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Context Parameter

Syntax​

When to use context parameters​

Always use context.Context for functions that interact with the system external.

  • update cache value di redis ? use context.Context
  • query ke postgres / mongodb ? use context.Context
  • call API dari 3rd party ? use context.Context
  • dial gRPC host / service ? use context.Context
  • etc

context. For. All. external. call.

Hati-hati menggunakan hardcoded timeout context​

Consider the following example:

func UpdateSomething(ctx context.Context, param string) error {
  // add span to ctx...
  span, ctx := apm.StartSpan(ctx, "myspan", spanType)
  defer span.End()

  rCtx, cancel := context.WithTimeout(ctx, 10*time.Second)
  defer cancel()

  // continue function...
}

context.WithTimeout will make a copy of the existing context, with a certain timeout. The above line means that for 1 function block, the timeout is 10 seconds.

This becomes a problem if the timeout is created in each function. Example:

  • controller.UpdatePhone -> service.UpdatePhone -> mongo.UpdatePhone
  • If each function has a timeout of 10s, it means that the total request is possible to run for 30s.
  • Even though the timeout from the user / android is a maximum of 10s
  • There is a possibility on the user's cellphone timeout, but on the server the program is still being executed.

Ideally the timeout is set from the echo / grpc server middleware side, so 1x is enough. Furthermore, functions that require context just take the parameters of the previous function.

If there is already a context.Context parameter of the function, there is no need to create a new context with a different timeout.

Reference​