So I’ve been trying to run queries from node.js, and wanted to document the process, if anyone is interested. I’m also hoping some of the workarounds that I found can be properly patched so we can use services like heroku without having to jump trough hoops.
:~/work/dfinity/node_test_2$ node -v
v10.19.0
:~/work/dfinity/node_test_2$ npm -v
6.14.4
:~/work/dfinity/node_test_2$ npm init
Following the readme from here, I installed the agent package.
npm i --save @dfinity/agent
I created a file app.js, with a simple import, and ran it with
node app.js
const actor = require("@dfinity/agent");
First series of errors seem to stem from the fact that npm doesn’t import other packages. I had to add them manually.
Error: Cannot find module '@dfinity/principal'
#fix:
npm i --save @dfinity/principal
Error: Cannot find module '@dfinity/candid'
#fix:
npm i --save @dfinity/candid
#will need later:
npm i --save node-fetch
With all importing errors fixed, I ran node app.js again, and got the following error:
ReferenceError: TextEncoder is not defined
at Object.<anonymous> (~/work/dfinity/node_test_2/node_modules/@dfinity/agent/lib/cjs/auth.js:19:50)
This can be fixed by patching the auth.js file, adding the following line after use strict:
global.TextEncoder = require("util").TextEncoder;
With the file patched, we can now import the agent without any errors. Now let’s build an actor for a local deployment, and make a call to a local canister:
app.js:
const Actor = require("@dfinity/agent").Actor;
const HttpAgent = require("@dfinity/agent").HttpAgent;
//a mix of greet, and whoami capsules, with another greetq (as query) added
const idlFactory = ({ IDL }) => {
return IDL.Service({
'greet': IDL.Func([IDL.Text], [IDL.Text], []),
'greetq': IDL.Func([IDL.Text], [IDL.Text], ['query']),
'whoami': IDL.Func([], [IDL.Principal], ['query']),
});
};
//replace with any canister id
const canisterId = "rrkah-fqaaa-aaaaa-aaaaq-cai";
const agent = new HttpAgent({
host: "http://localhost:8000",
});
//needed for update calls on local dev env, shouldn't be used in production!
agent.fetchRootKey();
const actor = Actor.createActor(idlFactory, {
agent,
canisterId,
});
let callCanister = async (message) => {
res = await actor.greet(message).catch(e => { return "Error" + e });
return res;
}
callCanister("TEST").then(res => { console.log(res) });
Running that code gives another error:
TypeError: Cannot read property 'bind' of undefined
at getDefaultFetch (~/work/dfinity/node_test_2/node_modules/@dfinity/agent/lib/cjs/agent/http/index.js:57:28)
We can again fix this by patching the index.js file, adding the following line after use strict:
global.fetch = require("node-fetch");
And finally, after all this we get the call to work:
~/work/dfinity/node_test_2$ node app.js
Hello, TEST!
Awesome!
Now, the question is, was I doing something wrong, or are there better ways of calling canisters from node.js? My eventual goal would be to run this on a service like heroku, so it would be great if this can get patched at source. (and of course someone should check if those hacks affect other areas of code)
…