fix(deploy): the sidecars' downloads try again within the hour after a failed round

A failed BRouter segment or listing, a failed tile cut or an unwritable folder waited the whole refresh period, 30 days without routes or a map; they try again after an hour, doubling to a day. Photon's failed download backs off from a day to a week, and a dead Photon is noticed within a minute. The downloads' network is an ordinary bridge the three share, as the comments now say.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

deploy/photon/data.sh

@@ -5,7 +5,9 @@
 # where none is there or the one there is older than PHOTON_REFRESH_DAYS days (30),
 # unpacked as it comes into /data/next and checked against its MD5 on the way, then
 # marked ready for serve.sh, which puts it in place. Its archive is never kept: only
-# the old database and the new one take room at once.
+# the old database and the new one take room at once. Looked at daily; after a failed
+# download, again a day later, the wait doubling up to a week while downloads keep
+# failing.
 set -eu
 
 base=https://download1.graphhopper.com/public
@@ -21,7 +23,9 @@ fresh() {
 }
 
 fetch() {
+  failed=1
   if [ -e next/ready ] || fresh; then
+    failed=0
     return 0
   fi
   rm -rf next
@@ -41,6 +45,7 @@ fetch() {
     : >next/fetched
     : >next/ready
     echo "Photon's database of $region is ready, $(du -sh next/photon_data | cut -f1)."
+    failed=0
   else
     wait "$sum" 2>/dev/null || true
     rm -rf next
@@ -48,7 +53,26 @@ fetch() {
   fi
 }
 
+# Seconds to wait after the $1th failed download in a row: $2, doubling up to $3.
+backoff() {
+  pause=$2 n=1
+  while [ "$n" -lt "$1" ] && [ "$pause" -lt "$3" ]; do
+    pause=$((pause * 2)) n=$((n + 1))
+  done
+  if [ "$pause" -gt "$3" ]; then pause=$3; fi
+  echo "$pause"
+}
+
+failures=0
 while :; do
   fetch
-  sleep 86400
+  if [ "$failed" -eq 0 ]; then
+    failures=0
+    sleep 86400
+  else
+    failures=$((failures + 1))
+    pause=$(backoff "$failures" 86400 604800)
+    echo "Trying again in $((pause / 3600)) hours." >&2
+    sleep "$pause"
+  fi
 done

deploy/photon/serve.sh

@@ -2,7 +2,9 @@
 # Serves Photon on the database in /data/current (Halkyon Train's ADR 0030, D50), once
 # data.sh has brought one; and where data.sh has made a newer one (/data/next/ready),
 # stops Photon, puts the new one in the old one's place and starts it again: a
-# minute or two without search, once a month. PHOTON_HEAP is Java's heap (6g).
+# minute or two without search, once a month. Looked at every minute, which also
+# starts a Photon that stopped (killed for memory) again. PHOTON_HEAP is Java's
+# heap (6g).
 set -eu
 
 cd /data
@@ -42,7 +44,7 @@ while [ ! -d current/photon_data ] && ! swap; do
 done
 start
 while :; do
-  sleep 3600 &
+  sleep 60 &
   wait $! || true
   if [ -e next/ready ]; then
     stop