Compdigitec Labs

us-east-1e doesn’t have t3 instances

By admin | March 15, 2024

us-east-1e (although AWS may randomize zone mappings) doesn’t have t3 instances! This may cause the following error messages.

“The requested configuration is currently not supported. Please check the documentation for supported configurations”

“Your requested instance type (t3.large) is not supported in your requested Availability Zone (us-east-1e). Please retry your request by not specifying an Availability Zone or choosing us-east-1a, us-east-1b, us-east-1c, us-east-1d, us-east-1f”

Topics: Internet | No Comments »


By admin | April 8, 2023

xfreerdp /v:rdp_server_address /admin /network:auto /u:username /p:password

Connecting to a Windows 10 machine yielded the following error. hints in that it might be an issue of hardware acceleration.

The solution is to disable RemoteFX for remote desktop.

[15:38:35:887] [24159:24160] [DEBUG][com.freerdp.core.rdp] - recv Set Error Info Data PDU (0x2F), length: 22
[15:38:35:887] [24159:24160] [INFO][com.freerdp.core] - ERRINFO_CLOSE_STACK_ON_DRIVER_FAILURE (0x00000011):The display driver in the remote session was unable to complete all the tasks required for startup.
[15:38:35:887] [24159:24160] [ERROR][com.freerdp.core] - rdp_set_error_info:freerdp_set_last_error_ex ERRINFO_CLOSE_STACK_ON_DRIVER_FAILURE [0x00010011]

Topics: Windows | No Comments »

Scala.js – Referring to non-existent class

By admin | September 9, 2021

Referring to non-existent class MyClass$
  called from JSClass$.jsMethod()void
  called from JSClass$.$js$exported$meth$jsMethod()java.lang.Object
  exported to JavaScript with @JSExport
involving instantiated classes:
    exported to JavaScript with @JSExport
Cannot access module for non-module MyClass$
  called from JSClass$.jsMethod()void
  called from JSClass$.$js$exported$meth$jsMethod()java.lang.Object
  exported to JavaScript with @JSExport
involving instantiated classes:
    exported to JavaScript with @JSExport

Related issue:

If the issue is coming from a shared module being used in both a Scala.js and JVM setting, the issue may be that the shared module is not being compiled for Scala.js. We can fix that as follows by compiling it for both. Mill example below:

object MyObject extends ScalaModule with ScalaJSModule with ScalafmtModule {
  // ...

// Instead of

object MyObject extends ScalaModule with ScalafmtModule {
  // ...

Topics: Code | No Comments »

Serving VNC via HTML5 using noVNC and x11vnc

By admin | July 22, 2021

# May need to set up x11vnc password beforehand!
# -forever and -loop are important to makes sure it keeps working
nohup x11vnc -create -forever -loop -usepw &

# noVNC
git clone --depth 2
cd noVNC

# Set up SSL
openssl req -x509 -nodes -newkey rsa:2048 -keyout novnc.pem -out novnc.pem -days 180

nohup ./utils/novnc_proxy --vnc localhost:5900 --cert novnc.pem --ssl-only --listen 443 &

Topics: (X)HTML, Internet, Linux | No Comments »

Accessing SQL databases from Scala

By admin | July 21, 2021

import scalikejdbc._
import scalikejdbc.scalikejdbcSQLInterpolationImplicitDef

// initialize JDBC driver & connection pool

scalikejdbc.ConnectionPool.singleton("jdbc:postgresql://localhost:5432/", "user", "abcdef888")

create table members (
  id serial not null primary key,
  fav_num integer NOT NULL,
  name text NOT NULL

INSERT INTO members (name, fav_num) VALUES ('Foo', 123)

INSERT INTO members (name, fav_num) VALUES ('Bar', 456)

scalikejdbc.DB.readOnly { implicit session =>
  sql"select * from members".foreach { (rs: scalikejdbc.WrappedResultSet) =>

You can run the database with Docker (example) as follows:

docker run --name mypsql -e POSTGRES_USER=user -e POSTGRES_PASSWORD=abcdef888 -p 5432:5432 postgres:13.3

Reference instructions for connecting to the docker instance:

psql -h localhost -U user
select * from members;

Topics: Code | 1 Comment »

Local build in npm

By admin | May 24, 2021

npm install # Install dependencies
npm run build # Needs a like like "build": "tsc" in package.json. For TypeScript, just run tsc directly if missing
npm install -g # Installed compiled result to global packages

Topics: Code | No Comments »

Python classes, metaclasses, and instances at a glance

By admin | February 16, 2021

For more details:

Topics: Code | 1 Comment »


By admin | February 15, 2021

git format-patch $1..HEAD -o wip && git reset --hard $1

Topics: Code | No Comments »

Getting files from sources in Scala

By admin | February 14, 2021

// Java-based ways

// Scala-native way

Topics: Code | 5 Comments »

Epson DS-30 on Ubuntu Linux

By admin | February 13, 2021

Use the attached ds-30-bundle, download from

Install the deb packages with ./ –dry-run

Use simple-scan to run the scan. Insert paper face down above/next to
the little scan marker and press the button

Topics: Linux | 1 Comment »

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