From 72b1efa5896c51e6009236fc334a95d3f202bf11 Mon Sep 17 00:00:00 2001
From: Yoshi Yamaguchi <yoshifumi@google.com>
Date: Mon, 24 Jun 2024 16:14:50 +0900
Subject: [PATCH] =?UTF-8?q?[ja]=20fix=20=E8=BB=BD=E8=A3=85=20to=20?=
 =?UTF-8?q?=E8=A8=88=E8=A3=85=20(#4733)?=
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---
 content/en/docs/languages/java/sampling.md | 57 ++++++++++++++++++++--
 content/ja/docs/what-is-opentelemetry.md   |  2 +-
 2 files changed, 55 insertions(+), 4 deletions(-)

diff --git a/content/en/docs/languages/java/sampling.md b/content/en/docs/languages/java/sampling.md
index 4f6d2ff58be2..3b56e6fa9570 100644
--- a/content/en/docs/languages/java/sampling.md
+++ b/content/en/docs/languages/java/sampling.md
@@ -8,6 +8,57 @@ spans that are generated by a system. Which sampler to use depends on your
 needs. In general, decide which sampler to use at the start of a trace and allow
 the sampling decision to propagate to other services.
 
+## Default behavior
+
+By default, all spans are sampled, and thus, 100% of traces are sampled. If you
+do not need to manage data volume, don't bother setting a sampler.
+
+## Environment variables
+
+You can configure the sampler with environment variables or system properties.
+Reference the [configuration](/docs/languages/java/configuration/) documentation
+for the available options.
+
+For example, to configure the SDK to sample spans such that only 10% of traces
+get created:
+
+```shell
+export OTEL_TRACES_SAMPLER="traceidratio"
+export OTEL_TRACES_SAMPLER_ARG="0.1"
+```
+
+## Samplers
+
+### ParentBasedSampler
+
+When sampling, the ParentBasedSampler is most often used for
+[head sampling](/docs/concepts/sampling/#head-sampling). It uses the sampling
+decision of the Span’s parent, or the fact that there is no parent, to know
+which secondary sampler to use.
+
+If the parent span is sampled, the child span will also be sampled. Conversely,
+if the parent span is not sampled, the child span will not be sampled either.
+This ensures consistency in sampling decisions within a trace.
+
+### TraceIDRatioBasedSampler
+
+The TraceIdRatioBasedSampler deterministically samples a percentage of traces
+that you pass in as a parameter.
+
+This sampler is useful when you want to control the overall sampling rate across
+all traces, regardless of their parent spans. It provides a consistent rate of
+sampling for all traces initiated.
+
+## Configuration in code
+
+{{% alert title="Note" %}} The use of the
+[Java agent](/docs/zero-code/java/agent/),
+[Spring Boot Starter](/docs/zero-code/java/spring-boot-starter/), or
+[SDK autoconfigure](/docs/languages/java/instrumentation/#autoconfiguration) is
+generally recommended for controlling sampling, rather than setting it directly
+in the code. Most users should find the default settings sufficient for their
+needs. {{% /alert %}}
+
 A sampler can be set on the tracer provider using the `setSampler` method, as
 follows:
 
@@ -37,9 +88,9 @@ Other samplers include:
 
 - `traceIdRatioBased`, which samples a fraction of spans, based on the fraction
   given to the sampler. If you set `0.5`, half of all the spans are sampled.
+  Currently, only the ratio of traces that are sampled can be relied on, not how
+  the sampled traces are determined. As such, it is recommended to only use this
+  sampler for root spans using `parentBased`.
 - `parentBased`, which uses the parent span to make sampling decisions, if
   present. By default, the tracer provider uses a parentBased sampler with the
   `alwaysOn` sampler.
-
-When in a production environment, consider using the `parentBased` sampler with
-the `traceIdRatioBased` sampler.
diff --git a/content/ja/docs/what-is-opentelemetry.md b/content/ja/docs/what-is-opentelemetry.md
index e6a7fb23693c..141a8a215f97 100644
--- a/content/ja/docs/what-is-opentelemetry.md
+++ b/content/ja/docs/what-is-opentelemetry.md
@@ -19,7 +19,7 @@ OpenTelemetryの主な目的は、あなたのアプリケーションやシス
 [オブザーバビリティ](/docs/concepts/observability-primer/#what-is-observability)とは、システムの出力を調べることによって、システムの内部状態を理解する能力のことです。
 ソフトウェアの文脈では、これは、トレース、メトリクス、ログを含むテレメトリーデータを調べることによって、システムの内部状態を理解できることを意味します。
 
-システムをオブザーバビリティがある状態にするには、[軽装されて](/docs/concepts/instrumentation)いなければなりません。
+システムをオブザーバビリティがある状態にするには、[計装されて](/docs/concepts/instrumentation)いなければなりません。
 つまり、コードが[トレース](/docs/concepts/signals/traces/)、[メトリクス](/docs/concepts/signals/metrics/)、または[ログ](/docs/concepts/signals/logs/)を出力しなければなりません。
 計装されたデータは、オブザーバビリティバックエンドに送信されなければなりません。