ci: retry failed nightly release on following weekdays (#9394)

Previously the nightly release was scheduled only on Mondays, so a
failed run left users without nightly builds for a whole week.

Now the schedule triggers every weekday at 00:00 UTC, but the release
only proceeds when the latest published nightly release is older than
NIGHTLY_RELEASE_MAX_AGE_DAYS (5) days. The check runs in
allocate-runners before any EC2 runner is allocated, and gates all
schedule-driven jobs (including the Slack notification, so a skipped
nightly is silent). Tag pushes and manual dispatches are unaffected.

Signed-off-by: Ning Sun <sunning@greptime.com>

.github/scripts/check-nightly-release.sh

@@ -0,0 +1,68 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+# Returns whether the current release run should proceed, 'true' or 'false'.
+#
+# The nightly schedule runs every weekday, but a scheduled release only proceeds
+# when the latest published nightly release is older than
+# NIGHTLY_RELEASE_MAX_AGE_DAYS days. This way, a failed nightly run is retried
+# by the next weekday schedule, instead of leaving a whole week without nightly
+# builds. Non-scheduled runs (tag pushes and manual dispatches) always proceed.
+#
+# Only the result is written to stdout, so that it can be used in GitHub Actions
+# outputs; all diagnostics go to stderr.
+#
+# You can run as following examples:
+#   GITHUB_EVENT_NAME=push ./check-nightly-release.sh
+#   GITHUB_EVENT_NAME=schedule GITHUB_REPOSITORY=GreptimeTeam/greptimedb GH_TOKEN=ghp_xxx ./check-nightly-release.sh
+#   GITHUB_EVENT_NAME=schedule NIGHTLY_RELEASE_MAX_AGE_DAYS=5 GITHUB_REPOSITORY=GreptimeTeam/greptimedb GH_TOKEN=ghp_xxx ./check-nightly-release.sh
+if [ -z "$GITHUB_EVENT_NAME" ]; then
+    echo "GITHUB_EVENT_NAME is empty" >&2
+    exit 1
+fi
+
+if [ "$GITHUB_EVENT_NAME" != "schedule" ]; then
+    echo "Not a scheduled run, the nightly check is skipped." >&2
+    echo "true"
+    exit 0
+fi
+
+MAX_AGE_DAYS="${NIGHTLY_RELEASE_MAX_AGE_DAYS:-5}"
+if ! [[ "$MAX_AGE_DAYS" =~ ^[0-9]+$ ]]; then
+    echo "Invalid NIGHTLY_RELEASE_MAX_AGE_DAYS: ${MAX_AGE_DAYS}" >&2
+    exit 1
+fi
+
+SECONDS_PER_DAY=86400
+
+# The publish time of the latest published nightly release, like the tag
+# 'v0.2.0-nightly-20230313'. Fail open on GitHub API errors: proceeding with
+# the release is safer than skipping it.
+if ! latest_nightly_published_at="$(gh api "repos/${GITHUB_REPOSITORY}/releases?per_page=100" \
+    --jq '[.[] | select(.draft == false and (.tag_name | contains("nightly")))][0].published_at // empty')"; then
+    echo "::warning::Failed to query the latest nightly release from the GitHub API, will proceed with the nightly release." >&2
+    echo "true"
+    exit 0
+fi
+
+if [ -z "$latest_nightly_published_at" ]; then
+    echo "No published nightly release found, will proceed with the nightly release." >&2
+    echo "true"
+    exit 0
+fi
+
+published_at_epoch="$(date --date="$latest_nightly_published_at" +%s)"
+now_epoch="$(date +%s)"
+age_seconds=$(( now_epoch - published_at_epoch ))
+age_days=$(( age_seconds / SECONDS_PER_DAY ))
+
+echo "The latest nightly release was published at ${latest_nightly_published_at} (${age_days} days ago)." >&2
+
+if [ "$age_seconds" -gt $(( MAX_AGE_DAYS * SECONDS_PER_DAY )) ]; then
+    echo "The latest nightly release is older than ${MAX_AGE_DAYS} days, will proceed with the nightly release." >&2
+    echo "true"
+else
+    echo "The latest nightly release is not older than ${MAX_AGE_DAYS} days, will skip the nightly release." >&2
+    echo "false"
+fi