okhttp run on thread or coroutine on ktor applcation - okhttp

Question

I'm using okhttp with ktor on my server application and run like this.
runBlocking {
launch {
okhttpClient.get(url)
}
}
and this is logging result.
2021-05-17 11:18:21.620 DEBUG 11928 --- [nio-8080-exec-2] o.s.web.servlet.DispatcherServlet : GET "/test/test2", parameters={}
2021-05-17 11:18:21.621 DEBUG 11928 --- [nio-8080-exec-2] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped to com.example.kotlinstudy.TestController#test2()
2021-05-17 11:18:21.788 DEBUG 11928 --- [alhost:8081/...] okhttp3.internal.concurrent.TaskRunner : Q10000 scheduled after 0 µs: OkHttp ConnectionPool
2021-05-17 11:18:21.789 DEBUG 11928 --- [Http TaskRunner] okhttp3.internal.concurrent.TaskRunner : Q10000 starting : OkHttp ConnectionPool
2021-05-17 11:18:21.789 DEBUG 11928 --- [ ConnectionPool] okhttp3.internal.concurrent.TaskRunner : Q10000 run again after 300 s : OkHttp ConnectionPool
2021-05-17 11:18:21.789 DEBUG 11928 --- [Http TaskRunner] okhttp3.internal.concurrent.TaskRunner : Q10000 finished run in 287 µs: OkHttp ConnectionPool
2021-05-17 11:18:21.828 DEBUG 11928 --- [#call-context#5] okhttp3.internal.concurrent.TaskRunner : Q10000 scheduled after 0 µs: OkHttp ConnectionPool
2021-05-17 11:18:21.828 DEBUG 11928 --- [Http TaskRunner] okhttp3.internal.concurrent.TaskRunner : Q10000 starting : OkHttp ConnectionPool
2021-05-17 11:18:21.828 DEBUG 11928 --- [ ConnectionPool] okhttp3.internal.concurrent.TaskRunner : Q10000 run again after 300 s : OkHttp ConnectionPool
2021-05-17 11:18:21.828 DEBUG 11928 --- [Http TaskRunner] okhttp3.internal.concurrent.TaskRunner : Q10000 finished run in 92 µs: OkHttp ConnectionPool
2021-05-17 11:18:21.883 DEBUG 11928 --- [nio-8080-exec-2] m.m.a.RequestResponseBodyMethodProcessor : Using 'text/plain', given [*/*] and supported [text/plain, */*, text/plain, */*, application/json, application/*+json, application/json, application/*+json, application/json, application/*+json]
2021-05-17 11:18:21.883 DEBUG 11928 --- [nio-8080-exec-2] m.m.a.RequestResponseBodyMethodProcessor : Writing ["test1"]
2021-05-17 11:18:21.890 DEBUG 11928 --- [nio-8080-exec-2] o.s.web.servlet.DispatcherServlet : Completed 200 OK
It's started tomcat nio thread and running on okhttp thread.
you know coroutine is light thread. I expect that runBlocking code working on coroutine thread.
but it seem another thread.
So okhttpClent run on coroutine thread? or normal thread?
What should I do to work with coroutine thread?
Using CIO client?
Thanks all.
This is CIO calling log. It looks like working coroutine thread
2021-05-17 13:05:16.271 DEBUG 20068 --- [nio-8080-exec-2] o.s.web.servlet.DispatcherServlet : GET "/test/test3", parameters={}
2021-05-17 13:05:16.273 DEBUG 20068 --- [nio-8080-exec-2] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped to com.example.kotlinstudy.TestController#test3()
2021-05-17 13:05:16.306 INFO 20068 --- [-2 #coroutine#5] io.ktor.client.HttpClient : REQUEST: http://localhost:8081/server1
2021-05-17 13:05:16.307 INFO 20068 --- [-2 #coroutine#5] io.ktor.client.HttpClient : METHOD: HttpMethod(value=GET)
2021-05-17 13:05:16.307 INFO 20068 --- [-2 #coroutine#5] io.ktor.client.HttpClient : COMMON HEADERS
2021-05-17 13:05:16.308 INFO 20068 --- [-2 #coroutine#5] io.ktor.client.HttpClient : -> Accept: application/json
2021-05-17 13:05:16.309 INFO 20068 --- [-2 #coroutine#5] io.ktor.client.HttpClient : -> Accept-Charset: UTF-8
2021-05-17 13:05:16.309 INFO 20068 --- [-2 #coroutine#5] io.ktor.client.HttpClient : -> User-Agent: Ktor client/1.3.1(npay-point)
2021-05-17 13:05:16.309 INFO 20068 --- [-2 #coroutine#5] io.ktor.client.HttpClient : CONTENT HEADERS
2021-05-17 13:05:16.309 INFO 20068 --- [-2 #coroutine#5] io.ktor.client.HttpClient : -> Content-Length: 0
2021-05-17 13:05:16.423 INFO 20068 --- [-2 #coroutine#5] io.ktor.client.HttpClient : RESPONSE: 200 OK
2021-05-17 13:05:16.423 INFO 20068 --- [-2 #coroutine#5] io.ktor.client.HttpClient : METHOD: HttpMethod(value=GET)
2021-05-17 13:05:16.423 INFO 20068 --- [-2 #coroutine#5] io.ktor.client.HttpClient : FROM: http://localhost:8081/server1
2021-05-17 13:05:16.423 INFO 20068 --- [-2 #coroutine#5] io.ktor.client.HttpClient : COMMON HEADERS
2021-05-17 13:05:16.423 INFO 20068 --- [-2 #coroutine#5] io.ktor.client.HttpClient : -> Content-Length: 20
2021-05-17 13:05:16.423 INFO 20068 --- [-2 #coroutine#5] io.ktor.client.HttpClient : -> Content-Type: text/plain; charset=UTF-8
Hello world! server1
2021-05-17 13:05:16.467 DEBUG 20068 --- [nio-8080-exec-2] m.m.a.RequestResponseBodyMethodProcessor : Using 'text/plain', given [*/*] and supported [text/plain, */*, text/plain, */*, application/json, application/*+json, application/json, application/*+json, application/json, application/*+json]
2021-05-17 13:05:16.468 DEBUG 20068 --- [nio-8080-exec-2] m.m.a.RequestResponseBodyMethodProcessor : Writing ["test1"]
2021-05-17 13:05:16.475 DEBUG 20068 --- [nio-8080-exec-2] o.s.web.servlet.DispatcherServlet : Completed 200 OK

Answer 1

Even though most people see coroutines as lightweight threads they are in fact not really that. A coroutine starts in a thread and then suspends until its ready to resume. See: Coroutines basics:
...a coroutine is not bound to any particular thread. It may suspend its execution in one thread and resume in another one.
Coroutines are not designed to stick to one thread and only use that. You'll need to clarify the use case you need this for as it could be more of a code design decision.