download: Add support for http long polling #3418
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| func (d *Downloader) doStart(ctx context.Context) { | ||
| ctx, cancel := context.WithCancel(context.Background()) | ||
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| d.wg.Add(1) |
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💭 Is there ever more than one entry in this waitgroup? That is, are there multiple bundles downloaded (or long-polled) in parallel? If so, I guess I don't see [edit] it...
If we don't need it for multiple entries, I suspect there might be some room for simplification here... we've got so many synchronisation stuff here...
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We wait for the goroutine that performs the actual download so that it can finish calling the callback function provided by the plugins. For example, in the bundle plugin, after we stop a bundle's downloader, we delete its status object. So if we don't wait for the goroutine to finish, it's possible that plugin may have already deleted the bundle's status object which would result in a panic in the callback function.
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Thanks, I see. What I still don't understand is if that waitgroup ever has more than 1 group member...? But I'll have another closer look tomorrow.
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Earlier the downloader package only supported the http short polling technique where the client sends periodic requests to the server to fetch bundles. A drawback of this method is that a low polling frequency could add unnecessary burden on the server and network. This commit adds support for http long polling which helps to minimize server/network resource usage and also reduces the delay in delivery of updates to the client. Signed-off-by: Ashutosh Narkar <anarkar4387@gmail.com>
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Earlier the downloader package only supported the http
short polling technique where the client sends periodic
requests to the server to fetch bundles. A drawback of this
method is that a low polling frequency could add unnecessary
burden on the server and network.
This commit adds support for http long polling which helps
to minimize server/network resource usage and also reduces
the delay in delivery of updates to the client.
Signed-off-by: Ashutosh Narkar anarkar4387@gmail.com