in glean/src/core/upload/manager.ts [236:248]
private enqueuePing(ping: QueuedPing): void {
if (this.processing.has(ping.identifier)) {
return;
}
for (const queuedPing of this.queue) {
if (queuedPing.identifier === ping.identifier) {
return;
}
}
this.queue.push(ping);
}