http downloading in chunks
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234
examples/http_download_actor.js
Normal file
234
examples/http_download_actor.js
Normal file
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// HTTP Download Actor
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// Handles download requests and progress queries
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var http = use('http');
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var os = use('os');
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// Actor state
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var state = {
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downloading: false,
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current_url: null,
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total_bytes: 0,
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downloaded_bytes: 0,
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start_time: 0,
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error: null,
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connection: null,
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download_msg: null,
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chunks: []
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};
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// Helper to calculate progress percentage
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function get_progress() {
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if (state.total_bytes === 0) {
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return 0;
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}
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return Math.round((state.downloaded_bytes / state.total_bytes) * 100);
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}
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// Helper to format status response
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function get_status() {
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if (!state.downloading) {
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return {
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status: 'idle',
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error: state.error
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};
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}
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var elapsed = os.now() - state.start_time;
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var bytes_per_sec = elapsed > 0 ? state.downloaded_bytes / elapsed : 0;
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return {
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status: 'downloading',
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url: state.current_url,
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progress: get_progress(),
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downloaded_bytes: state.downloaded_bytes,
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total_bytes: state.total_bytes,
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elapsed_seconds: elapsed,
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bytes_per_second: Math.round(bytes_per_sec)
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};
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}
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// Main message receiver
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$_.receiver(function(msg) {
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switch (msg.type) {
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case 'download':
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if (state.downloading) {
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send(msg, {
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type: 'error',
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error: 'Already downloading',
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current_url: state.current_url
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});
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return;
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}
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if (!msg.url) {
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send(msg, {
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type: 'error',
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error: 'No URL provided'
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});
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return;
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}
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// Start download
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state.downloading = true;
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state.current_url = msg.url;
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state.total_bytes = 0;
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state.downloaded_bytes = 0;
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state.start_time = os.now();
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state.error = null;
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state.download_msg = msg;
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state.chunks = [];
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try {
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// Start the connection
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state.connection = http.fetch_start(msg.url, msg.options || {});
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if (!state.connection) {
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throw new Error('Failed to start download');
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}
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// Schedule the first chunk read
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$_.delay(read_next_chunk, 0);
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} catch (e) {
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state.error = e.toString();
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state.downloading = false;
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send(msg, {
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type: 'error',
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error: state.error,
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url: msg.url
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});
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}
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break;
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case 'status':
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console.log(`got status request. current is ${json.encode(get_status())}`)
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send(msg, {
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type: 'status_response',
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...get_status()
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});
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break;
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case 'cancel':
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if (state.downloading) {
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// Cancel the download
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if (state.connection) {
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http.fetch_close(state.connection);
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state.connection = null;
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}
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state.downloading = false;
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state.current_url = null;
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state.download_msg = null;
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state.chunks = [];
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send(msg, {
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type: 'cancelled',
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message: 'Download cancelled',
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url: state.current_url
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});
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} else {
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send(msg, {
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type: 'error',
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error: 'No download in progress'
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});
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}
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break;
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default:
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send(msg, {
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type: 'error',
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error: 'Unknown message type: ' + msg.type
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});
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}
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});
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// Non-blocking chunk reader
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function read_next_chunk() {
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if (!state.downloading || !state.connection) {
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return;
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}
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try {
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var chunk = http.fetch_read_chunk(state.connection);
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if (chunk === null) {
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// Download complete
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finish_download();
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return;
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}
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// Store chunk
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state.chunks.push(chunk);
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// Update progress
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var info = http.fetch_info(state.connection);
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state.downloaded_bytes = info.bytes_read;
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if (info.headers_complete && info.content_length > 0) {
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state.total_bytes = info.content_length;
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}
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// Schedule next chunk read
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$_.delay(read_next_chunk, 0);
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} catch (e) {
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// Error during download
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state.error = e.toString();
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if (state.connection) {
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http.fetch_close(state.connection);
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}
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if (state.download_msg) {
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send(state.download_msg, {
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type: 'error',
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error: state.error,
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url: state.current_url
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});
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}
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// Reset state
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state.downloading = false;
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state.connection = null;
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state.download_msg = null;
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state.chunks = [];
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}
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}
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// Complete the download and send result
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function finish_download() {
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if (state.connection) {
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http.fetch_close(state.connection);
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}
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// Combine all chunks into single ArrayBuffer
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var total_size = 0;
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for (var i = 0; i < state.chunks.length; i++) {
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total_size += state.chunks[i].byteLength;
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}
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var result = new ArrayBuffer(total_size);
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var view = new Uint8Array(result);
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var offset = 0;
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for (var i = 0; i < state.chunks.length; i++) {
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var chunk_view = new Uint8Array(state.chunks[i]);
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view.set(chunk_view, offset);
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offset += state.chunks[i].byteLength;
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}
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// Send complete message
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if (state.download_msg) {
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send(state.download_msg, {
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type: 'complete',
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url: state.current_url,
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data: result,
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size: result.byteLength,
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duration: os.now() - state.start_time
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});
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}
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// Reset state
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state.downloading = false;
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state.connection = null;
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state.current_url = null;
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state.download_msg = null;
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state.chunks = [];
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}
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