26:35.342971 [INF]   Version:  2.6.1
  3. [89075] 2021/10/05 23:26:35.342974 [INF]   Git:      [not set]
  4. [89075] 2021/10/05 23:26:35.342976 [INF]   Name:     NDUYLGUUNSD53IUR77SQE2XK4PRCDJNPTICAGMGTAYAFN22KNL2GLJ23
  5. [89075] 2021/10/05 23:26:35.342979 [INF]   Node:     ESalpH2B
  6. [89075] 2021/10/05 23:26:35.342981 [INF]   ID:       NDUYLGUUNSD53IUR77SQE2XK4PRCDJNPTICAGMGTAYAFN22KNL2GLJ23
  7. [89075] 2021/10/05 23:26:35.343583 [INF] Starting JetStream
  8. [89075] 2021/10/05 23:26:35.343946 [INF]     _ ___ _____ ___ _____ ___ ___   _   __  __
  9. [89075] 2021/10/05 23:26:35.343955 [INF]  _ | | __|_   _/ __|_   _| _ \ __| /_\ |  \/  |
  10. [89075] 2021/10/05 23:26:35.343957 [INF] | || | _|  | | __ \ | | |   / _| / _ \| |\/| |
  11. [89075] 2021/10/05 23:26:35.343959 [INF]  __/|___| |_| |___/ |_| |_|____/_/ __|  |_|
  12. [89075] 2021/10/05 23:26:35.343960 [INF]
  13. [89075] 2021/10/05 23:26:35.343962 [INF]          https://docs.nats.io/jetstream
  14. [89075] 2021/10/05 23:26:35.343964 [INF]
  15. [89075] 2021/10/05 23:26:35.343967 [INF] ---------------- JETSTREAM ----------------
  16. [89075] 2021/10/05 23:26:35.343970 [INF]   Max Memory:      48.00 GB
  17. [89075] 2021/10/05 23:26:35.343973 [INF]   Max Storage:     581.03 GB
  18. [89075] 2021/10/05 23:26:35.343974 [INF]   Store Directory: "/var/folders/1b/wb_d92cd6cl_fshyy5qy2tlc0000gn/T/nats/jetstream"
  19. [89075] 2021/10/05 23:26:35.343979 [INF] -------------------------------------------

Run a publisher throughput test

Let’s run a test to see how fast a single publisher can publish one million 16 byte messages to the NATS server.

  1. nats bench foo --pub 1 --size 16

The output tells you the number of messages and the number of payload bytes that the client was able to publish per second:

  1. 23:33:51 Starting pub/sub benchmark [msgs=100,000, msgsize=16 B, pubs=1, subs=0, js=false]
  2. 23:33:51 Starting publisher, publishing 100,000 messages
  3. Finished      0s [======================================================================================================================================================] 100%
  5. Pub stats: 5,173,828 msgs/sec ~ 78.95 MB/sec

Now increase the number of messages published:

  1. nats bench foo --pub 1 --size 16 --msgs 10000000
  1. 23:34:29 Starting pub/sub benchmark [msgs=10,000,000, msgsize=16 B, pubs=1, subs=0, js=false]
  2. 23:34:29 Starting publisher, publishing 10,000,000 messages
  3. Finished      2s [======================================================================================================================================================] 100%
  5. Pub stats: 4,919,947 msgs/sec ~ 75.07 MB/sec

Run a publish/subscribe throughput test

When using both publishers and subscribers, nats bench reports aggregate, as well as individual publish and subscribe throughput performance.

Let’s look at throughput for a single publisher with a single subscriber:

  1. nats bench foo --pub 1 --sub 1 --size 16

Note that the output shows the aggregate throughput as well as the individual publisher and subscriber performance:

  1. 23:36:00 Starting pub/sub benchmark [msgs=100,000, msgsize=16 B, pubs=1, subs=1, js=false]
  2. 23:36:00 Starting subscriber, expecting 100,000 messages
  3. 23:36:00 Starting publisher, publishing 100,000 messages
  4. Finished      0s [======================================================================================================================================================] 100%
  5. Finished      0s [======================================================================================================================================================] 100%
  7. NATS Pub/Sub stats: 5,894,441 msgs/sec ~ 89.94 MB/sec
  8.  Pub stats: 3,517,660 msgs/sec ~ 53.68 MB/sec
  9.  Sub stats: 2,957,796 msgs/sec ~ 45.13 MB/sec

Run a 1:N throughput test

When specifying multiple publishers, or multiple subscribers, nats bench will also report statistics for each publisher and subscriber individually, along with min/max/avg and standard deviation.

Let’s increase both the number of messages, and the number of subscribers.:

  1. nats bench foo --pub 1 --sub 5 --size 16 --msgs 1000000
  1. 23:38:08 Starting pub/sub benchmark [msgs=1,000,000, msgsize=16 B, pubs=1, subs=5, js=false]
  2. 23:38:08 Starting subscriber, expecting 1,000,000 messages
  3. 23:38:08 Starting subscriber, expecting 1,000,000 messages
  4. 23:38:08 Starting subscriber, expecting 1,000,000 messages
  5. 23:38:08 Starting subscriber, expecting 1,000,000 messages
  6. 23:38:08 Starting subscriber, expecting 1,000,000 messages
  7. 23:38:08 Starting publisher, publishing 1,000,000 messages
  8. Finished      0s [======================================================================================================================================================] 100%
  9. Finished      0s [======================================================================================================================================================] 100%
  10. Finished      0s [======================================================================================================================================================] 100%
  11. Finished      0s [======================================================================================================================================================] 100%
  12. Finished      0s [======================================================================================================================================================] 100%
  13. Finished      0s [======================================================================================================================================================] 100%
  15. NATS Pub/Sub stats: 7,123,965 msgs/sec ~ 108.70 MB/sec
  16.  Pub stats: 1,188,419 msgs/sec ~ 18.13 MB/sec
  17.  Sub stats: 5,937,525 msgs/sec ~ 90.60 MB/sec
  18.   [1] 1,187,633 msgs/sec ~ 18.12 MB/sec (1000000 msgs)
  19.   [2] 1,187,597 msgs/sec ~ 18.12 MB/sec (1000000 msgs)
  20.   [3] 1,187,526 msgs/sec ~ 18.12 MB/sec (1000000 msgs)
  21.   [4] 1,187,528 msgs/sec ~ 18.12 MB/sec (1000000 msgs)
  22.   [5] 1,187,505 msgs/sec ~ 18.12 MB/sec (1000000 msgs)
  23.   min 1,187,505 | avg 1,187,557 | max 1,187,633 | stddev 48 msgs

Run a N:M throughput test

When more than 1 publisher is specified, nats bench evenly distributes the total number of messages (-msgs) across the number of publishers (-pub).

Now let’s increase the number of publishers and examine the output:

  1. nats bench foo --pub 5 --sub 5 --size 16 --msgs 1000000
  1. 23:39:28 Starting pub/sub benchmark [msgs=1,000,000, msgsize=16 B, pubs=5, subs=5, js=false]
  2. 23:39:28 Starting subscriber, expecting 1,000,000 messages
  3. 23:39:28 Starting subscriber, expecting 1,000,000 messages
  4. 23:39:28 Starting subscriber, expecting 1,000,000 messages
  5. 23:39:28 Starting subscriber, expecting 1,000,000 messages
  6. 23:39:28 Starting subscriber, expecting 1,000,000 messages
  7. 23:39:28 Starting publisher, publishing 200,000 messages
  8. 23:39:28 Starting publisher, publishing 200,000 messages
  9. 23:39:28 Starting publisher, publishing 200,000 messages
  10. 23:39:28 Starting publisher, publishing 200,000 messages
  11. 23:39:28 Starting publisher, publishing 200,000 messages
  12. Finished      0s [======================================================================================================================================================] 100%
  13. Finished      0s [======================================================================================================================================================] 100%
  14. Finished      0s [======================================================================================================================================================] 100%
  15. Finished      0s [======================================================================================================================================================] 100%
  16. Finished      0s [======================================================================================================================================================] 100%
  17. Finished      0s [======================================================================================================================================================] 100%
  18. Finished      0s [======================================================================================================================================================] 100%
  19. Finished      0s [======================================================================================================================================================] 100%
  20. Finished      0s [======================================================================================================================================================] 100%
  21. Finished      0s [======================================================================================================================================================] 100%
  23. NATS Pub/Sub stats: 7,019,849 msgs/sec ~ 107.11 MB/sec
  24.  Pub stats: 1,172,667 msgs/sec ~ 17.89 MB/sec
  25.   [1] 236,240 msgs/sec ~ 3.60 MB/sec (200000 msgs)
  26.   [2] 236,168 msgs/sec ~ 3.60 MB/sec (200000 msgs)
  27.   [3] 235,541 msgs/sec ~ 3.59 MB/sec (200000 msgs)
  28.   [4] 234,911 msgs/sec ~ 3.58 MB/sec (200000 msgs)
  29.   [5] 235,545 msgs/sec ~ 3.59 MB/sec (200000 msgs)
  30.   min 234,911 | avg 235,681 | max 236,240 | stddev 485 msgs
  31.  Sub stats: 5,851,064 msgs/sec ~ 89.28 MB/sec
  32.   [1] 1,171,181 msgs/sec ~ 17.87 MB/sec (1000000 msgs)
  33.   [2] 1,171,169 msgs/sec ~ 17.87 MB/sec (1000000 msgs)
  34.   [3] 1,170,867 msgs/sec ~ 17.87 MB/sec (1000000 msgs)
  35.   [4] 1,170,641 msgs/sec ~ 17.86 MB/sec (1000000 msgs)
  36.   [5] 1,170,250 msgs/sec ~ 17.86 MB/sec (1000000 msgs)
  37.   min 1,170,250 | avg 1,170,821 | max 1,171,181 | stddev 349 msgs

Run a request-reply latency test

In one shell start a nats bench in ‘reply mode’ and let it run

  1. nats bench foo --sub 1 --reply

And in another shell send some requests

  1. nats bench foo --pub 1 --request --msgs 10000
  1. 23:47:35 Benchmark in request-reply mode
  2. 23:47:35 Starting request-reply benchmark [msgs=10,000, msgsize=128 B, pubs=1, subs=0, js=false, request=true, reply=false]
  3. 23:47:35 Starting publisher, publishing 10,000 messages
  4. Finished      1s [==============================================================================================================================================================================================================================================================================================================================================================================================================================================================] 100%
  6. Pub stats: 8,601 msgs/sec ~ 1.05 MB/sec

In this case the average latency of request-reply between the two nats bench processes over NATS was 1/8,601th of a second (116.2655505 microseconds).

You can now hit control-c to kill that nats bench --reply process

Note: by default nats bench subscribers in ‘reply mode’ join a queue group, so you can use nats bench for example to simulate a bunch of load balanced server processes.

Run JetStream benchmarks

Measure JetStream publication performance

First let’s publish some messages into a stream, nats bench will automatically create a stream called benchstream using default attributes.

  1. nats bench bar --js --pub 1 --size 16 --msgs 1000000
  1. 00:00:10 Starting JetStream benchmark [msgs=1,000,000, msgsize=16 B, pubs=1, subs=0, js=true, stream=benchstream  storage=memory, syncpub=false, pubbatch=100, jstimeout=30s, pull=false, pullbatch=100, maxackpending=-1, replicas=1, purge=false]
  2. 00:00:10 Starting publisher, publishing 1,000,000 messages
  3. Finished      3s [======================================================================================================================================================] 100%
  5. Pub stats: 272,497 msgs/sec ~ 4.16 MB/sec

Measure JetStream consumption (replay) performance

We can now measure the speed of replay of messages stored in the stream to a consumer

  1. nats bench bar --js --sub 1 --msgs 1000000
  1. 00:05:04 JetStream ordered push consumer mode: subscribers will not acknowledge the consumption of messages
  2. 00:05:04 Starting JetStream benchmark [msgs=1,000,000, msgsize=128 B, pubs=0, subs=1, js=true, stream=benchstream  storage=memory, syncpub=false, pubbatch=100, jstimeout=30s, pull=false, pullbatch=100, maxackpending=-1, replicas=1, purge=false]
  3. 00:05:04 Starting subscriber, expecting 1,000,000 messages
  4. Finished      1s [======================================================================================================================================================] 100%
  6. Sub stats: 777,480 msgs/sec ~ 94.91 MB/sec

Push and pull consumers

By default nats bench --js subscribers use ‘ordered push’ consumers, which are ordered, reliable and flow controlled but not ‘acknowledged’ meaning that the subscribers do not send an acknowledgement back to the server upon receiving each message from the stream. Ordered push consumers are the preferred way for a single application instance to get it’s own copy of all (or some) of the data stored in a stream. However, you can also benchmark ‘pull consumers’, which are instead the preferred way to horizontally scale the processing (or consumption) of the messages in the stream where the subscribers do acknowledge the processing of every single message, but can leverage batching to increase the processing throughput.

Play around with the knobs

Don’t be afraid to test different JetStream storage and replication options (assuming you have access to a JetStream enabled cluster of servers if you want to go beyond --replicas 1), and of course the number of publishing/subscribing threads and the publish or pull subscribe batch sizes.

Note: If you change the attributes of a stream between runs you will have to delete the stream (e.g. run nats stream rm benchstream)

Leave no trace: clean up the resources when you are finished

Once you have finished benchmarking streams, remember that if you have stored many messages in the stream (which is very easy and fast to do) your stream may end up using a certain amount of resources on the nats-server(s) infrastructure (i.e. memory and files) that you may want to reclaim.

You can instruct use the --purge bench command flag to tell nats to purge the stream of messages before starting its benchmark, or purge the stream manually using nats stream purge benchstream or just delete it altogether using nats stream rm benchstream.