DEV Community: Franz Wong

Solving issue "The repository 'http://ports.ubuntu.com/ubuntu-ports noble-security InRelease' is not signed"

Franz Wong — Sat, 15 Mar 2025 08:30:24 +0000

Problem

When I create a docker image, the issue "The repository 'http://ports.ubuntu.com/ubuntu-ports noble-security InRelease' is not signed" appears.

The problem is a lack of storage space due to disk usage limit setting in Docker Desktop.

The error log:

RUN apt-get update && apt-get install -y     curl     && rm -rf /var/lib/apt/lists/*:                                    
0.807 Get:1 http://ports.ubuntu.com/ubuntu-ports noble InRelease [256 kB]                                                         
2.139 Err:1 http://ports.ubuntu.com/ubuntu-ports noble InRelease                                                                  
2.139   At least one invalid signature was encountered.                                                                           
2.390 Get:2 http://ports.ubuntu.com/ubuntu-ports noble-updates InRelease [126 kB]                                                 
2.463 Err:2 http://ports.ubuntu.com/ubuntu-ports noble-updates InRelease
2.463   At least one invalid signature was encountered.
2.696 Get:3 http://ports.ubuntu.com/ubuntu-ports noble-backports InRelease [126 kB]
2.798 Err:3 http://ports.ubuntu.com/ubuntu-ports noble-backports InRelease
2.798   At least one invalid signature was encountered.
3.005 Get:4 http://ports.ubuntu.com/ubuntu-ports noble-security InRelease [126 kB]
3.118 Err:4 http://ports.ubuntu.com/ubuntu-ports noble-security InRelease
3.118   At least one invalid signature was encountered.
3.120 Reading package lists...
3.124 W: GPG error: http://ports.ubuntu.com/ubuntu-ports noble InRelease: At least one invalid signature was encountered.
3.124 E: The repository 'http://ports.ubuntu.com/ubuntu-ports noble InRelease' is not signed.
3.124 W: GPG error: http://ports.ubuntu.com/ubuntu-ports noble-updates InRelease: At least one invalid signature was encountered.
3.124 E: The repository 'http://ports.ubuntu.com/ubuntu-ports noble-updates InRelease' is not signed.
3.124 W: GPG error: http://ports.ubuntu.com/ubuntu-ports noble-backports InRelease: At least one invalid signature was encountered.
3.124 E: The repository 'http://ports.ubuntu.com/ubuntu-ports noble-backports InRelease' is not signed.
3.124 W: GPG error: http://ports.ubuntu.com/ubuntu-ports noble-security InRelease: At least one invalid signature was encountered.
3.124 E: The repository 'http://ports.ubuntu.com/ubuntu-ports noble-security InRelease' is not signed.

Solution

Set the disk usage limit to a high value.

Write AI agent from scratch without LangChain and CrewAI

Franz Wong — Sun, 23 Feb 2025 05:12:27 +0000

We are going to create an AI agent which can perform timezone conversion with tools / function calling. Only openai library is used.

Full source code will be given at the end.

Set up

We only need to install openai library.

pip install openai

Define tools

We will define 2 tools. One is to get today's date and the other is to convert the timezone.

We also define tool_map which stores the details about the tools. The key of the map is the function name. prompt is the details we will send to LLM and function is the function we will call.

If your tools perform sensitive operations, you should verify or sanitize the parameters first.

def get_today_date(timezone):
    return datetime.datetime.now(ZoneInfo(timezone)).strftime("%Y-%m-%d")


def convert_timezone(source_timezone, target_timezone, year, month, day, hour, minute):
    dt = datetime.datetime(year, month, day, hour, minute, tzinfo=ZoneInfo(source_timezone))
    return dt.astimezone(ZoneInfo(target_timezone))

tool_map = {
    "get_today_date": {
        "prompt": """get_today_date(timezone)
e.g. get_today_date("Asia/Tokyo")
Description: Get the date of today.
""",
        "function": get_today_date,
    },
    "convert_timezone": {
        "prompt": """convert_timezone(source_timezone, target_timezone, year, month, day, hour, minute)
e.g. convert_timezone("Asia/Tokyo", "Europe/London" 2025, 2, 15, 13, 0)
Description: Convert time from source timezone to target timezone
""",
        "function": convert_timezone
    }
}

Define system prompt

We apply "ReAct Prompting" to enable act and reasoning abilities. This also allows us to use tools.

In order to make LLM stop generating after proposing an action, we ask it to output "PAUSE" text after an action.

system_prompt = f"""Answer the following questions as best you can. You have access to the following tools:

{"\n".join([tool["prompt"] for tool in tool_map.values()])}

If you need to use the tool, you MUST return PAUSE!!!! This is very IMPORTANT.

Use the following format:

Question: the input question you must answer
Thought: you should always think about what to do
Action: the action to take, should be one of [{", ".join(tool_map.keys())}]. This ONLY includes the name of the tool.
Action Input: the input to the action. This ONLY includes the parameters of the tool. Example: Action Input: a, "b", c
PAUSE
Observation: the result of the action
Thought: I now know the final answer
Final Answer: the final answer to the original input question

Begin!"""

Pseudocode of AI agent

Before we see the actual code of AI agent, we check the pseudocode first.

We have a loop to keep sending messages to LLM and performing actions.

messages = [system_prompt, question_prompt]

completion = chat(llm, messages)
add completion to messages with role 'assistant'

while 'Final Answer' is not in completion and maximum round is not reached:

  If 'Action' is not found in completion:
    continue
  action = parse_action(completion)

  If 'Action Input' is not in completion:
    continue
  action_input = parse_action_input(completion)

  result = action(acion_input)

  add result to messages with role 'assistant'

  completion = chat(llm, messages)
  add completion to messages with role 'assistant'

`chat` function

chat function is straight forward. It only creates chat completion with the messages we have.

Stop word "PAUSE" is used to make LLM stop generation after proposing an action.

def chat(client, messages) -> str:
    completion = client.chat.completions.create(messages=messages, model="gpt-4o", stop="PAUSE")
    completion_content = completion.choices[0].message.content
    print("Chat completion:")
    print(completion_content)
    return completion_content

`parse_action` function

We use regular expression to extract tool function name. Tool function will be returned. We also make sure tool function is defined in tool_map for security reason.

You can also change the system prompt to ask LLM returning JSON to ease parsing.

def parse_action(completion_content: str):
    action_pattern = r"Action: ([^\n]*)"
    match = re.search(action_pattern, completion_content)
    if not match:
        return None
    tool_name = match.group(1)
    if tool_name not in tool_map:
        raise ValueError(f"Tool '{tool_name}' does not exist")
    return tool_map[tool_name]

`parse_action_input` function

As same as parse_action, we use regular expression to extract parameters of tool.

def parse_action_input(completion_content: str):
    action_input_pattern = r"Action Input: ([^\n]*)"
    match = re.search(action_input_pattern, completion_content)
    if not match:
        return None
    args_string = match.group(1)
    return eval(f"({args_string},)")

AI agent main logic

Here is the implementaiton of the above pseudocode.

def main():
    client = OpenAI(api_key=os.environ.get("OPENAI_API_KEY"))

    question = "Convert 13:49 today in London time to Japan time. Please consider daylight saving."
    print(f"Question: {question}")

    messages = [{"role": "system", "content": system_prompt}, {"role": "user", "content": f"Question: {question}"}]

    completion_content = chat(client, messages)
    messages.append({"role": "assistant", "content": completion_content})

    current_round = 0
    max_round = 5

    while "Answer" not in completion_content and current_round < max_round:
        current_round += 1

        action = parse_action(completion_content)
        if action is None:
            continue

        action_input = parse_action_input(completion_content)
        if action_input is None:
            continue

        action_result = action["function"](*action_input)
        print(f"Action result: {action_result}")

        messages.append({"role": "assistant", "content": f"Observation: {action_result}"})

        completion_content = chat(client, messages)
        messages.append({"role": "assistant", "content": completion_content})


if __name__ == '__main__':
    main()

Sample result

Question: Convert 13:49 today in London time to Japan time. Please consider daylight saving.
Chat completion:
Thought: To accurately convert 13:49 London time to Japan time, it's important to consider the current date and whether daylight saving time is in effect. I'll first fetch the current date in the "Europe/London" timezone to understand if daylight saving time needs to be taken into account.
Action: get_today_date
Action Input: "Europe/London"

Action result: 2025-02-23
Chat completion:
Thought: Today is February 23, 2025. Daylight saving time in London typically starts on the last Sunday in March and ends on the last Sunday in October. Therefore, currently, London is on Greenwich Mean Time (GMT, UTC+0). Japan does not observe daylight saving time and is always on Japan Standard Time (JST, UTC+9). I will now convert 13:49 London time to Japan time for today.
Action: convert_timezone
Action Input: "Europe/London", "Asia/Tokyo", 2025, 2, 23, 13, 49

Action result: 2025-02-23 22:49:00+09:00
Chat completion:
Thought: I have successfully converted 13:49 London time to Japan time. The converted time is 22:49 on February 23, 2025.
Final Answer: 13:49 in London on February 23, 2025, is 22:49 in Japan time.

Full source code

import datetime
import os
import re
from zoneinfo import ZoneInfo

from openai import OpenAI


def get_today_date(timezone):
    return datetime.datetime.now(ZoneInfo(timezone)).strftime("%Y-%m-%d")


def convert_timezone(source_timezone, target_timezone, year, month, day, hour, minute):
    dt = datetime.datetime(year, month, day, hour, minute, tzinfo=ZoneInfo(source_timezone))
    return dt.astimezone(ZoneInfo(target_timezone))


tool_map = {
    "get_today_date": {
        "prompt": """get_today_date(timezone)
e.g. get_today_date("Asia/Tokyo")
Description: Get the date of today.
""",
        "function": get_today_date,
    },
    "convert_timezone": {
        "prompt": """convert_timezone(source_timezone, target_timezone, year, month, day, hour, minute)
e.g. convert_timezone("Asia/Tokyo", "Europe/London" 2025, 2, 15, 13, 0)
Description: Convert time from source timezone to target timezone
""",
        "function": convert_timezone
    }
}

system_prompt = f"""Answer the following questions as best you can. You have access to the following tools:

{"\n".join([tool["prompt"] for tool in tool_map.values()])}

If you need to use the tool, you MUST return PAUSE!!!! This is very IMPORTANT.

Use the following format:

Question: the input question you must answer
Thought: you should always think about what to do
Action: the action to take, should be one of [{", ".join(tool_map.keys())}]. This ONLY includes the name of the tool.
Action Input: the input to the action. This ONLY includes the parameters of the tool. Example: Action Input: a, "b", c
PAUSE
Observation: the result of the action
Thought: I now know the final answer
Final Answer: the final answer to the original input question

Begin!"""


def chat(client, messages) -> str:
    completion = client.chat.completions.create(messages=messages, model="gpt-4o", stop="PAUSE")
    completion_content = completion.choices[0].message.content
    print("Chat completion:")
    print(completion_content)
    return completion_content


def parse_action(completion_content: str):
    action_pattern = r"Action: ([^\n]*)"
    match = re.search(action_pattern, completion_content)
    if not match:
        return None
    tool_name = match.group(1)
    if tool_name not in tool_map:
        raise ValueError(f"Tool '{tool_name}' does not exist")
    return tool_map[tool_name]


def parse_action_input(completion_content: str):
    action_input_pattern = r"Action Input: ([^\n]*)"
    match = re.search(action_input_pattern, completion_content)
    if not match:
        return None
    args_string = match.group(1)
    return eval(f"({args_string},)")


def main():
    client = OpenAI(api_key=os.environ.get("OPENAI_API_KEY"))

    question = "Convert 13:49 today in London time to Japan time. Please consider daylight saving."
    print(f"Question: {question}")

    messages = [{"role": "system", "content": system_prompt}, {"role": "user", "content": f"Question: {question}"}]

    completion_content = chat(client, messages)
    messages.append({"role": "assistant", "content": completion_content})

    current_round = 0
    max_round = 5

    while "Final Answer" not in completion_content and current_round < max_round:
        current_round += 1

        action = parse_action(completion_content)
        if action is None:
            continue

        action_input = parse_action_input(completion_content)
        if action_input is None:
            continue

        action_result = action["function"](*action_input)
        print(f"Action result: {action_result}")

        messages.append({"role": "assistant", "content": f"Observation: {action_result}"})

        completion_content = chat(client, messages)
        messages.append({"role": "assistant", "content": completion_content})


if __name__ == '__main__':
    main()

Using Java Native Access (JNA) to call MacOS API

Franz Wong — Mon, 23 Sep 2024 06:30:39 +0000

Introduction

Here is a simple example about how to use JNA with MacOS API. I am not going to explain this, because I am still learning, but I keep code minimal to make it easier to understand and get the basic idea about how to do it for other purposes.

Most of the code is from Intellij-Community (Apache License).

Dependency

All we need is jna-platform.

<dependency>
  <groupId>net.java.dev.jna</groupId>
  <artifactId>jna-platform</artifactId>
  <version>5.13.0</version>
</dependency>

Code

There are totally 4 source code files. ID is copied from IntelliJ without modification. MyFoundation and MyFoundationLibrary are trimmed from Foundation and FoundationLibrary respectively.

Application.java

package org.example;

import com.sun.jna.Pointer;

import static org.example.MyFoundation.*;

public class Application {

    public static void main(String[] args) throws Exception {
        ID processInfoCls = getObjcClass("NSProcessInfo");
        Pointer processInfoSel = createSelector("processInfo");
        Pointer processNameSel = createSelector("processName");

        ID processInfo = invoke(processInfoCls, processInfoSel);
        ID processNameNSString = invoke(processInfo, processNameSel);
        String processName = toStringViaUTF8(processNameNSString);
        System.out.println(processName);
    }

}

ID.java

package org.example;

import com.sun.jna.NativeLong;

public final class ID extends NativeLong {

    public ID() {
    }

    public ID(long peer) {
        super(peer);
    }

    public static final ID NIL = new ID(0L);

    public boolean booleanValue() {
        return intValue() != 0;
    }
}

MyFoundationLibrary.java

public interface MyFoundationLibrary extends Library {

    int kCFStringEncodingUTF8 = 0x08000100;

    ID objc_getClass(String className);

    Pointer sel_registerName(String selectorName);

    int CFStringGetLength(ID theString);

    byte CFStringGetCString(ID theString, byte[] buffer, int bufferSize, int encoding);

}

MyFoundation.java

package org.example;

import com.sun.jna.*;

import java.lang.reflect.Proxy;
import java.util.Collections;

public class MyFoundation {
    private static final MyFoundationLibrary myFoundationLibrary;
    private static final Function myObjcMsgSend;

    static {
        myFoundationLibrary = Native.load("Foundation", MyFoundationLibrary.class, Collections.singletonMap("jna.encoding", "UTF8"));
        NativeLibrary nativeLibrary = ((Library.Handler) Proxy.getInvocationHandler(myFoundationLibrary)).getNativeLibrary();
        myObjcMsgSend = nativeLibrary.getFunction("objc_msgSend");
    }

    public static ID getObjcClass(String className) {
        return myFoundationLibrary.objc_getClass(className);
    }

    public static Pointer createSelector(String s) {
        return myFoundationLibrary.sel_registerName(s);
    }

    private static Object [] prepInvoke(ID id, Pointer selector, Object[] args) {
        Object[] invokArgs = new Object[args.length + 2];
        invokArgs[0] = id;
        invokArgs[1] = selector;
        System.arraycopy(args, 0, invokArgs, 2, args.length);
        return invokArgs;
    }

    public static ID invoke(final ID id, final Pointer selector, Object... args) {
        // objc_msgSend is called with the calling convention of the target method
        // on x86_64 this does not make a difference, but arm64 uses a different calling convention for varargs
        // it is therefore important to not call objc_msgSend as a vararg function
        return new ID(myObjcMsgSend.invokeLong(prepInvoke(id, selector, args)));
    }

    public static String toStringViaUTF8(ID cfString) {
        if (ID.NIL.equals(cfString)) return null;

        int lengthInChars = myFoundationLibrary.CFStringGetLength(cfString);
        int potentialLengthInBytes = 3 * lengthInChars + 1; // UTF8 fully escaped 16 bit chars, plus nul

        byte[] buffer = new byte[potentialLengthInBytes];
        byte ok = myFoundationLibrary.CFStringGetCString(cfString, buffer, buffer.length, MyFoundationLibrary.kCFStringEncodingUTF8);
        if (ok == 0) throw new RuntimeException("Could not convert string");
        return Native.toString(buffer);
    }

}

Install pip offline

Franz Wong — Sat, 24 Aug 2024 05:09:08 +0000

Download necessary files

Do the following with a computer WITH internet access

Download get-pip.py from https://bootstrap.pypa.io/get-pip.py
Download wheel (.whl files) from pypi to local machine
pip: https://pypi.org/project/pip/#files
setuptools: https://pypi.org/project/setuptools/#files
wheel: https://pypi.org/project/wheel/#files
Copy get-pip.py and wheel files to the computer without internet access

Install pip

Do the following with a computer WITHOUT internet access

Run the following command

python get-pip.py —no-index —find-links=<directory containing wheel files>

Example:

python get-pip.py —no-index —find-links=/Users/foo/Downloads

Fix "Cannot find a valid baseurl for repo" in CentOS

Franz Wong — Mon, 05 Aug 2024 02:25:24 +0000

Background

Since CentOS 7 has reached EOL, the mirror is moved to vault. When yum is executed, it will return an error "Cannot find a valid baseurl for repo: base/7/x86_64".

Solution

We need to update CentOS-Base.repo in /etc/yum.repos.d/CentOS-Base.repo.

Uncomment the lines starting with baseurl.
Update all http://mirrorlist.centos.org to http://vault.centos.org.
Update all http://mirror.centos.org to http://vault.centos.org.
We can clear the cache with sudo yum clean all.

Commands:

repo_file=/etc/yum.repos.d/CentOS-Base.repo
cp ${repo_file} ~/CentOS-Base.repo.backup
sudo sed -i s/#baseurl/baseurl/ ${repo_file}
sudo sed -i s/mirrorlist.centos.org/vault.centos.org/ ${repo_file}
sudo sed -i s/mirror.centos.org/vault.centos.org/ ${repo_file}
sudo yum clean all

This is how the file looks like.

# CentOS-Base.repo
#
# The mirror system uses the connecting IP address of the client and the
# update status of each mirror to pick mirrors that are updated to and
# geographically close to the client.  You should use this for CentOS updates
# unless you are manually picking other mirrors.
#
# If the mirrorlist= does not work for you, as a fall back you can try the 
# remarked out baseurl= line instead.
#
#

[base]
name=CentOS-$releasever - Base
mirrorlist=http://vault.centos.org/?release=$releasever&arch=$basearch&repo=os&infra=$infra
baseurl=http://vault.centos.org/centos/$releasever/os/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7

#released updates 
[updates]
name=CentOS-$releasever - Updates
mirrorlist=http://vault.centos.org/?release=$releasever&arch=$basearch&repo=updates&infra=$infra
baseurl=http://vault.centos.org/centos/$releasever/updates/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7

#additional packages that may be useful
[extras]
name=CentOS-$releasever - Extras
mirrorlist=http://vault.centos.org/?release=$releasever&arch=$basearch&repo=extras&infra=$infra
baseurl=http://vault.centos.org/centos/$releasever/extras/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7

#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-$releasever - Plus
mirrorlist=http://vault.centos.org/?release=$releasever&arch=$basearch&repo=centosplus&infra=$infra
baseurl=http://vault.centos.org/centos/$releasever/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7

Mount share folder in QEMU with same permission as host

Franz Wong — Sun, 14 Jul 2024 04:15:32 +0000

Background

I would like to share a folder between guest and host in QEMU. File permission should be the same as the user in host.

Solution

1. Create a folder called shared in host

mkdir -p shared

2. Add a parameter virtfs when starting VM with QEMU

-virtfs local,path=shared,mount_tag=shared,security_model=mapped-xattr

3. After the VM is started, login to the VM and create mount point

mkdir -p /mnt/shared

4. Mount the folder

sudo mount -t 9p -o trans=virtio,version=9p2000.L shared /mnt/shared

5. Check the permission of mount point

ls -l -d /mnt/shared

It should be something like the following. On my host machine, my user ID is 501 and primary group ID is 20. (It's common setting in MacOS). In the guest VM, the group with ID 20 is called dialout. (You can check in /etc/group).

drwxr-xr-x 3 501 dialout 96 Jul 14 03:44 /mnt/shared

However, my user in guest VM has uid 1000 and the primary group id is 1000 too. We need to make a mapping.

id
uid=1000(franz) gid=1000(dev_users) groups=1000(dev_users),27(sudo)

6. Install bindfs in guest VM

sudo apt install -y bindfs

7. Create the mapping

sudo bindfs --map=501/1000:@dialout/@1000 /mnt/shared /mnt/shared

8. Check the permission of mount point again

ls -l -d /mnt/shared

This time the permission is correct.

drwxr-xr-x 3 franz dev_users 96 Jul 14 03:44 /mnt/shared

Or you can make it as a systemd service (.service). Because the mount point is duplicated, we can't create systemd mount (.mount).

1. Create a file /etc/systemd/system/bindfs_mnt_shared.service

[Unit]
Description=Map uid and gid of /mnt/shared with bindfs
Requires=mnt-shared.mount

[Service]
Type=forking
ExecStart=bindfs --map=501/1000:@20/@1000 /mnt/shared /mnt/shared

[Install]
WantedBy=multi-user.target

2. Start and enable it.

sudo systemctl daemon-reload
sudo systemctl start bindfs_mnt_shared.service
sudo systemctl enable bindfs_mnt_shared.service

References:
9p/virtfs share not writable

Lots of debug log is written after commons-logging is upgraded to 1.3.0

Franz Wong — Tue, 09 Apr 2024 09:31:59 +0000

Background

The default log level of our applications is DEBUG because we aim to separate informative logs from diagnostic logs.

Recently, we received a vulnerability warning from commons-configuration2, prompting us to update the version. After the update, the application runs fine; however, the size of our log has grown from hundreds of kilobytes to a few gigabytes.

Investigation

The update of commons-configuration2 also upgraded commons-logging to version 1.3.0, which includes log4j-jcl. Previously, log4j-jcl was a standalone dependency. Now, all dependencies in our application (mainly commons-beanutils) are capable of writing logs through log4j loggers.

Solution

We modified log4j2.xml to suppress the excessive logging by package. In the long term, we may need to introduce a custom log level between INFO and DEBUG as our default log level; and have a fine grained logging configuration.

Create and delete Digital Ocean droplet with curl

Franz Wong — Sat, 23 Sep 2023 09:46:30 +0000

Assumed you have already get the Digital Ocean API key and SSH key.

digitalocean_token="<your API key>"
ssh_key="<your ssh key fingerprint>"

Create a droplet

Let's create a droplet. You can find values of available regions, size, distro images from https://slugs.do-api.dev/

droplet_name="<your droplet name>"

region="nyc1"
size="s-1vcpu-512mb-10gb"
image="ubuntu-22-04-x64"

# Create droplet
curl -s -X POST \
-H "Content-Type: application/json" \
-H "Authorization: Bearer ${digitalocean_token}" \
-d '{"name":"'"${droplet_name}"'","region":"'"${region}"'","size":"'"${size}"'","image":"'"${image}"'","ssh_keys":["'"${ssh_key}"'"],"backups":false,"ipv6":false,"monitoring":false}' \
"https://api.digitalocean.com/v2/droplets"

Get droplet status

We can get the status and wait until it becomes active.

curl -s -X GET \
-H "Content-Type: application/json" \
-H "Authorization: Bearer ${digitalocean_token}" \
"https://api.digitalocean.com/v2/droplets?name=${droplet_name}" | jq -r '.droplets[].status'

Get the IP address

After it is provisioned, we can get the public IP address.

droplet_ip=$(curl -s -X GET \
-H "Content-Type: application/json" \
-H "Authorization: Bearer ${digitalocean_token}" \
"https://api.digitalocean.com/v2/droplets?name=${droplet_name}" | jq -r '.droplets[].networks.v4[] | select(.type == "public") | .ip_address')

# Login to droplet
ssh -i "${your_ssh_key_path}" root@${droplet_ip}

Delete droplet

After we've done with the droplet, delete it to prevent from charging money.

# Get droplet id
droplet_id=$(curl -s -X GET \
-H "Content-Type: application/json" \
-H "Authorization: Bearer ${digitalocean_token}" \
"https://api.digitalocean.com/v2/droplets?name=${droplet_name}" | jq -r '.droplets[].id')

# Delete droplet
curl -s -X DELETE \
-H "Content-Type: application/json" \
-H "Authorization: Bearer ${digitalocean_token}" \
"https://api.digitalocean.com/v2/droplets/${droplet_id}"

# It should return no droplet details if it is deleted
curl -s -X GET \
-H "Content-Type: application/json" \
-H "Authorization: Bearer ${digitalocean_token}" \
"https://api.digitalocean.com/v2/droplets?name=${droplet_name}"

Add a Context Menu Item to Chrome Extension

Franz Wong — Fri, 31 Mar 2023 07:53:15 +0000

I tried adding a context menu item. But I failed to do that at first time.

The code itself is simple.

chrome.contextMenus.create({
  id: 'my_menu_item',
  title: 'Click me',
  contexts: ['selection']
});
chrome.contextMenus.onClicked.addListener((info, tab) => {
  if (info.menuItemId === 'my_menu_item') {
    console.log('hello');
  }
});

The first question is where I should put it.

I should put it in background script. I added a background script to manifest.json. (I am using v3.) Of course, I should also give it permission to change context menu.

"permissions": ["contextMenus"],
"background": {
  "service_worker": "background.js"
}

I put the code to background.js and reload it. Now it shows an error.

Unchecked runtime.lastError: Cannot create item with duplicate id my_menu_item

I should add it once. But how? It turns out that I should put it in the runtime's installed event listener.

chrome.runtime.onInstalled.addListener(() => {
  chrome.contextMenus.create({
    id: 'my_menu_item',
    title: 'Click me',
    contexts: ['selection']
  });
});
chrome.contextMenus.onClicked.addListener((info, tab) => {
  if (info.menuItemId === 'my_menu_item') {
    console.log('hello');
  }
});

Now the context menu works as expected.

One last thing, there is another problem I encountered when I worked on a extension. We can't add the installed event listener in asynchronous way. The event is not caught.

The following doesn't work.

(async() {
  chrome.runtime.onInstalled.addListener(() => {
    chrome.contextMenus.create({
      id: 'my_menu_item',
      title: 'Click me',
      contexts: ['selection']
    });
  });
})();

ZonedDateTime and toLocalDate / toLocalTime

Franz Wong — Thu, 09 Feb 2023 10:14:47 +0000

I need to deal with New York, London and Tokyo time zone in the same application. Some time it is quite difficult to manage.

This is how I convert ZonedDateTime to LocalDate. In functionOne, you can't guarantee the timezone of parameter dateTime is the one you expect. Before you convert to LocalDate, you always need to change the timezone first.

void functionOne(ZonedDateTime dateTime) {
    var date = dateTime.withZoneSameInstance(londonZoneId).toLocalDate();
    // use the date
}

If they provide a function ZonedDateTime.toLocalDate(ZoneId zoneId), it would be less error prone I think. It can force people to provide a ZoneId when they get the LocalDate.

This is another solution I can think of. We create a date time type for each timezone.

class LondonDateTime {
  private final ZonedDateTime dateTime;

  public LondonDateTime(ZonedDateTime dateTime) {
    this.dateTime = dateTime.withZoneSameInstance(londonZoneId);
  }

  public ZonedDateTime getDateTime() { return dateTime; }

  public LocalDate getLocalDate() { return dateTime.getLocalDate(); }
}

void functionTwo(LondonDateTime dateTime) {
  var date1 = dateTime.getDateTime().toLocalDate();
  // or 
  var date2 = dateTime.toLocalDate();
}

Runtime check on borrowing rule with RefCell

Franz Wong — Sat, 24 Dec 2022 02:39:54 +0000

Rust does compile time check on borrowing rule. But there are some scenarios we need to defer it to runtime. Let me show a simplified version from one of the examples in the book

We have a trait with one method. No change on internal states is allowed inside this method. (&self is used instead of &mut self)

pub trait Messenger {
    fn send(&self, msg: &str);
}

What if we want to store the messages sent? (e.g. it's common when we create a mock object for testing) It means we need to change the internal states. For some reasons (e.g. it is from 3rd party), we can't modify this trait, so we can't change to &mut self. Anyway, let's do it first and see what will happen.

struct MyMessenger {
    messages: Vec<String>
}

impl MyMessenger {
    fn new() -> MyMessenger {
        MyMessenger { messages: vec![] }
    }
}

impl Messenger for MyMessenger {
    fn send(&self, msg: &str) {
        self.messages.push(String::from(msg));
    }
}

On the line push method is called, the compiler complains.

cannot borrow `self.messages` as mutable, as it is behind a `&` reference

`self` is a `&` reference, so the data it refers to cannot be borrowed as mutablerustcClick for full compiler diagnostic

main.rs(2, 13): consider changing that to be a mutable reference: `&mut self`

We want to make it passes the compilation. Let's rewrite it with RefCell.

use std::cell::RefCell;

struct MyMessenger {
    messages: RefCell<Vec<String>>
}

impl MyMessenger {
    fn new() -> MyMessenger {
        MyMessenger { messages: RefCell::new(vec![]) }
    }
}

impl Messenger for MyMessenger {
    fn send(&self, msg: &str) {
        self.messages.borrow_mut().push(String::from(msg));
    }
}

We use borrow_mut to borrow a mutable value. Compilation passes this time.

The borrowing rule is still checked in runtime. Runtime error will occur if we do this.

(This violates the rule "At any given time, we can have either one mutable reference or any number of immutable references".)

let x = RefCell::new(String::from("Hello World"));
let y = x.borrow_mut();
let z = x.borrow(); // Error occurs here in runtime

Mock S3 for integration test

Franz Wong — Sun, 07 Aug 2022 03:50:54 +0000

Although we can use S3 mock library (e.g. adobe/S3Mock), sometimes we just want to make thing simple.

The full source code is put at the end of this page.

Add 3rd party dependencies

Undertow is used as S3 mock server. AWS SDK v2 is used for S3 client.

<dependency>
    <groupId>io.undertow</groupId>
    <artifactId>undertow-core</artifactId>
    <version>2.2.17.Final</version>
    <scope>test</scope>
</dependency>
<dependency>
    <groupId>software.amazon.awssdk</groupId>
    <artifactId>s3</artifactId>
    <version>2.17.247</version>
    <scope>test</scope>
</dependency>
<dependency>
    <groupId>software.amazon.awssdk</groupId>
    <artifactId>url-connection-client</artifactId>
    <version>2.17.247</version>
    <scope>test</scope>
</dependency>
<dependency>
    <groupId>org.junit.jupiter</groupId>
    <artifactId>junit-jupiter</artifactId>
    <version>5.9.0</version>
    <scope>test</scope>
</dependency>

Create S3 mock server

First we create a HttpHandler. It will return the content of S3 object.

static class S3HttpHandler implements HttpHandler {

    @Override
    public void handleRequest(HttpServerExchange exchange) throws Exception {
        if (exchange.isInIoThread()) {
            exchange.dispatch(this);
            return;
        }

        System.out.printf("Request method: %s%n", exchange.getRequestMethod());
        System.out.printf("Request path: %s%n", exchange.getRequestPath());

        try (BlockingHttpExchange blockingExchange = exchange.startBlocking();
             OutputStream outputStream = exchange.getOutputStream();
             OutputStreamWriter outputStreamWriter = new OutputStreamWriter(outputStream);
             BufferedWriter writer = new BufferedWriter(outputStreamWriter)) {

            writer.write("Hello world");
        }
    }

}

Then we start the mock server with our HttpHandler.

final int S3_MOCK_SERVER_PORT = 9999;

Undertow s3Server = Undertow.builder()
    .addHttpListener(S3_MOCK_SERVER_PORT, "0.0.0.0")
    .setHandler(new S3HttpHandler())
    .build();
s3Server.start();

Don't forget to stop our server at the end.

s3Server.stop();

Setup S3 client

We need to create a S3Client with the service endpoint pointing to our S3 mock server.

String serviceEndpoint = String.format("http://localhost:%d", S3_MOCK_SERVER_PORT);

try (S3Client s3Client = S3Client.builder()
    .endpointOverride(URI.create(serviceEndpoint))
    .httpClient(UrlConnectionHttpClient.builder().build())
    .build()) {

}

Send a request to the mock server.

GetObjectRequest request = GetObjectRequest.builder()
    .bucket("my-bucket")
    .key("my-object")
    .build();

Path targetPath = tempDir.resolve("result");

s3Client.getObject(request, targetPath);

String objectContent = Files.readString(targetPath);
System.out.printf("Object content: %s%n", objectContent);
assertEquals("Hello world", objectContent);

Full source code

public class S3IntegrationTest {

    @Test
    public void shouldReturnS3Object(@TempDir Path tempDir) throws Exception {
        final int S3_MOCK_SERVER_PORT = 9999;

        Undertow s3Server = Undertow.builder()
            .addHttpListener(S3_MOCK_SERVER_PORT, "0.0.0.0")
            .setHandler(new S3HttpHandler())
            .build();

        s3Server.start();

        String serviceEndpoint = String.format("http://localhost:%d", S3_MOCK_SERVER_PORT);

        try (S3Client s3Client = S3Client.builder()
            .endpointOverride(URI.create(serviceEndpoint))
            .httpClient(UrlConnectionHttpClient.builder().build())
            .build()) {

            GetObjectRequest request = GetObjectRequest.builder()
                .bucket("my-bucket")
                .key("my-object")
                .build();

            Path targetPath = tempDir.resolve("result");

            s3Client.getObject(request, targetPath);

            String objectContent = Files.readString(targetPath);
            System.out.printf("Object content: %s%n", objectContent);
            assertEquals("Hello world", objectContent);
        }

        s3Server.stop();
    }

    static class S3HttpHandler implements HttpHandler {

        @Override
        public void handleRequest(HttpServerExchange exchange) throws Exception {
            if (exchange.isInIoThread()) {
                exchange.dispatch(this);
                return;
            }

            System.out.printf("Request method: %s%n", exchange.getRequestMethod());
            System.out.printf("Request path: %s%n", exchange.getRequestPath());

            try (BlockingHttpExchange blockingExchange = exchange.startBlocking();
                 OutputStream outputStream = exchange.getOutputStream();
                 OutputStreamWriter outputStreamWriter = new OutputStreamWriter(outputStream);
                 BufferedWriter writer = new BufferedWriter(outputStreamWriter)) {

                writer.write("Hello world");
            }
        }

    }

}

DEV Community: Franz Wong

Solving issue "The repository 'http://ports.ubuntu.com/ubuntu-ports noble-security InRelease' is not signed"

Problem

Solution

Write AI agent from scratch without LangChain and CrewAI

Set up

Define tools

Define system prompt

Pseudocode of AI agent

chat function

parse_action function

parse_action_input function

AI agent main logic

Sample result

Full source code

Using Java Native Access (JNA) to call MacOS API

Introduction

Dependency

Code

Application.java

ID.java

MyFoundationLibrary.java

MyFoundation.java

Install pip offline

Download necessary files

Install pip

Fix "Cannot find a valid baseurl for repo" in CentOS

Background

Solution

Mount share folder in QEMU with same permission as host

Background

Solution

Lots of debug log is written after commons-logging is upgraded to 1.3.0

Background

Investigation

Solution

Create and delete Digital Ocean droplet with curl

Create a droplet

Get droplet status

Get the IP address

Delete droplet

Add a Context Menu Item to Chrome Extension

ZonedDateTime and toLocalDate / toLocalTime

Runtime check on borrowing rule with RefCell

Mock S3 for integration test

Add 3rd party dependencies

Create S3 mock server

Setup S3 client

Full source code

`chat` function

`parse_action` function

`parse_action_input` function