Derive overlay minimum disk space from feature flags

Overlay analysis required 20 GB of available disk space, lowered to
14 GB when overlay_analysis_resource_checks_v2 was enabled. That gave
us a single step to roll out, and any further reduction needed another
flag and another release.

Determine the threshold from the new overlay_analysis_min_disk_N_gb
flags instead, taking the lowest one that is enabled so that a lower
limit can be rolled out to a subset of repositories without first
disabling the flag above it. When none are enabled, the 14 GB limit
now applies unconditionally, replacing the 20 GB default.

Thresholds remain in decimal MB, matching the bytes-per-MB convention
the disk check already used, so the effective byte values are unchanged
from the previous 14 GB path. Also log the available and required space
at debug level when the check passes, so that run logs show which
threshold took effect.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Author: sim

lib/entry-points.js

@@ -1295,17 +1295,36 @@ checkOverlayEnablementMacro.serial(
 );
 
 checkOverlayEnablementMacro.serial(
-  "No overlay-base database on default branch if runner disk space is below v2 limit and v2 resource checks enabled",
+  "Overlay-base database on default branch if runner disk space is above the default limit",
   {
     languages: [BuiltInLanguage.javascript],
     features: [
       Feature.OverlayAnalysis,
       Feature.OverlayAnalysisCodeScanningJavascript,
-      Feature.OverlayAnalysisResourceChecksV2,
     ],
     isDefaultBranch: true,
     diskUsage: {
-      numAvailableBytes: 5_000_000_000,
+      numAvailableBytes: 15_000_000_000,
+      numTotalBytes: 100_000_000_000,
+    },
+  },
+  {
+    overlayDatabaseMode: OverlayDatabaseMode.OverlayBase,
+    useOverlayDatabaseCaching: true,
+  },
+);
+
+checkOverlayEnablementMacro.serial(
+  "No overlay-base database on default branch if runner disk space is below the default limit",
+  {
+    languages: [BuiltInLanguage.javascript],
+    features: [
+      Feature.OverlayAnalysis,
+      Feature.OverlayAnalysisCodeScanningJavascript,
+    ],
+    isDefaultBranch: true,
+    diskUsage: {
+      numAvailableBytes: 10_000_000_000,
       numTotalBytes: 100_000_000_000,
     },
   },
@@ -1315,17 +1334,17 @@ checkOverlayEnablementMacro.serial(
 );
 
 checkOverlayEnablementMacro.serial(
-  "Overlay-base database on default branch if runner disk space is between v2 and v1 limits and v2 resource checks enabled",
+  "Overlay-base database on default branch if runner disk space is above the limit lowered by a feature flag",
   {
     languages: [BuiltInLanguage.javascript],
     features: [
       Feature.OverlayAnalysis,
       Feature.OverlayAnalysisCodeScanningJavascript,
-      Feature.OverlayAnalysisResourceChecksV2,
+      Feature.OverlayAnalysisMinDisk10Gb,
     ],
     isDefaultBranch: true,
     diskUsage: {
-      numAvailableBytes: 15_000_000_000,
+      numAvailableBytes: 11_000_000_000,
       numTotalBytes: 100_000_000_000,
     },
   },
@@ -1336,16 +1355,40 @@ checkOverlayEnablementMacro.serial(
 );
 
 checkOverlayEnablementMacro.serial(
-  "No overlay-base database on default branch if runner disk space is between v2 and v1 limits and v2 resource checks not enabled",
+  "Overlay-base database on default branch if runner disk space is exactly at the lowest limit enabled by a feature flag",
   {
     languages: [BuiltInLanguage.javascript],
     features: [
       Feature.OverlayAnalysis,
       Feature.OverlayAnalysisCodeScanningJavascript,
+      Feature.OverlayAnalysisMinDisk9Gb,
+      Feature.OverlayAnalysisMinDisk12Gb,
     ],
     isDefaultBranch: true,
     diskUsage: {
-      numAvailableBytes: 15_000_000_000,
+      numAvailableBytes: 9_000_000_000,
+      numTotalBytes: 100_000_000_000,
+    },
+  },
+  {
+    overlayDatabaseMode: OverlayDatabaseMode.OverlayBase,
+    useOverlayDatabaseCaching: true,
+  },
+);
+
+checkOverlayEnablementMacro.serial(
+  "No overlay-base database on default branch if runner disk space is below the lowest limit enabled by a feature flag",
+  {
+    languages: [BuiltInLanguage.javascript],
+    features: [
+      Feature.OverlayAnalysis,
+      Feature.OverlayAnalysisCodeScanningJavascript,
+      Feature.OverlayAnalysisMinDisk9Gb,
+      Feature.OverlayAnalysisMinDisk12Gb,
+    ],
+    isDefaultBranch: true,
+    diskUsage: {
+      numAvailableBytes: 8_500_000_000,
       numTotalBytes: 100_000_000_000,
     },
   },

src/config-utils.test.ts

@@ -48,7 +48,7 @@ import {
 import { prepareDiffInformedAnalysis } from "./diff-informed-analysis-utils";
 import { EnvVar } from "./environment";
 import * as errorMessages from "./error-messages";
-import { Feature, FeatureEnablement } from "./feature-flags";
+import { Feature, FeatureEnablement, FeatureWithoutCLI } from "./feature-flags";
 import {
   RepositoryProperties,
   RepositoryPropertyName,
@@ -101,19 +101,28 @@ export { type Config } from "./config/action-config";
  * whether to perform overlay analysis, then the action will not perform overlay
  * analysis unless overlay analysis has been explicitly enabled via environment
  * variable.
+ *
+ * This threshold can be lowered by the feature flags in
+ * `OVERLAY_MINIMUM_DISK_SPACE_FEATURES`.
  */
-const OVERLAY_MINIMUM_AVAILABLE_DISK_SPACE_MB = 20000;
-const OVERLAY_MINIMUM_AVAILABLE_DISK_SPACE_BYTES =
-  OVERLAY_MINIMUM_AVAILABLE_DISK_SPACE_MB * 1_000_000;
+const OVERLAY_MINIMUM_AVAILABLE_DISK_SPACE_MB = 14000;
 
 /**
- * The v2 minimum available disk space (in MB) required to perform overlay
- * analysis. This is a lower threshold than the v1 limit, allowing overlay
- * analysis to run on runners with less available disk space.
+ * Feature flags that lower the minimum available disk space required to perform
+ * overlay analysis, paired with the threshold (in MB) that each one enables.
+ *
+ * If several of these are enabled, the lowest threshold takes effect.
  */
-const OVERLAY_MINIMUM_AVAILABLE_DISK_SPACE_V2_MB = 14000;
-const OVERLAY_MINIMUM_AVAILABLE_DISK_SPACE_V2_BYTES =
-  OVERLAY_MINIMUM_AVAILABLE_DISK_SPACE_V2_MB * 1_000_000;
+const OVERLAY_MINIMUM_DISK_SPACE_FEATURES: ReadonlyArray<
+  [FeatureWithoutCLI, number]
+> = [
+  [Feature.OverlayAnalysisMinDisk8Gb, 8000],
+  [Feature.OverlayAnalysisMinDisk9Gb, 9000],
+  [Feature.OverlayAnalysisMinDisk10Gb, 10000],
+  [Feature.OverlayAnalysisMinDisk11Gb, 11000],
+  [Feature.OverlayAnalysisMinDisk12Gb, 12000],
+  [Feature.OverlayAnalysisMinDisk13Gb, 13000],
+];
 
 /**
  * The minimum memory (in MB) that must be available for CodeQL to perform overlay analysis. If
@@ -588,24 +597,42 @@ async function checkOverlayAnalysisFeatureEnabled(
   return new Success(undefined);
 }
 
+/**
+ * Returns the minimum available disk space (in MB) required to perform overlay
+ * analysis, which is the lowest threshold enabled by a feature flag, or the
+ * default threshold if no such feature flag is enabled.
+ */
+async function getMinimumDiskSpaceMb(
+  features: FeatureEnablement,
+): Promise<number> {
+  let minimumMb = OVERLAY_MINIMUM_AVAILABLE_DISK_SPACE_MB;
+  for (const [feature, thresholdMb] of OVERLAY_MINIMUM_DISK_SPACE_FEATURES) {
+    if (await features.getValue(feature)) {
+      minimumMb = Math.min(minimumMb, thresholdMb);
+    }
+  }
+  return minimumMb;
+}
+
 /** Checks if the runner has enough disk space for overlay analysis. */
 function runnerHasSufficientDiskSpace(
   diskUsage: DiskUsage,
   logger: Logger,
-  useV2ResourceChecks: boolean,
+  minimumDiskSpaceMb: number,
 ): boolean {
-  const minimumDiskSpaceBytes = useV2ResourceChecks
-    ? OVERLAY_MINIMUM_AVAILABLE_DISK_SPACE_V2_BYTES
-    : OVERLAY_MINIMUM_AVAILABLE_DISK_SPACE_BYTES;
-  if (diskUsage.numAvailableBytes < minimumDiskSpaceBytes) {
-    const diskSpaceMb = Math.round(diskUsage.numAvailableBytes / 1_000_000);
-    const minimumDiskSpaceMb = Math.round(minimumDiskSpaceBytes / 1_000_000);
+  const diskSpaceMb = Math.round(diskUsage.numAvailableBytes / 1_000_000);
+  if (diskUsage.numAvailableBytes < minimumDiskSpaceMb * 1_000_000) {
     logger.info(
       `Setting overlay database mode to ${OverlayDatabaseMode.None} ` +
         `due to insufficient disk space (${diskSpaceMb} MB, needed ${minimumDiskSpaceMb} MB).`,
     );
     return false;
   }
+
+  logger.debug(
+    `Disk space available for CodeQL analysis is ${diskSpaceMb} MB, which is above the minimum ` +
+      `of ${minimumDiskSpaceMb} MB.`,
+  );
   return true;
 }
 
@@ -648,12 +675,13 @@ async function runnerHasSufficientMemory(
  */
 async function checkRunnerResources(
   codeql: CodeQL,
+  features: FeatureEnablement,
   diskUsage: DiskUsage,
   ramInput: string | undefined,
   logger: Logger,
-  useV2ResourceChecks: boolean,
 ): Promise<Result<void, OverlayDisabledReason>> {
-  if (!runnerHasSufficientDiskSpace(diskUsage, logger, useV2ResourceChecks)) {
+  const minimumDiskSpaceMb = await getMinimumDiskSpaceMb(features);
+  if (!runnerHasSufficientDiskSpace(diskUsage, logger, minimumDiskSpaceMb)) {
     return new Failure(OverlayDisabledReason.InsufficientDiskSpace);
   }
   if (!(await runnerHasSufficientMemory(codeql, ramInput, logger))) {
@@ -752,9 +780,6 @@ export async function checkOverlayEnablement(
     Feature.OverlayAnalysisSkipResourceChecks,
     codeql,
   ));
-  const useV2ResourceChecks = await features.getValue(
-    Feature.OverlayAnalysisResourceChecksV2,
-  );
   const checkOverlayStatus = await features.getValue(
     Feature.OverlayAnalysisStatusCheck,
   );
@@ -770,10 +795,10 @@ export async function checkOverlayEnablement(
     performResourceChecks && diskUsage !== undefined
       ? await checkRunnerResources(
           codeql,
+          features,
           diskUsage,
           ramInput,
           logger,
-          useV2ResourceChecks,
         )
       : new Success<void>(undefined);
   if (resourceResult.isFailure()) {