---
title: read stochastic -source 'srch_cluster' | Juttle Language Reference
---

read stochastic -source 'srch_cluster'
=======================================

Simulate a cluster of search engine hosts.
This source is similar to [read -source 'cdn'](./stochastic_cdn.md),
but with defaults that simulate multiple hosts undergoing a
denial-of-service attack.`

```
read stochastic -source 'srch_cluster' source-params read-params
```

#### Source parameters

Parameter  |  Description  |  Required?
---------- | ------------- | ---------:
`-every`   | Historic points are downsampled at the specified interval <p>See [Time notation in Juttle](../reference/time.md) for syntax information. </p> | No; default is the same as `-max_samples`
`-max_samples`  | Historic points are downsampled at an interval calculated so that there are no more than int intervals  |  No; default is 1000
`-nhosts`  |  The number of hosts to simulate  |  No; the default is 5
`-pops`  |  A list of Point of Presence (PoP) names to use with -nhosts <p>Host names are generated by assigning numbers to PoPs in a round-robin fashion, such as pop1.1, pop2.2, pop1.3, pop1.4, and so on. </p> |  No
`-host_names`  | A list of host names to use, in which case -nhosts is ignored and the number of hosts equals the number of specified host names | No; when -nhosts is more than 1, and -host_names is omitted, then host names are randomly generated.
`-service_names`  |  A list of service names to use, including one or more of the following: <ul><li>search</li><li>index</li><li>authentication</li></ul> |  No; the default is all three service names
`-host_capacities`  |  The relative capacities of hosts <p>Daily CDN demand are divided among them by these proportions.</p> |  No
`-daily`  |  The scale factor for daily demand wave <p>A value of n will max out n hosts during peak hours.</p> |  No
`-dos`  |  The scale of DOS demand load on a host, between 0 and 1. A value of 1 will max out any host it hits.   |  No; the default is 0.7
`-dos_dur`  |  The average time that an attack spends on a host before moving to another host <p>Simulation times increase with this number; keep it to seconds or small minutes. </p>  |  No; defaults to 15 seconds
`-dos_id`  |  The customer ID of the DOS attacker  |  No; default is 13
`-dos_router`  |  The method for selecting the next host for the DOS demand. Roundrobin cycles through the host list, each for dos\_dur seconds. markov is more interesting.   |  No
`-errp`  |  The syslog error percentage at peak demand  |  No; defaults to 0.02
`-lpm`  |  The average number of syslog lines per minute per host  |  No; defaults to 60
`-debug`  |  "1" to emit additional points with behind-the-scenes information  |  No

#### Read parameters

Parameter  |  Description  |  Required?
---------- | ------------- | ---------:
`-from`    | Stream points whose time stamps are greater than or equal to the specified moment <p>See [Time notation in Juttle](../reference/time.md)  for syntax information. </p>  | Required only if -to is not present; defaults to :now:
`-to`  |  Stream points whose time stamps are less than the specified moment, which is less than or equal to :now:  <p>See [Time notation in Juttle](../reference/time.md) for syntax information. </p><p>:information_source: `Note:` To stream live data only, omit `-from` and specify `-to :end:`. To combine historical and live data, specify a `-from` value in the past and `-to :end:`.|  Required if -from is not present; defaults to :now:
`-last`  |  Given a duration, shorthand for `-from (:now: - duration) -to :now:` |  No
`filter-expression`  |  A field comparison, where multiple terms are joined with AND, OR, or NOT <p>See [Filtering](../concepts/filtering.md) for additional details.  </p>  |  No

_Example: Compare response times from the last two minutes to live streaming response times_

```
{!docs/examples/adapters/stochastic_search_cluster_live_stream.juttle!}
```