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Fix eventsource reconnection: proper backoff and close() behavior #649

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Fix eventsource reconnection: proper backoff and close() behavior #649

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24 changes: 19 additions & 5 deletions src/eventsource.js
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Original file line number Diff line number Diff line change
Expand Up @@ -47,6 +47,8 @@
eventSource: null,
listeners: [],
retryCount: 0,
closed: false,
reconnectTimeout: null,
open: function (url) {
// calculate default values for URL argument.
if (url == undefined) {
Expand All @@ -68,6 +70,9 @@
}
}

// Mark as not explicitly closed (allow reconnection)
stub.closed = false;

// Open the EventSource and get ready to populate event handlers
stub.eventSource = new EventSource(url, {
withCredentials: withCredentials,
Expand All @@ -78,13 +83,17 @@
stub.retryCount = 0;
});

// On connection error, use exponential backoff to retry (random values from 1 second to 2^7 (128) seconds
// On connection error, use exponential backoff to retry
stub.eventSource.addEventListener("error", function (event) {
// If the EventSource is closed, then try to reopen
if (stub.eventSource.readyState == EventSource.CLOSED) {
// Close the EventSource to prevent the browser's native auto-reconnect,
// which does not use backoff and can cause rapid-fire retries.
stub.eventSource.close();

// Only reconnect if the user has not explicitly called close()
if (!stub.closed) {
stub.retryCount = Math.min(7, stub.retryCount + 1);
var timeout = Math.random() * (2 ^ stub.retryCount) * 500;
window.setTimeout(stub.open, timeout);
var timeout = Math.random() * Math.pow(2, stub.retryCount) * 500;
stub.reconnectTimeout = window.setTimeout(stub.open, timeout);
}
});

Expand All @@ -95,6 +104,11 @@
}
},
close: function () {
stub.closed = true;
if (stub.reconnectTimeout != null) {
window.clearTimeout(stub.reconnectTimeout);
stub.reconnectTimeout = null;
}
if (stub.eventSource != undefined) {
stub.eventSource.close();
}
Expand Down