Add Docker Compose example.

.gitignore

@@ -20,3 +20,4 @@ oidc-role.json
 **/tmp/*
 __pycache__/
 *.tar.gz
+.env

docs/storage-transfer.md

@@ -87,6 +87,38 @@ Run the agent container with the following settings:
 | Locked memory limit | `64000000` bytes |
 | Arguments | `--project-id=${PROJECT_ID} --creds-file=/transfer_root/etc/sts-agent/cred.json --hostname=$(hostname) --agent-pool=${STS_AGENT_POOL}` |
 
+With Docker:
+
+```bash
+sudo docker run --ulimit memlock=64000000 -d --rm \
+    -v /mnt/ext-storage:/mnt/ext-storage:ro \
+    -v /etc/sts-agent:/transfer_root/etc/sts-agent:ro \
+    -v /var/lib/vault-cert/wif:/transfer_root/var/lib/vault-cert/wif:ro \
+    --env GOOGLE_API_CERTIFICATE_CONFIG=/transfer_root/etc/sts-agent/certificate_config.json \
+    gcr.io/cloud-ingest/tsop-agent:latest \
+    --project-id="${PROJECT_ID}" \
+    --creds-file=/transfer_root/etc/sts-agent/cred.json \
+    --hostname="$(hostname)" \
+    --agent-pool="${STS_AGENT_POOL}"
+```
+
+With Docker Compose, `sts-agent/compose.yaml` holds the same settings. It reads `PROJECT_ID`, `STS_AGENT_POOL` and `HOSTNAME` from `sts-agent/.env`. Create the file with the values of `env.sh` and the host name printed by `hostname`:
+
+`sts-agent/.env`:
+
+```bash
+PROJECT_ID=my-project
+STS_AGENT_POOL=my-agents
+HOSTNAME=agent-host
+```
+
+Start the agent:
+
+```bash
+cd sts-agent
+sudo docker compose up -d
+```
+
 The source directory is mounted at the same path as on the host, because the transfer job refers to it by that path. The agent requires the `--creds-file` path to start with `/transfer_root` unless the whole host filesystem is mounted with `--enable-mount-directory`.
 
 The connected agents of the pool are listed on the Agent pools page of the Google Cloud console. An agent appears there only after it has authenticated.

sts-agent/compose.yaml

@@ -0,0 +1,16 @@
+services:
+  sts-agent:
+    image: gcr.io/cloud-ingest/tsop-agent:latest
+    ulimits:
+      memlock: 64000000
+    volumes:
+      - /mnt/ext-storage:/mnt/ext-storage:ro
+      - /etc/sts-agent:/transfer_root/etc/sts-agent:ro
+      - /var/lib/vault-cert/wif:/transfer_root/var/lib/vault-cert/wif:ro
+    environment:
+      GOOGLE_API_CERTIFICATE_CONFIG: /transfer_root/etc/sts-agent/certificate_config.json
+    command:
+      - --project-id=${PROJECT_ID}
+      - --creds-file=/transfer_root/etc/sts-agent/cred.json
+      - --hostname=${HOSTNAME}
+      - --agent-pool=${STS_AGENT_POOL}