Skip to main content

parallel execution - flowstaller

The orchestration tool I'm working on got a shot today.  Go has some interesting properties. For example there is something called a Zero value than can be applied to structures as well as first class attributes.
an empty string is the zero value for a string
a 0 (zero) is the zero value for an integer
False is a zero value for a boolean 
A zero value for a struct is when all of the member attributes have their zero value.

When decoding or Unmarshaling it's impossible to know whether the string you decoded yielded an object instance or a zero value.
type SomeStructType struct {
    MyValue string
}
In order to Unmarshal something into this structure I need a wrapper structure:
type SomeStructWrapper struct {
    Something SomeStructType `json:"
SomeStructType"`
}
Unmarshaling a string like:
{ "SomeStructType":{"MyValue":"Hello World"}}
Only works when you're Unmarshaling into a wrapper instance.
s := &SomeStructWrapper{}
err := json.Unmarshal(buffer, s)
But unless you know for certain that the types and buffer are really meant to match then... you need to check. Since you've already allocated the target object instance and it's already the zero value. There is no way to know whether or not the Unmarshal was successful.  The error return value may not be helpful.

I found that if I changed the wrapper to:

type SomeStructWrapper struct {
    Something []SomeStructType `json:"
SomeStructType"`
}
Notice that Something is now a slice/array. And if I change the input document syntax a little:
{ "SomeStructType":[{"MyValue":"Hello World"}]}
Now I can check the length of the Something attribute once the Unmarshal returns.  If the len()=0 or with reflection of something==nil then I know that it failed (arrays are pointers; which is a symantic difference with other types).

PS: I added a minmax tag so I could identify the number of items in the array.

PS: and when there is multiple items in the array/slice I run them in different goroutines.

Comments

Popular posts from this blog

Entry level cost for CoreOS+Tectonic

CoreOS and Tectonic start their pricing at 10 servers. Managed CoreOS starts at $1000 per month for those first 10 servers and Tectonic is $5000 for the same 10 servers. Annualized that is $85K or at least one employee depending on your market. As a single employee company I'd rather hire the employee. Specially since I only have 3 servers.

The pricing is biased toward the largest servers with the largest capacities; my dual core 32GB i5 IntelNuc can never be mistaken for a 96-CPU dual or quad core DELL

If CoreOS does not figure out a different barrier of entry they are going to follow the Borland path to obscurity.

UPDATE 2017-10-30: With gratitude the CoreOS team has provided updated information on their pricing, however, I stand by my conclusion that the effective cost is lower when you deploy monster machines. The cost per node of my 1 CPU Intel NUC is the same as a 96 CPU server when you get beyond 10 nodes. I'll also reiterate that while my pricing notes are not currently…

eGalax touch on default Ubuntu 14.04.2 LTS

I have not had success with the touch drivers as yet.  The touch works and evtest also seems to report events, however, I have noticed that the button click is not working and no matter what I do xinput refuses to configure the buttons correctly.  When I downgraded to ubuntu 10.04 LTS everything sort of worked... there must have been something in the kermel as 10.04 was in the 2.6 kernel and 4.04 is in the 3.x branch.

One thing ... all of the documentation pointed to the wrong website or one in Taiwanese. I was finally able to locate the drivers again: http://www.eeti.com.tw/drivers_Linux.html (it would have been nice if they provided the install instructions in text rather than PDF)
Please open the document "EETI_eGTouch_Programming_Guide" under the Guide directory, and follow the Guidline to install driver.
download the appropriate versionunzip the fileread the programming manual And from that I'm distilling to the following: execute the setup.sh answer all of the questio…

Prometheus vs Bosun

In conclusion... while Bosun(B) is still not the ideal monitoring system neither is Prometheus(P).

TL;DR;

I am running Bosun in a Docker container hosted on CoreOS. Fleet service/unit files keep it running. However in once case I have experienced at least one severe crash as a result of a disk full condition. That it is implemented as part golang, java and python is an annoyance. The MIT license is about the only good thing.

I am trying to integrate Prometheus into my pipeline but losing steam fast. The Prometheus design seems to desire that you integrate your own cache inside your application and then allow the server to scrape the data, however, if the interval between scrapes is shorter than the longest transient session of your application then you need a gateway. A place to shuttle your data that will be a little more persistent.

(1) storing the data in my application might get me started more quickly
(2) getting the server to pull the data might be more secure
(3) using a push g…