Move conceptual docs about ActionListener
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This information is more discoverable as the class-level javadocs for `ActionListener` itself rather than hidden away in a separate Markdown file. Also this way the links all stay up to date.
DaveCTurner
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Pinging @elastic/es-distributed (Team:Distributed) |
DaveCTurner
commented
Apr 24, 2024
| channel with which to pass the response back to the network caller. Netty has a many-to-one association of network callers to channels, so a | ||
| call taking a long time generally won't hog resources: it's cheap. A transport action can take hours to respond and that's alright, barring | ||
| caller timeouts. | ||
| See the [Javadocs for `ActionListener`](https://github.com/elastic/elasticsearch/blob/main/server/src/main/java/org/elasticsearch/action/ActionListener.java) |
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I expect this link isn't going to break for a very long time, and if it ever does it should be easy enough to fix it up, but in principle once these docs land in a released version we can pin this to that version instead.
| * <li>Most commonly, they can be passed on to other methods that themselves require a callback.</li> | ||
| * <li>They can be wrapped in another callback which modifies the behaviour of the original callback, perhaps adding some extra code to run | ||
| * before or after completion, before passing them on.</li> | ||
| * </ul> |
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Should we mention that action listener is our preferred alternative to Future/CompletableFutre as that is a well known way to pass a result of async computation in java?
idegtiarenko
approved these changes
Apr 25, 2024
DiannaHohensee
approved these changes
Apr 26, 2024
| * expensive to waste with unnecessary blocking) and at worst outright broken (the blocking can lead to deadlock). Unfortunately this means | ||
| * that most of our code ends up having to be written with callbacks, simply because it's ultimately calling into some other code that takes | ||
| * a callback. The entry points for all Elasticsearch APIs are callback-based (e.g. REST APIs all start at {@link | ||
| * org.elasticsearch.rest.BaseRestHandler}{@code #prepareRequest} and transport APIs all start at {@link |
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Yeah unfortunately BaseRestHandler#prepareRequest is protected so we can't link to it directly here. I still think it's better to link to it like this, although this obstacle suggests that we should consider moving some of these docs onto BaseRestHandler (or maybe org.elasticsearch.rest).
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May 9, 2024
This information is more discoverable as the class-level javadocs for `ActionListener` itself rather than hidden away in a separate Markdown file. Also this way the links all stay up to date.
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This information is more discoverable as the class-level javadocs for
ActionListeneritself rather than hidden away in a separate Markdownfile. Also this way the links all stay up to date.