Created
September 9, 2016 06:56
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GCP metadata server long polling
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// https://cloud.google.com/compute/docs/storing-retrieving-metadata#waitforchange | |
// curl "http://metadata.google.internal/computeMetadata/v1/project/attributes/hoge?wait_for_change=true" -H "Metadata-Flavor: Google" | |
const http = require('http'); | |
function longPollMetadataServer(path) { | |
return new Promise((resolve, reject) => { | |
http.get({ | |
hostname: "metadata.google.internal", | |
path: path + "?wait_for_change=true", | |
headers: { | |
"Metadata-Flavor": "Google", | |
}, | |
}, (res) => { | |
let body = ''; | |
res.on('data', (data) => { body += data; }); | |
res.on('end', () => { | |
try { | |
resolve(JSON.parse(body)); | |
} catch(e) { | |
reject(e); | |
} | |
}); | |
}); | |
}); | |
} | |
function longPollProjectMetadata(key) { | |
return longPollMetadataServer("/computeMetadata/v1/project/attributes/" + key); | |
} | |
function longPollAndProcessMetadata(key) { | |
return longPollProjectMetadata(key).then((data) => { | |
console.log(data); // XXX | |
}).catch((e) => { | |
console.error("err: ", e); | |
}); | |
}; | |
function forever(generator, args) { | |
return generator.apply(this, args).then(() => { | |
return forever(generator, args); | |
}); | |
} | |
forever(() => { return longPollAndProcessMetadata('hoge'); }); |
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