add hedgedoc docs (#30)

Author: wizzdom

docs/services/codimd.md

@@ -0,0 +1,82 @@
+---
+title: HedgeDoc
+author:
+  - wizzdom
+tags:
+  - aperture
+  - nomad
+  - docker
+---
+
+# HedgeDoc - `wizzdom`
+
+HedgeDoc is deployed with [nomad](nomad.md) on [`aperture`](../hardware/aperture/index.md) as a docker container. It is accessible through [md.redbrick.dcu.ie](https://md.redbrick.dcu.ie).
+
+HedgeDoc auths against LDAP and its configuration is available [here](https://github.com/redbrick/nomad/blob/master/jobs/services/hedgedoc.hcl)
+
+All sensitive variables are stored in the [`consul`](consul.md) KV store. 
+
+The important points are as follows:
+
+- connecting to the database:
+
+```bash
+CMD_DB_URL = "postgres://{{ key "hedgedoc/db/user" }}:{{ key "hedgedoc/db/password" }}@{{ env "NOMAD_ADDR_db" }}/{{ key "hedgedoc/db/name" }}"
+```
+
+- disabling anonymous users and email signup:
+
+```bash
+CMD_ALLOW_EMAIL_REGISTER = "false"
+CMD_ALLOW_ANONYMOUS      = "false"
+CMD_EMAIL                = "false"
+```
+
+- LDAP configuration:
+
+```bash
+CMD_LDAP_URL             = "{{ key "hedgedoc/ldap/url" }}"
+CMD_LDAP_SEARCHBASE      = "ou=accounts,o=redbrick"
+CMD_LDAP_SEARCHFILTER    = "{{`(uid={{username}})`}}"
+CMD_LDAP_PROVIDERNAME    = "Redbrick"
+CMD_LDAP_USERIDFIELD     = "uidNumber"
+CMD_LDAP_USERNAMEFIELD   = "uid"
+```
+
+See the [HedgeDoc docs](https://docs.hedgedoc.org/configuration/) for more info on configuration. 
+
+## Backups
+
+The HedgeDoc database is backed up periodically by a [nomad](nomad.md) job, the configuration for which is [here](https://github.com/redbrick/nomad/blob/master/jobs/services/hedgedoc-backup.hcl).
+
+The bulk of this job is this script which:
+- grabs the `alloc_id` of the currently running HedgeDoc allocation from nomad
+- execs into the container running `pg_dumpall` dumping the database into a file with the current date and time
+- if the backup is unsuccessful the script notifies the admins on discord via a webhook.
+
+```bash
+#!/bin/bash
+
+file=/storage/backups/nomad/postgres/hedgedoc/postgresql-hedgedoc-$(date +%Y-%m-%d_%H-%M-%S).sql
+
+mkdir -p /storage/backups/nomad/postgres/hedgedoc
+
+alloc_id=$(nomad job status hedgedoc | grep running | tail -n 1 | cut -d " " -f 1)
+
+job_name=$(echo ${NOMAD_JOB_NAME} | cut -d "/" -f 1)
+
+nomad alloc exec -task hedgedoc-db $alloc_id pg_dumpall -U {{ key "hedgedoc/db/user" }} > "${file}"
+
+find /storage/backups/nomad/postgres/hedgedoc/postgresql-hedgedoc* -ctime +3 -exec rm {} \; || true
+
+if [ -s "$file" ]; then # check if file exists and is not empty
+  echo "Backup successful"
+  exit 0
+else
+  rm $file
+  curl -H "Content-Type: application/json" -d \
+  '{"content": "<@&585512338728419341> `PostgreSQL` backup for **'"${job_name}"'** has just **FAILED**\nFile name: `'"$file"'`\nDate: `'"$(TZ=Europe/Dublin date)"'`\nTurn off this script with `nomad job stop '"${job_name}"'` \n\n## Remember to restart this backup job when fixed!!!"}' \
+  {{ key "postgres/webhook/discord" }}
+fi
+```
+