DEV Community: David Velho

Stop-gap measure to debug a Native Node Addon on Windows

David Velho — Mon, 07 Aug 2023 12:50:59 +0000

While working on building a project that includes a NodeJs addon using N-API for Windows (and *nix), I found that binaries built on my machine work but the same binaries do not work on another machine.

But the file(s) are all present. What is happening? The same behaviour was observed on Linux and MacOS machines other than mine.

I would have switched to Linux and used strace to see what was happening, but I wanted to see if Windows has any good alternatives. After some quick Google searching, I realized that I could use the built-in Visual Studio debugger.

Note: I assume that you have the Visual Studio environment setup for C++ development on windows, along with the required SDKs installed

The commands I used to load and test the libtorrent build are (in a NodeJs shell) -

const lib = require('./libtorrent.node');

So I tried to find a Debug target (using the CMake extension that populates Visual Studio with stuff)

No luck. Next, I opened Visual Studio and tried to start a NodeJs process using the debugger -

But the "Start Debugging" option was greyed out. However, the "Attach to Process" option is available. Choosing that option opens the following menu -

The Module window will be of interest to us

Notice the timestamp column. Lets sort the list by timestamp and focus on the rows with a timestamp -

This makes sense as we haven't loaded the addon yet. Let's load the addon through Node and check the window again

We see a few more entries. On observing them, we see the following:

libcrypto-3-x64.dll
libssl-3-x64.dll

Going through the dependencies, we see that our project's main dependency libtorrent depends on OpenSSL. Finally it clicked that I installed OpenSSL through choco

Solution 1: Bundle and distribute required DLLs

Let's try to bundle the required DLLs with the project

And we see that libtorrent is successfully loaded

But that's not a feasible solution. There might be scenarios where one cannot bundle multiple DLLs due to some restriction. How do we proceed?

Solution 2: If it works, it ain't stupid

We know that the project depends on libcrypto and libssl, but probably uses a few functions or items from them. To test this theory out, I modified my project's CMakeLists.txt file to fetch openssl from Github using CMake's built in (version 3.11 and later) FetchContent

The following is an extract of the CMakeLists.txt file:

include(FetchContent)
FetchContent_Declare(
    openssl
    GIT_REPOSITORY https://github.com/janbar/openssl-cmake.git
    SOURCE_DIR ${CMAKE_SOURCE_DIR}/lib/openssl
    GIT_TAG 392d455cd0b0fe992b312c9648eb5ea87e3afcea
)

FetchContent_MakeAvailable(openssl)
set(OPENSSL_ROOT_DIR ${CMAKE_SOURCE_DIR}/lib/openssl/*)

if(CMAKE_BUILD_TYPE STREQUAL "Debug")
    set(OPENSSL_CRYPTO_LIBRARY ${CMAKE_SOURCE_DIR}/build/_deps/openssl-build/crypto/Debug)
elseif(CMAKE_BUILD_TYPE STREQUAL "Release")
    set(OPENSSL_CRYPTO_LIBRARY ${CMAKE_SOURCE_DIR}/build/_deps/openssl-build/crypto/Release)
endif()

The statement to set OPENSSL_CRYPTO_LIBRARY can be optimised further

This resulted in the following files being generated -

the openssl binary is built as default behaviour that can be customized

Shaky cam courtesy of a friend

Include custom CMake modules

David Velho — Tue, 28 Feb 2023 15:24:47 +0000

Lets abstract some configuration of our project to a user defined Config.cmake file.

Let's assume your project uses CMake and has a directory structure similar to the one shown below

The Config.cmake file has the following stuff -

set_target_properties(
  ${CMAKE_PROJECT_NAME}
  PROPERTIES CXX_STANDARD 17
             CXX_STANDARD_REQUIRED YES
             CXX_EXTENSIONS NO)

include(CheckIPOSupported)
check_ipo_supported(RESULT result)
if(result)
  set_target_properties(${CMAKE_PROJECT_NAME}
                        PROPERTIES INTERPROCEDURAL_OPTIMIZATION TRUE)
endif()

find_program(CCACHE_PROGRAM ccache)
if(CCACHE_PROGRAM)
  set(CMAKE_CXX_COMPILER_LAUNCHER "${CCACHE_PROGRAM}")
  set(CMAKE_CUDA_COMPILER_LAUNCHER "${CCACHE_PROGRAM}") # CMake 3.9+
endif()

Then, in our root CMakeLists.txt file, lets add the following lines -

list(APPEND CMAKE_MODULE_PATH "${PROJECT_SOURCE_DIR}/cmake/Modules")

This line must go after your project configuration

And finally,

include(Config)

Where Config is the name of file with our abstractions

Dockerize Apache Tomcat Servlets

David Velho — Tue, 01 Jun 2021 11:47:13 +0000

Step 1 - Dependencies

Make sure you have Java EE, a compatible version of JDK and Docker installed.
If you don't have Java EE installed, or if you have OpenJDK , you can use the Java EE jar file downloaded from this link

Step 2 - Compile source code

Let's use the Java source code from this link and compile it using

javac -cp .:<path to javaee jar> -target 1.7 -source 1.7 TestingServlet.java

If you're using windows, you have to use ; instead of : in classpath
The -target is the version number of the runtime environment of tomcat. Similarly for -source

Step 3 - Environment Setup

Let's use the Dockerfile from here and let's add some stuff.

FROM tomcat:8.0-alpine
LABEL maintainer="deepak@softwareyoga.com"

COPY ./web.xml /usr/local/tomcat/webapps/ROOT/WEB-INF
COPY ./TestingServlet.class /usr/local/tomcat/webapps/ROOT/WEB-INF/classes/TestingServlet.class
COPY ./tomcat-users.xml /usr/local/tomcat/conf/tomcat-users.xml

EXPOSE 8080
CMD ["catalina.sh", "run"]

We define web.xml and tomcat-users.xml later. The file TestingServlet.class is important and we'll remember the name for later.

Step 4 - Configuration

Let's define web.xml as follows:

<?xml version="1.0" encoding="ISO-8859-1"?>
<!--
 Licensed to the Apache Software Foundation (ASF) under one or more
  contributor license agreements.  See the NOTICE file distributed with
  this work for additional information regarding copyright ownership.
  The ASF licenses this file to You under the Apache License, Version 2.0
  (the "License"); you may not use this file except in compliance with
  the License.  You may obtain a copy of the License at

      http://www.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
-->
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
                      http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
  version="3.1"
  metadata-complete="true">

  <display-name>Welcome to Tomcat</display-name>
  <description>
     Welcome to Tomcat
  </description>

  <servlet>
   <servlet-name>Testing</servlet-name>
   <servlet-class>TestingServlet </servlet-class>
  </servlet>

 <servlet-mapping>
 <servlet-name>Testing</servlet-name>
 <url-pattern>/servlet/TestingServlet</url-pattern>
 </servlet-mapping>
</web-app>

servlet-class is the name of the .class file and url-pattern is the HTTP url you want to access it by.

Let's define tomcat-users.xml as follows:

<?xml version='1.0' encoding='utf-8'?>
<!--
  Licensed to the Apache Software Foundation (ASF) under one or more
  contributor license agreements.  See the NOTICE file distributed with
  this work for additional information regarding copyright ownership.
  The ASF licenses this file to You under the Apache License, Version 2.0
  (the "License"); you may not use this file except in compliance with
  the License.  You may obtain a copy of the License at

      http://www.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
-->
<tomcat-users xmlns="http://tomcat.apache.org/xml"
              xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
              xsi:schemaLocation="http://tomcat.apache.org/xml tomcat-users.xsd"
              version="1.0">
<!--
  NOTE:  By default, no user is included in the "manager-gui" role required
  to operate the "/manager/html" web application.  If you wish to use this app,
  you must define such a user - the username and password are arbitrary. It is
  strongly recommended that you do NOT use one of the users in the commented out
  section below since they are intended for use with the examples web
  application.
-->
<!--
  NOTE:  The sample user and role entries below are intended for use with the
  examples web application. They are wrapped in a comment and thus are ignored
  when reading this file. If you wish to configure these users for use with the
  examples web application, do not forget to remove the <!.. ..> that surrounds
  them. You will also need to set the passwords to something appropriate.
-->

  <role rolename="manager"/>
  <role rolename="manager-gui"/>
  <user username="admin" password="admin" roles="manager-gui"/>
</tomcat-users>

Apache Tomcat defines a list of roles here

Step 5 - Deployment

Let's build the Docker image

docker build -t tomcat .

And run it with

docker run -d -p 8080:8080 --name tomcat tomcat

Apache Tomcat runs on port 8080 in the container

You can now visit http://localhost:8080/servlet/TestingServlet and see the following message

Step 6 - Debugging

If you see an error like this

It means that you have to select a differente target and source version, either higher or lower depending on the version of the target runtime. You can check the Java Runtime version through the Tomcat UI at the bottom of the page

Alternatively, you can run bash version.sh in /usr/local/tomcat/bin when inside the running Docker container

References

Packaging with CMake CPack and NSIS on Windows

David Velho — Tue, 27 Apr 2021 10:06:35 +0000

Assuming you have your base project(ABC) setup with CMake, let's get started.

Download and Install NSIS from here. We'll need this to use CPack with NSIS.

Let's add an icon to our built application by creating a file called abc.rc which is a resource file used by MSVCC to apply icons, among other stuff.

IDI_ICON1               ICON        DISCARDABLE            "abc.ico"

Add this definition to our add_executable command

add_executable(abc 
${ABC_SOURCE_DIR}/assets/abc.rc
${SOURCES} 
# other stuff
)

Next we need to define our install targets that CPack will pick up on

install(TARGETS abc 
         #other stuff
         DESTINATION bin
    )

Here, bin is any folder you want to put your built application in. In this case, running the installer will install abc.exe into C:\Program Files(x86)\abc\bin\abc.exe .

Normally, you would set the install target's DESTINATION to ${CMAKE_INSTALL_PREFIX}. However, CPack will give you an error :
ABSOLUTE path INSTALL DESTINATION forbidden (by caller):

After what seemed like an eternity of google searching, I came across a solution

You are trying to install some files using an ABSOLUTE path DESTINATION.
99.999% of the time this is an error on the Windows platform.

Normally you should be installing files to a RELATIVE path DESTINATION.

Cpack Config

Additional stuff that you can configure

    include(InstallRequiredSystemLibraries)
    set(CPACK_PACKAGE_INSTALL_DIRECTORY "
    set(CPACK_GENERATOR "NSIS")
    set(CPACK_PACKAGE_NAME ${PROJECT_NAME})
    set(CPACK_PACKAGE_VERSION "${ABC_VERSION_MAJOR}.${ABC_VERSION_MINOR}")
    set(CPACK_PACKAGE_VERSION_PATCH "0")
    set(CPACK_PACKAGE_VENDOR "David Velho")
    set (CPACK_NSIS_MODIFY_PATH "ON")
    set(CPACK_PACKAGE_INSTALL_REGISTRY_KEY ${PROJECT_NAME})
    set(CPACK_SOURCE_GENERATOR "TGZ")
    set(CPACK_SOURCE_PACKAGE_FILE_NAME "${CPACK_PACKAGE_NAME}-${CPACK_PACKAGE_VERSION}")
    set(CPACK_SOURCE_IGNORE_FILES ${CPACK_IGNORE_FILES})

Some additional fields

    set(CPACK_NSIS_INSTALLED_ICON_NAME "${ABC_SOURCE_DIR}/assets/abc.ico")
    set(CPACK_NSIS_HELP_LINK ${APP_URL})
    set(CPACK_NSIS_URL_INFO_ABOUT ${APP_URL})
    set(CPACK_NSIS_CONTACT ${APP_EMAIL})
 set(CPACK_NSIS_CREATE_ICONS_EXTRA
    "CreateShortCut '$SMPROGRAMS\\\\$STARTMENU_FOLDER\\\\abc.lnk' '$INSTDIR\\\\bin\\\\abc.exe' "
    )

Let's give the generated installer an icon

set(CPACK_NSIS_MUI_ICON "${ABC_SOURCE_DIR}/assets/abc.ico")

And last, the NSIS installer script that CMake will read from and substitute the values into

set(CMAKE_MODULE_PATH  ${PROJECT_SOURCE_DIR}/assets/nsis ${CMAKE_MODULE_PATH})

Where assets/nsis has a file called NSIS.definitions.nsh.in which is a script file needed by NSIS. CMake will read this file and substitute the values in so that NSIS can read it

NSIS.definitions.nsh.in :

!define VERSION "@APP_VERSION@"
!define APP_VERSION "@APP_VERSION@"
!define APP_NAME "@APP_NAME@"
!define EXE_NAME "@EXE_NAME@"
!define README_FILE "README"
!define LICENSE_FILE "@PROJECT_SOURCE_DIR@resourcestextLICENSE"
!define MUI_ICON "@PROJECT_SOURCE_DIR@resourcesgraphics@APP_LOW_NAME@.ico"
!define MUI_UNICON "@PROJECT_SOURCE_DIR@resourcesgraphics@APP_LOW_NAME@.ico"
!define MUI_WELCOMEFINISHPAGE_BITMAP "@PROJECT_SOURCE_DIR@resourcesgraphics@APP_LOW_NAME@-banner.bmp"
!define MUI_UNWELCOMEFINISHPAGE_BITMAP "@PROJECT_SOURCE_DIR@resourcesgraphics@APP_LOW_NAME@-banner.bmp"
!define PATCH  "0"

Let's include CPack and some NSIS config files

    include(CPack)
    configure_file(
    ${PROJECT_SOURCE_DIR}/assets/nsis/NSIS.definitions.nsh.in
    ${CMAKE_CURRENT_BINARY_DIR}/assets/nsis/NSIS.definitions.nsh
    )

Assuming you've added CMake to PATH during installation, you should have cpack in path. You can (while in the build directory) build the installer with

mkdir build
cd build
cmake -DCMAKE_BUILD_TYPE=Release ..
MSBuild.exe abc.sln
cpack -C Release

Additional Resources

Not so pro tips for mail-in-a-box users

David Velho — Wed, 14 Oct 2020 15:17:40 +0000

Disclaimer: I am in no way a professional. I'm just a student who has had the (un)fortunate experience of maintaining a mailinabox server. I thought i would share my experiences along the way so that i may save some time for those looking for it.
I've used DigitalOcean here , but similar steps can be followed with your cloud provider of choice.

I want to move Mail-in-a-box to another Digital Ocean account (The Shortcut, but not recommended)

If you have any important data, be sure to always keep a backup
Create a snapshot of your droplet (you can power off the droplet after the snapshot)
Change the owner of your snapshot, see this guide
Resume the transferred snapshot
Change the DNS records to point to the new droplet
Log into the web admin panel at /admin . If there are no errors, everything is good. If there are errors (red text), re-install Mail-in-a-box

How do i re-install Mail-in-a-box ? (Unofficial, however, this should work in most cases)

Delete the mailinabox directory commonly located at ~/mailinabox
Rename the /etc/nginx/conf.d/local.conf to /etc/nginx/conf.d/local.conf.deleted if you would want a copy - Rename the /etc/nginx/conf.d/ssl.conf to /etc/nginx/conf.d/ssl.conf.deleted if you want to keep a copy - Restart nginx systemctl reload nginx . - Run the installer from the official website and once its done, everything should continue to work as normal.

BCC-ing people: (credits namsnath )

BCC all mails sent to a given address:

nano /etc/postfix/main.cnf
add to the end: sender_bcc_maps = hash:/etc/postfix/sender_bcc_maps
nano /etc/postfix/sender_bcc_maps
Add lines in this format: <sender@email.com> <bcc@email.com>

BCC all mails recieved on a given address:

nano /etc/postfix/main.cnf
add to the end: recipient_bcc_maps = hash:/etc/postfix/recipient_bcc_maps
nano /etc/postfix/recipient_bcc_maps
Add lines in this format: <recipient@email.com> <bcc@email.com>

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