15 KiB
Deno Documentation
Disclaimer
A word of caution: Deno is very much under development. We encourage brave early adopters, but expect bugs large and small. The API is subject to change without notice.
Bug reports do help!
Install
Deno works on OSX, Linux, and Windows. Deno is a single binary executable. It has no external dependencies.
deno_install provides convenience scripts to download and install the binary.
Using Python:
curl -L https://deno.land/x/install/install.py | python
Or using PowerShell:
iex (iwr https://deno.land/x/install/install.ps1)
Note: Depending on your security settings, you may have to run
Set-ExecutionPolicy RemoteSigned -Scope CurrentUser
first to allow downloaded
scripts to be executed.
Deno can also be installed manually, by downloading a tarball or zip file at github.com/denoland/deno/releases. These packages contain just a single executable file. You will have to set the executable bit on Mac and Linux.
Try it:
> deno https://deno.land/thumb.ts
API Reference
To get an exact reference of deno's runtime API, run the following in the command line:
> deno --types
Or see the doc website.
If you are embedding deno in a Rust program, see the rust docs.
Tutorial
An implementation of the unix "cat" program
In this program each command-line argument is assumed to be a filename, the file is opened, and printed to stdout.
import * as deno from "deno";
(async () => {
for (let i = 1; i < deno.args.length; i++) {
let filename = deno.args[i];
let file = await deno.open(filename);
await deno.copy(deno.stdout, file);
file.close();
}
})();
The copy()
function here actually makes no more than the necessary kernel ->
userspace -> kernel copies. That is, the same memory from which data is read
from the file, is written to stdout. This illustrates a general design goal for
I/O streams in Deno.
Try the program:
> deno https://deno.land/x/examples/cat.ts /etc/passwd
TCP echo server
This is an example of a simple server which accepts connections on port 8080, and returns to the client anything it sends.
import { listen, copy } from "deno";
(async () => {
const addr = "0.0.0.0:8080";
const listener = listen("tcp", addr);
console.log("listening on", addr);
while (true) {
const conn = await listener.accept();
copy(conn, conn);
}
})();
When this program is started, the user is prompted for permission to listen on the network:
> deno https://deno.land/x/examples/echo_server.ts
deno requests network access to "listen". Grant? [yN] y
listening on 0.0.0.0:8080
For security reasons, deno does not allow programs to access the network without explicit permission. To avoid the console prompt, use a command-line flag:
> deno https://deno.land/x/examples/echo_server.ts --allow-net
To test it, try sending a HTTP request to it by using curl. The request gets written directly back to the client.
> curl http://localhost:8080/
GET / HTTP/1.1
Host: localhost:8080
User-Agent: curl/7.54.0
Accept: */*
It's worth noting that like the cat.ts
example, the copy()
function here
also does not make unnecessary memory copies. It receives a packet from the
kernel and sends back, without further complexity.
Linking to third party code
In the above examples, we saw that Deno could execute scripts from URLs. Like browser JavaScript, Deno can import libraries directly from URLs. This example uses a URL to import a test runner library:
import { test, assertEqual } from "https://deno.land/x/testing/testing.ts";
test(function t1() {
assertEqual("hello", "hello");
});
test(function t2() {
assertEqual("world", "world");
});
Try running this:
> deno https://deno.land/x/examples/example_test.ts
Compiling /Users/rld/src/deno_examples/example_test.ts
Downloading https://deno.land/x/testing/testing.ts
Downloading https://deno.land/x/testing/util.ts
Compiling https://deno.land/x/testing/testing.ts
Compiling https://deno.land/x/testing/util.ts
running 2 tests
test t1
... ok
test t2
... ok
test result: ok. 2 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out
Note that we did not have to provide the --allow-net
flag for this program,
and yet it accessed the network. The runtime has special access to download
imports and cache them to disk.
Deno caches remote imports in a special directory specified by the $DENO_DIR
environmental variable. It default to $HOME/.deno
if $DENO_DIR
is not
specified. The next time you run the program, no downloads will be made. If the
program hasn't changed, it won't be recompiled either.
But what if https://deno.land/
goes down? Relying on external servers is
convenient for development but brittle in production. Production software should
always bundle its dependencies. In Deno this is done by checking the $DENO_DIR
into your source control system, and specifying that path as the $DENO_DIR
environmental variable at runtime.
How do you import to a specific version? Simply specify the version in the
URL. For example, this URL fully specifies the code being run:
https://unpkg.com/liltest@0.0.5/dist/liltest.js
. Combined with the
aforementioned technique of setting $DENO_DIR
in production to stored code,
one can fully specify the exact code being run, and execute the code without
network access.
It seems unwieldy to import URLs everywhere. What if one of the URLs links to
a subtly different version of a library? Isn't it error prone to maintain URLs
everywhere in a large project? The solution is to import and re-export your
external libraries in a central package.ts
file (which serves the same purpose
as Node's package.json
file). For example, let's say you were using the above
testing library across a large project. Rather than importing
"https://deno.land/x/testing/testing.ts"
everywhere, you could create a
package.ts
file the exports the third-party code:
export { test, assertEqual } from "https://deno.land/x/testing/testing.ts";
And throughout project one can import from the package.ts
and avoid having
many references to the same URL:
import { test, assertEqual } from "./package.ts";
This design circumvents a plethora of complexity spawned by package management software, centralized code repositories, and superfluous file formats.
Useful command line flags
V8 has many many command-line flags, that you can see with --v8-options
. Here
are a few particularly useful ones:
--async-stack-traces
How to Profile deno
To start profiling,
# Make sure we're only building release.
export DENO_BUILD_MODE=release
# Build deno and V8's d8.
./tools/build.py d8 deno
# Start the program we want to benchmark with --prof
./target/release/deno tests/http_bench.ts --allow-net --prof &
# Exercise it.
third_party/wrk/linux/wrk http://localhost:4500/
kill `pgrep deno`
V8 will write a file in the current directory that looks like this:
isolate-0x7fad98242400-v8.log
. To examine this file:
D8_PATH=target/release/ ./third_party/v8/tools/linux-tick-processor
isolate-0x7fad98242400-v8.log > prof.log
# on macOS, use ./third_party/v8/tools/mac-tick-processor instead
prof.log
will contain information about tick distribution of different calls.
To view the log with Web UI, generate JSON file of the log:
D8_PATH=target/release/ ./third_party/v8/tools/linux-tick-processor
isolate-0x7fad98242400-v8.log --preprocess > prof.json
Open third_party/v8/tools/profview/index.html
in your brower, and select
prof.json
to view the distribution graphically.
To learn more about d8
and profiling, check out the following links:
How to Debug deno
We can use LLDB to debug deno.
lldb -- target/debug/deno tests/worker.js
> run
> bt
> up
> up
> l
To debug Rust code, we can use rust-lldb
. It should come with rustc
and is a
wrapper around LLDB.
rust-lldb -- ./target/debug/deno tests/http_bench.ts --allow-net
# On macOS, you might get warnings like
# `ImportError: cannot import name _remove_dead_weakref`
# In that case, use system python by setting PATH, e.g.
# PATH=/System/Library/Frameworks/Python.framework/Versions/2.7/bin:$PATH
(lldb) command script import "/Users/kevinqian/.rustup/toolchains/1.30.0-x86_64-apple-darwin/lib/rustlib/etc/lldb_rust_formatters.py"
(lldb) type summary add --no-value --python-function lldb_rust_formatters.print_val -x ".*" --category Rust
(lldb) type category enable Rust
(lldb) target create "../deno/target/debug/deno"
Current executable set to '../deno/target/debug/deno' (x86_64).
(lldb) settings set -- target.run-args "tests/http_bench.ts" "--allow-net"
(lldb) b op_start
(lldb) r
Build Instructions (for advanced users only)
Prerequisites:
To ensure reproducible builds, deno has most of its dependencies in a git submodule. However, you need to install separately:
- Rust >= 1.30.0
- Node
- Python 2. Not 3.
- ccache (Optional but helpful for speeding up rebuilds of V8.)
- Extra steps for Windows users:
- Add
python.exe
toPATH
(e.g.set PATH=%PATH%;C:\Python27\python.exe
) - Get VS Community 2017. Make sure to select the option to install C++ tools and the Windows SDK.
- Enable
Debugging Tools for Windows
. Go toControl Panel
->Windows 10 SDK
-> Right-Click ->Change
->Change
->Check Debugging Tools for Windows
->Change
->Finish
.
- Add
Build:
# Fetch deps.
git clone --recurse-submodules https://github.com/denoland/deno.git
cd deno
./tools/setup.py
# Build.
./tools/build.py
# Run.
./target/debug/deno tests/002_hello.ts
# Test.
./tools/test.py
# Format code.
./tools/format.py
Other useful commands:
# Call ninja manually.
./third_party/depot_tools/ninja -C target/debug
# Build a release binary.
DENO_BUILD_MODE=release ./tools/build.py :deno
# List executable targets.
./third_party/depot_tools/gn ls target/debug //:* --as=output --type=executable
# List build configuration.
./third_party/depot_tools/gn args target/debug/ --list
# Edit build configuration.
./third_party/depot_tools/gn args target/debug/
# Describe a target.
./third_party/depot_tools/gn desc target/debug/ :deno
./third_party/depot_tools/gn help
# Update third_party modules
git submodule update
Environment variables: DENO_BUILD_MODE
, DENO_BUILD_PATH
, DENO_BUILD_ARGS
,
DENO_DIR
.
Internals
Internal: libdeno API.
deno's privileged side will primarily be programmed in Rust. However there will be a small C API that wraps V8 to 1) define the low-level message passing semantics, 2) provide a low-level test target, 3) provide an ANSI C API binding interface for Rust. V8 plus this C API is called "libdeno" and the important bits of the API is specified here: https://github.com/denoland/deno/blob/master/libdeno/deno.h https://github.com/denoland/deno/blob/master/js/libdeno.ts
Internal: Flatbuffers provide shared data between Rust and V8
We use Flatbuffers to define common structs and enums between TypeScript and Rust. These common data structures are defined in https://github.com/denoland/deno/blob/master/src/msg.fbs
Contributing
See CONTRIBUTING.md.
Changelog
2018.11.27 / v0.2.0 / Mildly usable
Stability and usability improvements. fetch()
is 90% functional now. Basic
REPL support was added. Shebang support was added. Command-line argument parsing
was improved. A forwarding service https://deno.land/x
was set up for Deno
code. Example code has been posted to
deno.land/x/examples and
deno.land/x/net.
The resources table was added to abstract various types of I/O streams and other allocated state. A resource is an integer identifier which maps to some Rust object. It can be used with various ops, particularly read and write.
2018.10.18 / v0.1.8 / Connecting to Tokio / Fleshing out APIs
Most file system ops were implemented. Basic TCP networking is implemented. Basic stdio streams exposed. And many random OS facilities were exposed (e.g. environmental variables)
Tokio was chosen as the backing event loop library. A careful mapping of JS Promises onto Rust Futures was made, preserving error handling and the ability to execute synchronously in the main thread.
Continuous benchmarks were added: https://denoland.github.io/deno/ Performance issues are beginning to be addressed.
"deno --types" was added to reference runtime APIs.
Working towards https://github.com/denoland/deno/milestone/2 We expect v0.2 to be released in last October or early November.
2018.09.09 / v0.1.3 / Scale binding infrastructure
ETA v.0.2 October 2018 https://github.com/denoland/deno/milestone/2
We decided to use Tokio https://tokio.rs/ to provide asynchronous I/O, thread pool execution, and as a base for high level support for various internet protocols like HTTP. Tokio is strongly designed around the idea of Futures - which map quite well onto JavaScript promises. We want to make it as easy as possible to start a Tokio future from JavaScript and get a Promise for handling it. We expect this to result in preliminary file system operations, fetch() for http. Additionally we are working on CI, release, and benchmarking infrastructure to scale development.
2018.08.23 / v0.1.0 / Rust rewrite / V8 snapshot
Complete! https://github.com/denoland/deno/milestone/1
Go is a garbage collected language and we are worried that combining it with V8's GC will lead to difficult contention problems down the road.
The V8Worker2 binding/concept is being ported to a new C++ library called libdeno. libdeno will include the entire JS runtime as a V8 snapshot. It still follows the message passing paradigm. Rust will be bound to this library to implement the privileged part of deno. See deno2/README.md for more details.
V8 Snapshots allow deno to avoid recompiling the TypeScript compiler at startup. This is already working.
When the rewrite is at feature parity with the Go prototype, we will release binaries for people to try.
2018.09.32 / v0.0.0 / Golang Prototype / JSConf talk
https://github.com/denoland/deno/tree/golang
https://www.youtube.com/watch?v=M3BM9TB-8yA
https://tinyclouds.org/jsconf2018.pdf
2007-2017 / Prehistory
https://github.com/ry/v8worker
https://tinyclouds.org/iocp-links.html