adjust delay to account for runtime length

README.md

@@ -11,11 +11,12 @@ A simple Docker image that repeatedly runs a command with a specified delay.
 
 #### Environment variables:
 
-| Name            | Required | Default value | Example value                                                 | Description                                     |
-|-----------------|----------|---------------|---------------------------------------------------------------|-------------------------------------------------|
-| `COMMAND`       | Yes      |               | `echo Hello`                                                  |                                                 |
-| `AFTER_COMMAND` | No       |               | `echo Hello after`                                            | Command that should be executed after `COMMAND` |
-| `DELAY`         | No       | `1d`          | `7d` (or any other permissible value for the `sleep` command) |                                                 |
+| Name                 | Required | Default value | Example value                                                 | Description                                                                                                                                                  |
+|----------------------|----------|---------------|---------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| `COMMAND`            | Yes      |               | `echo Hello`                                                  |                                                                                                                                                              |
+| `AFTER_COMMAND`      | No       |               | `echo Hello after`                                            | Command that should be executed after `COMMAND`                                                                                                              |
+| `DELAY`              | No       | `1d`          | `7d` (or any other permissible value for the `sleep` command) |                                                                                                                                                              |
+| `ADJUST_FOR_RUNTIME` | No       | `true`        | `false`                                                       | If set to true, subtracts the execution time of the task from the delay, ensuring the scheduler runs at consistent intervals (e.g., the same time each day). |
 
 ### As the base image of another project
 

src/scheduler.sh

@@ -1,10 +1,39 @@
 #!/bin/sh
 echo "$(date) - start scheduler"
+
+# Convert a duration like "1d" or "3600" into seconds
+duration_to_seconds() {
+    case "$1" in
+        *d) echo $(( ${1%d} * 86400 )) ;;
+        *h) echo $(( ${1%h} * 3600 )) ;;
+        *m) echo $(( ${1%m} * 60 )) ;;
+        *s) echo $(( ${1%s} )) ;;
+        *) echo "$1" ;; # assume seconds if no suffix
+    esac
+}
+
+DELAY="${DELAY:-1d}"
+ADJUST_FOR_RUNTIME="${ADJUST_FOR_RUNTIME:-true}"
+
 while :; do
     echo "$(date) - execute"
 
+    start_time=$(date +%s)
     ./execute.sh
+    end_time=$(date +%s)
+
+    if [ "$ADJUST_FOR_RUNTIME" = "true" ]; then
+        runtime=$(( end_time - start_time ))
+        delay_seconds=$(duration_to_seconds "$DELAY")
+        sleep_time=$(( delay_seconds - runtime ))
+        if [ "$sleep_time" -lt 0 ]; then
+            echo "$(date) - Execution took longer than the delay ($runtime > $delay_seconds), skipping sleep"
+            sleep_time=0
+        fi
+    else
+        sleep_time=$delay_seconds
+    fi
 
-    echo "$(date) - sleep for ${DELAY:-1d}"
-    sleep "${DELAY:-1d}"
+    echo "$(date) - sleeping for $sleep_time seconds"
+    sleep "$sleep_time"
 done

version.txt

@@ -1 +1 @@
-2
+3