feat(postgres-backup): add prometheus metrics exporter

postgres-backup-s3/Dockerfile

@@ -2,7 +2,7 @@ FROM alpine:3.9
 LABEL maintainer="Johannes Schickling <schickling.j@gmail.com>"
 
 ADD install.sh install.sh
-RUN sh install.sh && rm install.sh
+RUN sh install.sh && rm install.sh && mkdir -p /metrics
 
 ENV POSTGRES_DATABASE **None**
 ENV POSTGRES_HOST **None**
@@ -18,8 +18,10 @@ ENV S3_PATH 'backup'
 ENV S3_ENDPOINT **None**
 ENV S3_S3V4 no
 ENV SCHEDULE **None**
+ENV ENABLE_METRICS false
 
 ADD run.sh run.sh
 ADD backup.sh backup.sh
+ADD write_metrics.sh write_metrics.sh
 
 CMD ["sh", "run.sh"]

postgres-backup-s3/README.md

@@ -32,6 +32,7 @@ pgbackups3:
     POSTGRES_USER: user
     POSTGRES_PASSWORD: password
     POSTGRES_EXTRA_OPTS: '--schema=public --blobs'
+    ENABLE_METRICS: true
 ```
 
 ### Automatic Periodic Backups
@@ -40,3 +41,12 @@ You can additionally set the `SCHEDULE` environment variable like `-e SCHEDULE="
 
 More information about the scheduling can be found [here](http://godoc.org/github.com/robfig/cron#hdr-Predefined_schedules).
 
+### Metrics exporter
+
+Optionally you can also export backup metrics, e.g. size, start time in Prometheus
+file format. To read the metrics, you'll have to mount the metrics folder to your host at `/metrics`.
+The file is called `metrics.txt`.
+
+```sh
+$ docker run -v $(pwd)/metrics:/metrics -e ENABLE_METRICS=true -e ... schickling/postgres-backup-s3
+```

postgres-backup-s3/backup.sh

@@ -58,11 +58,17 @@ export PGPASSWORD=$POSTGRES_PASSWORD
 POSTGRES_HOST_OPTS="-h $POSTGRES_HOST -p $POSTGRES_PORT -U $POSTGRES_USER $POSTGRES_EXTRA_OPTS"
 
 echo "Creating dump of ${POSTGRES_DATABASE} database from ${POSTGRES_HOST}..."
+START=$(date +%s)
 
 pg_dump $POSTGRES_HOST_OPTS $POSTGRES_DATABASE | gzip > dump.sql.gz
+SIZE=$(ls -nlt dump.sql.gz | head -n1 | awk '{print $5}')
 
 echo "Uploading dump to $S3_BUCKET"
-
 cat dump.sql.gz | aws $AWS_ARGS s3 cp - s3://$S3_BUCKET/$S3_PREFIX/${POSTGRES_DATABASE}_$(date +"%Y-%m-%dT%H:%M:%SZ").sql.gz || exit 2
+END=$(date +%s)
+
+if [ "$ENABLE_METRICS" = true ]; then
+  write_metrics.sh "${START}" "${END}" "${SIZE}"
+fi
 
 echo "SQL backup uploaded successfully"

postgres-backup-s3/write_metrics.sh

@@ -0,0 +1,20 @@
+METRICS_LOCATION=$1
+START=$2
+END=$3
+SIZE=$4
+
+# Write to a temporary file invisible to prometheus
+cat > $(pwd)/postgres_backup.prom.$$ <<EOT
+# HELP postgres backup start time, in unixtime.
+# TYPE postgres_backup_start gauge
+postgres_backup_backup_start ${START}
+# HELP postgres_backup_end backup end time, in unixtime.
+# TYPE postgres_backup_end gauge
+postgres_backup_end ${END}
+# HELP postgres_backup_size backup size, in bytes.
+# TYPE postgres_backup_size gauge
+postgres_backup_size ${SIZE}
+EOT
+
+# Atomic move so prometheus can see it
+mv $(pwd)/postgres_backup.prom.$$ "/metrics/metrics.txt"