async version bump

Added changelog.
Added info about Docker Hub pull limit.

README.md

@@ -16,14 +16,16 @@
 
 <h4 align="center">For Podman - see the fork <a href="https://github.com/sudo-kraken/podcheck">sudo-kraken/podcheck</a>!</h4>
 
+<h4 align="center">:whale: Docker Hub pull limit :chart_with_downwards_trend: not an issue for checks but for actual pulls - <a href="#whale-docker-hub-pull-limit-chart_with_downwards_trend-not-an-issue-for-checks-but-for-actual-pulls">read more</a></h4>
+
 ___
 ## :bell: Changelog
 
+- **v0.5.6.0**: Heavily improved performance due to async checking for updates. 
 - **v0.5.5.0**: osx and bsd compatibility changes + rewrite of dependency installer
 - **v0.5.4.0**: Added support for a Prometheus+node_exporter metric collection through a file collector.
 - **v0.5.3.0**: Local image check changed (use imageId instead of name) and Gotify-template fixed (whale icon removed).
 - **v0.5.2.1**: Rewrite of dependency downloads, jq can be installed with package manager or static binary.
-- **v0.5.1**: DEPENDENCY WARNING: now requires **jq**. + Upstreaming changes from [sudo-kraken/podcheck](https://github.com/sudo-kraken/podcheck)
 ___
 
 
@@ -77,6 +79,7 @@ ___
 ## :nut_and_bolt: Dependencies
 - Running docker (duh) and compose, either standalone or plugin. (see [Podman fork](https://github.com/sudo-kraken/podcheck)  
 - Bash shell or compatible shell of at least v4.3
+  - POSIX `xargs`, usually default but can be installed with the `findutils` package - to enable async.
 - [jq](https://github.com/jqlang/jq)
   - User will be prompted to install with package manager or download static binary.
 - [regclient/regctl](https://github.com/regclient/regclient) (Licensed under [Apache-2.0 License](http://www.apache.org/licenses/LICENSE-2.0))  
@@ -177,7 +180,15 @@ chmod 755 regctl
 ```
 Test it with `./regctl --help` and then either add the file to the same path as *dockcheck.sh* or in your path (eg. `~/.local/bin/regctl`).
 
-## :guardsman: Function to auth with docker hub before running
+## :whale: Docker Hub pull limit :chart_with_downwards_trend: not an issue for checks but for actual pulls
+Due to recent changes in [Docker Hub usage and limits](https://docs.docker.com/docker-hub/usage/)
+>Unauthenticated users: 10 pulls/hour   
+>Authenticated users with a free account: 100 pulls/hour
+
+This is not an issue for registry checks. But if you have a large stack and pull more than 10 updates at once consider updating more often or to create a free account.
+You could use/modify the login-wrapper function in the example below to automate the login prior to running `dockcheck.sh`.
+
+### :guardsman: Function to auth with docker hub before running
 **Example** - Change names, paths, and remove cat+password flag if you rather get prompted:
 ```sh
 function dchk {

dockcheck.sh

@@ -1,6 +1,6 @@
 #!/usr/bin/env bash
-VERSION="v0.5.5.0"
-### ChangeNotes: osx and bsd compatibility changes + rewrite of dependency installer
+VERSION="v0.5.6.0"
+### ChangeNotes: Heavily improved performance due to asynchronous update checks. 
 Github="https://github.com/mag37/dockcheck"
 RawUrl="https://raw.githubusercontent.com/mag37/dockcheck/main/dockcheck.sh"
 
@@ -46,6 +46,7 @@ c_blue="\033[0;34m"
 c_teal="\033[0;36m"
 c_reset="\033[0m"
 
+MaxAsync=32
 Timeout=10
 Stopped=""
 while getopts "aynpfrhlisvmc:e:d:t:" options; do
@@ -282,31 +283,70 @@ if [[ $t_out ]]; then
 else t_out=""
 fi
 
-# Check the image-hash of every running container VS the registry
-for i in $(docker ps $Stopped --filter "name=$SearchName" --format '{{.Names}}') ; do
-  ((RegCheckQue+=1))
-  progress_bar "$RegCheckQue" "$ContCount"
-  # Looping every item over the list of excluded names and skipping
-  for e in "${Excludes[@]}" ; do [[ "$i" == "$e" ]] && continue 2 ; done
+check_image() {
+  i="$1"
+  local Excludes=($Excludes_string)
+  for e in "${Excludes[@]}" ; do 
+    if [[ "$i" == "$e" ]]; then
+      echo Skip $i
+      return
+    fi
+  done
+
+  local NoUpdates GotUpdates GotErrors
   ImageId=$(docker inspect "$i" --format='{{.Image}}')
   RepoUrl=$(docker inspect "$i" --format='{{.Config.Image}}')
   LocalHash=$(docker image inspect "$ImageId" --format '{{.RepoDigests}}')
+
   # Checking for errors while setting the variable
   if RegHash=$(${t_out} $regbin -v error image digest --list "$RepoUrl" 2>&1) ; then
     if [[ "$LocalHash" = *"$RegHash"* ]] ; then
-      NoUpdates+=("$i")
+      echo NoUpdates "$i"
     else
       if [[ -n "$DaysOld" ]] && ! datecheck ; then
-        NoUpdates+=("+$i ${ImageAge}d")
+        echo NoUpdates "+$i ${ImageAge}d"
       else
-        GotUpdates+=("$i")
+        echo GotUpdates "$i"
       fi
     fi
   else
     # Here the RegHash is the result of an error code
-    GotErrors+=("$i - ${RegHash}")
+    echo GotErrors "$i - ${RegHash}"
   fi
-done
+}
+
+# Make required functions and variables available to subprocesses
+export -f check_image datecheck
+export Excludes_string="${Excludes[@]}" # Can only export scalar variables
+export t_out regbin RepoUrl DaysOld
+
+# Check for POSIX xargs with -P option, fallback without async 
+if (echo "test" | xargs -P 10 >/dev/null 2>&1)  ; then
+  XargsAsync="-P $MaxAsync"
+else
+  XargsAsync=""
+  printf "%bMissing POSIX xargs, consider installing 'findutils' for asynchronous lookups.%b\n" "$c_red" "$c_reset"
+fi
+
+# Asynchronously check the image-hash of every running container VS the registry
+while read -r line; do
+  ((RegCheckQue+=1))
+  progress_bar "$RegCheckQue" "$ContCount"
+
+  Got=${line%% *}  # Extracts the first word (NoUpdates, GotUpdates, GotErrors)
+  item=${line#* }
+
+  case "$Got" in
+    NoUpdates) NoUpdates+=("$item") ;;
+    GotUpdates) GotUpdates+=("$item") ;;
+    GotErrors) GotErrors+=("$item") ;;
+    Skip) ;;
+    *) echo "Error! Unexpected output from subprocess: ${line}" ;;
+  esac
+done < <( \
+  docker ps $Stopped --filter "name=$SearchName" --format '{{.Names}}' | \
+  xargs ${XargsAsync} -I {} bash -c 'check_image "{}"' \
+)
 
 # Sort arrays alphabetically
 IFS=$'\n'