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stream.ts
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stream.ts
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import { decodeMultiStream, ExtensionCodec } from "@msgpack/msgpack";
import { stringifyJSON, retry, FatalError, sleep } from "./utils";
import { MimeTypes } from "./MimeTypes";
import logger from "./logger";
import DecompressionStream from "./DecompressionStream";
function createExtensionCodec() {
const extensionCodec = new ExtensionCodec();
extensionCodec.register({
type: 0x01,
encode() {
throw new Error("Not implemented");
},
decode(buffer: Uint8Array) {
return new Blob([buffer], { type: "application/vnd.mayu.session" });
},
});
return extensionCodec;
}
async function startStream(sessionId: string, encryptedState?: Blob) {
const res = await resume(sessionId, encryptedState);
if (!res.ok) {
const text = await res.text();
if (res.status == 503) {
// Server is shutting down, so retry..
throw new Error(`${res.status}: ${text}`);
}
throw new FatalError(`${res.status}: ${text}`);
}
if (!res.body) {
throw new FatalError("body is null");
}
const decompressionStream = new DecompressionStream("deflate-raw");
return res.body.pipeThrough(decompressionStream);
}
type ServerMessage = [id: string, event: string, payload: any];
type SessionStreamMessage = [string, any];
function resume(sessionId: string, encryptedState?: Blob) {
if (!encryptedState) {
return retry(() =>
fetch(`/__mayu/session/${sessionId}/init`, {
method: "POST",
})
);
}
return retry(() =>
fetch(`/__mayu/session/${sessionId}/resume`, {
method: "POST",
headers: { "content-type": MimeTypes.MAYU_SESSION },
body: encryptedState,
})
);
}
function errorMessage(e: any) {
if (e instanceof Error) {
return e.message;
}
if (typeof e === "string") {
return e;
}
return String(e);
}
export async function* sessionStream(
sessionId: string
): AsyncGenerator<SessionStreamMessage> {
let isRunning = true;
let encryptedState: Blob | undefined;
let isConnected = false;
const extensionCodec = createExtensionCodec();
let reason: string | undefined;
while (isRunning) {
try {
const stream = await retry(() => startStream(sessionId, encryptedState));
try {
for await (const message of decodeMultiStream(stream, {
extensionCodec,
})) {
const [id, event, payload] = message as ServerMessage;
if (!isConnected) {
isConnected = true;
yield ["system.connected", {}];
}
if (encryptedState) {
logger.info("Clearing encryptedState");
encryptedState = undefined;
}
try {
switch (event) {
case "session.transfer":
yield ["session.transfer", {}];
encryptedState = payload;
logger.info("Setting encryptedState", payload);
break;
case "pong":
yield [
"ping",
{
values: {
client: performance.now() - Number(payload.pong),
server: payload.server,
},
region: payload.region,
instance: payload.instance,
},
];
break;
case "ping":
postCallback(sessionId, "ping", {
pong: payload,
ping: performance.now(),
});
break;
default:
yield [event, payload];
}
} catch (e) {
reason = errorMessage(e);
logger.error(e);
}
}
} catch (e) {
reason = errorMessage(e);
logger.error(e);
}
isConnected = false;
if (isRunning) {
reason ||= "Stream ended unexpectedly";
}
yield ["system.disconnected", { transferring: !!encryptedState, reason }];
} catch (e) {
logger.error(e);
if (e instanceof FatalError) {
isRunning = false;
isConnected = false;
yield ["system.disconnected", { reason: e.message }];
return;
}
await sleep(1000);
}
}
}
async function postCallback(sessionId: string, callbackId: string, data: any) {
return fetch(`/__mayu/session/${sessionId}/${callbackId}`, {
method: "POST",
headers: { "content-type": "application/json" },
body: stringifyJSON(data),
});
}