Express postgres


  • Build a Simple REST API with Node and Postgres
  • Node.js, Express.js, and PostgreSQL: CRUD REST API example
  • Creating a REST API Backend using Node.js, Express and Postgres
  • Getting Started With Express, VueJS & PostgreSQL
  • NodeJs Express PostgreSQL Tutorial (Part 1)
  • Dockerizing a Node.js Web Application
  • What is the game PostgreSQL distributed architecture?
  • Build a Simple REST API with Node and Postgres

    Create an empty repository to host your code: Go to GitHub and sign up. Use the New button under Repositories to create a new repository. In Add. Create the repository. Make sure to run npm install so that npm can get all of your Node.

    Configuring the Database All person routes require a database to store the data. Create a file called database. The model has only two fields: firstName and lastName, you can add more fields if you feel like experimenting. Check the sequelize model doc for more details. Delete the person. We only need to add the new routes to the main file: app.

    Add the persons router object to the application near to the other app. You would be correct, Docker is everywhere. Find platform-specific steps on the Mac page and the Windows page. In Linux: most distributions include modern versions of Docker in its repositories. For more details, consult the installation page. But Docker can do much more; it can create portable images so others can run our software. There are many ways to use Docker, but one of the most useful is through the creation of Dockerfiles.

    These are files that essentially give build instructions to Docker when you build a container image. This is where the magic happens. To get started, we need to choose which base image to pull from.

    RUN: executes commands inside the container. USER: changes the active user for the rest of the commands. CMD: defines the command to run when the container starts. Every time a command is executed, it acts as a sort of git commit-like action in that it takes the current image, executes commands on top of it, and then returns a new image with the committed changes.

    This creates a build process that has high granularity—any point in the build phases should be a valid image—and lets us think of the build more atomically where each step is self-contained. This part is crucial for understanding how to speed up our container builds. Since Docker will intelligently cache files between incremental builds, the further down the pipeline we can move build steps, the better.

    Create a file called. This will happen even if the PostgreSQL container is running. This shows an interesting property of containers: they get their own network stack.

    The application, by default, tries to find the database in localhost, but technically, the database is in a different host. Even though all containers are running on the same machine, each container is its own localhost, so the application fails to connect. Docker Compose Docker Compose is a tool for managing multi-container applications. On Linux, it has to be installed separately, check the installation page for details Docker Compose can: Start and stop multiple containers in sequence. Connect containers using a virtual network.

    Handle persistence of data using Docker Volumes. Set environment variables. Build or download container images as required. Create a file called docker-compose. The Hub is a free service provided by Docker to store images on the cloud: Go to Docker Hub and get a free account. Go to Semaphore and sign up using the Sign up with GitHub button. Use your GitHub account to log in.

    Semaphore will be able to push the images to the registry on your behalf. Pipelines are made of blocks that are executed from left to right. Agent: The agent is the virtual machine that powers the pipeline. We have three machine types to choose from. The machine runs an optimized Ubuntu Block: blocks group jobs with a similar purpose. Jobs in a block are executed in parallel and have similar commands and configurations.

    Once all jobs in a block complete, the next block begins. Job: jobs define the commands that do the work. They inherit their configuration from their parent block. Before continuing, we can do a trial run: Click on Run the Workflow on the top-right corner. Select the master branch. Click on Start. The starter CI pipeline builds the image for us. But before we can use it, we have to modify the pipeline: Click on Edit Workflow on the top-right corner. Click on the Build block. If a previous image was pulled, Docker can speed up the build process with layer caching.

    As a result, each new image overwrites the previous one. Once the build process is complete, you should find the image on Docker Hub: Testing the Image An effective CI pipeline will not only build the image but test it. Semaphore maintains a Docker registry with popular base images. Click on Edit Workflow. Semaphore is building and testing the image on each update.

    For an example of using a reverse proxy, check our Ruby on Rails tutorial. Add more tests: you can put all kinds of tests into the CI pipeline for better quality control. Add a deployment pipeline: once you decide you want to release your application, you can add more pipelines to your workflow so it automatically deploys to your platform of choice.

    Dockerizing the application is the first step towards portable deployments. The next thing is to decide where we want to run it. There are many alternatives: Self-hosted: run the containers in your server.

    PaaS: run the containers directly on a Platform as a Service provider such as Heroku. Orchestration: run the application with an orchestrator such as Docker Swarm or Kubernetes. Check these tutorials to learn how you can deploy your application: More about deploying to Kubernetes:.

    Node.js, Express.js, and PostgreSQL: CRUD REST API example

    The NodeJs express web application is a simple framework that allows for the easy creation of mobile and web applications using just a few lines of code. Once set up, the app will be able to query data using the NodeJs JavaScript runtime environment, the pg Postgres client module and the Express framework library.

    A Postgres database and an existing table holding some records. Create a project directory for the NodeJs Express application Create a directory for the web app project using mkdir in a terminal. Enter the directory with the cd command followed by the folder name. Once inside the project directory, create a new JavaScript file.

    Use the Node Package Manager to install the necessary Node modules A Node package manager, referred to as NPM, must be installed on the machine in order to install the necessary packages for the Postgres and Express web application. If it is already installed, executing the following command will return the current NPM version number: 1 npm -V Now execute the npm init command inside the project directory to initialize the package.

    Execute the text prompts for the package name, version number and other criteria. The following screenshot provides an example: NOTE: Things can be change anything after the initial setup by editing the package.

    Of particular importance, the value for the "main" field must match the JavaScript file for the Node application. Install the NodeJs body-parser package for parsing middleware If using Express version 4. Execute the following command to install the Node body parser: 1 npm install body-parser --save Install nodemon for the Node application Installing the nodemon command-line interface utility will allow changes to be made to the Node application without having to restart the Express server each time.

    Execute the following command to install the nodemon module globally: 1 The following command will install nodemon as a dependency for the project: 1 npm install nodemon --save-dev As shown below, executing the nodemon command followed by the JavaScript file name will run the Node application via the CLI utility: 1 nodemon app. Try reinstalling the application with sudo npm install -g --force nodemon.

    Alternatively, try installing and running the application locally with npx nodemon.

    Creating a REST API Backend using Node.js, Express and Postgres

    A Postgres database and an existing table holding some records. Create a project directory for the NodeJs Express application Create a directory for the web app project using mkdir in a terminal.

    Enter the directory with the cd command followed by the folder name.

    Getting Started With Express, VueJS & PostgreSQL

    Once inside the project directory, create a new JavaScript file. Use the Node Package Manager to install the necessary Node modules A Node package manager, referred to as NPM, must be installed on the machine in order to install the necessary packages for the Postgres and Express web application. If it is already installed, executing the following command will return the current NPM version number: 1 npm -V Now execute the npm init command inside the project directory to initialize the package.

    Execute the text prompts for the package name, version number and other criteria. The following screenshot provides an example: NOTE: Things can be change anything after the initial setup by editing the package.

    NodeJs Express PostgreSQL Tutorial (Part 1)

    For relational databases, it is required that the updated data can be seen by subsequent access, which is a strong consistency. In short, at any time, the data in all nodes is the same. The final consistency of base theory belongs to weak consistency. Next, we introduce another important concept of distributed database: distributed transaction. After browsing several articles on distributed transactions, I found that there will be different descriptions, but the general meaning is the same.

    Distributed transactions are first transactions, which need to meet the acid characteristics of transactions. It is mainly considered that the data processed by business access is scattered on multiple nodes between networks.

    For the distributed database system, under the requirements of ensuring data consistency, it can distribute transactions and cooperate with multiple nodes to complete business requests. Whether multi nodes can work together normally and smoothly to complete transactions is the key, which directly determines the consistency of access data and the timeliness of response to requests. Therefore, it needs scientific and effective consistency algorithm to support. Consistency algorithm At present, the main consistency algorithms include 2pc, 3pc, Paxos and raft.

    Most relational databases use two-phase commit protocol to complete distributed transaction processing.

    It mainly includes the following two stages: Stage 1: submit transaction request voting stage Phase II: execution transaction submission execution phase Advantages: simple principle and convenient implementation Disadvantages: synchronization blocking, single point problem, inconsistent data, too conservative 3pc: Three — phase commit three-phase commit includes three phases: cancommit, precommit and docommit.

    In order to avoid that when all participants are notified to commit a transaction, when one of the participants crashes inconsistently, a three-stage commit method appears.

    The three-phase submission adds a precommit process to the two-phase submission. When all participants receive the precommit, it will not be executed game Action until a commit is received or after a certain period of time.

    Advantages: reduce the blocking range of participants and continue to reach an agreement after a single point of failure. Disadvantages: the precommit stage is introduced. In this stage, if a network partition occurs, the coordinator cannot communicate with the participants normally, and the participants will still commit transactions, resulting in data inconsistency. These data fragments may be distributed on different servers.

    Paxos, raft and Zab algorithms are used to ensure data consistency among multiple copies of the same data slice. The following is an overview of the three algorithms. Paxos algorithm mainly solves the single point problem of data fragmentation.

    The purpose is to make the nodes of the whole cluster agree on the change of a value. Paxos strong consistency belongs to the majority algorithm. Any point can propose a proposal to modify some data. Whether the proposal is passed depends on whether more than half of the nodes in the cluster agree.

    Therefore, Paxos algorithm requires that the nodes in the cluster are singular. Raft algorithm is a simplified version of Paxos. Raft is divided into three sub problems: one is leader election; Second, log replication; Third, safety.

    Raft defines three roles: leader, follower and candidate. At first, everyone is a follower. When the follower cannot listen to the leader, he can become a candidate, initiate a vote and elect a new leader. The one who gets the most votes in the recent stage is selected as l eader. The raft consistency algorithm simplifies the management of log copies by selecting a leader. For example, log entries are only allowed to flow from leader to follower. Zab is basically the same as raft.

    Officials say it is not only suitable for OLTP applications with high write operation pressure, but also suitable for big data applications dominated by read operation. Its predecessor is Postgres XC pgxc for short.

    Pgxl is an upgraded product based on pgxc, adding some features suitable for OLAP applications, such as massively parallel processing MPP. Generally speaking, pgxl code contains PG code. Installing PG cluster with pgxl does not require installing PG separately. Fortunately, pgxl follows up PG in a timely manner.

    Dockerizing a Node.js Web Application

    Only the coordinator node directly provides application services. The coordinator node distributes and stores data on multiple data nodes. Global transaction node GTMthe core component of Postgres Xc, is used for global transaction control and tuple visibility control. GTM is a module for allocating gxid and managing pgxc mvcc.

    There can only be one master GTM in a cluster. It is used to group the tasks submitted by the coordinator node. It is responsible for receiving user requests, generating and executing distributed queries, and sending SQL statements to the corresponding data nodes. The coordinator node does not physically store the table data.

    What is the game PostgreSQL distributed architecture?

    The table data is distributed in the form of fragmentation or replication, and the table data is stored on the data node. When an application initiates SQL, it will first reach the coordinator node, and then the coordinator node will distribute the SQL to each data node to summarize the data.

    This system process is controlled through gxid and global snapshot. Data nodes physically store table data. Table data storage methods are divided into distributed and replicated. Data nodes store only local data. Extend distributed solution citus 1 What is citus Citus is an open-source distributed database based on PostgreSQL, which automatically inherits the powerful SQL support capability and application ecology of PostgreSQL not only the compatibility of client protocols, but also the full compatibility of server-side expansion and management tools.

    Citus is not a fork of PostgreSQL. It adopts the shared nothing architecture.


    Express postgres