About

  • Software developer at Google.
  • Former software developer at Stratoscale.
  • Former mechanical engineer.

Creations Repertoire

I love building things on my free time. Here are a few open source projects I’ve been working on.

complete

Bash completion written in go + bash completion for go command.

My most popular creation, mainly because it is used by hashicorp in some of their products. It enables a go binary to bash-complete itself (or other binary). All the completion logic is done in Go code. The way it works is that when the completion is needed, the same binary runs with special environment variables, and it then functions as completion logic for the shell.

A bonus package in this project is gocomplete which is bash completion for the Go command line, written in Go.

gitfs

A complete solution for static files in Go code.

I thought it would be nice to be able to import static file without the burden of go generate command any time they are changed. In this project I’m using mostly Github APIs to get static files the program wants to open. The usage is as simple as:

fs, err := gitfs.New("github.com/user/repo/path@version")
// Handle err…
f, err := fs.Open("file.txt")
// Handle err and use f.

One of the nice things here is that the fs object is an implementation of the standard http.FileSystem interface.

I then extended the library to be able to load the files from local directory for development purposes. And then extended it to convert the filesystem to be contained in a Go file that enables binary packing of the filesystem. Transiting from either of these modes is automatic.

This library also contains some http.FileSystem goodies in the fsutil package, which enable walking over the files in the filesystem and loading Go templates from them - they can be used with any implementation of http.FileSystem.

h2conn

HTTP2 client-server full-duplex connection.

A wrapper around Go’s standard http2 functions, that provide a simple reader and writer interfaces for using both on the server side and the client side.

wstest

Go websocket client for unit testing of a websocket handler.

If you have a Gorilla websocket handler, and want to test it without starting the server (similar to the http testing in Go), this package is for you.

orm

Go Typed ORM.

I was working with gorm, and got frustrated about the abundance of type safety. In this project I was trying to create an ORM that generates type-safe go code for accessing databases. It works great, but not production ready.

Stratoscale/logserver

Web log viewer that combines logs from several sources

A hackathon project that was developed to a useful product. In Stratoscale, our product was a distributed system that ran on multiple servers. We had services that were logging to a local storage, and they could run on each server, several servers, or a single server. If something went wrong, you would want to check any of the server to see if the service ran there in the time of the failure and then could read what went wrong in the logs. This task was OK if there were a few nodes, but when there were tens of them, it became impossible only to understand where to look for the logs.

In this project, we created a service that connects to all the nodes and provides a single merged directory web view of all of them. For each in the files in the directory tree it shows on which nodes the file is located, and enables you to read and search in the logs.

Stratoscale/swagger

An extension of go-swagger with custom templates. I was working on this at Stratoscale when we’ve start standardizing our Go services. After a while I helped merging its content to go-swagger as a contrib option.

goreadme

Update readme.md from go doc.

Command line tool that loads the documentation of a Go package and generates a markdown file that can be used as README.md.

There is also an open-source service that generates README files automatically for Github projects. Here is the code, and here it is live: https://goreadme.herokuapp.com.

client-timing

An HTTP client for go-server-timing middleware.

The go-server-timing middleware is very cool. It adds timing details to response headers (Instead of sending them to an external service) and it is a standard web header, so web browsers knows to plot it nicely. This timing details can tell how much time took each part of creating the response (calling database, calling other service, etc…)

This small addition that I provide enables automatic timing propagation through http calls between servers. So when service A calls service B which calls service C, The headers will be joined such that whoever called A will get the full details of the whole stack.

cmd

A minimalistic library that enables sub commands with the standard flag library.

The standard flag library is a great library for adding support for flag parsing for binaries. It has clean API and easy to use. However, when using it, it is not trivial to add a sub commands for the main command. Most programs have sub commands, for example, the go command have sub commands such as go run, go build or go test.

The cmd library adds support for sub commands in a way that retains the look and feel of the standard flag library. It also enables automatic bash completion, flag value enforcement, positional argument definition and enforcement and automatic usage.

Check out the example.

order

Enables easier ordering and comparison tasks

This package provides functionality to easily define and apply order on values. It works out of the box for most primitive types and their pointer versions, and enable order of any object using three-way comparison with a given func(T, T) int function, or by implementing the generic interface: func (T) Compare(T) int.

Read more about it in the blog post.

script

Easily write scripts with Go. Improvements for https://github.com/bitfield/script.

I went across the really cool library https://github.com/bitfield/script which helps writing scripts in Go. Writing scripts in Go may result in quite verbose code, and the standard library does not provide all the required tooling around it (mainly because it is not intended to). This tool enables running short and clear scripts in Go, imitating the piping features of shell commands.

For example: numErrors, err := script.File("test.txt").Match("Error").CountLines() reads a file, filters only for lines with the word “Error” and return the number of lines.

I really liked the library and took a deeper look into the implementation. One thing that I poped out was that the piping is done by reading all the data from a previous command into the memory and manipulating it there, not as shell pipes work, or as piping should be handled. For example, in the above example, we can read each line from the file. Then, in the match function, process each line and pass on only matching lines. Then, in the count lines we can just store a counter and not even store the line data. To perform the above pipe, we only need memory that the largest line can fit into (actually not even that). We certainly not need memory that is large enough to fit the “test.txt” file.

I came up with an improvement that takes advantage of Go’s io.Reader interface. There are two building blocks:

The Command struct, which represent a single command in the stream. It can be read by the exposed io.Reader, and can be optionally closed with io.Closer. Opposed to shell commands, the Command do not have an stderr output, but uses Go errors to report when an error occurs. As in shell commands, having error does not necessarily result in no output from the command - a command can have output and an error.

The Stream struct enables chaining commands one to another. There are some factory methods that create streams from different inputs such as Stdin, Cat that streams file content, Ls that lists files, or so forth. The stream can be chain using different commands, such as Grep to filter for a regexp, Head to get the beginning or the ending of the stream, Cut to take certain fields of each line, Sort, Uniq or so forth. Then, the stream can be dumped to different writers, such as ToStdout, ToFile, ToString or so forth. These methods also return to the users all the errors that occured in all the commands in the stream.

Another way to process the stream is the the Exec command which got special attention. It enables running a shell command, which can take the stream as its stdin, and continue the stream with the program stdout. If the program fails, its stdout still continue to the stream, but an error will be added (just as shell commands do). If the user is interested in the program’s stderr, it can provide an extra writer.

A custom command can be used using the Stream’s PipeTo method. This method gets a function that given a io.Reader, representing the stdin for the command, returns a Command. This way a user can define a custom command to interact with the stream.

tiler

A Go port of https://github.com/nuno-faria/tiler.

Tiles an image from a set of given small images.

chrome-github-godoc

Chrome extension that replaces Github view of git commit messages with useful godoc.org synopsis.

I found the github last-commit synopsis very unuseful when I look on a repository on Github. I thought it would be nice to replace it with the godoc synopsis in case it is a Go package. You can download it from the chrome extensions webstore.

fcontext

Context implementation with (pseudo) constant access-time.

Since the standard library context value is implemented as a tree, the search of the value is going in all the nodes to the root of the tree (the context.Background() node). This is O(height of tree). This implementation provides best case O(1) lookup time, with worst case as the standard implementation. The challenging part is that nodes can only know about values stored in the nodes between them and the root, but not on any other node. This implementation is also fully compatible with the standard library context.

As a result of this project, I updated a related Github issue in the Go language (Issue #28728) to “enable first class citizenship of third party implementations”, with a proposal about how to improve the cooperation of the standard library with third party implementations. The proposal was declined, but Russ Cox came up with an elegant solution that actually solved the discussed problem (Commit).

contexttest

Test package for context implementations.

One of the results of the fcontext package was the creation of a standard library to test context implementations. The context is an interface, which can have any underlying implementation. This library checks that the implementation does what it is expected of.

ctxutil

A collection of context utility functions.

Some functions that I missed when I use contexts.

posener/context

A proof of concept implementation of scoped context, following my blog post Goroutine Scoped Context Proposal.

tarfs

An implementation of the FileSystem interface for tar files.

flag

Like the flag package, but with bash completion support!

A small package that extends the API of the standard flag package, but with bash completion enabled.

sharedsecret

Implementation of Shamir’s Secret Sharing algorithm.

fuzzing

A package that enables easy fuzzing with go-fuzz. Go-fuzz invokes Fuzz functions with a sequence of bytes that should explore the space of inputs. In many cases this sequence of bytes should be converted to other objects as input to the tested function. This library helps with the conversion. See the example to understand how to use it.

ps1

A lightweight script that sets a nice shell prompt (similar to powershell, but fast).

Like the flag package, but with bash completion support!

eztables

iptables in web browser

githubapp

Oauth2 Github-App authentication client