From 766fa4f300511a7f0703327248bd9cc8cdbe0c3b Mon Sep 17 00:00:00 2001
From: Erik Arvstedt <erik.arvstedt@gmail.com>
Date: Sun, 12 Jan 2020 20:52:36 +0100
Subject: [PATCH] travis: cache all build outputs with cachix

This further speeds up builds, in particular the modules test in the
next commit. By checking if the expected final build output has already
been cached, we can even skip the download of cached builds.
---
 .travis.yml                     | 26 +++++++++++++++++++++++++-
 helper/wait-for-network-idle.rb | 29 +++++++++++++++++++++++++++++
 2 files changed, 54 insertions(+), 1 deletion(-)
 create mode 100755 helper/wait-for-network-idle.rb

diff --git a/.travis.yml b/.travis.yml
index cbb568a..3835300 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -14,6 +14,9 @@ install:
   - cachix use nix-bitcoin
   - VER="$(nix eval nixpkgs.lib.version)"
 env:
+  global:
+    # CACHIX_SIGNING_KEY
+  - secure: "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"
   jobs:
   - PKG=nodeinfo STABLE=1
   - PKG=hwi STABLE=1
@@ -30,4 +33,25 @@ env:
   - PKG=liquid-swap STABLE=1
 script:
   - printf '%s (%s)\n' "$NIX_PATH" "$VER"
-  - nix-build -A $PKG
+  - time nix-instantiate -A $PKG --add-root ./drv --indirect
+  - outPath=$(nix-store --query ./drv)
+  - |
+    if nix path-info --store https://nix-bitcoin.cachix.org $outPath &>/dev/null; then
+      echo "$outPath" has already been built successfully.
+      travis_terminate 0
+    fi
+    # Travis doesn't expose secrets to pull-request builds,
+    # so skip cache uploading in this case
+  - |
+    if [[ $CACHIX_SIGNING_KEY ]]; then
+      cachix push nix-bitcoin --watch-store &
+      cachixPid=$!
+    fi
+  - nix-build ./drv
+  - |
+    if [[ $CACHIX_SIGNING_KEY ]]; then
+      # Wait until cachix has finished uploading
+      # Run as root because yama/ptrace_scope != 0
+      ruby=$(nix-build '<nixpkgs>' -A ruby)/bin/ruby
+      time sudo $ruby helper/wait-for-network-idle.rb $cachixPid
+    fi
diff --git a/helper/wait-for-network-idle.rb b/helper/wait-for-network-idle.rb
new file mode 100755
index 0000000..18b5a9a
--- /dev/null
+++ b/helper/wait-for-network-idle.rb
@@ -0,0 +1,29 @@
+#!/usr/bin/env ruby
+require 'open3'
+
+# Wait until the given PID had no network activity for `Timeout` seconds, then exit.
+
+pid = ARGV.first
+Timeout = 2
+
+stdin, out, err, wait_thread = Open3.popen3("strace -f -e trace=network -s 1 -q -p #{pid}")
+while IO.select([err], nil, nil, Timeout)
+  begin
+    out = err.read_nonblock(1 << 10)
+  rescue EOFError
+    status = wait_thread.value
+    if status.success?
+      puts "Monitored process #{pid} exited"
+      exit 0
+    else
+      puts "Strace failed with exit code #{status.to_i}. Last output:\n#{out}"
+      # strace often fails with code 256 which looks like success to shells. fail with 1 instead.
+      exit 1
+    end
+  end
+end
+
+# If we exit without an explicit kill,
+# ptrace can fail on reattachment:  ptrace(PTRACE_SEIZE, $PID): Operation not permitted
+# Only relevant for testing.
+Process.kill("TERM", wait_thread.pid)