From a9f9014edd32dc22844054628db24cb12107ed19 Mon Sep 17 00:00:00 2001
From: Konstantin Demin <rockdrilla@gmail.com>
Date: Fri, 19 Jul 2024 16:52:06 +0300
Subject: [PATCH] initial commit

---
 .ci/build-all.sh        |  21 +++++
 .ci/build.sh            |  20 +++++
 .ci/envsh.build         |  44 ++++++++++
 .ci/envsh.common        |  72 +++++++++++++++++
 .ci/envsh.registry      |  14 ++++
 .ci/image-all.sh        |  50 ++++++++++++
 .ci/image.sh            |  27 +++++++
 .ci/registry-login.sh   |  21 +++++
 .ci/sync-all.sh         |  56 +++++++++++++
 .ci/sync-latest.sh      |  47 +++++++++++
 .dockerignore           |   3 +
 .gitignore              |   4 +
 .woodpecker/.build.yml  |  75 +++++++++++++++++
 .woodpecker/.latest.yml |  43 ++++++++++
 Dockerfile              |  35 ++++++++
 Dockerfile.ci           |  12 +++
 LICENSE                 | 175 ++++++++++++++++++++++++++++++++++++++++
 Makefile                |  69 ++++++++++++++++
 fiber.go                |  50 ++++++++++++
 fiber_debug.go          |  20 +++++
 fiber_nodebug.go        |  11 +++
 go.mod                  |  19 +++++
 go.sum                  |  28 +++++++
 main.go                 |  50 ++++++++++++
 return-code.go          |  48 +++++++++++
 25 files changed, 1014 insertions(+)
 create mode 100755 .ci/build-all.sh
 create mode 100755 .ci/build.sh
 create mode 100644 .ci/envsh.build
 create mode 100644 .ci/envsh.common
 create mode 100644 .ci/envsh.registry
 create mode 100755 .ci/image-all.sh
 create mode 100755 .ci/image.sh
 create mode 100755 .ci/registry-login.sh
 create mode 100755 .ci/sync-all.sh
 create mode 100755 .ci/sync-latest.sh
 create mode 100644 .dockerignore
 create mode 100644 .gitignore
 create mode 100644 .woodpecker/.build.yml
 create mode 100644 .woodpecker/.latest.yml
 create mode 100644 Dockerfile
 create mode 100644 Dockerfile.ci
 create mode 100644 LICENSE
 create mode 100644 Makefile
 create mode 100644 fiber.go
 create mode 100644 fiber_debug.go
 create mode 100644 fiber_nodebug.go
 create mode 100644 go.mod
 create mode 100644 go.sum
 create mode 100644 main.go
 create mode 100644 return-code.go

diff --git a/.ci/build-all.sh b/.ci/build-all.sh
new file mode 100755
index 0000000..c3bfe3d
--- /dev/null
+++ b/.ci/build-all.sh
@@ -0,0 +1,21 @@
+#!/bin/sh
+# SPDX-License-Identifier: Apache-2.0
+# (c) 2024, Konstantin Demin
+set -ef
+
+[ -z "${CI_DEBUG}" ] || set -xv
+
+r=0
+
+TARGET_PLATFORMS=$(printf '%s' "${TARGET_PLATFORMS:?}" | tr ',' ' ')
+for TARGET_PLATFORM in ${TARGET_PLATFORMS} ; do
+    export TARGET_PLATFORM
+
+    . .ci/envsh.build
+    .ci/build.sh || r=$?
+    [ "$r" = 0 ] || break
+done
+
+make ci-clean
+
+exit "$r"
diff --git a/.ci/build.sh b/.ci/build.sh
new file mode 100755
index 0000000..3145a44
--- /dev/null
+++ b/.ci/build.sh
@@ -0,0 +1,20 @@
+#!/bin/sh
+# SPDX-License-Identifier: Apache-2.0
+# (c) 2024, Konstantin Demin
+set -ef
+
+[ -z "${CI_DEBUG}" ] || set -xv
+
+mkdir -p dist
+OUTDIR=dist
+OUTSFX='-'$(printf '%s' "${TARGET_PLATFORM:?}" | tr '/' '-')
+
+export OUTDIR OUTSFX
+
+idle() {
+    nice -n +40 \
+    chrt -i 0 \
+    ionice -c 3 \
+    "$@"
+}
+idle make clean build || make clean build
diff --git a/.ci/envsh.build b/.ci/envsh.build
new file mode 100644
index 0000000..b3ab1cc
--- /dev/null
+++ b/.ci/envsh.build
@@ -0,0 +1,44 @@
+#!/bin/sh
+# SPDX-License-Identifier: Apache-2.0
+# (c) 2024, Konstantin Demin
+set -ef
+
+unset GOAMD64 GOARM GOPPC64 GOMIPS GOMIPS64
+
+## produce GOOS and GOARCH from TARGET_PLATFORM
+unset GOOS GOARCH _variant
+IFS=/ read -r GOOS GOARCH _variant <<-EOF
+${TARGET_PLATFORM:?}
+EOF
+## verify that GOOS and GOARCH are not empty
+: "${GOOS:?}" "${GOARCH:?}"
+export GOOS GOARCH
+## fill env with Go-related variables
+if [ -n "${_variant}" ] ; then
+    case "${GOARCH}" in
+    amd64 )
+        export GOAMD64="${_variant}" ;;
+    arm )
+        export GOARM="${_variant#v}" ;;
+    ppc64 | ppc64le )
+        export GOPPC64="${_variant}" ;;
+    mips | mipsle )
+        export GOMIPS="${_variant}" ;;
+    mips64 | mips64le )
+        export GOMIPS64="${_variant}" ;;
+    esac
+fi
+unset _variant
+
+unset RELMODE
+while : ; do
+    [ -n "${CI_COMMIT_BRANCH}" ]       || break
+    [ -n "${CI_REPO_DEFAULT_BRANCH}" ] || break
+
+    ## RELMODE is for default branch only
+    [ "${CI_COMMIT_BRANCH}" = "${CI_REPO_DEFAULT_BRANCH}" ] || break
+    export RELMODE=1
+
+    break
+done
+[ -z "${CI_COMMIT_TAG}" ] || export RELMODE=1
diff --git a/.ci/envsh.common b/.ci/envsh.common
new file mode 100644
index 0000000..b66907c
--- /dev/null
+++ b/.ci/envsh.common
@@ -0,0 +1,72 @@
+#!/bin/sh
+# SPDX-License-Identifier: Apache-2.0
+# (c) 2024, Konstantin Demin
+set -ef
+
+## shifty-nifty shell goodies :)
+
+## do same thing as GitLab does for CI_COMMIT_REF_SLUG:
+## 1. lowercase string
+## 2. replace not allowed chars with '-' (squeezing repeats)
+##    allowed chars are: `0-9`, `a-z` and '-'
+## 3. remove leading and trailing '-' (if any)
+## 4. truncate string up to 63 chars
+## 5. remove trailing '-' (if any)
+ref_slug() {
+    printf '%s' "${1:?}" \
+    | sed -Ez 's/^(.+)$/\L\1/;s/[^0-9a-z]+/-/g;s/^-//;s/-$//;s/^(.{1,63}).*$/\1/;s/-$//' \
+    | tr -d '\0'
+}
+
+## normalize image tag
+## performs like ref_slug() except:
+## - symbols '_' and '.' are allowed too
+## - truncate string up to 96 chars
+## - squeeze symbol sequences:
+##   - '-' has higher priority than surrounding (leading and trailing) symbols
+##   - first symbol in sequence has higher priority than following symbols
+## NB: implementation is rather demonstrative than effective
+image_tag_norm() {
+    printf '%s' "${1:?}" \
+    | sed -Ez 's/^(.+)$/\L\1/;s/[^0-9a-z_.]+/-/g' \
+    | sed -Ez 's/\.+/./g;s/_+/_/g;s/[_.]+-/-/g;s/-[_.]+/-/g;s/([_.])[_.]+/\1/g' \
+    | sed -Ez 's/^[_.-]//;s/[_.-]$//;s/^(.{1,95}).*$/\1/;s/[_.-]$//' \
+    | tr -d '\0'
+}
+
+## misc CI things
+# CI_COMMIT_SHORT_SHA="${CI_COMMIT_SHA:0:8}"
+CI_COMMIT_SHORT_SHA=$(printf '%s' "${CI_COMMIT_SHA}" | cut -c 1-8)
+if [ -n "${CI_COMMIT_BRANCH}" ] ; then
+    CI_COMMIT_REF_SLUG="${CI_COMMIT_BRANCH}"
+fi
+if [ -n "${CI_COMMIT_SOURCE_BRANCH}" ] ; then
+    CI_COMMIT_REF_SLUG="${CI_COMMIT_SOURCE_BRANCH}"
+fi
+if [ -n "${CI_COMMIT_TAG}" ] ; then
+    CI_COMMIT_REF_SLUG="${CI_COMMIT_TAG}"
+fi
+CI_COMMIT_REF_SLUG="$(image_tag_norm "${CI_COMMIT_REF_SLUG}")"
+
+## image tag(s)
+IMAGE_TAG="${CI_COMMIT_SHORT_SHA}-b${CI_PIPELINE_NUMBER}-${CI_COMMIT_REF_SLUG}"
+EXTRA_TAGS=$(image_tag_norm "branch-${CI_COMMIT_BRANCH}")
+if [ -n "${CI_COMMIT_TAG}" ] ; then
+    IMAGE_TAG="${CI_COMMIT_SHORT_SHA}"
+    EXTRA_TAGS="${CI_COMMIT_REF_SLUG}"
+    ## TODO: think about "latest" tag: it should be error-prone for "backward tag push"
+    # EXTRA_TAGS="${CI_COMMIT_REF_SLUG} latest"
+else
+    if [ -n "${CI_COMMIT_SOURCE_BRANCH}" ] ; then
+        echo "Running on branch '${CI_COMMIT_SOURCE_BRANCH}'"
+    else
+        if [ "${CI_COMMIT_BRANCH}" != "${CI_REPO_DEFAULT_BRANCH}" ] ; then
+            echo "Running on branch '${CI_COMMIT_BRANCH}'"
+        else
+            IMAGE_TAG="${CI_COMMIT_SHORT_SHA}"
+        fi
+    fi
+fi
+IMAGE_TAG=$(image_tag_norm "${IMAGE_TAG}")
+
+export CI_COMMIT_SHORT_SHA CI_COMMIT_REF_SLUG IMAGE_TAG EXTRA_TAGS
diff --git a/.ci/envsh.registry b/.ci/envsh.registry
new file mode 100644
index 0000000..4033b69
--- /dev/null
+++ b/.ci/envsh.registry
@@ -0,0 +1,14 @@
+#!/bin/sh
+# SPDX-License-Identifier: Apache-2.0
+# (c) 2024, Konstantin Demin
+set -ef
+
+## setup image registry authentication
+export REGISTRY_AUTH_FILE="${PWD}/.ci/.auth.json"
+if ! [ -s "${REGISTRY_AUTH_FILE}" ] ; then
+    if [ -z "${REGISTRY_AUTH}" ] ; then
+        echo 'REGISTRY_AUTH is missing'
+        exit 1
+    fi
+    printf '%s' "${REGISTRY_AUTH}" > "${REGISTRY_AUTH_FILE}"
+fi
diff --git a/.ci/image-all.sh b/.ci/image-all.sh
new file mode 100755
index 0000000..4813b17
--- /dev/null
+++ b/.ci/image-all.sh
@@ -0,0 +1,50 @@
+#!/bin/sh
+# SPDX-License-Identifier: Apache-2.0
+# (c) 2024, Konstantin Demin
+set -ef
+
+[ -z "${CI_DEBUG}" ] || set -xv
+
+: "${TARGET_PLATFORMS:?}"
+
+. .ci/envsh.common
+. .ci/envsh.registry
+
+: "${IMAGE_NAME:?}" "${IMAGE_TAG:?}"
+IMAGE="${IMAGE_NAME}:${IMAGE_TAG}"
+
+## used by .ci/image.sh
+export IMAGE_MANIFEST="${IMAGE}"
+
+if buildah manifest exists "${IMAGE}" ; then
+    buildah manifest rm "${IMAGE}"
+fi
+buildah manifest create "${IMAGE}"
+
+r=0
+
+TARGET_PLATFORMS=$(printf '%s' "${TARGET_PLATFORMS}" | tr ',' ' ')
+for TARGET_PLATFORM in ${TARGET_PLATFORMS} ; do
+    export TARGET_PLATFORM
+
+    . .ci/envsh.build
+
+    PLATFORM_SUFFIX='-'$(printf '%s' "${TARGET_PLATFORM}" | tr '/' '-')
+    export PLATFORM_SUFFIX
+
+    .ci/image.sh || r=$?
+    [ "$r" = 0 ] || break
+
+    buildah manifest add "${IMAGE}" "${IMAGE}${PLATFORM_SUFFIX}"
+done
+
+[ "$r" = 0 ] || exit "$r"
+
+## list built image(s)
+echo
+echo 'IMAGES:'
+echo
+buildah images --all --noheading --format 'table {{.ID}} {{.Name}}:{{.Tag}} {{.Size}} {{.CreatedAtRaw}}' --filter "reference=${IMAGE_NAME}"
+echo
+
+buildah manifest push --all "${IMAGE}" "docker://${IMAGE}"
diff --git a/.ci/image.sh b/.ci/image.sh
new file mode 100755
index 0000000..f847f84
--- /dev/null
+++ b/.ci/image.sh
@@ -0,0 +1,27 @@
+#!/bin/sh
+# SPDX-License-Identifier: Apache-2.0
+# (c) 2024, Konstantin Demin
+set -ef
+
+. .ci/envsh.registry
+
+[ -z "${CI_DEBUG}" ] || set -xv
+
+## produce _real_ BASE_IMAGE because "static-debian12:debug-nonroot" is not multiarch image (yet)
+export BASE_IMAGE="${BASE_IMAGE:?}-${GOARCH:?}"
+
+buildah pull \
+    --platform "${TARGET_PLATFORM}" \
+    --retry 3 --retry-delay 30s \
+"${BASE_IMAGE}"
+
+## build image
+buildah bud \
+    -t "${IMAGE_NAME}:${IMAGE_TAG}${PLATFORM_SUFFIX}" \
+    -f ./Dockerfile.ci \
+    ${IMAGE_MANIFEST:+ --manifest "${IMAGE_MANIFEST}" } \
+    --platform "${TARGET_PLATFORM}" \
+    --build-arg "TARGET_PLATFORM=${TARGET_PLATFORM}" \
+    --build-arg "PLATFORM_SUFFIX=${PLATFORM_SUFFIX}" \
+    --build-arg "BASE_IMAGE=${BASE_IMAGE}" \
+    --network=host
diff --git a/.ci/registry-login.sh b/.ci/registry-login.sh
new file mode 100755
index 0000000..e6d77e2
--- /dev/null
+++ b/.ci/registry-login.sh
@@ -0,0 +1,21 @@
+#!/bin/sh
+# SPDX-License-Identifier: Apache-2.0
+# (c) 2024, Konstantin Demin
+set -ef
+
+[ -z "${CI_DEBUG}" ] || set -xv
+
+unset _bin
+for i in podman buildah skopeo ; do
+    if command -V "$i" >/dev/null ; then
+        _bin=$i
+        break
+    fi
+done
+: "${_bin:?}"
+
+. .ci/envsh.registry
+
+for i ; do
+    "${_bin}" login "$i" </dev/null
+done
diff --git a/.ci/sync-all.sh b/.ci/sync-all.sh
new file mode 100755
index 0000000..ae44e2b
--- /dev/null
+++ b/.ci/sync-all.sh
@@ -0,0 +1,56 @@
+#!/bin/sh
+# SPDX-License-Identifier: Apache-2.0
+# (c) 2024, Konstantin Demin
+set -ef
+
+[ -z "${CI_DEBUG}" ] || set -xv
+
+: "${IMAGE_NAME:?}" "${EXT_IMAGE_NAME:?}"
+
+. .ci/envsh.common
+. .ci/envsh.registry
+
+image_src="docker://${IMAGE_NAME}"
+image_dst="docker://${EXT_IMAGE_NAME}"
+
+oci_dir="${PWD}/oci-layers"
+image_interim="oci:${oci_dir}:$(basename "${IMAGE_NAME}"):${IMAGE_TAG}"
+
+rm -rf "${oci_dir}" ; mkdir "${oci_dir}"
+
+r=0
+
+img_copy() {
+    for i in $(seq 1 3) ; do
+        if skopeo copy --all "$@" ; then
+            return 0
+        fi
+    done
+    return 1
+}
+
+while : ; do
+    img_copy "${image_src}:${IMAGE_TAG}" "${image_interim}" || r=$?
+    [ "$r" = 0 ] || break
+
+    echo " -> ${image_dst}:${IMAGE_TAG}"
+    img_copy "${image_interim}" "${image_dst}:${IMAGE_TAG}" || r=$?
+    [ "$r" = 0 ] || break
+
+    for tag in ${EXTRA_TAGS} ; do
+        [ -n "${tag}" ] || continue
+
+        echo " -> ${image_src}:${tag}"
+        img_copy "${image_interim}" "${image_src}:${tag}" || r=$?
+        [ "$r" = 0 ] || break
+
+        echo " -> ${image_dst}:${tag}"
+        img_copy "${image_interim}" "${image_dst}:${tag}" || r=$?
+        [ "$r" = 0 ] || break
+    done
+
+    break
+done
+
+rm -rf "${oci_dir}"
+exit "$r"
diff --git a/.ci/sync-latest.sh b/.ci/sync-latest.sh
new file mode 100755
index 0000000..a9a1179
--- /dev/null
+++ b/.ci/sync-latest.sh
@@ -0,0 +1,47 @@
+#!/bin/sh
+# SPDX-License-Identifier: Apache-2.0
+# (c) 2024, Konstantin Demin
+set -ef
+
+[ -z "${CI_DEBUG}" ] || set -xv
+
+: "${IMAGE_NAME:?}" "${EXT_IMAGE_NAME:?}" "${LATEST_TAG:?}"
+
+. .ci/envsh.registry
+
+image_src="docker://${IMAGE_NAME}"
+image_dst="docker://${EXT_IMAGE_NAME}"
+
+oci_dir="${PWD}/oci-layers"
+image_interim="oci:${oci_dir}:$(basename "${IMAGE_NAME}"):${LATEST_TAG}"
+
+rm -rf "${oci_dir}" ; mkdir "${oci_dir}"
+
+r=0
+
+img_copy() {
+    for i in $(seq 1 3) ; do
+        if skopeo copy --all "$@" ; then
+            return 0
+        fi
+    done
+    return 1
+}
+
+while : ; do
+    img_copy "${image_src}:${LATEST_TAG}" "${image_interim}" || r=$?
+    [ "$r" = 0 ] || break
+
+    echo " -> ${image_src}:latest"
+    img_copy "${image_interim}" "${image_src}:latest" || r=$?
+    [ "$r" = 0 ] || break
+
+    echo " -> ${image_dst}:latest"
+    img_copy "${image_interim}" "${image_dst}:latest" || r=$?
+    [ "$r" = 0 ] || break
+
+    break
+done
+
+rm -rf "${oci_dir}"
+exit "$r"
diff --git a/.dockerignore b/.dockerignore
new file mode 100644
index 0000000..e70b330
--- /dev/null
+++ b/.dockerignore
@@ -0,0 +1,3 @@
+.ci
+.vscode
+rngpotd*
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..8bb16ec
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,4 @@
+/.ci/.auth.json
+/.vscode/
+/dist/
+/rngpotd
diff --git a/.woodpecker/.build.yml b/.woodpecker/.build.yml
new file mode 100644
index 0000000..50e38c3
--- /dev/null
+++ b/.woodpecker/.build.yml
@@ -0,0 +1,75 @@
+when:
+  - event: [ push, tag, cron, manual ]
+    evaluate: 'LATEST_TAG == ""'
+
+variables:
+  - &image_name 'quay.krd.sh/krd/rngpotd'
+  - &ext_image_name 'docker.io/rockdrilla/rngpotd'
+  - &buildah_image 'quay.krd.sh/quay_io/containers/buildah:v1.36.0'
+  - &skopeo_image 'quay.krd.sh/quay_io/containers/skopeo:v1.15.2'
+  - &go_image 'quay.krd.sh/golang:1.22.5-bookworm'
+  - &base_image 'quay.krd.sh/gcr_io/distroless/static-debian12:nonroot'
+  ## value list depends on base image
+  ## ref: https://github.com/GoogleContainerTools/distroless#debian-12
+  - &target_platforms 'linux/amd64,linux/arm,linux/arm64,linux/ppc64le,linux/s390x'
+
+## kind of fixup (remove in near future)
+## ref: https://github.com/woodpecker-ci/plugin-git/releases
+clone:
+  git:
+    image: quay.krd.sh/docker_io/woodpeckerci/plugin-git:2.5.1
+
+## NB: ${variable} expressions are subject to pre-processing.
+## ref: https://woodpecker-ci.org/docs/usage/environment
+
+steps:
+
+  - name: verify-registry-credentials
+    image: *skopeo_image
+    environment:
+      GOMAXPROCS: "4"
+      MALLOC_ARENA_MAX: "4"
+    secrets: [ REGISTRY_AUTH ]
+    commands:
+      - .ci/registry-login.sh quay.krd.sh docker.io
+
+  - name: build-all
+    image: *go_image
+    environment:
+      GOMAXPROCS: "4"
+      MALLOC_ARENA_MAX: "4"
+      ##
+      TARGET_PLATFORMS: *target_platforms
+    ## these secrets are server-wide
+    secrets: [ GOPRIVATE, GOPROXY, GOSUMDB ]
+    commands:
+      - .ci/build-all.sh
+
+  - name: image-all
+    image: *buildah_image
+    privileged: true
+    environment:
+      GOMAXPROCS: "4"
+      MALLOC_ARENA_MAX: "4"
+      ##
+      BUILDAH_FORMAT: "docker"
+      TARGET_PLATFORMS: *target_platforms
+      BASE_IMAGE: *base_image
+      IMAGE_NAME: *image_name
+    commands:
+      - .ci/image-all.sh
+
+  - name: image-sync
+    image: *skopeo_image
+    environment:
+      GOMAXPROCS: "4"
+      MALLOC_ARENA_MAX: "4"
+      ##
+      IMAGE_NAME: *image_name
+      EXT_IMAGE_NAME: *ext_image_name
+    commands:
+      - .ci/sync-all.sh
+
+## personal tweaks :)
+labels:
+  network: dmz
diff --git a/.woodpecker/.latest.yml b/.woodpecker/.latest.yml
new file mode 100644
index 0000000..38d6ef6
--- /dev/null
+++ b/.woodpecker/.latest.yml
@@ -0,0 +1,43 @@
+when:
+  - event: [ manual ]
+    evaluate: 'LATEST_TAG != ""'
+
+variables:
+  - &image_name 'quay.krd.sh/krd/rngpotd'
+  - &ext_image_name 'docker.io/rockdrilla/rngpotd'
+  - &skopeo_image 'quay.krd.sh/quay_io/containers/skopeo:v1.15.2'
+
+## kind of fixup (remove in near future)
+## ref: https://github.com/woodpecker-ci/plugin-git/releases
+clone:
+  git:
+    image: quay.krd.sh/docker_io/woodpeckerci/plugin-git:2.5.1
+
+## NB: ${variable} expressions are subject to pre-processing.
+## ref: https://woodpecker-ci.org/docs/usage/environment
+
+steps:
+
+  - name: verify-registry-credentials
+    image: *skopeo_image
+    environment:
+      GOMAXPROCS: "4"
+      MALLOC_ARENA_MAX: "4"
+    secrets: [ REGISTRY_AUTH ]
+    commands:
+      - .ci/registry-login.sh quay.krd.sh docker.io
+
+  - name: image-sync-latest
+    image: *skopeo_image
+    environment:
+      GOMAXPROCS: "4"
+      MALLOC_ARENA_MAX: "4"
+      ##
+      IMAGE_NAME: *image_name
+      EXT_IMAGE_NAME: *ext_image_name
+    commands:
+      - .ci/sync-latest.sh
+
+## personal tweaks :)
+labels:
+  network: dmz
diff --git a/Dockerfile b/Dockerfile
new file mode 100644
index 0000000..4de36ec
--- /dev/null
+++ b/Dockerfile
@@ -0,0 +1,35 @@
+ARG GO_IMAGE=docker.io/library/golang:1.22.5-bookworm
+ARG BASE_IMAGE=gcr.io/distroless/static-debian12:nonroot
+
+## ---
+
+FROM ${GO_IMAGE} as build
+SHELL [ "/bin/sh", "-ec" ]
+
+ARG GOPROXY
+ARG GOSUMDB
+ARG GOPRIVATE
+
+ARG RELMODE
+
+WORKDIR /go/src
+
+COPY . .
+
+ENV GOMAXPROCS=4 \
+    MALLOC_ARENA_MAX=4
+
+RUN go env | grep -F -e GOPROXY -e GOSUMDB ; \
+    make OUTDIR=/go/bin ; \
+    make ci-clean
+
+## ---
+
+FROM ${BASE_IMAGE}
+
+COPY --from=build /go/bin/rngpotd /bin/
+
+ENTRYPOINT [ "/bin/rngpotd" ]
+CMD [ ]
+
+USER nonroot:nonroot
diff --git a/Dockerfile.ci b/Dockerfile.ci
new file mode 100644
index 0000000..f75cf58
--- /dev/null
+++ b/Dockerfile.ci
@@ -0,0 +1,12 @@
+ARG TARGET_PLATFORM
+ARG BASE_IMAGE
+
+FROM --platform=${TARGET_PLATFORM} ${BASE_IMAGE}
+
+ARG PLATFORM_SUFFIX
+COPY /dist/rngpotd${PLATFORM_SUFFIX} /bin/rngpotd
+
+ENTRYPOINT [ ]
+CMD [ "/bin/rngpotd" ]
+
+USER nonroot:nonroot
diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..67db858
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,175 @@
+
+                                 Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+   1. Definitions.
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+      "License" shall mean the terms and conditions for use, reproduction,
+      and distribution as defined by Sections 1 through 9 of this document.
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+      otherwise, or (ii) ownership of fifty percent (50%) or more of the
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+      "You" (or "Your") shall mean an individual or Legal Entity
+      exercising permissions granted by this License.
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+      including but not limited to software source code, documentation
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+      "Work" shall mean the work of authorship, whether in Source or
+      Object form, made available under the License, as indicated by a
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+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
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+      You may add Your own copyright statement to Your modifications and
+      may provide additional or different license terms and conditions
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+      reproduction, and distribution of the Work otherwise complies with
+      the conditions stated in this License.
+
+   5. Submission of Contributions. Unless You explicitly state otherwise,
+      any Contribution intentionally submitted for inclusion in the Work
+      by You to the Licensor shall be under the terms and conditions of
+      this License, without any additional terms or conditions.
+      Notwithstanding the above, nothing herein shall supersede or modify
+      the terms of any separate license agreement you may have executed
+      with Licensor regarding such Contributions.
+
+   6. Trademarks. This License does not grant permission to use the trade
+      names, trademarks, service marks, or product names of the Licensor,
+      except as required for reasonable and customary use in describing the
+      origin of the Work and reproducing the content of the NOTICE file.
+
+   7. Disclaimer of Warranty. Unless required by applicable law or
+      agreed to in writing, Licensor provides the Work (and each
+      Contributor provides its Contributions) on an "AS IS" BASIS,
+      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+      implied, including, without limitation, any warranties or conditions
+      of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
+      PARTICULAR PURPOSE. You are solely responsible for determining the
+      appropriateness of using or redistributing the Work and assume any
+      risks associated with Your exercise of permissions under this License.
+
+   8. Limitation of Liability. In no event and under no legal theory,
+      whether in tort (including negligence), contract, or otherwise,
+      unless required by applicable law (such as deliberate and grossly
+      negligent acts) or agreed to in writing, shall any Contributor be
+      liable to You for damages, including any direct, indirect, special,
+      incidental, or consequential damages of any character arising as a
+      result of this License or out of the use or inability to use the
+      Work (including but not limited to damages for loss of goodwill,
+      work stoppage, computer failure or malfunction, or any and all
+      other commercial damages or losses), even if such Contributor
+      has been advised of the possibility of such damages.
+
+   9. Accepting Warranty or Additional Liability. While redistributing
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+      on Your own behalf and on Your sole responsibility, not on behalf
+      of any other Contributor, and only if You agree to indemnify,
+      defend, and hold each Contributor harmless for any liability
+      incurred by, or claims asserted against, such Contributor by reason
+      of your accepting any such warranty or additional liability.
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..fa9df2e
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,69 @@
+#!/usr/bin/make -f
+# SPDX-License-Identifier: Apache-2.0
+# (c) 2024, Konstantin Demin
+
+SHELL       :=/bin/sh
+.SHELLFLAGS :=-ec
+
+.NOTPARALLEL:
+
+BIN := rngpotd
+
+OUTDIR ?= .
+OUTSFX ?=
+OUTBIN ?= $(OUTDIR)/$(BIN)$(OUTSFX)
+
+export GO ?= go
+export CGO_ENABLED ?= 0
+TAGS ?=
+LDFLAGS ?=
+GO_BUILDFLAGS ?=
+GO_LDFLAGS := -w $(LDFLAGS)
+
+comma :=,
+ifeq ($(RELMODE),1)
+  TAGS := rngpot_nodebug$(if $(strip $(TAGS)),$(comma)$(strip $(TAGS)))
+
+  GO_LDFLAGS += -s
+endif
+
+.PHONY: all
+all: build
+
+.PHONY: clean build dev-build ci-clean
+
+clean:
+	$(if $(wildcard $(OUTBIN)),rm -fv $(OUTBIN),:)
+
+build: $(OUTBIN)
+
+test_git = git -c log.showsignature=false show -s --format=%H:%ct
+
+$(OUTBIN):
+	@:; \
+	GO_BUILDFLAGS='$(strip $(GO_BUILDFLAGS))' ; \
+	if ! $(test_git) >/dev/null 2>&1 ; then \
+	    echo "!!! git information is asbent !!!" >&2 ; \
+	    GO_BUILDFLAGS="-buildvcs=false $${GO_BUILDFLAGS}" ; \
+	fi ; \
+	for i in $$(seq 1 3) ; do \
+	    if $(GO) get ; then break ; fi ; \
+	done ; \
+	$(GO) build -o $@ \
+	  $${GO_BUILDFLAGS} \
+	  $(if $(strip $(TAGS)),-tags '$(strip $(TAGS))') \
+	  $(if $(strip $(GO_LDFLAGS)),-ldflags '$(strip $(GO_LDFLAGS))') \
+	  $(if $(VERBOSE),-v) ; \
+	$(GO) version -m $@
+
+dev-build: GO_BUILDFLAGS := -race $(GO_BUILDFLAGS)
+dev-build: CGO_ENABLED := 1
+dev-build: RELMODE := 0
+dev-build: build
+
+ci-clean:
+	for d in '$(shell $(GO) env GOCACHE)' '$(shell $(GO) env GOMODCACHE)' ; do \
+	    [ -n "$$d" ] || continue ; \
+	    [ -d "$$d" ] || continue ; \
+	    rm -rf "$$d" ; \
+	done
diff --git a/fiber.go b/fiber.go
new file mode 100644
index 0000000..9535fe9
--- /dev/null
+++ b/fiber.go
@@ -0,0 +1,50 @@
+package main
+
+import (
+	"math/rand"
+	"time"
+
+	"github.com/gofiber/fiber/v2"
+)
+
+var (
+	fiberConfig = fiber.Config{
+		AppName:      userAgent,
+		ServerHeader: serverAgent,
+
+		StrictRouting: true,
+		CaseSensitive: true,
+		Immutable:     true,
+
+		BodyLimit:   -1,
+		ReadTimeout: 10 * time.Millisecond,
+
+		DisableKeepalive:             true,
+		DisableHeaderNormalizing:     true,
+		DisablePreParseMultipartForm: true,
+		DisableDefaultDate:           true,
+		DisableDefaultContentType:    true,
+
+		ErrorHandler: fiberErrorHandler,
+	}
+)
+
+func initFiberApp() *fiber.App {
+	preinitFiberConfig()
+
+	app := fiber.New(fiberConfig)
+	preinitFiberApp(app)
+	app.Use(fiberRngPot)
+
+	return app
+}
+
+func fiberRngPot(c *fiber.Ctx) error {
+	return c.SendStatus(
+		rngRetCodes[rand.Intn(n_rngRetCodes)],
+	)
+}
+
+func fiberErrorHandler(c *fiber.Ctx, err error) error {
+	return fiberRngPot(c)
+}
diff --git a/fiber_debug.go b/fiber_debug.go
new file mode 100644
index 0000000..e466fa7
--- /dev/null
+++ b/fiber_debug.go
@@ -0,0 +1,20 @@
+//go:build !rngpot_nodebug
+
+package main
+
+import (
+	"time"
+
+	"github.com/gofiber/fiber/v2"
+	"github.com/gofiber/fiber/v2/middleware/logger"
+)
+
+func preinitFiberConfig() {
+	fiberConfig.EnablePrintRoutes = true
+}
+
+func preinitFiberApp(app *fiber.App) {
+	app.Use(logger.New(logger.Config{
+		TimeInterval: 100 * time.Millisecond,
+	}))
+}
diff --git a/fiber_nodebug.go b/fiber_nodebug.go
new file mode 100644
index 0000000..7e7d91b
--- /dev/null
+++ b/fiber_nodebug.go
@@ -0,0 +1,11 @@
+//go:build rngpot_nodebug
+
+package main
+
+import "github.com/gofiber/fiber/v2"
+
+func preinitFiberConfig() {
+}
+
+func preinitFiberApp(app *fiber.App) {
+}
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..11261ca
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,19 @@
+module git.krd.sh/krd/rngpotd
+
+go 1.22
+
+require github.com/gofiber/fiber/v2 v2.52.5
+
+require (
+	github.com/andybalholm/brotli v1.1.0 // indirect
+	github.com/google/uuid v1.6.0 // indirect
+	github.com/klauspost/compress v1.17.9 // indirect
+	github.com/mattn/go-colorable v0.1.13 // indirect
+	github.com/mattn/go-isatty v0.0.20 // indirect
+	github.com/mattn/go-runewidth v0.0.15 // indirect
+	github.com/rivo/uniseg v0.4.7 // indirect
+	github.com/valyala/bytebufferpool v1.0.0 // indirect
+	github.com/valyala/fasthttp v1.55.0 // indirect
+	github.com/valyala/tcplisten v1.0.0 // indirect
+	golang.org/x/sys v0.22.0 // indirect
+)
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..09f1559
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,28 @@
+github.com/andybalholm/brotli v1.1.0 h1:eLKJA0d02Lf0mVpIDgYnqXcUn0GqVmEFny3VuID1U3M=
+github.com/andybalholm/brotli v1.1.0/go.mod h1:sms7XGricyQI9K10gOSf56VKKWS4oLer58Q+mhRPtnY=
+github.com/gofiber/fiber/v2 v2.52.5 h1:tWoP1MJQjGEe4GB5TUGOi7P2E0ZMMRx5ZTG4rT+yGMo=
+github.com/gofiber/fiber/v2 v2.52.5/go.mod h1:KEOE+cXMhXG0zHc9d8+E38hoX+ZN7bhOtgeF2oT6jrQ=
+github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
+github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
+github.com/klauspost/compress v1.17.9 h1:6KIumPrER1LHsvBVuDa0r5xaG0Es51mhhB9BQB2qeMA=
+github.com/klauspost/compress v1.17.9/go.mod h1:Di0epgTjJY877eYKx5yC51cX2A2Vl2ibi7bDH9ttBbw=
+github.com/mattn/go-colorable v0.1.13 h1:fFA4WZxdEF4tXPZVKMLwD8oUnCTTo08duU7wxecdEvA=
+github.com/mattn/go-colorable v0.1.13/go.mod h1:7S9/ev0klgBDR4GtXTXX8a3vIGJpMovkB8vQcUbaXHg=
+github.com/mattn/go-isatty v0.0.16/go.mod h1:kYGgaQfpe5nmfYZH+SKPsOc2e4SrIfOl2e/yFXSvRLM=
+github.com/mattn/go-isatty v0.0.20 h1:xfD0iDuEKnDkl03q4limB+vH+GxLEtL/jb4xVJSWWEY=
+github.com/mattn/go-isatty v0.0.20/go.mod h1:W+V8PltTTMOvKvAeJH7IuucS94S2C6jfK/D7dTCTo3Y=
+github.com/mattn/go-runewidth v0.0.15 h1:UNAjwbU9l54TA3KzvqLGxwWjHmMgBUVhBiTjelZgg3U=
+github.com/mattn/go-runewidth v0.0.15/go.mod h1:Jdepj2loyihRzMpdS35Xk/zdY8IAYHsh153qUoGf23w=
+github.com/rivo/uniseg v0.2.0/go.mod h1:J6wj4VEh+S6ZtnVlnTBMWIodfgj8LQOQFoIToxlJtxc=
+github.com/rivo/uniseg v0.4.7 h1:WUdvkW8uEhrYfLC4ZzdpI2ztxP1I582+49Oc5Mq64VQ=
+github.com/rivo/uniseg v0.4.7/go.mod h1:FN3SvrM+Zdj16jyLfmOkMNblXMcoc8DfTHruCPUcx88=
+github.com/valyala/bytebufferpool v1.0.0 h1:GqA5TC/0021Y/b9FG4Oi9Mr3q7XYx6KllzawFIhcdPw=
+github.com/valyala/bytebufferpool v1.0.0/go.mod h1:6bBcMArwyJ5K/AmCkWv1jt77kVWyCJ6HpOuEn7z0Csc=
+github.com/valyala/fasthttp v1.55.0 h1:Zkefzgt6a7+bVKHnu/YaYSOPfNYNisSVBo/unVCf8k8=
+github.com/valyala/fasthttp v1.55.0/go.mod h1:NkY9JtkrpPKmgwV3HTaS2HWaJss9RSIsRVfcxxoHiOM=
+github.com/valyala/tcplisten v1.0.0 h1:rBHj/Xf+E1tRGZyWIWwJDiRY0zc1Js+CV5DqwacVSA8=
+github.com/valyala/tcplisten v1.0.0/go.mod h1:T0xQ8SeCZGxckz9qRXTfG43PvQ/mcWh7FwZEA7Ioqkc=
+golang.org/x/sys v0.0.0-20220811171246-fbc7d0a398ab/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.22.0 h1:RI27ohtqKCnwULzJLqkv897zojh5/DwS/ENaMzUOaWI=
+golang.org/x/sys v0.22.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
diff --git a/main.go b/main.go
new file mode 100644
index 0000000..7a7a57e
--- /dev/null
+++ b/main.go
@@ -0,0 +1,50 @@
+package main
+
+import (
+	"flag"
+	"log"
+	"runtime"
+)
+
+const (
+	appName     = "rngpotd"
+	appVersion  = "0.0.1"
+	userAgent   = appName + "/" + appVersion
+	serverAgent = "nginx/1.27.0"
+
+	minimumGoMaxProcs = 2
+	maximumGoMaxProcs = 4
+)
+
+var (
+	listenEndpoint string
+)
+
+func init() {
+	flag.StringVar(&listenEndpoint, "listen", ":8888", "listen (\":port\", \"address:port\")")
+}
+
+func main() {
+	gmp := runtime.GOMAXPROCS(0)
+	if gmp < minimumGoMaxProcs {
+		runtime.GOMAXPROCS(minimumGoMaxProcs)
+	}
+	if gmp > maximumGoMaxProcs {
+		runtime.GOMAXPROCS(maximumGoMaxProcs)
+	}
+
+	n_rngRetCodes = len(rngRetCodes)
+
+	log.SetFlags(log.Flags() | log.Lmicroseconds)
+	flag.Parse()
+
+	log.Printf("%s: starting\n", userAgent)
+
+	app := initFiberApp()
+
+	log.Printf("%s: ready\n", userAgent)
+	log.Printf("%s: going to listen %q\n", userAgent, listenEndpoint)
+	if err := app.Listen(listenEndpoint); err != nil {
+		log.Fatal(err)
+	}
+}
diff --git a/return-code.go b/return-code.go
new file mode 100644
index 0000000..d3c0d80
--- /dev/null
+++ b/return-code.go
@@ -0,0 +1,48 @@
+package main
+
+import (
+	"github.com/gofiber/fiber/v2"
+)
+
+var (
+	rngRetCodes = [...]int{
+		fiber.StatusTeapot,
+
+		fiber.StatusEarlyHints,
+
+		fiber.StatusNonAuthoritativeInformation,
+		fiber.StatusNoContent,
+		fiber.StatusResetContent,
+		fiber.StatusMultiStatus,
+		fiber.StatusAlreadyReported,
+		fiber.StatusIMUsed,
+		267, // https://github.com/maximal/http-267
+
+		fiber.StatusSwitchProxy,
+
+		fiber.StatusPaymentRequired,
+		fiber.StatusNotAcceptable,
+		fiber.StatusProxyAuthRequired,
+		fiber.StatusConflict,
+		fiber.StatusGone,
+		fiber.StatusPreconditionFailed,
+		fiber.StatusRequestEntityTooLarge,
+		fiber.StatusRequestURITooLong,
+		fiber.StatusUnsupportedMediaType,
+		fiber.StatusRequestedRangeNotSatisfiable,
+		fiber.StatusExpectationFailed,
+		fiber.StatusMisdirectedRequest,
+		fiber.StatusUnprocessableEntity,
+		fiber.StatusLocked,
+		fiber.StatusFailedDependency,
+		fiber.StatusTooEarly,
+		fiber.StatusUpgradeRequired,
+		fiber.StatusPreconditionRequired,
+		fiber.StatusTooManyRequests,
+		fiber.StatusRequestHeaderFieldsTooLarge,
+		444, // nginx gone wild
+		fiber.StatusUnavailableForLegalReasons,
+		499, // try harder comrade!
+	}
+	n_rngRetCodes = 1
+)