From 727509cc77b0e21fd59b491bf2298938c71e038c Mon Sep 17 00:00:00 2001
From: Gerry Agbobada <gerry@fiberplane.com>
Date: Thu, 30 Nov 2023 11:36:17 +0100
Subject: [PATCH] Read Otel metric export configuration from env vars

---
 go.work.sum                     |  1 +
 otel/autometrics/init.go        |  6 ++++++
 otel/autometrics/otel.go        | 26 ++++++++++++++++++++++++--
 pkg/autometrics/global_state.go | 10 ++++++++++
 4 files changed, 41 insertions(+), 2 deletions(-)

diff --git a/go.work.sum b/go.work.sum
index cf32a8a..cb6f727 100644
--- a/go.work.sum
+++ b/go.work.sum
@@ -355,6 +355,7 @@ github.com/kr/pretty v0.3.1/go.mod h1:hoEshYVHaxMs3cyo3Yncou5ZscifuDolrwPKZanG3x
 github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
 github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
 github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
+github.com/matttproud/golang_protobuf_extensions v1.0.4 h1:mmDVorXM7PCGKw94cs5zkfA9PSy5pEvNWRP0ET0TIVo=
 github.com/modern-go/concurrent v0.0.0-20180228061459-e0a39a4cb421/go.mod h1:6dJC0mAP4ikYIbvyc7fijjWJddQyLn8Ig3JB5CqoB9Q=
 github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd h1:TRLaZ9cD/w8PVh93nsPXa1VrQ6jlwL5oN8l14QlcNfg=
 github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd/go.mod h1:6dJC0mAP4ikYIbvyc7fijjWJddQyLn8Ig3JB5CqoB9Q=
diff --git a/otel/autometrics/init.go b/otel/autometrics/init.go
index 48f592b..057638d 100644
--- a/otel/autometrics/init.go
+++ b/otel/autometrics/init.go
@@ -175,6 +175,9 @@ func WithPushJobName(pushJobName string) InitOption {
 
 // WithPushPeriod sets the duration between consecutive metrics pushes.
 //
+// The standard `OTEL_METRIC_EXPORT_INTERVAL` environment variable overrides
+// this initialization argument.
+//
 // The default value is 10 seconds.
 func WithPushPeriod(pushPeriod time.Duration) InitOption {
 	return initOptionFunc(func(initArgs *initArguments) error {
@@ -185,6 +188,9 @@ func WithPushPeriod(pushPeriod time.Duration) InitOption {
 
 // WithPushTimeout sets the timeout duration of a single metric push
 //
+// The standard `OTEL_METRIC_EXPORT_TIMEOUT` environment variable overrides
+// this initialization argument.
+//
 // The default value is 5 seconds.
 func WithPushTimeout(pushTimeout time.Duration) InitOption {
 	return initOptionFunc(func(initArgs *initArguments) error {
diff --git a/otel/autometrics/otel.go b/otel/autometrics/otel.go
index 690490f..601e488 100644
--- a/otel/autometrics/otel.go
+++ b/otel/autometrics/otel.go
@@ -5,6 +5,7 @@ import (
 	"errors"
 	"fmt"
 	"os"
+	"strconv"
 	"sync"
 	"time"
 
@@ -314,10 +315,31 @@ func initProvider(pushExporter metric.Exporter, initArgs initArguments) (*metric
 		timeout := defaultPushTimeout
 		interval := defaultPushPeriod
 
-		if initArgs.pushPeriod > 0 {
+		readInitArgs := false
+		if pushPeriod, ok := os.LookupEnv(autometrics.OTelPushPeriodEnv); ok {
+			pushPeriodMs, err := strconv.ParseInt(pushPeriod, 10, 32)
+			if err != nil {
+				autometrics.GetLogger().Warn("opentelemetry: the push period environment variable has non-integer value, ignoring: %s", err)
+				readInitArgs = true
+			} else {
+				interval = time.Duration(pushPeriodMs) * time.Millisecond
+			}
+		}
+		if readInitArgs && initArgs.pushPeriod > 0 {
 			interval = initArgs.pushPeriod
 		}
-		if initArgs.pushTimeout > 0 {
+
+		readInitArgs = false
+		if pushTimeout, ok := os.LookupEnv(autometrics.OTelPushTimeoutEnv); ok {
+			pushTimeoutMs, err := strconv.ParseInt(pushTimeout, 10, 32)
+			if err != nil {
+				autometrics.GetLogger().Warn("opentelemetry: the push timeout environment variable has non-integer value, ignoring: %s", err)
+				readInitArgs = true
+			} else {
+				timeout = time.Duration(pushTimeoutMs) * time.Millisecond
+			}
+		}
+		if readInitArgs && initArgs.pushTimeout > 0 {
 			timeout = initArgs.pushTimeout
 		}
 
diff --git a/pkg/autometrics/global_state.go b/pkg/autometrics/global_state.go
index 0501880..dd572f9 100644
--- a/pkg/autometrics/global_state.go
+++ b/pkg/autometrics/global_state.go
@@ -26,6 +26,16 @@ const (
 	// the repository provider to use as a label. This environment variable has precedence over
 	// over hardcoding the variable directly in [BuildInfo] struct in the Init call.
 	AutometricsRepoProviderEnv = "AUTOMETRICS_REPOSITORY_PROVIDER"
+	// OTelPushPeriodEnv is the name of the environment variable to declare to change the interval
+	// between 2 metrics pushes in milliseconds.
+	//
+	// Reference: https://opentelemetry.io/docs/specs/otel/configuration/sdk-environment-variables/#periodic-exporting-metricreader
+	OTelPushPeriodEnv = "OTEL_METRIC_EXPORT_INTERVAL"
+	// OTelPushTimeoutEnv is the name of the environment variable to declare to change the timeout
+	// threshold of a single metrics push in milliseconds.
+	//
+	// Reference: https://opentelemetry.io/docs/specs/otel/configuration/sdk-environment-variables/#periodic-exporting-metricreader
+	OTelPushTimeoutEnv = "OTEL_METRIC_EXPORT_TIMEOUT"
 )
 
 var (