From 05f73ba6b678302b070b914258b1d3e18c49e1e1 Mon Sep 17 00:00:00 2001
From: Anton-Latukha <anton.latukha@gmail.com>
Date: Sun, 19 Dec 2021 14:15:24 +0200
Subject: [PATCH 1/2] CI: caching: add early termination

---
 .github/workflows/caching.yml | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/.github/workflows/caching.yml b/.github/workflows/caching.yml
index b1a57c1906..ebecde0701 100644
--- a/.github/workflows/caching.yml
+++ b/.github/workflows/caching.yml
@@ -130,6 +130,7 @@ jobs:
           restore-keys: ${{ env.cache-name }}-
 
       - name: Compiled deps cache
+        id: compiled-deps
         uses: actions/cache@v2
         env:
           cache-name: compiled-deps
@@ -141,9 +142,12 @@ jobs:
                 ${{ env.cache-name }}-${{ runner.os }}-${{ matrix.ghc }}-
                 ${{ env.cache-name }}-${{ runner.os }}-
 
-      - run: cabal update
+      - if: (! steps.compiled-deps.outputs.cache-hit)
+        run: |
+          cabal update
 
-      - name: Download all sources
+      - if: (! steps.compiled-deps.outputs.cache-hit)
+        name: Download all sources
         run: |
           cabal $cabalBuild --only-download
 
@@ -152,7 +156,8 @@ jobs:
       # but to cache what can be cached, so step is fault tolerant & would always succseed.
       # 2021-12-11: NOTE: Building all targets, since
       # current Cabal does not allow `all --enable-tests --enable-benchmarks --only-dependencies`
-      - name: Build all targets; try 3 times
+      - if: (! steps.compiled-deps.outputs.cache-hit)
+        name: Build all targets; try 3 times
         continue-on-error: true
         run: |
           cabal $cabalBuild || cabal $cabalBuild || cabal $cabalBuild

From bab815712383793923fbb36af94ce756fae80716 Mon Sep 17 00:00:00 2001
From: Anton-Latukha <anton.latukha@gmail.com>
Date: Sat, 18 Dec 2021 22:25:30 +0200
Subject: [PATCH 2/2] CI: caching: run cache check 3 times a day

Recently there is a lot of PRs/builds from internal repo branches. Repo cache
has 10G pool limit & PR caches are not shared between PRs, but main branch cache
is.

Checking & when missing rebuilding it ensures that if internal branch PRs pushed main state
out of the pool - it gets reinstituted.

*afaik* there is no way to prioritize main branch cache better, since GitHub CI
FIFO caches out of the pool by build time.
---
 .github/workflows/caching.yml | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/.github/workflows/caching.yml b/.github/workflows/caching.yml
index ebecde0701..7fc49fda55 100644
--- a/.github/workflows/caching.yml
+++ b/.github/workflows/caching.yml
@@ -30,6 +30,18 @@ on:
   push:
     branches:
       - master
+  schedule:
+    # Refresh snapshot every (02+8*x):25 UTC
+    # When cache is present it is a light check workflow with early termination.
+    # When primary cache is not hit - runs the cache generation.
+    # Why: GitHub repo has 10G pool & on overflow GitHub removes caches in FIFO manner.
+    # When internal branche PRs save into the same pool -
+    #   their cache is accessible only inside of the scope of the PR.
+    # If main cache is forced out - there are no cache shared between PRs,
+    #   which implies all PRs would start to create & save their cache.
+    # Reinstitution of the main chache puts it back into FIFO
+    #   & so it gets shared across all PRs.
+    - cron: "25 2/8 * * *"
 
 env:
   cabalBuild: "v2-build all --enable-tests --enable-benchmarks"