cosmos · technicallyty · Oct 29, 2025 · Oct 29, 2025 · Oct 29, 2025 · Oct 30, 2025
diff --git a/UPGRADING.md b/UPGRADING.md
@@ -74,4 +74,77 @@ The [README.md](telemetry/README.md) in the `telemetry` package provides more de
 1. application developers should follow the official [go OpenTelemetry](https://pkg.go.dev/go.opentelemetry.io/otel) guidelines when instrumenting their applications.
 2. node operators who want to configure OpenTelemetry exporters should set the `OTEL_EXPERIMENTAL_CONFIG_FILE` environment variable to the path of a yaml file which follows the OpenTelemetry declarative configuration format specified here: https://pkg.go.dev/go.opentelemetry.io/contrib/otelconf. As long as the `telemetry` package has been imported somewhere (it should already be imported if you are using the SDK), OpenTelemetry will be initialized automatically based on the configuration file.
 
-NOTE: the go implementation of [otelconf](https://pkg.go.dev/go.opentelemetry.io/contrib/otelconf) is still under development and we will update our usage of it as it matures.
+NOTE: the go implementation of [otelconf](https://pkg.go.dev/go.opentelemetry.io/contrib/otelconf) is still under development and we will update our usage of it as it matures.
+
+## Log v2
+
+The log package has been refactored to support OpenTelemetry tracing correlation. If you have basic usage of the logger, such as getting it from sdk.Context and logging to the console; nothing changes. You are unaffected.
+
+If you implement your own logger, or setup the logger manually, a few things have been changed.
+
+
+### Logger Interface
+
+The interface has 1 new method:
+
+```go
+type Logger interface {
+	Ctx(context.Context) Logger
+}
+```
+
+This method attaches a context to the logger, allowing logs to be correlated with OpenTelemetry traces.
+Note that if OpenTelemetry is not used in your application, ZeroLogger will be used, and the Ctx method will be a noop.
+
+### Constructor
+
+If you construct your own logger, the constructor function arguments and option names have changed.
+
+Old constructor: 
+```go
+func NewLogger(dst io.Writer, options ...Option) Logger
+```
+
+New constructor:
+```go
+func NewLogger(name string, opts ...Option) Logger
+```
+
+### Options
+
+All option functions are now prefixed with `With` to make option discovery easier and more clear.
+
+Example:
+
+Before:
+```go
+func FilterOption(filter FilterFunc) Option
+```
+
+After:
+```go
+func WithFilter(filter FilterFunc) Option
+```
+
+Additionally, new options have been added. See log/options.go for all usable options.
+
+### Default Behavior
+
+By default, the logger will log to the console AND to OpenTelemetry if a logger provider has been set in the optional OpenTelemetry configuration.
+
+For production nodes, we have introduced a new flag, `--log_no_console` to disable the overhead of logging to the console. This is useful in situations where you ONLY want OpenTelemetry log forwarding.
+
+### Log Levels
+
+Levels have been changed to achieve parity with slog. The supported levels are:
+
+- info
+- debug
+- warn
+- error
+
+The following levels are no longer supported:
+
+- trace
+- fatal
+- panic
diff --git a/baseapp/abci.go b/baseapp/abci.go
@@ -41,7 +41,7 @@ const (
 )
 
 func (app *BaseApp) InitChain(req *abci.RequestInitChain) (*abci.ResponseInitChain, error) {
-	_, span := tracer.Start(context.Background(), "InitChain")
+	ctx, span := tracer.Start(context.Background(), "InitChain")
 	defer span.End()
 
 	if req.ChainId != app.chainID {
@@ -51,7 +51,7 @@ func (app *BaseApp) InitChain(req *abci.RequestInitChain) (*abci.ResponseInitCha
 	// On a new chain, we consider the init chain block height as 0, even though
 	// req.InitialHeight is 1 by default.
 	initHeader := cmtproto.Header{ChainID: req.ChainId, Time: req.Time}
-	app.logger.Info("InitChain", "initialHeight", req.InitialHeight, "chainID", req.ChainId)
+	app.logger.Ctx(ctx).Info("InitChain", "initialHeight", req.InitialHeight, "chainID", req.ChainId)
 
 	// Set the initial height, which will be used to determine if we are proposing
 	// or processing the first block or not.

diff --git a/baseapp/baseapp_test.go b/baseapp/baseapp_test.go
@@ -72,7 +72,7 @@ func NewBaseAppSuite(t *testing.T, opts ...func(*baseapp.BaseApp)) *BaseAppSuite
 
 	txConfig := authtx.NewTxConfig(cdc, authtx.DefaultSignModes)
 	db := dbm.NewMemDB()
-	logger := log.NewLogger(os.Stdout, log.ColorOption(false))
+	logger := log.NewLogger("baseapp-test", log.WithConsoleWriter(os.Stdout), log.WithColor(false))
 
 	app := baseapp.NewBaseApp(t.Name(), logger, db, txConfig.TxDecoder(), opts...)
 	require.Equal(t, t.Name(), app.Name())

diff --git a/client/flags/flags.go b/client/flags/flags.go
@@ -91,6 +91,7 @@ const (
 	FlagVerboseLogLevel = "verbose_log_level"
 	FlagLogFormat       = "log_format"
 	FlagLogNoColor      = "log_no_color"
+	FlagLogNoConsole    = "log_no_console"
 )
 
 // List of supported output formats

diff --git a/client/pruning/main.go b/client/pruning/main.go
@@ -77,7 +77,7 @@ Supported app-db-backend types include 'goleveldb', 'rocksdb', 'pebbledb'.`,
 			// in our test, it's important to close db explicitly for pebbledb to write to disk.
 			defer db.Close()
 
-			logger := log.NewLogger(cmd.OutOrStdout())
+			logger := log.NewLogger("pruning", log.WithConsoleWriter(cmd.OutOrStdout()))
 			app := appCreator(logger, db, nil, vp)
 			cms := app.CommitMultiStore()
 

diff --git a/client/snapshot/export.go b/client/snapshot/export.go
@@ -28,7 +28,7 @@ func ExportSnapshotCmd(appCreator servertypes.AppCreator) *cobra.Command {
 			if err != nil {
 				return err
 			}
-			logger := log.NewLogger(cmd.OutOrStdout())
+			logger := log.NewLogger("snapshot", log.WithConsoleWriter(cmd.OutOrStdout()))
 			app := appCreator(logger, db, nil, ctx.Viper)
 
 			if height == 0 {

diff --git a/client/snapshot/restore.go b/client/snapshot/restore.go
@@ -37,7 +37,7 @@ func RestoreSnapshotCmd(appCreator servertypes.AppCreator) *cobra.Command {
 			if err != nil {
 				return err
 			}
-			logger := log.NewLogger(cmd.OutOrStdout())
+			logger := log.NewLogger("snapshot", log.WithConsoleWriter(cmd.OutOrStdout()))
 			app := appCreator(logger, db, nil, ctx.Viper)
 
 			sm := app.SnapshotManager()

diff --git a/client/v2/go.mod b/client/v2/go.mod
@@ -157,6 +157,7 @@ require (
 	github.com/zondax/ledger-go v1.0.1 // indirect
 	go.etcd.io/bbolt v1.4.0 // indirect
 	go.opentelemetry.io/auto/sdk v1.2.1 // indirect
+	go.opentelemetry.io/contrib/bridges/otelslog v0.14.0 // indirect
 	go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc v0.64.0 // indirect
 	go.opentelemetry.io/contrib/instrumentation/host v0.64.0 // indirect
 	go.opentelemetry.io/contrib/instrumentation/runtime v0.64.0 // indirect
@@ -207,6 +208,7 @@ require (
 // 	<temporary replace>
 // )
 replace (
+	cosmossdk.io/log => ../../log
 	cosmossdk.io/store => ../../store
 	github.com/cosmos/cosmos-sdk => ../../.
 	github.com/tidwall/btree => github.com/cosmos/btree v0.0.0-20250924232609-2c6195d95951

diff --git a/client/v2/go.sum b/client/v2/go.sum
@@ -10,8 +10,6 @@ cosmossdk.io/depinject v1.2.1 h1:eD6FxkIjlVaNZT+dXTQuwQTKZrFZ4UrfCq1RKgzyhMw=
 cosmossdk.io/depinject v1.2.1/go.mod h1:lqQEycz0H2JXqvOgVwTsjEdMI0plswI7p6KX+MVqFOM=
 cosmossdk.io/errors v1.0.2 h1:wcYiJz08HThbWxd/L4jObeLaLySopyyuUFB5w4AGpCo=
 cosmossdk.io/errors v1.0.2/go.mod h1:0rjgiHkftRYPj//3DrD6y8hcm40HcPv/dR4R/4efr0k=
-cosmossdk.io/log v1.6.1 h1:YXNwAgbDwMEKwDlCdH8vPcoggma48MgZrTQXCfmMBeI=
-cosmossdk.io/log v1.6.1/go.mod h1:gMwsWyyDBjpdG9u2avCFdysXqxq28WJapJvu+vF1y+E=
 cosmossdk.io/math v1.5.3 h1:WH6tu6Z3AUCeHbeOSHg2mt9rnoiUWVWaQ2t6Gkll96U=
 cosmossdk.io/math v1.5.3/go.mod h1:uqcZv7vexnhMFJF+6zh9EWdm/+Ylyln34IvPnBauPCQ=
 cosmossdk.io/schema v1.1.0 h1:mmpuz3dzouCoyjjcMcA/xHBEmMChN+EHh8EHxHRHhzE=
@@ -737,6 +735,8 @@ go.opencensus.io v0.20.2/go.mod h1:6WKK9ahsWS3RSO+PY9ZHZUfv2irvY6gN279GOPZjmmk=
 go.opencensus.io v0.22.2/go.mod h1:yxeiOL68Rb0Xd1ddK5vPZ/oVn4vY4Ynel7k9FzqtOIw=
 go.opentelemetry.io/auto/sdk v1.2.1 h1:jXsnJ4Lmnqd11kwkBV2LgLoFMZKizbCi5fNZ/ipaZ64=
 go.opentelemetry.io/auto/sdk v1.2.1/go.mod h1:KRTj+aOaElaLi+wW1kO/DZRXwkF4C5xPbEe3ZiIhN7Y=
+go.opentelemetry.io/contrib/bridges/otelslog v0.14.0 h1:eypSOd+0txRKCXPNyqLPsbSfA0jULgJcGmSAdFAnrCM=
+go.opentelemetry.io/contrib/bridges/otelslog v0.14.0/go.mod h1:CRGvIBL/aAxpQU34ZxyQVFlovVcp67s4cAmQu8Jh9mc=
 go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc v0.64.0 h1:RN3ifU8y4prNWeEnQp2kRRHz8UwonAEYZl8tUzHEXAk=
 go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc v0.64.0/go.mod h1:habDz3tEWiFANTo6oUE99EmaFUrCNYAAg3wiVmusm70=
 go.opentelemetry.io/contrib/instrumentation/host v0.64.0 h1:/o7fG3CXOlVK8fUzK+p8CyHU9Opha3IL4DZR3UXGZ1w=

diff --git a/go.mod b/go.mod
@@ -48,7 +48,6 @@ require (
 	github.com/mdp/qrterminal/v3 v3.2.1
 	github.com/prometheus/client_golang v1.23.2
 	github.com/prometheus/common v0.67.5
-	github.com/rs/zerolog v1.34.0
 	github.com/spf13/cast v1.10.0
 	github.com/spf13/cobra v1.10.2
 	github.com/spf13/pflag v1.0.10
@@ -208,6 +207,7 @@ require (
 	github.com/rcrowley/go-metrics v0.0.0-20250401214520-65e299d6c5c9 // indirect
 	github.com/rogpeppe/go-internal v1.14.1 // indirect
 	github.com/rs/cors v1.11.1 // indirect
+	github.com/rs/zerolog v1.34.0 // indirect
 	github.com/sagikazarmark/locafero v0.11.0 // indirect
 	github.com/sasha-s/go-deadlock v0.3.6 // indirect
 	github.com/shirou/gopsutil/v4 v4.25.11 // indirect
@@ -227,6 +227,7 @@ require (
 	github.com/zondax/ledger-go v1.0.1 // indirect
 	go.etcd.io/bbolt v1.4.0 // indirect
 	go.opentelemetry.io/auto/sdk v1.2.1 // indirect
+	go.opentelemetry.io/contrib/bridges/otelslog v0.14.0 // indirect
 	go.opentelemetry.io/contrib/detectors/gcp v1.38.0 // indirect
 	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.62.0 // indirect
 	go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploggrpc v0.15.0 // indirect
@@ -268,6 +269,7 @@ require (
 
 // Below are the long-lived replace of the Cosmos SDK
 replace (
+	cosmossdk.io/log => ./log
 	// use cosmos fork of keyring
 	github.com/99designs/keyring => github.com/cosmos/keyring v1.2.0
 	// dgrijalva/jwt-go is deprecated and doesn't receive security updates.

diff --git a/go.sum b/go.sum
@@ -32,8 +32,6 @@ cosmossdk.io/depinject v1.2.1 h1:eD6FxkIjlVaNZT+dXTQuwQTKZrFZ4UrfCq1RKgzyhMw=
 cosmossdk.io/depinject v1.2.1/go.mod h1:lqQEycz0H2JXqvOgVwTsjEdMI0plswI7p6KX+MVqFOM=
 cosmossdk.io/errors v1.0.2 h1:wcYiJz08HThbWxd/L4jObeLaLySopyyuUFB5w4AGpCo=
 cosmossdk.io/errors v1.0.2/go.mod h1:0rjgiHkftRYPj//3DrD6y8hcm40HcPv/dR4R/4efr0k=
-cosmossdk.io/log v1.6.1 h1:YXNwAgbDwMEKwDlCdH8vPcoggma48MgZrTQXCfmMBeI=
-cosmossdk.io/log v1.6.1/go.mod h1:gMwsWyyDBjpdG9u2avCFdysXqxq28WJapJvu+vF1y+E=
 cosmossdk.io/math v1.5.3 h1:WH6tu6Z3AUCeHbeOSHg2mt9rnoiUWVWaQ2t6Gkll96U=
 cosmossdk.io/math v1.5.3/go.mod h1:uqcZv7vexnhMFJF+6zh9EWdm/+Ylyln34IvPnBauPCQ=
 cosmossdk.io/schema v1.1.0 h1:mmpuz3dzouCoyjjcMcA/xHBEmMChN+EHh8EHxHRHhzE=
@@ -854,6 +852,8 @@ go.opencensus.io v0.20.2/go.mod h1:6WKK9ahsWS3RSO+PY9ZHZUfv2irvY6gN279GOPZjmmk=
 go.opencensus.io v0.22.2/go.mod h1:yxeiOL68Rb0Xd1ddK5vPZ/oVn4vY4Ynel7k9FzqtOIw=
 go.opentelemetry.io/auto/sdk v1.2.1 h1:jXsnJ4Lmnqd11kwkBV2LgLoFMZKizbCi5fNZ/ipaZ64=
 go.opentelemetry.io/auto/sdk v1.2.1/go.mod h1:KRTj+aOaElaLi+wW1kO/DZRXwkF4C5xPbEe3ZiIhN7Y=
+go.opentelemetry.io/contrib/bridges/otelslog v0.14.0 h1:eypSOd+0txRKCXPNyqLPsbSfA0jULgJcGmSAdFAnrCM=
+go.opentelemetry.io/contrib/bridges/otelslog v0.14.0/go.mod h1:CRGvIBL/aAxpQU34ZxyQVFlovVcp67s4cAmQu8Jh9mc=
 go.opentelemetry.io/contrib/detectors/gcp v1.38.0 h1:ZoYbqX7OaA/TAikspPl3ozPI6iY6LiIY9I8cUfm+pJs=
 go.opentelemetry.io/contrib/detectors/gcp v1.38.0/go.mod h1:SU+iU7nu5ud4oCb3LQOhIZ3nRLj6FNVrKgtflbaf2ts=
 go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc v0.64.0 h1:RN3ifU8y4prNWeEnQp2kRRHz8UwonAEYZl8tUzHEXAk=

diff --git a/log/CHANGELOG.md b/log/CHANGELOG.md
@@ -22,6 +22,8 @@ Each entry must include the Github issue reference in the following format:
 
 ## [Unreleased]
 
+* [#25701](https://github.com/cosmos/cosmos-sdk/pull/25701) Introduce log v2, enabling OpenTelemetry logging with slog. The logging interface has been updated to accommodate Context attachment, which allows correlation of logs with traces. To see the impact of these changes, check out the [Upgrade](../UPGRADING.md) document.
+
 ## [v1.6.0](https://github.com/cosmos/cosmos-sdk/releases/tag/log/v1.6.0) - 2025-05-13
 
 * [#24720](https://github.com/cosmos/cosmos-sdk/pull/24720) add `VerboseModeLogger` extension interface and `VerboseLevel` configuration option for increasing log verbosity during sensitive operations such as upgrades.