Load tests a NATS server: connecting and reading the INFO greeting, and the monitoring endpoints healthz, varz and connz. It shows how quickly the server accepts connections and answers monitoring scrapes.
It holds 15 ready-made jobs: 4 single scenarios and an enterprise test plan of 11 stages to run in order, 8 of them with pass/fail targets (SLOs). Each job is a plain request pattern you can change before running.
Scenarios include connect and read INFO, monitoring: healthz, monitoring: varz and monitoring: connz.
How to load test NATS
Open the template in BLASTA.
Set host and monitor to point at your own NATS system, ideally a staging copy.
Pick a job and choose the rate and duration.
Start the run and watch requests per second, latency percentiles and errors live; the result is saved to your history.
Enterprise plan, step 1 of 10. One request a second for 30 seconds. Run this first, every time: it proves the address, credentials and headers are right and that the environment is up before any real load is applied. Gate: zero errors. Reference request: connect and read INFO.
Step 2 of 10. About a fifth of normal traffic for 5 minutes: the uncontended latency of this request. Every later result is judged against it, so record p50 and p95. Gate: at most 0.5% errors and the default latency targets. Reference request: connect and read INFO.
Step 3 of 10. Normal busy-hour traffic for 10 minutes. The rate is the reference job's rate: raise it to your measured production peak-hour rate. This is the run that proves (or breaks) your SLO. Gate: at most 1% errors, p95 and p99 inside the targets. Reference request: connect and read INFO.
Step 4 of 10. Twice the average for 10 minutes: the busiest hour of the year plus headroom. Latency may rise, but must stay in SLO; if it does not, you have no headroom. Gate: at most 2% errors, latency targets doubled. Reference request: connect and read INFO.
Step 5 of 10. Ramps to four times average over 10 minutes, then holds for 2. Finds where it degrades and HOW: gracefully (latency rises, errors stay low) or badly (errors, timeouts, crashes, restarts). Observation only, no gate. Reference request: connect and read INFO.
Step 6 of 10. Reaches ten times average within 10 seconds and holds for 2 minutes: a campaign email, a news link, a failover. Checks autoscaling, queue limits and load shedding. Gate: at most 5% errors, because shedding load is acceptable and crashing is not. Reference request: connect and read INFO.
Step 7 of 10. Run IMMEDIATELY after the spike, at average load for 5 minutes. Latency and errors must return to the baseline from step 2. If they do not, something is stuck: queues, connection pools, GC, an autoscaler cool-down. Gate: same as average load. Reference request: connect and read INFO.
Step 8 of 10. One hour of steady load. Finds leaks and slow decay in memory, connections, file descriptors, disk, log volume and cache churn. Watch the resource graphs: any line that climbs and never flattens is a finding. Gate: at most 0.5% errors. Reference request: connect and read INFO.
Step 9 of 10. Ramps to twenty times average over 20 minutes. Stop it when errors pass about 5%: the rate at that moment is your ceiling, and ceiling divided by peak is your capacity margin. Use a production-like environment, never production. Reference request: connect and read INFO.
Step 10 of 10. Average load for 15 minutes. About 5 minutes in, cause the event you are testing: kill a pod or node, fail over the database, roll out a new version, drain a zone. Errors in the window are your real availability loss. Gate: at most 1% errors overall; read the time series for how long the dip lasted. Reference request: connect and read INFO.
Ramps new connections per second to ten times normal: a fleet reconnecting after an outage, a deploy that restarts every pod, a network blip. Shows accept-queue, file descriptor and handshake limits. Reference request: connect and read INFO.
Frequently asked questions
What does the NATS load test cover?
The NATS template has 15 jobs: 4 single scenarios and an enterprise test plan of 11 stages (smoke, baseline, load, stress, spike, soak, breakpoint and failover window). Scenarios include connect and read INFO, monitoring: healthz, monitoring: varz and monitoring: connz. 8 of them have pass/fail targets (SLOs), so a run can be judged against limits you set.
How do I load test NATS with BLASTA?
Open the template in BLASTA and set host and monitor, then pick a job and start it. Results stream live: requests per second, latency percentiles and errors, and the run is kept in your history. To run from the command line, use blasta preset new nats with your address.
Is it safe to run the NATS load test against production?
All 15 jobs in this template are read-only: they request pages or data and do not change anything. Even so, a load test can slow a live system down, so start with a low rate and prefer a staging copy. Only test systems you own or have permission to test.
Set up a target above and press Start test. Charts and numbers appear here as the test runs.
Load generator resources
CPU used by BLASTA % of capacity
RAM used by BLASTA
Requests per second
Latency p95 lower is better
Response time
Status codes
Errors
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