mirror of
https://github.com/shaka-project/shaka-player.git
synced 2026-06-15 16:06:41 +03:00
Joey Parrish
43e086dbaf
This updates the debugging tutorial to clarify a few things: - Formatting in the sample console output is not exact - Log level should be set in the top of initApp() before we construct the Player object - Verbose messages are only seen after we change the log level and reload Closes #653 Change-Id: Id0d7dabff225c3d82a9c54c05bb356a0bfa9b241
166 lines
5.5 KiB
Markdown
166 lines
5.5 KiB
Markdown
# Debugging
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#### Create an error
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Let's say that we have some kind of error, and we want to debug it.
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To simulate this, we'll start with the code from {@tutorial basic-usage}
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and make a bad change.
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First, let's change `manifestUri` by removing the last letter.
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```js
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var manifestUri = '//storage.googleapis.com/shaka-demo-assets/angel-one/dash.mp';
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```
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Now reload the page. This causes an error in the JS console that says "Error
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code 1001".
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#### Looking up error codes
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Look at the Error we just logged. It has `category: 1`, `code: 1001`. To find
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out what that means, check the docs for {@link shaka.util.Error}. There we find
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that `1001` means `BAD_HTTP_STATUS`:
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> An HTTP network request returned an HTTP status that indicated a failure.
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> error.data[0] is the URI.
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> ...
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So some HTTP request failed, and we can see the failed URI in `data[0]`.
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#### Loading the uncompiled library
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The compiled library has no usable stack traces and no logging. So to get more
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information, we need to switch to the uncompiled library.
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Instead of the single-file compiled library, we need to load three scripts in
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our HTML file:
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1. Closure's base library. (This is a small JavaScript library related to the
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Closure compiler used when we build Shaka.) This is what loads Shaka without
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requiring you to list all 50+ source files.
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2. A dependency file which maps Shaka's class names to source files. This is
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how Closure's base library can locate all of Shaka's individual source files.
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3. The uncompiled Shaka library's bootstrap file, "shaka-player.uncompiled.js".
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This uses Closure to load the top-level parts of the library. Each of those
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files in turn load their internal dependencies.
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Once we're using the uncompiled library, we will be able to see detailed logs
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and line numbers for errors.
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```html
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<head>
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<!-- Closure base: -->
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<script src="third_party/closure/goog/base.js"></script>
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<!-- Deps file: -->
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<script src="dist/deps.js"></script>
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<!-- Shaka Player uncompiled library: -->
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<script src="shaka-player.uncompiled.js"></script>
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<!-- Your application source: -->
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<script src="myapp.js"></script>
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</head>
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```
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Reload the page and look in the JavaScript console. Now we see something
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similar to this (formatted a bit differently in the console):
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```js
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HEAD http://storage.googleapis.com/shaka-demo-assets/angel-one/dash.mp 404 (Not Found) http_plugin.js:94
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HEAD http://storage.googleapis.com/shaka-demo-assets/angel-one/dash.mp 404 (Not Found) http_plugin.js:94
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HEAD request to guess manifest type failed! shaka.util.Error manifest_parser.js:179
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Error code 1001 object shaka.util.Error myapp.js:45
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```
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We have a little more information from the library now, and we can expand the
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Error object and see a human-readable message and a stack trace:
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```js
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shaka.util.Error
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category: 1
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code: 1001
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data: Array[3]
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0: "http://storage.googleapis.com/shaka-demo-assets/angel-one/dash.mp"
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1: 404
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2: ""
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length: 3
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message:
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"Shaka Error NETWORK.BAD_HTTP_STATUS (...)"
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stack: "Error: Shaka Error NETWORK.BAD_HTTP_STATUS (http://storage.googleapis.com/shaka-demo-assets/angel-one/dash.mp,404,)
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at new shaka.util.Error (http://localhost/shaka/lib/util/error.js:77:13)
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at XMLHttpRequest.xhr.onload (http://localhost/shaka/lib/net/http_plugin.js:70:16)"
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```
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With the information from the uncompiled library, we have the error name as well
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as the code. So we could avoid looking up the number in the documentation. The
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stack trace gives us clues about where the error was generated, so we can look
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more closely at the source code if we need to.
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#### Setting the log level
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Sometimes the error and stack trace isn't enough. Sometimes you need to see a
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long sequence of events leading up to an error. You may also be asked to attach
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logs as part of a bug report to help the Shaka Player team understand your bug.
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For this, you want to set the log level. The log level lets you control what
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logs are shown by the uncompiled library. To set the log level, add one of
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these to the top of `initApp()` in myapp.js:
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```js
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// Debug logs, when the default of INFO isn't enough:
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shaka.log.setLevel(shaka.log.Level.DEBUG);
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// Verbose logs, which can generate a lot of output:
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shaka.log.setLevel(shaka.log.Level.V1);
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// Verbose 2, which is extremely noisy:
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shaka.log.setLevel(shaka.log.Level.V2);
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```
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Please note that this method is not available from the compiled library.
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If we set the level to `V1` and reload, we get something like this in the
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JavaScript console:
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```js
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HEAD http://storage.googleapis.com/shaka-demo-assets/angel-one/dash.mp 404 (Not Found) http_plugin.js:94
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Unable to find byte-order-mark, making an educated guess. string_utils.js:130
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HTTP error text: http_plugin.js:69
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HEAD http://storage.googleapis.com/shaka-demo-assets/angel-one/dash.mp 404 (Not Found) http_plugin.js:94
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Unable to find byte-order-mark, making an educated guess. string_utils.js:130
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HTTP error text: http_plugin.js:69
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HEAD request to guess manifest type failed! shaka.util.Error manifest_parser.js:179
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load() failed: shaka.util.Error player.js:498
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Error code 1001 object shaka.util.Error myapp.js:48
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```
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So much more information! We can now see that the failed HEAD request caused
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load() to fail.
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#### Wrap up
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To sum up, remember these points when debugging your application:
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- Use the uncompiled version of Shaka Player for debugging and integration work
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- Refer to the docs for error codes
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- Increase the log level when you need more detail
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#### Continue the Tutorials
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Next, check out {@tutorial config}.
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