From 96fa8af0c23d7f20224e67ffa4c34e68e0b24199 Mon Sep 17 00:00:00 2001
From: Aaron Abbott <aaronabbott@google.com>
Date: Fri, 15 Sep 2023 14:57:50 +0000
Subject: [PATCH] Allow instrument names to have '/' and up to 255 characters

Fixes #3431
---
 CHANGELOG.md                                  |  2 ++
 .../metrics/_internal/instrument.py           |  2 +-
 .../tests/metrics/test_instruments.py         | 22 ++++++++++++++-----
 3 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index f5a7a983987..2c2f63b4b2c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#3335](https://github.com/open-telemetry/opentelemetry-python/pull/3335))
 - Fix error when no LoggerProvider configured for LoggingHandler
   ([#3423](https://github.com/open-telemetry/opentelemetry-python/pull/3423))
+- Allow instrument names to have '/' and up to 255 characters
+  ([#3442](https://github.com/open-telemetry/opentelemetry-python/pull/3442))
 
 
 ## Version 1.20.0/0.41b0 (2023-09-04)
diff --git a/opentelemetry-api/src/opentelemetry/metrics/_internal/instrument.py b/opentelemetry-api/src/opentelemetry/metrics/_internal/instrument.py
index fec2879ef6c..54b2fb7597e 100644
--- a/opentelemetry-api/src/opentelemetry/metrics/_internal/instrument.py
+++ b/opentelemetry-api/src/opentelemetry/metrics/_internal/instrument.py
@@ -38,7 +38,7 @@
 
 _logger = getLogger(__name__)
 
-_name_regex = re_compile(r"[a-zA-Z][-_.a-zA-Z0-9]{0,62}")
+_name_regex = re_compile(r"[a-zA-Z][-_./a-zA-Z0-9]{0,254}")
 _unit_regex = re_compile(r"[\x00-\x7F]{0,63}")
 
 
diff --git a/opentelemetry-api/tests/metrics/test_instruments.py b/opentelemetry-api/tests/metrics/test_instruments.py
index 4a3d3d448b3..2e6082d873e 100644
--- a/opentelemetry-api/tests/metrics/test_instruments.py
+++ b/opentelemetry-api/tests/metrics/test_instruments.py
@@ -564,14 +564,13 @@ def test_observable_up_down_counter_callback(self):
         )
 
     def test_name_check(self):
-
         instrument = ChildInstrument("name")
 
         self.assertEqual(
             instrument._check_name_unit_description(
-                "a" * 63, "unit", "description"
+                "a" * 255, "unit", "description"
             )["name"],
-            "a" * 63,
+            "a" * 255,
         )
         self.assertEqual(
             instrument._check_name_unit_description(
@@ -591,12 +590,25 @@ def test_name_check(self):
             )["name"],
             "a_",
         )
+        self.assertEqual(
+            instrument._check_name_unit_description(
+                "a/", "unit", "description"
+            )["name"],
+            "a/",
+        )
 
-        self.assertIsNone(
+        # the old max length
+        self.assertIsNotNone(
             instrument._check_name_unit_description(
                 "a" * 64, "unit", "description"
             )["name"]
         )
+        self.assertIsNone(
+            instrument._check_name_unit_description(
+                "a" * 256, "unit", "description"
+            )["name"]
+        )
+
         self.assertIsNone(
             instrument._check_name_unit_description(
                 "Ñ", "unit", "description"
@@ -619,7 +631,6 @@ def test_name_check(self):
         )
 
     def test_unit_check(self):
-
         instrument = ChildInstrument("name")
 
         self.assertEqual(
@@ -653,7 +664,6 @@ def test_unit_check(self):
         )
 
     def test_description_check(self):
-
         instrument = ChildInstrument("name")
 
         self.assertEqual(