zhangchiqing / concurrency

concurrency models in different languages

Concurreny Models in different languages

Golang Concurreny With Channels and Goroutines

Chaining and block

There is no concurrency in this example. One async call chained after another

▸ cd golang/chain
▸ go run main.go
[2019-01-27T16:12:44Z] [run start]
[2019-01-27T16:12:44Z] [getA start]
[2019-01-27T16:12:47Z] ...[getA end. a, err: A <nil>]
[2019-01-27T16:12:47Z] ...[getBWithA start. a: A]
[2019-01-27T16:12:50Z] ......[getBWithA end. b, err: 3 <nil>]
[2019-01-27T16:12:50Z] ......[getCWithAB start. a, b: A 3]
[2019-01-27T16:12:53Z] .........[getCWithAB end. c, err: C <nil>]
[2019-01-27T16:12:53Z] .........[run end C <nil>]

Multiple async calls run concurrently

Async calls running concurrently could have different types of input and output.

In this example, getA and getB have different types, they run concurrently and getCWithAB is not called until both getA and getB are finished. And the return values of getA and getB will be passed to getCWIthAB.

▸ cd golang/batch
▸ go run main.go
[2019-01-27T15:59:19Z] [run start]
[2019-01-27T15:59:19Z] [getB start]
[2019-01-27T15:59:19Z] [getA start]
[2019-01-27T15:59:20Z] .[getB end: 3 <nil>]
[2019-01-27T15:59:22Z] ...[getA end: A <nil>]
[2019-01-27T15:59:22Z] ...[getCWithAB start aV: A <nil> bV: 3 <nil>]
[2019-01-27T15:59:24Z] .....[getCWithAB end  failed]
[2019-01-27T15:59:24Z] .....[run end:  failed]

Making async calls in a batch

This example shows how to make a batch of async calls concurrently with inputs from a list of values, and how to wait and return the list of return values when all the async calls finish.

▸ cd golang/all
▸ go run main.go
[2019-01-27T15:59:44Z] [run start]
[2019-01-27T15:59:44Z] [getNWithC start: E]
[2019-01-27T15:59:44Z] [getNWithC start: B]
[2019-01-27T15:59:44Z] [getNWithC start: C]
[2019-01-27T15:59:44Z] [getNWithC start: A]
[2019-01-27T15:59:44Z] [getNWithC start: D]
[2019-01-27T15:59:46Z] ..[getNWithC end: C 2 <nil>]
[2019-01-27T15:59:46Z] ..[getNWithC end: D 2 <nil>]
[2019-01-27T15:59:46Z] ..[getNWithC end: B 2 <nil>]
[2019-01-27T15:59:47Z] ...[getNWithC end: A 3 <nil>]
[2019-01-27T15:59:49Z] .....[getNWithC end: E 5 <nil>]
[2019-01-27T15:59:49Z] .....[run end [3 2 2 2 5] <nil>]

A fixed-length queue could be added to throttle the number of async calls running concurrently.

Timeout

This example shows how to give a timeout for an async call. The implementation can also be used the same for racing two async calls.

▸ cd golang/timeout
▸ go run main.go
[2019-01-27T16:01:44Z] [run start]
[2019-01-27T16:01:44Z] [getA start]
[2019-01-27T16:01:47Z] ...[getA end: 0 getA Timeout after 3 secs]
[2019-01-27T16:01:47Z] ...[run end 0 getA Timeout after 3 secs]

Pulling asynchronously and then extract synchronously

This example shows how to making first calls (pull) asynchronously and then run the second call (extract) synchronously.

The behavior is similar to how docker pull and extract images, where it pulls different layers asynchronously and then extracted one after the other in order.

▸ go run main.go
[2019-03-01T22:53:39Z] [run start]
[2019-03-01T22:53:39Z] [pulling...: E]
[2019-03-01T22:53:39Z] [pulling...: B]
[2019-03-01T22:53:39Z] [pulling...: D]
[2019-03-01T22:53:39Z] [pulling...: C]
[2019-03-01T22:53:39Z] [pulling...: A]
[2019-03-01T22:53:40Z] .[pulled: A 1 <nil>]
[2019-03-01T22:53:40Z] .[extracting...: A 1]
[2019-03-01T22:53:41Z] ..[pulled: E 2 <nil>]
[2019-03-01T22:53:41Z] ..[extracted: A 1]
[2019-03-01T22:53:42Z] ...[pulled: B 3 <nil>]
[2019-03-01T22:53:42Z] ...[extracting...: B 3]
[2019-03-01T22:53:43Z] ....[extracted: B 3]
[2019-03-01T22:53:44Z] .....[pulled: D 5 <nil>]
[2019-03-01T22:53:44Z] .....[pulled: C 5 <nil>]
[2019-03-01T22:53:44Z] .....[extracting...: C 5]
[2019-03-01T22:53:46Z] .......[extracted: C 5]
[2019-03-01T22:53:46Z] .......[extracting...: D 5]
[2019-03-01T22:53:48Z] .........[extracted: D 5]
[2019-03-01T22:53:48Z] .........[extracting...: E 2]
[2019-03-01T22:53:51Z] ............[extracted: E 2]
[2019-03-01T22:53:51Z] ............[run end [1 3 5 5 2] <nil>]