NB5 Docs► User Guide▼ Core Activity Params 🖺

Activity parameters are passed as named arguments for an activity, either on the command line or from a scenario script. On the command line, these take the form of

... <param>=<value> ...

Some activity parameters are universal in that they can be used with any driver type. These parameters are called core activity params. Only core activity parameters are documented here. When starting out, you want to familiarize yourself with these parameters.

👉 To see what activity parameters are valid for a given driver, see the documentation for that driver with nb5 help <driver>. Each driver comes with documentation that describes what how to configure it with additional driver params as well as what op template forms it can understand.


The activity params described in this section are those which you will use almost all the time when configuring activities.

👉 If you aren't using one of these options with a run or start command, or otherwise in your named scenarios, double check that you aren't missing something important.


Every activity can have a default driver. If provided, it will be used for any op template which does not have one directly assigned as an op field. For each op template in the workload, if no driver is set, an error is thrown.

As each activity can have multiple op templates, and each op template can have its own driver, the available activity params for a workload are determined by the superset of valid params for all active drivers.

You can find out what drivers are available in nb5 with the --list-drivers option from discovery options. You can then get details on what each of these drivers allow with nb5 help <driver>.

The driver selection for an op template determines the valid constructions for the op template. For example:

# file test.yaml
      driver: stdout
      stmt: "example {{Identity()}}"

If an activity were started up which references this file as workload=test.yaml, then all the activity params recognized by the stdout driver would be valid, in addition to the core activity params documented in this section.



The workload param tells an activity where to load its [workload template] (@/workloads-101/_index.md) from. The workload template is a collection of op templates which are blueprints for the operations that an activity runs.

If the file is a Jsonnet file (by extension), then a local jsonnet interpreter will be run against it before being handled as above. Within this evaluation context, all provided activity parameters are available as external variables and accessible via the standard Jsonnet APIs, specifically std.extVar(str). For doing robust data type conversion, use std.parseJson(str) by default.


This is a serialized version of an operation to be parsed as an op template. It can be in one of a few supported forms: JSON, as indicated by a leading { character, or a simple params map, which is indicated by interior name=value assignments. If you want to provide a simpler form which is representative a string statement, use the stmt form below.


This is a short form version of an op template which contains a single op field for stmt, which is the default form for any statement-oriented operations in common protocols like CQL, SQL, stdout, or similar. If you need to provide more op template details than this form allows, then either use the op form above, or provide a full workload.


Tags are used to filter the set of op templates presented for sequencing in an activity. Each op template has a set of tags, which include two auto-tags that are provided by the runtime:

The rules for tag filtering are explained in depth in the Op Tags of the Workloads 101 tutorial.


You should set the threads parameter when you need to ramp up a workload.

This controls how many threads will be started up for an activity to run its cycles with.

default value : For now, the default is simply 1. Users must be aware of this setting and adjust it to a reasonable value for their workloads.

threads=auto : Set the number of threads to 10x the number of cores in your system. There is no distinction here between full cores and hardware threads. This is generally a reasonable number of threads to tap into the processing power of a client system.

threads=__x : When you set threads=5x or threads=10x, you will Set the number of threads to some multiplier of the logical CPUs in the local system.

A good rule of thumb for setting threads for maximum effect is to set it relatively high, such as 10XvCPU when running synchronous workloads (when not providing the async parameter), and to 5XvCPU for all async workloads. Variation in system dynamics make it difficult to peg an ideal number, so experimentation is encouraged while you dial in your settings initially.



The cycles parameter determines the starting and ending point for an activity. It determines the range of values which will act as seed values for each operation. For each cycle of the activity, a statement is built from a statement template and executed as an operation.

For each cycle in an activity, the cycle is used as the input to the binding functions. This allows you to create numerical relationships between all of the data used in your activity.

If you do not set the cycles parameter, then it will automatically be set to the size of the sequence. The sequence is simply the length of the op sequence that is constructed from the active op templates and ratios in your activity.

You should set the cycles for every activity except for schema-like activities, or activities which you run just as a sanity check of active statements.

In the cycles=<cycle count> version, the count indicates the total number of cycles, and is equivalent to cycles=0..<cycle max>. In both cases, the max value is not the actual number of the last cycle. This is because all cycle parameters define a closed-open interval. In other words, the minimum value is either zero by default or the specified minimum value, but the maximum value is the first value not included in the interval. This means that you can easily stack intervals over subsequent runs while knowing that you will cover all logical cycles without gaps or duplicates. For example, given cycles=1000 and then cycles=1000..2000, and then cycles=2000..5K, you know that all cycles between 0 (inclusive) and 5000 (exclusive) have been specified.



This is another layer of iteration around the cycles values. With this, it is easy to set any activity to repeat arbitrarily, or to have multiple specific iterations of some base workload. Recycles is effectively the higher-order ordinal which wraps repeated use of the same cycles interval. The combination of cycle and recycle is mathematically consistent. If you set recycles=1 cycles=1, then you will have one total cycle executed. If you set recycles=10 cycles=10, then you will have 100. If either of them is effectively set to zero, then no cycles will occur.

They are also both interval-specific, so canonically, recycles=37..39 cycles=7..11 is distinct from recycles=39..41 cycles=7..11, although this is of limited utility until recycles is hoisted further into op execution. In the future, this value may be used, for example, to bracket instancing of metrics around specific recycle values, so that metrics are collected distinctly for each recycle.


This activity param allows you to specify what happens when an exception is thrown during execution of an operation (within a cycle). You can configure any named exception to be handled with any of the available handler verbs in the order your choosing.

👉 By default, any single error in any operation will cause your test to stop. This is not generally what you want to do for significant test scenarios.

You generally want to configure this so that you can run an activity as long as needed without a single error stopping the whole thing. However, it is important for users to know exactly how this is configured, so it is up to the user to set this appropriately.

The detailed configuration of error handlers is covered in error handlers


This sets the number of times an operation will be retried in the event that it fails and the error handler is set to retry it.


The labels provided in this form will be appended to the labels for this activity, used in metrics reporting and annotations.


These params allow you to see more closely how an activity works for the purpose of troubleshooting or test verification.


This option is checked at various stages of activity initialization in order to modify the way an activity runs. Some of the dryrun options stop an activity and dump out a summary of some specific step. Others wrap normal mechanisms in a noop in order to exercise other parts of the machinery at full speed.




You should set the alias parameter when you have multiple activities, when you want to name metrics per-activity, or when you want to control activities via scripting.

Each activity can be given a symbolic name known as an alias. It is good practice to give all your activities an alias, since this determines the named used in logging, metrics, and even scripting control.

default value : The name of any provided YAML filename is used as the basis for the default alias. Otherwise, the activity type name is used. This is a convenience for simple test scenarios only.


This activity param allows you to set the default value for the instrument op field.


This parameter determines the number of significant digits used in all HDR histograms for metrics collected from this activity. The default of 4 allows 4 significant digits, which means up to 10000 distinct histogram buckets per named metric, per histogram interval. This does not mean that there will be 10000 distinct buckets, but it means there could be if there is significant volume and variety in the measurements.

If you are running a scenario that creates many activities, then you can set hdr_digits=1 on some of them to save client resources.



The cyclerate parameter sets a maximum op rate for individual cycles within the activity, across the whole activity, irrespective of how many threads are active.

👉 The cyclerate is a rate limiter, and can thus only throttle an activity to be slower than it would otherwise run. Rate limiting is also an invasive element in a workload, and will always come at a cost. For extremely high throughput testing, consider carefully whether your testing would benefit more from concurrency-based throttling such as adjust the number of threads.

When the cyclerate parameter is provided, two additional metrics are tracked: the wait time and the response time. See Timing Terms Explained for more details.

When you try to set very high cyclerate values on systems with many cores, the performance will degrade. Be sure to use dryrun features to test this if you think it is a limitation. You can always set the rate high enough that the rate limiter can't sustain. This is like telling it to get in the way and then get out of the way even faster. This is just the nature of this type of rate limiter.

There are plans to make the rate limiter adaptive across a wider variety of performance scenarios, which will improve this.


burst ratio

This is only an optional part of the cyclerate as shown in examples above. If you do not specify it when you initialize a cyclerate, then it defaults 1.1. The burst ratio is only valid as part of a rate limit and can not be specified by itself.

The NoSQLBench rate limiter provides a sliding scale between strict rate limiting and average rate limiting. The difference between them is controlled by a burst ratio parameter. When the burst ratio is 1.0 (burst up to 100% relative rate), the rate limiter acts as a strict rate limiter, disallowing faster operations from using time that was previously forfeited by prior slower operations. This is a "use it or lose it" mode that means things like GC events can steal throughput from a running client as a necessary effect of losing time in a strict timing sense.

When the burst ratio is set to higher than 1.0, faster operations may recover lost time from previously slower operations. For example, a burst ratio of 1.3 means that the rate limiter will allow bursting up to 130% of the base rate, but only until the average rate is back to 100% relative speed. This means that any valleys created in the actual op rate of the client can be converted into plateaus of throughput above the strict rate, but only at a speed that fits within (op rate * burst ratio). This allows for workloads to approximate the average target rate over time, with controllable bursting rates. This ability allows for near-strict behavior while allowing clients to still track truer to rate limit expectations, so long as the overall workload is not saturating resources.

👉 The default burst ratio of 1.1 makes testing results slightly more stable on average, but can also hide some short-term slow-downs in system throughput. It is set at the default to fit most tester's expectations for averaging results, but it may not be strict enough for your testing purposes. However, a strict setting of 1.0 nearly always adds cold/startup time to the result, so if you are testing for steady state, be sure to account for this across test runs.


The striderate parameter allows you to limit the start of a stride according to some rate. This works almost exactly like the cyclerate parameter, except that it blocks a whole group of operations from starting instead of a single operation. The striderate can use a burst ratio just as the cyclerate.

This sets the target rate for strides. In NoSQLBench, a stride is a group of operations that are dispatched and executed together within the same thread. This is useful, for example, to emulate application behaviors in which some outside request translates to multiple internal requests. It is also a way to optimize a client runtime for more efficiency and throughput. The stride rate limiter applies to the whole activity irrespective of how many threads it has.

WARNING: When using the cyclerate and striderate options together, operations are delayed based on both rate limiters. If the relative rates are not synchronised with the size of a stride, then one rate limiter will artificially throttle the other. Thus, it usually doesn't make sense to use both of these settings in the same activity.


Usually, you don't want to provide a setting for stride, but it is still important to understand what it does. Within NoSQLBench, each time a thread needs to allocate a set of cycles to run, it takes a contiguous range of values from an activity-wide source, usually an atomic sequence. Thus, the stride is the unit of micro-batching within NoSQLBench. It also means that you can use stride to optimize a workload by setting the value higher than the default. For example if you are running a single-statement workload at a very high rate, it doesn't make sense for threads to allocate one op at a time from a shared atomic value. You can simply set stride=1000 to cause (ballpark estimation) about 1000X less internal contention. The stride is initialized to the calculated sequence length. The sequence length is simply the number of operations in the op sequence that is planned from your active statements and their ratios.

You usually do not want to set the stride directly. If you do, make sure it is a multiple of what it would normally be set to if you need to ensure that sequences are not divided up differently. This can be important when simulating the access patterns of applications.



The seq=<bucket|concat|interval> parameter determines the type of sequencing that will be used to plan the op sequence. The op sequence is a look-up-table that is used for each stride to pick statement forms according to the cycle offset. It is simply the sequence of statements from your YAML that will be executed, but in a pre-planned, and highly efficient form.

An op sequence is planned for every activity. With the default ratio on every statement as 1, and the default bucket scheme, the basic result is that each active statement will occur once in the order specified. Once you start adding ratios to statements, the most obvious thing that you might expect will happen: those statements will occur multiple times to meet their ratio in the op mix. You can customize the op mix further by changing the seq parameter to concat or interval.

👉 The op sequence is a look-up table of op templates, not individual statements or operations. Thus, the cycle still determines the uniqueness of an operation as you would expect. For example, if statement form ABC occurs 3x per sequence because you set its ratio to 3, then each of these would manifest as a distinct operation with fields determined by distinct cycle values.

There are three schemes to pick from:


This is a round-robin planner which draws operations from buckets in circular fashion, removing each bucket as it is exhausted. For example, the ratios A:4, B:2, C:1 would yield the sequence A B C A B A A. The ratios A:1, B5 would yield the sequence A B B B B B.


This simply takes each statement template as it occurs in order and duplicates it in place to achieve the ratio. The ratios above (A:4, B:2, C:1) would yield the sequence A A A A B B C for the concat sequencer.


This is arguably the most complex sequencer. It takes each ratio as a frequency over a unit interval of time, and apportions the associated operation to occur evenly over that time. When two operations would be assigned the same time, then the order of appearance establishes precedence. In other words, statements appearing first win ties for the same time slot. The ratios A:4 B:2 C:1 would yield the sequence A B C A A B A. This occurs because, over the unit interval (0.0,1.0), A is assigned the positions A: 0.0, 0.25, 0.5, 0.75, B is assigned the positions B: 0.0, 0.5, and C is assigned position C: 0.0. These offsets are all sorted with a position-stable sort, and then the associated ops are taken as the order.

In detail, the rendering appears as 0.0(A), 0.0(B), 0.0(C), 0.25(A), 0.5(A), 0.5(B), 0.75(A), which yields A B C A A B A as the op sequence.

This sequencer is most useful when you want a stable ordering of operation from a rich mix of statement types, where each operation is spaced as evenly as possible over time, and where it is not important to control the cycle-by-cycle sequencing of statements.

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