# Run a background daemon process from the queue environment
In many rendering use cases, loading the application and scene data can take a significant amount of time. If a job reloads them for every frame, it will spend most of its time on overhead. It's often possible to load the application once as a background daemon process, have it load the scene data, and then send it commands via inter-process communication (IPC) to perform the renders.
Many of the open source Deadline Cloud integrations use this pattern. The Open Job Description project provides an [adaptor runtime library](https://github.com/OpenJobDescription/openjd-adaptor-runtime-for-python) with reliable IPC patterns on all supported operating systems.
To demonstrate this pattern, there is a [self-contained sample job bundle](https://github.com/aws-deadline/deadline-cloud-samples/tree/mainline/job_bundles/job_env_daemon_process/template.yaml) that uses Python and bash code to implement a background daemon and the IPC for tasks to communicate with it. The daemon is implemented in Python, and listens for a POSIX SIGUSR1 signal for when to process a task. The task details are passed to the daemon in a specific JSON file, and the results of running the task are returned as another JSON file.
## Prerequisites
Perform the following steps to run the [sample job bundle with a daemon process](https://github.com/aws-deadline/deadline-cloud-samples/tree/mainline/job_bundles/job_env_daemon_process/template.yaml) from the Deadline Cloud samples github repository.
1. If you do not have a Deadline Cloud farm with a queue and associated Linux fleet, follow the guided onboarding experience in the [Deadline Cloud console](https://console.aws.amazon.com/deadlinecloud/home) to create one with default settings.
1. If you do not have the Deadline Cloud CLI and Deadline Cloud monitor on your workstation, follow the steps in [Set up Deadline Cloud submitters](https://docs.aws.amazon.com/deadline-cloud/latest/userguide/submitter.html) from the user guide.
1. Use `git` to clone the [Deadline Cloud samples GitHub repository](https://github.com/aws-deadline/deadline-cloud-samples).
```
git clone https://github.com/aws-deadline/deadline-cloud-samples.git
Cloning into 'deadline-cloud-samples'...
...
cd deadline-cloud-samples/job_bundles
```
## Run the daemon sample
1. Use the Deadline Cloud CLI to submit the `job_env_daemon_process` sample.
```
git clone https://github.com/aws-deadline/deadline-cloud-samples.git
Cloning into 'deadline-cloud-samples'...
...
cd deadline-cloud-samples/job_bundles
```
1. In the Deadline Cloud monitor application, you will see the new job and can monitor its progress. Once the Linux fleet associated with the queue has a worker available to run the job's task, it completes in about a minute. With one of the tasks selected, choose the **View logs** option in the top right menu of the tasks panel.
On the right there are two session actions, **Launch DaemonProcess** and **Task run**. The log viewer in the center of the window corresponds to the selected session action on the right.
Select the option **View logs for all tasks**. The timeline shows the rest of the tasks that ran as part of the session, and the `Shut down DaemonProcess` action that exited the environment.
## View the daemon logs
1. In this section you use the Deadline Cloud monitor to compare the session actions with where they are defined in the job template. It continues from the previous section.
Open the file [job\_env\_daemon\_process/template.yaml](https://github.com/aws-deadline/deadline-cloud-samples/tree/mainline/job_bundles/job_env_daemon_process/template.yaml) in a text editor. Compare the session actions to where they are defined in the job template.
1. Select the `Launch DaemonProcess` session action in Deadline Cloud monitor. You will see log output as follows.
```
2024/07/17 16:27:20-07:00
2024/07/17 16:27:20-07:00 ==============================================
2024/07/17 16:27:20-07:00 --------- Entering Environment: DaemonProcess
2024/07/17 16:27:20-07:00 ==============================================
2024/07/17 16:27:20-07:00 ----------------------------------------------
2024/07/17 16:27:20-07:00 Phase: Setup
2024/07/17 16:27:20-07:00 ----------------------------------------------
2024/07/17 16:27:20-07:00 Writing embedded files for Environment to disk.
2024/07/17 16:27:20-07:00 Mapping: Env.File.Enter -> /sessions/session-972e21d98dde45e59c7153bd9258a64dohwg4yg1/embedded_fileswy00x5ra/enter-daemon-process-env.sh
2024/07/17 16:27:20-07:00 Mapping: Env.File.Exit -> /sessions/session-972e21d98dde45e59c7153bd9258a64dohwg4yg1/embedded_fileswy00x5ra/exit-daemon-process-env.sh
2024/07/17 16:27:20-07:00 Mapping: Env.File.DaemonScript -> /sessions/session-972e21d98dde45e59c7153bd9258a64dohwg4yg1/embedded_fileswy00x5ra/daemon-script.py
2024/07/17 16:27:20-07:00 Mapping: Env.File.DaemonHelperFunctions -> /sessions/session-972e21d98dde45e59c7153bd9258a64dohwg4yg1/embedded_fileswy00x5ra/daemon-helper-functions.sh
2024/07/17 16:27:20-07:00 Wrote: Enter -> /sessions/session-972e21d98dde45e59c7153bd9258a64dohwg4yg1/embedded_fileswy00x5ra/enter-daemon-process-env.sh
2024/07/17 16:27:20-07:00 Wrote: Exit -> /sessions/session-972e21d98dde45e59c7153bd9258a64dohwg4yg1/embedded_fileswy00x5ra/exit-daemon-process-env.sh
2024/07/17 16:27:20-07:00 Wrote: DaemonScript -> /sessions/session-972e21d98dde45e59c7153bd9258a64dohwg4yg1/embedded_fileswy00x5ra/daemon-script.py
2024/07/17 16:27:20-07:00 Wrote: DaemonHelperFunctions -> /sessions/session-972e21d98dde45e59c7153bd9258a64dohwg4yg1/embedded_fileswy00x5ra/daemon-helper-functions.sh
2024/07/17 16:27:20-07:00 ----------------------------------------------
2024/07/17 16:27:20-07:00 Phase: Running action
2024/07/17 16:27:20-07:00 ----------------------------------------------
2024/07/17 16:27:20-07:00 Running command sudo -u job-user -i setsid -w /sessions/session-972e21d98dde45e59c7153bd9258a64dohwg4yg1/tmp_u8slys3.sh
2024/07/17 16:27:20-07:00 Command started as pid: 2187
2024/07/17 16:27:20-07:00 Output:
2024/07/17 16:27:21-07:00 openjd_env: DAEMON_LOG=/sessions/session-972e21d98dde45e59c7153bd9258a64dohwg4yg1/daemon.log
2024/07/17 16:27:21-07:00 openjd_env: DAEMON_PID=2223
2024/07/17 16:27:21-07:00 openjd_env: DAEMON_BASH_HELPER_SCRIPT=/sessions/session-972e21d98dde45e59c7153bd9258a64dohwg4yg1/embedded_fileswy00x5ra/daemon-helper-functions.sh
```
The following lines from the job template specified this action.
```
stepEnvironments:
- name: DaemonProcess
description: Runs a daemon process for the step's tasks to share.
script:
actions:
onEnter:
command: bash
args:
- "{{Env.File.Enter}}"
onExit:
command: bash
args:
- "{{Env.File.Exit}}"
embeddedFiles:
- name: Enter
filename: enter-daemon-process-env.sh
type: TEXT
data: |
#!/bin/env bash
set -euo pipefail
DAEMON_LOG='{{Session.WorkingDirectory}}/daemon.log'
echo "openjd_env: DAEMON_LOG=$DAEMON_LOG"
nohup python {{Env.File.DaemonScript}} > $DAEMON_LOG 2>&1 &
echo "openjd_env: DAEMON_PID=$!"
echo "openjd_env: DAEMON_BASH_HELPER_SCRIPT={{Env.File.DaemonHelperFunctions}}"
echo 0 > 'daemon_log_cursor.txt'
...
```
1. Select one of the Task run: N session action in Deadline Cloud monitor. You will see log output as follows.
```
2024/07/17 16:27:22-07:00
2024/07/17 16:27:22-07:00 ==============================================
2024/07/17 16:27:22-07:00 --------- Running Task
2024/07/17 16:27:22-07:00 ==============================================
2024/07/17 16:27:22-07:00 Parameter values:
2024/07/17 16:27:22-07:00 Frame(INT) = 2
2024/07/17 16:27:22-07:00 ----------------------------------------------
2024/07/17 16:27:22-07:00 Phase: Setup
2024/07/17 16:27:22-07:00 ----------------------------------------------
2024/07/17 16:27:22-07:00 Writing embedded files for Task to disk.
2024/07/17 16:27:22-07:00 Mapping: Task.File.Run -> /sessions/session-972e21d98dde45e59c7153bd9258a64dohwg4yg1/embedded_fileswy00x5ra/run-task.sh
2024/07/17 16:27:22-07:00 Wrote: Run -> /sessions/session-972e21d98dde45e59c7153bd9258a64dohwg4yg1/embedded_fileswy00x5ra/run-task.sh
2024/07/17 16:27:22-07:00 ----------------------------------------------
2024/07/17 16:27:22-07:00 Phase: Running action
2024/07/17 16:27:22-07:00 ----------------------------------------------
2024/07/17 16:27:22-07:00 Running command sudo -u job-user -i setsid -w /sessions/session-972e21d98dde45e59c7153bd9258a64dohwg4yg1/tmpv4obfkhn.sh
2024/07/17 16:27:22-07:00 Command started as pid: 2301
2024/07/17 16:27:22-07:00 Output:
2024/07/17 16:27:23-07:00 Daemon PID is 2223
2024/07/17 16:27:23-07:00 Daemon log file is /sessions/session-972e21d98dde45e59c7153bd9258a64dohwg4yg1/daemon.log
2024/07/17 16:27:23-07:00
2024/07/17 16:27:23-07:00 === Previous output from daemon
2024/07/17 16:27:23-07:00 ===
2024/07/17 16:27:23-07:00
2024/07/17 16:27:23-07:00 Sending command to daemon
2024/07/17 16:27:23-07:00 Received task result:
2024/07/17 16:27:23-07:00 {
2024/07/17 16:27:23-07:00 "result": "SUCCESS",
2024/07/17 16:27:23-07:00 "processedTaskCount": 1,
2024/07/17 16:27:23-07:00 "randomValue": 0.2578537967668988,
2024/07/17 16:27:23-07:00 "failureRate": 0.1
2024/07/17 16:27:23-07:00 }
2024/07/17 16:27:23-07:00
2024/07/17 16:27:23-07:00 === Daemon log from running the task
2024/07/17 16:27:23-07:00 Loading the task details file
2024/07/17 16:27:23-07:00 Received task details:
2024/07/17 16:27:23-07:00 {
2024/07/17 16:27:23-07:00 "pid": 2329,
2024/07/17 16:27:23-07:00 "frame": 2
2024/07/17 16:27:23-07:00 }
2024/07/17 16:27:23-07:00 Processing frame number 2
2024/07/17 16:27:23-07:00 Writing result
2024/07/17 16:27:23-07:00 Waiting until a USR1 signal is sent...
2024/07/17 16:27:23-07:00 ===
2024/07/17 16:27:23-07:00
2024/07/17 16:27:23-07:00 ----------------------------------------------
2024/07/17 16:27:23-07:00 Uploading output files to Job Attachments
2024/07/17 16:27:23-07:00 ----------------------------------------------
```
The following lines from the job template are what specified this action. ``` steps:
```
steps:
- name: EnvWithDaemonProcess
parameterSpace:
taskParameterDefinitions:
- name: Frame
type: INT
range: "{{Param.Frames}}"
stepEnvironments:
...
script:
actions:
onRun:
timeout: 60
command: bash
args:
- '{{Task.File.Run}}'
embeddedFiles:
- name: Run
filename: run-task.sh
type: TEXT
data: |
# This bash script sends a task to the background daemon process,
# then waits for it to respond with the output result.
set -euo pipefail
source "$DAEMON_BASH_HELPER_SCRIPT"
echo "Daemon PID is $DAEMON_PID"
echo "Daemon log file is $DAEMON_LOG"
print_daemon_log "Previous output from daemon"
send_task_to_daemon "{\"pid\": $$, \"frame\": {{Task.Param.Frame}} }"
wait_for_daemon_task_result
echo Received task result:
echo "$TASK_RESULT" | jq .
print_daemon_log "Daemon log from running the task"
hostRequirements:
attributes:
- name: attr.worker.os.family
anyOf:
- linux
```