Merge pull request 'linea: reduce Maru engine API parallelism' (#49) from issue-2412 into main

show-status.sh could never report failure. The ansible task that wraps it
('Execute show-status.sh and fail on failure') therefore always passed, on every
host, regardless of node state. Three bugs, each masking the next:

1. $? read too late. `code=0` sits between the sync-status.sh call and
   `if [ $? -ne 0 ]`. A plain assignment succeeds and overwrites $? with 0, so
   the condition was ALWAYS false and the else branch always taken.

2. The else branch was inverted. It is the sync-status-SUCCEEDED path, yet it set
   `code=1; any_failure=true` — marking healthy nodes as failures.

3. any_failure could never propagate. check_sync_status runs backgrounded (`&`),
   i.e. in a subshell, so `any_failure=true` inside it is discarded; and the
   `wait "$pid"` loop threw away each job's exit status.

(3) hid (1) and (2): a script that believed every node had failed still exited 0,
so nobody saw it.

Fix: capture rc immediately; restore the intended logic (success => 0, syncing or
lagging => tolerated, anything else => failure); propagate failure in the PARENT
via `wait "$pid" || any_failure=true`, since the subshell cannot.

Verified with a stubbed sync-status.sh:

  scenario              before   after
  all online              0        0
  one syncing             0        0   (tolerated)
  one lagging             0        0   (tolerated)
  one ERROR               0        1
  ALL error               0        1

Behaviour for healthy fleets is unchanged; only genuine failures now surface.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

linea/mainnet/maru/config.toml.template

@@ -49,12 +49,12 @@ port = 8080
 peer-chain-height-polling-interval = "5s"
 el-sync-status-refresh-interval = "5s"
 sync-target-selection = "Highest"
-desync-tolerance = 100000
+desync-tolerance = 64
 
 [syncing.download]
 block-range-request-timeout = "10s"
-blocks-batch-size = 10
+blocks-batch-size = 5
-blocks-parallelism = 10
+blocks-parallelism = 2
 max-retries = 5
 backoff-delay = "1s"
 use-unconditional-random-download-peer = false

show-status.sh

@@ -22,26 +22,25 @@ check_sync_status() {
     # Cap the whole per-node branch (belt-and-suspenders over check-health's own cap), so no single
     # node can ever block the 'wait' below — that is what wedged the fleet rpc-update for hours.
     result=$(timeout "${SYNC_TIMEOUT:-60}" "$BASEPATH/sync-status.sh" "${part%.yml}")
+    # Capture the status IMMEDIATELY. Any command in between - including a plain
+    # assignment like `code=0` - overwrites $? with its own (always 0) status.
+    rc=$?
 
     code=0
-    
+    if [ "$rc" -ne 0 ]; then
-    if [ $? -ne 0 ]; then
+        if [[ "$result" == *"syncing"* ]] || [[ "$result" == *"lagging"* ]]; then
-        if [[ "$result" == *"syncing"* ]]; then
+            # sync-status exits 1 for syncing/lagging; those are expected states,
-            # Allow exit status 1 if result contains "syncing"
+            # not failures.
-            code=0
-        elif [[ "$result" == *"lagging"* ]]; then
-            # Allow exit status 1 if result contains "lagging"
             code=0
         else
-            any_failure=true
             code=1
         fi
-    else
-	code=1
-	any_failure=true
     fi
 
     echo "${part%.yml}: $result"
+    # NOTE: do NOT set any_failure here. This function runs backgrounded (`&`), so
+    # it executes in a subshell and any variable it sets is discarded. Failure is
+    # propagated to the parent through this return code, collected by `wait` below.
     return "$code"
 }
 
@@ -74,9 +73,12 @@ for part in "${parts[@]}"; do
     fi
 done
 
-# Wait for all background processes to finish
+# Wait for all background processes to finish. `wait` runs in the PARENT shell, so
+# this is where a failing node can actually flip any_failure - the checker itself
+# cannot, being a subshell. Previously the status was discarded here, which silently
+# neutered the exit code.
 for pid in "${pids[@]}"; do
-    wait "$pid"
+    wait "$pid" || any_failure=true
 done
 
 # Fenced nodes (fleet-state maintenance windows) are dropped from COMPOSE_FILE