2 |
10 |
11 |
12 |
13 | - Posted {{ post.date | date: site.date_format }}
14 | {% if post.last_updated %}
15 | - Updated {{ post.last_updated | date: site.date_format }}
16 | {% endif %}
17 |
18 | {% assign tag_count = post.tags.size %}
19 |
20 | {% if tag_count > 0 %}
21 | - Tagged with
22 | {% assign sorted_tags = post.tags | sort %}
23 | {% for tag in sorted_tags %}
24 | {{ tag }}{% if forloop.index != tag_count %}, {% endif %}
25 | {% endfor %}
26 |
27 | {% endif %}
28 |
29 | {% if post.link %}
30 | - ∞
31 | {% endif %}
32 |
33 |
34 |
Content warning: {{ post.content_warning }}
40 | {% endif %}
41 |
42 | {% if is_index and post.content contains '' %}
43 | {% assign splitcontent = post.content | split: '' %}
44 | {{ splitcontent.first | cleanup_text | smartify }}
45 | Read more →
46 | {% else %}
47 | {{ post.content | cleanup_text | smartify }}
48 | {% endif %}
49 |
50 |
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/src/_posts/2019/2019-05-09-scanamo-conditional-updates-on-nested-fields.md:
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1 | ---
2 | layout: post
3 | title: "DynamoDB: Conditional updates on nested fields"
4 | date: 2019-05-09 12:12:24 +0100
5 | tags: java aws aws:dynamodb scala scala:scanamo
6 | ---
7 |
8 | I always struggle with the ConditionalUpdate syntax for DynamoDB, so here's a snippet for the Java SDK that works (with a bit of Scanamo magic to turn case class instances into instances of `AttributeValue`):
9 |
10 | ```scala
11 | import com.gu.scanamo.DynamoFormat
12 | import com.amazonaws.services.dynamodbv2.model.{
13 | AttributeValue,
14 | UpdateItemRequest
15 | }
16 |
17 | import scala.collection.JavaConverters._
18 |
19 | case class Versioned[T](payload: T, version: Version)
20 |
21 | val value: Versioned[T]
22 |
23 | val evidenceV: DynamoFormat[Version]
24 | val evidenceT: DynamoFormat[T]
25 |
26 | val versionAv: AttributeValue = evidenceV.write(value.version)
27 | val payloadAv: AttributeValue = evidenceT.write(value.payload)
28 |
29 | val updateItemRequest = new UpdateItemRequest()
30 | .withTableName(dynamoConfig.table)
31 | .addKeyEntry("id", new AttributeValue().withS(value.version.id))
32 | .withUpdateExpression(
33 | "SET payload = :payload, version = :version"
34 | )
35 | .withConditionExpression("attribute_not_exists(id) OR version < :currentVersion")
36 | .withExpressionAttributeValues(
37 | Map(
38 | ":currentVersion" -> new AttributeValue(value.version.version.toString),
39 | ":payload" -> payloadAv,
40 | ":version" -> versionAv
41 | ).asJava
42 | )
43 | ```
44 |
45 | Here is the equivalent code in the Scanamo DSL:
46 |
47 | ```scala
48 | val ops = table
49 | .given(
50 | not(attributeExists('id)) or
51 | (attributeExists('id) and 'version \ 'version < value.version.version)
52 | )
53 | .update(
54 | 'id -> value.version.id,
55 | set('version -> value.version) and set('payload -> value.payload)
56 | )
57 |
58 | Scanamo.exec(dynamoClient)(ops)
59 | ```
60 |
61 | Note especially the use of `'version \ 'version` to access the nested field.
62 |
63 | References:
64 |
65 | - {% github_issue scanamo/scanamo#136 %}
66 |
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/src/_plugins/theming.rb:
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1 | Jekyll::Hooks.register :site, :post_read do |site|
2 | src = site.config["source"]
3 | site.posts.docs.each { |post|
4 | if post["theme"] && post["theme"]["color"]
5 | color = post["theme"]["color"]
6 | create_scss_theme(src, color)
7 | create_banner_image(src, color)
8 | end
9 | }
10 | end
11 |
12 |
13 | # Create an SCSS theme with this color as the $primary-color variable.
14 | #
15 | # This will be picked up by the SCSS processor for the site, and cause
16 | # the creation of a CSS theme with this as the primary color.
17 | def create_scss_theme(src, color)
18 | mainfile = "#{src}/theme/style_#{color}.scss"
19 | if ! File.file?(mainfile)
20 | File.open(mainfile, 'w') { |file| file.write(<<-EOT
21 | ---
22 | ---
23 |
24 | $primary-color: ##{color};
25 |
26 | @import "_main.scss";
27 | EOT
28 | ) }
29 | puts(mainfile)
30 | end
31 | end
32 |
33 |
34 | # Create a Specktre-based banner image with this color as the primary color.
35 | #
36 | # This will be picked up by the rsync plugin, and used by the CSS theme
37 | # created above.
38 | def create_banner_image(src, color)
39 | banner_file = "#{src}/theme/specktre_#{color}.png"
40 | if ! File.file?(banner_file)
41 |
42 | puts("Building the banner file for #{color}")
43 |
44 | red = (color.to_i(16) >> 16) % 256
45 | green = (color.to_i(16) >> 8) % 256
46 | blue = (color.to_i(16) % 256)
47 |
48 | start_color = (
49 | red * 0.9 * 65536 +
50 | green * 0.9 * 256 +
51 | blue * 0.9).to_i()
52 | end_color = (
53 | [red * 1.05, 255].min.to_i() * 65536 +
54 | [green * 1.05, 255].min.to_i() * 256 +
55 | [blue * 1.05, 255].min.to_i())
56 |
57 | start_color = "%06x" % start_color
58 | end_color = "%06x" % end_color
59 |
60 | if !system("specktre new --size=3000x250 --start=#{start_color} --end=#{end_color} --squares --name=#{banner_file}")
61 | raise RuntimeError, "Error running the Specktre process for #{color}!"
62 | end
63 |
64 | if !system("optipng #{banner_file}")
65 | raise RuntimeError, "Error running optipng on #{banner_file}"
66 | end
67 | end
68 | end
69 |
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/src/_posts/2018/2018-07-17-beware-the-order-of-inheritance-in-scala.md:
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1 | ---
2 | layout: post
3 | title: Beware the order of inheritance in Scala
4 | date: 2018-07-17 23:27:06 +0100
5 | tags: scala
6 | ---
7 |
8 | Context:
9 |
10 | We used to have a monorepo, but build times led us to remove the storage library and ship it separately. I’m migrating the repo to use the external lib, and exactly one of the tests is throwing a NullPointerException for an unknown reason.
11 |
12 | Cue much cursing and debugging…
13 |
14 | The lesson here is “the order in which you extend traits may be significant”. Commit message reproduced below.
15 |
16 | ---
17 |
18 | [platform#c546f2a](https://github.com/wellcometrust/platform/pull/2428/commits/c546f2ad17c33df83b45184ca23c389ee3dc58f4)
19 |
20 | Why inheritance is evil, ingestor edition
21 |
22 | This test was throwing a NullPointerException when run with the new
23 | storage library, which is pretty annoying and unhelpful. The exception
24 | came from the `eventually` block that checks if the Elasticsearch
25 | container has started, which hadn't changed. Hmm.
26 |
27 | I removed all the test cases, and it wasn't anything to do with them.
28 | Then I started removing the traits we extend from (I'd call them mixins
29 | in Python, but I don't know what they're called in Scala). The only
30 | difference came when I removed both `Messaging` and `S3`, which makes
31 | more sense because at least the `S3` trait has changed.
32 |
33 | Digging another level down, note that the `S3` trait has the
34 | `ExtendedPatience` trait, which sets some patience configuration for
35 | `eventually` blocks. If you remove that, the problem goes away.
36 |
37 | And then it hits me.
38 |
39 | When we removed the storage library, we created a second copy of
40 | `ExtendedPatience` -- and the two are somehow treading on each other's
41 | toes, and throwing this (unhelpful) error. Even though they contain
42 | identical configuration.
43 |
44 | This isn't the only test that has both instances of `ExtendedPatience`,
45 | so what's different?
46 |
47 | Hmm, the order in which the traits are extended is different... and
48 | therein lies the bug.
49 |
50 | I hate computers.
51 |
--------------------------------------------------------------------------------
/src/_posts/2018/2018-11-10-some-notes-on-using-typesafe-for-config.md:
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1 | ---
2 | layout: post
3 | title: Using Typesafe for config in Scala apps
4 | date: 2018-11-10 16:59:30 +0000
5 | tags: scala
6 | ---
7 |
8 | I've just been doing a bunch of work (see [wellcometrust/platform#2967](https://github.com/wellcometrust/platform/issues/2967) and related patches) to use Typesafe for config in our Scala apps, and ditch our use of Guice/Finatra and dependency injection.
9 |
10 | Disentangling the key bits was moderately fiddly, so these are notes on how I got it working.
11 |
12 | 1. Config file.
13 | An example is easiest:
14 |
15 | ```ini
16 | app.contextURL="https://example.org/context.json"
17 | app.namespace=notifier
18 | ```
19 |
20 | Note that strings have to be quoted, or the Typesafe parser things they're part of the format.
21 |
22 | 2. Pass the path to the config file with the `-Dconfig.file` flag.
23 | For example:
24 |
25 | ```console
26 | $ /opt/docker/bin/application -Dconfig.file=/opt/docker/conf/application.conf
27 | ```
28 |
29 | 3. Load the config using the factory:
30 |
31 | ```scala
32 | import com.typesafe.config.{Config, ConfigFactory}
33 |
34 | object Main extends App {
35 | val config: Config = ConfigFactory.load()
36 |
37 | ...
38 | }
39 | ```
40 |
41 | 4. Add the helper class for reading config flags:
42 |
43 | ```scala
44 | import com.typesafe.config.Config
45 |
46 | object EnrichConfig {
47 | implicit class RichConfig(val underlying: Config) extends AnyVal {
48 | def get[T](path: String): Option[T] =
49 | if (underlying.hasPath(path)) {
50 | Some(underlying.getAnyRef(path).asInstanceOf[T])
51 | } else {
52 | None
53 | }
54 |
55 | def required[T](path: String): T =
56 | get(path).getOrElse {
57 | throw new RuntimeException(s"No value found for path $path")
58 | }
59 |
60 | def getOrElse[T](path: String)(default: T): T =
61 | get(path).getOrElse(default)
62 | }
63 | }
64 | ```
65 |
66 | 5. Read values from the config.
67 | For example:
68 |
69 | ```scala
70 | import EnrichConfig._
71 |
72 | object Main extends App {
73 | ...
74 |
75 | val namespace: String = config
76 | .required[String]("app.namespace")
77 |
78 | val contextUrl = config
79 | .getOrElse[String]("app.contextURL")(default = "context.json")
80 |
81 | val waitTime: Option[Int] = config
82 | .get[Int]("app.startUpTime")(default = 10)
83 | }
84 | ```
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/src/static/notebook.js:
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1 | function filterToTag(t) {
2 | li_tags = document.getElementById("notebook_index").getElementsByTagName("li");
3 | for (i = 0; i < li_tags.length; i++) {
4 | item = li_tags.item(i);
5 |
6 | if (item.classList.contains("tagged_with_" + t)) {
7 | continue;
8 | }
9 |
10 | if (item.classList.contains("not_tagged_with_" + t)) {
11 | continue;
12 | }
13 |
14 | item.classList.add("not_tagged_with_" + t);
15 | item.style.display = "none";
16 | }
17 |
18 | url = new URL(window.location.href);
19 | if (!url.searchParams.getAll("tag").includes(t)) {
20 | url.searchParams.append("tag", t);
21 | window.history.pushState({path: url.href}, "", url.href);
22 | }
23 |
24 | filters = document.getElementById("notebook_filters");
25 | filters.style.display = "block";
26 |
27 | if (document.getElementById("tag_filter__" + t) === null) {
28 | filters.innerHTML += '