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In-reply-to » Progress! so i have moved into working on aggregates. Which are a grouping of events that replayed on an object set the current state of the object. I came up with this little bit of generic wonder.

(cont.)

Just to give some context on some of the components around the code structure.. I wrote this up around an earlier version of aggregate code. This generic bit simplifies things by removing the need of the Crud functions for each aggregate.

Domain Objects

A domain object can be used as an aggregate by adding the event.AggregateRoot struct and finish implementing event.Aggregate. The AggregateRoot implements logic for adding events after they are either Raised by a command or Appended by the eventstore Load or service ApplyFn methods. It also tracks the uncommitted events that are saved using the eventstore Save method.

type User struct {
  Identity string ```json:"identity"`

  CreatedAt time.Time

  event.AggregateRoot
}

// StreamID for the aggregate when stored or loaded from ES.
func (a *User) StreamID() string {
	return "user-" + a.Identity
}
// ApplyEvent to the aggregate state.
func (a *User) ApplyEvent(lis ...event.Event) {
	for _, e := range lis {
		switch e := e.(type) {
		case *UserCreated:
			a.Identity = e.Identity
			a.CreatedAt = e.EventMeta().CreatedDate
        /* ... */
		}
	}
}
Events

Events are applied to the aggregate. They are defined by adding the event.Meta and implementing the getter/setters for event.Event

type UserCreated struct {
	eventMeta event.Meta

	Identity string
}

func (c *UserCreated) EventMeta() (m event.Meta) {
	if c != nil {
		m = c.eventMeta
	}
	return m
}
func (c *UserCreated) SetEventMeta(m event.Meta) {
	if c != nil {
		c.eventMeta = m
	}
}
Reading Events from EventStore

With a domain object that implements the event.Aggregate the event store client can load events and apply them using the Load(ctx, agg) method.

// GetUser populates an user from event store.
func (rw *User) GetUser(ctx context.Context, userID string) (*domain.User, error) {
	user := &domain.User{Identity: userID}

	err := rw.es.Load(ctx, user)
	if err != nil {
		if err != nil {
			if errors.Is(err, eventstore.ErrStreamNotFound) {
				return user, ErrNotFound
			}
			return user, err
		}
		return nil, err
	}
	return user, err
}
OnX Commands

An OnX command will validate the state of the domain object can have the command performed on it. If it can be applied it raises the event using event.Raise() Otherwise it returns an error.

// OnCreate raises an UserCreated event to create the user.
// Note: The handler will check that the user does not already exsist.
func (a *User) OnCreate(identity string) error {
    event.Raise(a, &UserCreated{Identity: identity})
    return nil
}

// OnScored will attempt to score a task.
// If the task is not in a Created state it will fail.
func (a *Task) OnScored(taskID string, score int64, attributes Attributes) error {
	if a.State != TaskStateCreated {
		return fmt.Errorf("task expected created, got %s", a.State)
	}
	event.Raise(a, &TaskScored{TaskID: taskID, Attributes: attributes, Score: score})
	return nil
}
Crud Operations for OnX Commands

The following functions in the aggregate service can be used to perform creation and updating of aggregates. The Update function will ensure the aggregate exists, where the Create is intended for non-existent aggregates. These can probably be combined into one function.

// Create is used when the stream does not yet exist.
func (rw *User) Create(
  ctx context.Context,
  identity string,
  fn func(*domain.User) error,
) (*domain.User, error) {
	session, err := rw.GetUser(ctx, identity)
	if err != nil && !errors.Is(err, ErrNotFound) {
		return nil, err
	}

	if err = fn(session); err != nil {
		return nil, err
	}

	_, err = rw.es.Save(ctx, session)

	return session, err
}

// Update is used when the stream already exists.
func (rw *User) Update(
  ctx context.Context,
  identity string,
  fn func(*domain.User) error,
) (*domain.User, error) {
	session, err := rw.GetUser(ctx, identity)
	if err != nil {
		return nil, err
	}

	if err = fn(session); err != nil {
		return nil, err
	}

	_, err = rw.es.Save(ctx, session)
	return session, err
}

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@prologic@twtxt.net

#!/bin/sh

# Validate environment
if ! command -v msgbus > /dev/null; then
    printf "missing msgbus command. Use:  go install git.mills.io/prologic/msgbus/cmd/msgbus@latest"
    exit 1
fi

if ! command -v salty > /dev/null; then
    printf "missing salty command. Use:  go install go.mills.io/salty/cmd/salty@latest"
    exit 1
fi

if ! command -v salty-keygen > /dev/null; then
    printf "missing salty-keygen command. Use:  go install go.mills.io/salty/cmd/salty-keygen@latest"
    exit 1
fi

if [ -z "$SALTY_IDENTITY" ]; then
    export SALTY_IDENTITY="$HOME/.config/salty/$USER.key"
fi

get_user () {
    user=$(grep user: "$SALTY_IDENTITY" | awk '{print $3}')
    if [ -z "$user" ]; then
        user="$USER"
    fi
    echo "$user"
}

stream () {
    if [ -z "$SALTY_IDENTITY" ]; then
        echo "SALTY_IDENTITY not set"
        exit 2
    fi

    jq -r '.payload' | base64 -d | salty -i "$SALTY_IDENTITY" -d
}

lookup () {
    if [ $# -lt 1 ]; then
    printf "Usage: %s nick@domain\n" "$(basename "$0")"
    exit 1
    fi

    user="$1"
    nick="$(echo "$user" | awk -F@ '{ print $1 }')"
    domain="$(echo "$user" | awk -F@ '{ print $2 }')"

    curl -qsSL "https://$domain/.well-known/salty/${nick}.json"
}

readmsgs () {
    topic="$1"

    if [ -z "$topic" ]; then
        topic=$(get_user)
    fi

    export SALTY_IDENTITY="$HOME/.config/salty/$topic.key"
    if [ ! -f "$SALTY_IDENTITY" ]; then
        echo "identity file missing for user $topic" >&2
        exit 1
    fi

    msgbus sub "$topic" "$0"
}

sendmsg () {
    if [ $# -lt 2 ]; then
        printf "Usage: %s nick@domain.tld <message>\n" "$(basename "$0")"
        exit 0
    fi

    if [ -z "$SALTY_IDENTITY" ]; then
        echo "SALTY_IDENTITY not set"
        exit 2
    fi

    user="$1"
    message="$2"

    salty_json="$(mktemp /tmp/salty.XXXXXX)"

    lookup "$user" > "$salty_json"

    endpoint="$(jq -r '.endpoint' < "$salty_json")"
    topic="$(jq -r '.topic' < "$salty_json")"
    key="$(jq -r '.key' < "$salty_json")"

    rm "$salty_json"

    message="[$(date +%FT%TZ)] <$(get_user)> $message"

    echo "$message" \
        | salty -i "$SALTY_IDENTITY" -r "$key" \
        | msgbus -u "$endpoint" pub "$topic"
}

make_user () {
    mkdir -p "$HOME/.config/salty"

    if [ $# -lt 1 ]; then
        user=$USER
    else
        user=$1
    fi

    identity_file="$HOME/.config/salty/$user.key"

    if [ -f "$identity_file" ]; then
        printf "user key exists!"
        exit 1
    fi

    # Check for msgbus env.. probably can make it fallback to looking for a config file?
    if [ -z "$MSGBUS_URI" ]; then
        printf "missing MSGBUS_URI in environment"
        exit 1
    fi


    salty-keygen -o "$identity_file"
    echo "# user: $user" >> "$identity_file"

    pubkey=$(grep key: "$identity_file" | awk '{print $4}')

    cat <<- EOF
Create this file in your webserver well-known folder. https://hostname.tld/.well-known/salty/$user.json

{
  "endpoint": "$MSGBUS_URI",
  "topic": "$user",
  "key": "$pubkey"
}

EOF
}

# check if streaming
if [ ! -t 1 ]; then
    stream
    exit 0
fi

# Show Help
if [ $# -lt 1 ]; then
    printf "Commands: send read lookup"
    exit 0
fi


CMD=$1
shift

case $CMD in
    send)
        sendmsg "$@"
    ;;
    read)
        readmsgs "$@"
    ;;
    lookup)
        lookup "$@"
    ;;
    make-user)
        make_user "$@"
    ;;
esac

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The updated plugin should become available for download in your Openfire admin console in the course of the next few hours. Alternative … ⌘ Read more

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oliviersm199/Tweet-Generator

Image

The Tweet Generator uses a Markov chain to generate random tweet based off of past tweets. It uses Python and the Twitter API to obtain the last 200 tweets from a particular user, organizes them into a JSON tree structure and then executes a random walk on that tree structure. This results in sometimes hilarious sometimes nonsense tweets that mimic the Twitter user’s past tweets.

Language: Py … ⌘ Read more

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大家好,我是渔夫子。

工欲善其事,必先利其器。今天我们讲解 Goland 是如何高效的处理 json 的。

01 将 json 直接转换成结构体

首先我们有一个段 json 格式的数据如下,看下 Goland 是如何快捷的转换成结构体的。

”`
{

</span><span class="nl">"email"</span><span class="p">:</span><span class="w"> </span><span class="s2">"noah.poulsen@example.com"</sp ... ⌘ [Read more](https://gocn.vip/topics/20923)```

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[WIP] Query any data source using SQL, building Presto or AWS Athena alternative
xyr is a very lightweight, simple, and powerful data ETL platform that helps you to query available data sources using SQL.

Use Cases
  • Simple Presto Alternative.
  • Simple AWS Athena Alternative.
  • Convert your JSON documents into a SQL DB.
  • Query your CSV files easily and join them with other data.
How does it work?

internaly xyr utilizes SQLite as an embeded sql datastore (it may be changed in future and we c … ⌘ Read more

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I agree clients should present things better (part of why I’m writing one!). But that should be additive. There’s a reason we’re not passing json around.

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