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張 旭

Production Notes - MongoDB Manual - 0 views

docs.mongodb.com/...production-notes

mongodb database performance

shared by 張 旭 on 29 Apr 21 - No Cached
  • mongod will not start if dbPath contains data files created by a storage engine other than the one specified by --storageEngine.
  • mongod must possess read and write permissions for the specified dbPath.
  • WiredTiger supports concurrent access by readers and writers to the documents in a collection
  • ...9 more annotations...
  • Journaling guarantees that MongoDB can quickly recover write operations that were written to the journal but not written to data files in cases where mongod terminated due to a crash or other serious failure.
  • To use read concern level of "majority", replica sets must use WiredTiger storage engine.
  • Write concern describes the level of acknowledgement requested from MongoDB for write operations.
  • With stronger write concerns, clients must wait after sending a write operation until MongoDB confirms the write operation at the requested write concern level.
  • By default, authorization is not enabled, and mongod assumes a trusted environment
  • The HTTP interface is disabled by default. Do not enable the HTTP interface in production environments.
  • Avoid overloading the connection resources of a mongod or mongos instance by adjusting the connection pool size to suit your use case.
  • ensure that each mongod or mongos instance has access to two real cores or one multi-core physical CPU.
  • The WiredTiger storage engine is multithreaded and can take advantage of additional CPU cores
crazylion lee

Eve - 0 views

programming.witheve.com

programming ide visual

shared by crazylion lee on 31 Oct 16 - No Cached
  • crazylion lee on 31 Oct 16
     
    "Eve is a programming language and IDE based on years of research into building a human-first programming platform. From code embedded in documents to a language without order, it presents an alternative take on what programming could be - one that focuses on us instead of the machine. This is Eve:"
crazylion lee

Supervisor: A Process Control System - supervisor 3.1a1-dev documentation - 1 views

supervisord.org

monitoring sysadmin python linux unix supervisor

shared by crazylion lee on 13 Feb 14 - Cached
  • crazylion lee on 13 Feb 14
     
    Supervisor is a client/server system that allows its users to monitor and control a number of processes on UNIX-like operating systems. It shares some of the same goals of programs like launchd, daemontools, and runit. Unlike some of these programs, it is not meant to be run as a substitute for init as "process id 1". Instead it is meant to be used to control processes related to a project or a customer, and is meant to start like any other program at boot time.
crazylion lee

The memory models that underlie programming languages - 0 views

canonical.org/...memory-models

ai memory

shared by crazylion lee on 30 Jan 17 - No Cached
  • crazylion lee on 30 Jan 17
     
    " There are about six major conceptualizations of memory, which I'm calling "memory models"², that dominate today's programming. Three of them derive from the three most historically important programming languages of the 1950s - COBOL, LISP, and FORTRAN - and the other three derive from the three historically important data storage systems: magnetic tape, Unix-style hierarchical filesystems, and relational databases."
crazylion lee

Goodbye, Object Oriented Programming - Medium - 0 views

medium.com/...ented-programming-a59cda4c0e53

oop programming design

shared by crazylion lee on 30 Jan 17 - No Cached
  • crazylion lee on 30 Jan 17
     
    "Goodbye, Object Oriented Programming"
張 旭

How Percona XtraBackup Works - 0 views

www.percona.com/...how_xtrabackup_works.html

mysql database backup percona xtradb

shared by 張 旭 on 30 Nov 19 - No Cached
  • Percona XtraBackup is based on InnoDB‘s crash-recovery functionality.
  • it performs crash recovery on the files to make them a consistent, usable database again
  • InnoDB maintains a redo log, also called the transaction log. This contains a record of every change to InnoDB data.
  • ...14 more annotations...
  • When InnoDB starts, it inspects the data files and the transaction log, and performs two steps. It applies committed transaction log entries to the data files, and it performs an undo operation on any transactions that modified data but did not commit.
  • Percona XtraBackup works by remembering the log sequence number (LSN) when it starts, and then copying away the data files.
  • Percona XtraBackup runs a background process that watches the transaction log files, and copies changes from it.
  • Percona XtraBackup needs to do this continually
  • Percona XtraBackup needs the transaction log records for every change to the data files since it began execution.
  • Percona XtraBackup uses Backup locks where available as a lightweight alternative to FLUSH TABLES WITH READ LOCK.
  • Locking is only done for MyISAM and other non-InnoDB tables after Percona XtraBackup finishes backing up all InnoDB/XtraDB data and logs.
  • xtrabackup tries to avoid backup locks and FLUSH TABLES WITH READ LOCK when the instance contains only InnoDB tables. In this case, xtrabackup obtains binary log coordinates from performance_schema.log_status
  • When backup locks are supported by the server, xtrabackup first copies InnoDB data, runs the LOCK TABLES FOR BACKUP and then copies the MyISAM tables.
  • the STDERR of xtrabackup is not written in any file. You will have to redirect it to a file, e.g., xtrabackup OPTIONS 2> backupout.log
  • During the prepare phase, Percona XtraBackup performs crash recovery against the copied data files, using the copied transaction log file. After this is done, the database is ready to restore and use.
  • the tools enable you to do operations such as streaming and incremental backups with various combinations of copying the data files, copying the log files, and applying the logs to the data.
  • To restore a backup with xtrabackup you can use the --copy-back or --move-back options.
  • you may have to change the files’ ownership to mysql before starting the database server, as they will be owned by the user who created the backup.
  • 張 旭 on 30 Nov 19
     
    "Percona XtraBackup is based on InnoDB's crash-recovery functionality."
張 旭

Language Server Protocol - Wikipedia - 0 views

en.wikipedia.org/...Language_Server_Protocol

vim programming

shared by 張 旭 on 28 Jan 22 - No Cached
  • Modern IDEs provide developers with sophisticated features like code completion, refactoring, navigating to a symbol's definition, syntax highlighting, and error and warning markers.
  • an IDE needs a sophisticated understanding of the programming language that the program's source is written in.
  • Conventional compilers or interpreters for a specific programming language are typically unable to provide these language services, because they are written with the goal of either transforming the source code into object code or immediately executing the code.
  • ...5 more annotations...
  • Prior to the design and implementation of the Language Server Protocol for the development of Visual Studio Code, most language services were generally tied to a given IDE or other editor.
  • The Language Server Protocol allows for decoupling language services from the editor so that the services may be contained within a general purpose language server.
  • LSP is not restricted to programming languages. It can be used for any kind of text-based language, like specifications[7] or domain-specific languages (DSL).
  • When a user edits one or more source code files using a language server protocol-enabled tool, the tool acts as a client that consumes the language services provided by a language server.
  • The protocol does not make any provisions about how requests, responses and notifications are transferred between client and server.
crazylion lee

crystal-lang/crystal: The Crystal Programming Language - 1 views

github.com/crystal

programming language ruby

shared by crazylion lee on 25 Dec 16 - No Cached
  • crazylion lee on 25 Dec 16
     
    "Crystal is a programming language with the following goals: Have a syntax similar to Ruby (but compatibility with it is not a goal) Statically type-checked but without having to specify the type of variables or method arguments. Be able to call C code by writing bindings to it in Crystal. Have compile-time evaluation and generation of code, to avoid boilerplate code. Compile to efficient native code. "
crazylion lee

GNU Octave - 0 views

www.gnu.org/octave

matlab opensource math

shared by crazylion lee on 10 Jun 16 - No Cached
  • crazylion lee on 10 Jun 16
     
    "GNU Octave is a high-level interpreted language, primarily intended for numerical computations. It provides capabilities for the numerical solution of linear and nonlinear problems, and for performing other numerical experiments. It also provides extensive graphics capabilities for data visualization and manipulation. Octave is normally used through its interactive command line interface, but it can also be used to write non-interactive programs. The Octave language is quite similar to Matlab so that most programs are easily portable."
crazylion lee

Coconut Programming Language - 0 views

coconut-lang.org

python functional programming

shared by crazylion lee on 27 Jun 16 - No Cached
  • crazylion lee on 27 Jun 16
     
    "Simple, elegant, Pythonic functional programming."
張 旭

The Rubyist's Guide to Environment Variables - Honeybadger.io Blog - 0 views

blog.honeybadger.io/by-guide-environment-variables

ruby environment development shell

shared by 張 旭 on 12 Jun 15 - No Cached
  • If you want to be able to effectively manage web apps in development and in production, you have to understand environment variables.
  • Every program you run on your server has at least one process. That process gets its own set of environment variables.
  • Once it has them, nothing outside of that process can change them.
  • ...9 more annotations...
  • Every program you run on your server gets its own set of environment variables at the moment you launch it.
  • Environment variables die with their process
  • Every process has a parent. That’s because every program has to be started by some other program.
  • Child processes inherit env vars from their parent
  • By default a child will get copies of every environment variable that its parent has. But the parent has control over this.
  • Changes to the environment don’t sync between running processes
  • shells do provide their own “local” shell variable systems
  • Environment variables are NOT the same as shell variables
  • use the export command to convert the local variable into an environment variable.
crazylion lee

Writing a Bootloader | Blog of Osanda - 1 views

osandamalith.wordpress.com/...writing-a-bootloader

bootloader linux c

shared by crazylion lee on 06 Nov 15 - No Cached
  • crazylion lee on 06 Nov 15
     
    "A bootloader is a special program that is executed each time a bootable device is initialized by the computer during its power on or reset that will load the kernel image into the memory. This application is very close to hardware and to the architecture of the CPU. All x86 PCs boot in Real Mode. In this mode you have only 16-bit instructions. Our bootloader runs in Real Mode and our bootloader is a 16-bit program."
張 旭

Ruby and AOP: Decouple your code even more - Arkency Blog - 0 views

blog.arkency.com/...p-decouple-your-code-even-more

ruby aop programming algorithm pattern code

shared by 張 旭 on 03 Jun 17 - No Cached
  • Dark Parts in our apps - persistence, networking, logging, notifications… these parts are scattered in our code
  • aspect-oriented programming!
  • components are parts we can easily encapsulate into some kind of code abstraction - a methods, objects or procedures.
  • ...16 more annotations...
  • application’s logic is a great example of a component
  • Aspects cross-cut our application - when we use some kind of persistence (e.g. a database) or network communication (such as ZMQ sockets) our components need to know about it.
  • Aspect-oriented programming aims to get rid of cross-cuts by separating aspect code from component code using injections of our aspects in certain join points in our component code.
  • It’s responsible for pushing snippets scenario
  • SRP-conformant object
  • the join points in Ruby
  • advice
    • 張 旭
      張 旭 on 03 Jun 17
       
      AOP 裡面的術語
  • In most cases after and before advice are sufficient.
  • what does it mean to “evaluate code around” something? In our case it means: Don’t run this method. Take it and push to my advice as an argument and evaluate this advice
  • to provide a join point
  • You’ll often see empty methods in code written in AOP paradigm
  • provide aspect code to link with our use case
  • use case is a pure domain object, without even knowing it’s connected with some kind of persistence and logging layer.
  • Aspect-oriented programming is fixing the problem with polluting pure logic objects with technical context of our applications.
  • we treat our glues as a configuration part, not the logic part of our apps.
  • Glues should not contain any logic at all
張 旭

The Backup Cycle - Full Backups - 0 views

www.percona.com/...full_backup.html

database mysql backup percona xtradb

shared by 張 旭 on 02 Dec 19 - No Cached
  • xtrabackup will not overwrite existing files, it will fail with operating system error 17, file exists.
  • Log copying thread checks the transactional log every second to see if there were any new log records written that need to be copied, but there is a chance that the log copying thread might not be able to keep up with the amount of writes that go to the transactional logs, and will hit an error when the log records are overwritten before they could be read.
  • It is safe to cancel at any time, because xtrabackup does not modify the database.
  • ...15 more annotations...
  • need to prepare it in order to restore it.
  • Data files are not point-in-time consistent until they are prepared, because they were copied at different times as the program ran, and they might have been changed while this was happening.
  • You can run the prepare operation on any machine; it does not need to be on the originating server or the server to which you intend to restore.
  • you simply run xtrabackup with the --prepare option and tell it which directory to prepare,
  • All following prepares will not change the already prepared data files
  • It is not recommended to interrupt xtrabackup process while preparing backup
  • Backup validity is not guaranteed if prepare process was interrupted.
  • If you intend the backup to be the basis for further incremental backups, you should use the --apply-log-only option when preparing the backup, or you will not be able to apply incremental backups to it.
  • Backup needs to be prepared before it can be restored.
  • xtrabackup --copy-back --target-dir=/data/backups/
  • The datadir must be empty before restoring the backup.
  • MySQL server needs to be shut down before restore is performed.
  • You cannot restore to a datadir of a running mysqld instance (except when importing a partial backup).
  • rsync -avrP /data/backup/ /var/lib/mysql/
  • chown -R mysql:mysql /var/lib/mysql
張 旭

Replication - MongoDB Manual - 0 views

docs.mongodb.com/...replication

database mongodb

shared by 張 旭 on 13 Oct 20 - No Cached
  • A replica set in MongoDB is a group of mongod processes that maintain the same data set.
  • Replica sets provide redundancy and high availability, and are the basis for all production deployments.
  • With multiple copies of data on different database servers, replication provides a level of fault tolerance against the loss of a single database server.
  • ...18 more annotations...
  • replication can provide increased read capacity as clients can send read operations to different servers.
  • A replica set is a group of mongod instances that maintain the same data set.
  • A replica set contains several data bearing nodes and optionally one arbiter node.
  • one and only one member is deemed the primary node, while the other nodes are deemed secondary nodes.
  • A replica set can have only one primary capable of confirming writes with { w: "majority" } write concern; although in some circumstances, another mongod instance may transiently believe itself to also be primary.
  • The secondaries replicate the primary’s oplog and apply the operations to their data sets such that the secondaries’ data sets reflect the primary’s data set
  • add a mongod instance to a replica set as an arbiter. An arbiter participates in elections but does not hold data
  • An arbiter will always be an arbiter whereas a primary may step down and become a secondary and a secondary may become the primary during an election.
  • Secondaries replicate the primary’s oplog and apply the operations to their data sets asynchronously.
  • These slow oplog messages are logged for the secondaries in the diagnostic log under the REPL component with the text applied op: <oplog entry> took <num>ms.
  • Replication lag refers to the amount of time that it takes to copy (i.e. replicate) a write operation on the primary to a secondary.
  • When a primary does not communicate with the other members of the set for more than the configured electionTimeoutMillis period (10 seconds by default), an eligible secondary calls for an election to nominate itself as the new primary.
  • The replica set cannot process write operations until the election completes successfully.
  • The median time before a cluster elects a new primary should not typically exceed 12 seconds, assuming default replica configuration settings.
  • Factors such as network latency may extend the time required for replica set elections to complete, which in turn affects the amount of time your cluster may operate without a primary.
  • Your application connection logic should include tolerance for automatic failovers and the subsequent elections.
  • MongoDB drivers can detect the loss of the primary and automatically retry certain write operations a single time, providing additional built-in handling of automatic failovers and elections
  • By default, clients read from the primary [1]; however, clients can specify a read preference to send read operations to secondaries.
crazylion lee

Carbide Alpha | Buggy But Live! - 0 views

alpha.trycarbide.com

javascript programming ide visual

shared by crazylion lee on 27 Aug 16 - No Cached
  • crazylion lee on 27 Aug 16
     
    "Carbide is a new kind of programming environment"
crazylion lee

Scratchapixel - 0 views

scratchapixel.com

graphics programming

shared by crazylion lee on 04 Sep 16 - No Cached
  • crazylion lee on 04 Sep 16
     
    "Learn Computer Graphics Programming from Scratch "
crazylion lee

Flood fill - Wikipedia - 0 views

en.wikipedia.org/Flood_fill

computer programming Science algorithm fill

shared by crazylion lee on 30 Jan 17 - Cached
  • crazylion lee on 30 Jan 17
     
    "Flood fill, also called seed fill, is an algorithm that determines the area connected to a given node in a multi-dimensional array. It is used in the "bucket" fill tool of paint programs to fill connected, similarly-colored areas with a different color, and in games such as Go and Minesweeper for determining which pieces are cleared. When applied on an image to fill a particular bounded area with color, it is also known as boundary fill."
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