terraform/aws: Parallelize region discovery in gen_kconfig_location

The gen_kconfig_location script was querying AWS for availability zone
information for each region (20-30 regions) sequentially. Each region
query required a separate AWS API call to describe_availability_zones,
resulting in 5-15 seconds of serial API calls.

This change parallelizes the availability zone discovery using
ThreadPoolExecutor, allowing all regions to be queried concurrently.
This reduces the total execution time from the sum of all requests to
approximately the time of the slowest single request, providing a
10-20x speedup for first-time runs.

The output order is preserved by collecting results in a dictionary and
printing them in the original region order.

Generated-by: Claude AI
Signed-off-by: Chuck Lever <[email protected]>

Author: chucklever

terraform/aws/scripts/gen_kconfig_location

@@ -9,6 +9,7 @@ it to construct the "locations" Kconfig menu.
 import sys
 import argparse
 
+from concurrent.futures import ThreadPoolExecutor, as_completed
 from botocore.exceptions import ClientError, NoCredentialsError
 
 from aws_common import (
@@ -136,9 +137,36 @@ def output_locations_kconfig(regions):
     )
 
     template = environment.get_template("zone.j2")
+
+    # Parallelize availability zone discovery for all regions
+    region_infos = {}
+    with ThreadPoolExecutor(max_workers=20) as executor:
+        # Submit all tasks
+        future_to_region = {
+            executor.submit(
+                get_region_info, regions, region["region_name"], True
+            ): region["region_name"]
+            for region in regions
+        }
+
+        # Collect results as they complete
+        for future in as_completed(future_to_region):
+            region_name = future_to_region[future]
+            try:
+                region_info = future.result()
+                if region_info:
+                    region_infos[region_name] = region_info
+            except Exception as exc:
+                print(
+                    f"Error discovering availability zones for {region_name}: {exc}",
+                    file=sys.stderr,
+                )
+
+    # Print results in original order
     for region in regions:
-        region_info = get_region_info(regions, region["region_name"], True)
-        if region_info:
+        region_name = region["region_name"]
+        if region_name in region_infos:
+            region_info = region_infos[region_name]
             print()
             print(
                 template.render(