# Rally and Httperf

**URL:** <https://discuss.elastic.co/t/rally-and-httperf/124457>\
**Category:** Elasticsearch\
**Tags:** rally\
**Created:** [March 18, 2018, 8:18pm UTC](https://discuss.elastic.co/t/rally-and-httperf/124457 "2018-03-18T20:18:32Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![dliappis](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/dliappis/32/56174_2.png) [@dliappis](https://discuss.elastic.co/u/dliappis)\
**Post date:** [March 19, 2018, 1:26pm UTC](https://discuss.elastic.co/t/rally-and-httperf/124457/2 "2018-03-19T13:26:56Z")

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Hello @jlwysf,

Some replies below (caveat: I am also currently learning Rally):

> [@jlwysf](#):
>
> I do see we can set up clients in schedule, does one client means one node in elasticsearch cluster?

No, client is an Elasticsearch client (they are actually implemented using the elasticsearch-python client).  
When you increase the clients, e.g. for a bulk operation, you will see more python3 processes getting spawned.

The following links in [docs](http://esrally.readthedocs.io/en/stable/track.html?highlight=clients#defining-operations) and discuss replies ([1](https://discuss.elastic.co/t/any-limitations-with-distributed-load-drivers/107939/11), [2](https://discuss.elastic.co/t/rally-consumes-all-cluster-threads-and-crashes-with-small-clusters/117599/2), [3](https://discuss.elastic.co/t/whats-the-frequnce-for-rally-send-bulk-requests/66665/2)) have more detail.

> [@jlwysf](#):
>
> In httperf we can set concurrent connections, does Rally also support that?

You should take a look at adjusting clients, as mentioned earlier and [running tasks in parallel](http://esrally.readthedocs.io/en/stable/track.html?highlight=parallel#time-based-vs-iteration-based).

The [documentation](http://esrally.readthedocs.io/en/stable/track.html?highlight=parallel#running-tasks-in-parallel) provides some examples and the amount of clients can be decided by Rally or be specified.

> [@jlwysf](#):
>
> is there anyway Rally can help get CPU usage, Disk IO during testing?

Rally has internal telemetry devices through which it stores a number of very useful metric keys, documented [here](http://esrally.readthedocs.io/en/latest/metrics.html#metric-keys). Among these metrics, you will a find a number of cpu utilization and disk\_io related ones. See also this [discuss reply](https://discuss.elastic.co/t/about-running-rally-with-error/63284/4).

Dimitris

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