Deploy a Software Heritage stack with docker deploy#

Intended audience

mirror operators

Prerequisites#

We assume that you have a properly set up docker swarm cluster with support for the docker stack deploy command, e.g.:

~/swh-mirror$ docker node ls
ID                            HOSTNAME  STATUS   AVAILABILITY  MANAGER STATUS  ENGINE VERSION
py47518uzdb94y2sb5yjurj22     host2     Ready    Active                        18.09.7
n9mfw08gys0dmvg5j2bb4j2m7 *   host1     Ready    Active        Leader          18.09.7

Note: on some systems (centos for example), making docker swarm work requires some permission tuning regarding the firewall and selinux. Please refer to the upstream docker-swarm documentation.

In the following how-to, we will assume that the service STACK name is swh (this name is the last argument of the docker stack deploy command below).

Several preparation steps will depend on this name.

We also use docker-compose to merge compose files, so make sure it is available on your system.

You also need to clone the git repository:

https://gitlab.softwareheritage.org/swh/infra/swh-mirror.git

Set up volumes#

Before starting the swh service, you will certainly want to specify where the data should be stored on your docker hosts.

By default docker will use docker volumes for storing databases and the content of the objstorage (thus put them in /var/lib/docker/volumes).

Optional: if you want to specify a different location to put the data in, you should create the docker volumes before starting the docker service. For example, the objstorage service uses a volume named <STACK>_objstorage:

~/swh-mirror$ docker volume create -d local \
  --opt type=none \
  --opt o=bind \
  --opt device=/data/docker/swh-objstorage \
  swh_objstorage

If you want to deploy services like the objstorage on several hosts, you will need a shared storage area in which blob objects will be stored. Typically a NFS storage can be used for this, or any existing docker volume driver like REX-Ray. This is not covered in this documentation.

Please read the documentation of docker volumes to learn how to use such a device/driver as volume provider for docker.

Note that the provided base-services.yaml file has placement constraints for the db-storage, db-web and objstorage containers, that depend on the availability of specific volumes (respectively <STACK>_storage-db, <STACK>_web-db and <STACK>_objstorage). These services are pinned to specific nodes using labels named org.softwareheritage.mirror.volumes.<base volume name> (e.g. org.softwareheritage.mirror.volumes.objstorage).

When you create a local volume for a given container, you should add the relevant label to the docker swarm node metadata with:

docker node update \
    --label-add org.softwareheritage.mirror.volumes.objstorage=true \
    <node_name>

You have to set the node labels, or to adapt the placement constraints to your local requirements, for the services to start.

Managing secrets#

Shared passwords (between services) are managed via docker secret. Before being able to start services, you need to define these secrets.

Namely, you need to create a secret for:

swh-mirror-db-postgres-password
swh-mirror-web-postgres-password

For example:

~/swh-mirror$ xkcdpass -d- | docker secret create swh-mirror-db-postgres-password -
[...]

Spawning the swh base services#

If you haven’t done it yet, clone this git repository:

~$ git clone https://gitlab.softwareheritage.org/swh/infra/swh-mirror.git
~$ cd swh-mirror

This repository provides the docker compose/stack manifests to deploy all the relevant services.

Note

These manifests use a set of docker images published in the docker hub. By default, the manifests will use the latest version of these images, but for production uses, you should set the SWH_IMAGE_TAG environment variable to pin them to a specific version.

To specify the tag to be used, simply set the SWH_IMAGE_TAG environment variable:

~/swh-mirror$ export SWH_IMAGE_TAG=20211022-121751

You can then spawn the base services using the following command:

~/swh-mirror$ docker stack deploy -c base-services.yml swh

Creating network swh_default
Creating config swh_storage
Creating config swh_objstorage
Creating config swh_nginx
Creating config swh_web
Creating service swh_grafana
Creating service swh_prometheus-statsd-exporter
Creating service swh_web
Creating service swh_objstorage
Creating service swh_db-storage
Creating service swh_memcache
Creating service swh_storage
Creating service swh_nginx
Creating service swh_prometheus

~/swh-mirror$ docker service ls

ID             NAME                             MODE         REPLICAS   IMAGE                                       PORTS
tc93talbe2tg   swh_db-storage                   global       1/1        postgres:13
42q5jtxsh029   swh_db-web                       global       1/1        postgres:13
rtlz62ok6s96   swh_grafana                      replicated   1/1        grafana/grafana:latest
jao3rt0et17n   swh_memcache                     replicated   1/1        memcached:latest
rulxakqgu2ko   swh_nginx                        replicated   1/1        nginx:latest                                *:5081->5081/tcp
q560pvw3q3ls   swh_objstorage                   replicated   2/2        softwareheritage/base:20211022-121751
a2h3ltaqdt56   swh_prometheus                   global       1/1        prom/prometheus:latest
lm24et9gjn2k   swh_prometheus-statsd-exporter   replicated   1/1        prom/statsd-exporter:latest
gwqinrao5win   swh_storage                      replicated   2/2        softwareheritage/base:20211022-121751
7g46blmphfb4   swh_web                          replicated   1/1        softwareheritage/web:20211022-121751

This will start a series of containers with:

an objstorage service,
a storage service using a postgresql database as backend,
a web app front end using a postgresql database as backend,
a memcache for the web app,
a prometheus monitoring app,
a prometeus-statsd exporter,
a grafana server,
an nginx server serving as reverse proxy for grafana and swh-web.

using the pinned version of the docker images.

The nginx frontend will listen on the 5081 port, so you can use:

http://localhost:5081/ to navigate your local copy of the archive,
http://localhost:5081/grafana/ to explore the monitoring probes (log in with admin/admin).

Warning

Please make sure that the SWH_IMAGE_TAG variable is properly set for any later docker stack deploy command you type, otherwise all the running containers will be recreated using the :latest image (which might not be the latest available version, nor consistent among the docker nodes on your swarm cluster).

Updating a configuration#

Configuration files are exposed to docker services via the docker config system. Unfortunately, docker does not support updating these config objects. The usual method to update a config in a service is:

create a new config entry with updated config content,
update targeted running services to replace the original config entry by the new one,
destroy old (now unused) docker config objects.

For example, if you edit the file conf/storage.yml:

~/swh-mirror$ docker config create storage-2 conf/storage.yml
h0m8jvsacvpl71zdcq3wnud6c
~/swh-mirror$ docker service update \
                --config-rm storage \
                --config-add source=storage-2,target=/etc/softwareheritage/config.yml \
                swh_storage
swh_storage
overall progress: 2 out of 2 tasks
verify: Service converged
~/swh-mirror$ docker config rm storage

Warning

this procedure will update the live configuration of the service stack, which will then be out of sync with the stack described in the compose file used to create the stack. This needs to be kept in mind if you try to apply the stack configuration using docker stack deploy later on. However if you destroy the unused config entry as suggested above, an execution of the docker stack deploy will not break anything (just recreate containers) since it will recreate original config object with the proper content.

See https://docs.docker.com/engine/swarm/configs/ for more details on how to use the config system in a docker swarm cluster.

Note that the docker service update command can be used for many other things, for example it can be used to change the debug level of a service:

~/swh-mirror$ docker service update --env-add LOG_LEVEL=DEBUG swh_storage

Then you can revert to the previous setup using:

~/swh-mirror$ docker service update --rollback swh_storage

See the documentation of the swh service update command for more details.

Updating an image#

When a new version of the softwareheritage image is published, running services must updated to use it.

In order to prevent inconsistency caveats due to dependency in deployed versions, we recommend that you deploy the new image on all running services at once.

This can be done as follow:

~/swh-mirror$ export SWH_IMAGE_TAG=<new version>
~/swh-mirror$ docker stack deploy -c base-services.yml swh

Note that this will reset the replicas config to their default values.

If you want to update only a specific service, you can also use (here for a replayer service):

~/swh-mirror$ docker service update --image \
       softwareheritage/replayer:${SWH_IMAGE_TAG} \
       swh_graph-replayer

Set up the mirroring components#

A Software Heritage mirror consists in base Software Heritage services, as described above, without any worker related to web scraping nor source code repository loading. Instead, filling local storage and objstorage is the responsibility of kafka based replayer services:

the graph replayer which is in charge of filling the storage (aka the graph), and
the content replayer which is in charge of filling the object storage.

Examples of docker deploy files and configuration files are provided in the graph-replayer.yml deploy file for replayer services using configuration from yaml files in conf/graph-replayer.yml.

Copy these example files as plain yaml ones then modify them to replace the XXX markers with proper values (also make sure the kafka server list is up to date). The parameters to check/update are:

journal_client.brokers: list of kafka brokers.
journal_client.group_id: unique identifier for this mirroring session; you can choose whatever you want, but changing this value will make kafka start consuming messages from the beginning; kafka messages are dispatched among consumers with the same group_id, so in order to distribute the load among workers, they must share the same group_id.
journal_client.sasl.username: kafka authentication username.
journal_client.sasl.password: kafka authentication password.

Then you need to merge the compose files “by hand” (due to this still unresolved bugs). For this we will use docker compose as helper tool to merge the compose files.

To merge 2 (or more) compose files together, typically base-services.yml with a mirror-related file:

~/swh-mirror$ docker-compose \
    -f base-services.yml \
    -f graph-replayer-override.yml \
    config > mirror.yml

Then use this generated file as argument of the docker stack deploy command, e.g.:

~/swh-mirror$ docker stack deploy -c mirror.yml swh

Graph replayer#

To run the graph replayer component of a mirror:

~/swh-mirror$ cd conf
~/swh-mirror/conf$ cp graph-replayer.yml.example graph-replayer.yml
~/swh-mirror/conf$ $EDITOR graph-replayer.yml
~/swh-mirror/conf$ cd ..

Once you have properly edited the conf/graph-replayer.yml config file, you can start these services with:

~/swh-mirror$ docker-compose \
    -f base-services.yml \
    -f graph-replayer-override.yml \
    config > stack-with-graph-replayer.yml
~/swh-mirror$ docker stack deploy \
    -c stack-with-graph-replayer.yml \
    swh
[...]

You can check everything is running with:

~/swh-mirror$ docker stack ls

NAME         SERVICES            ORCHESTRATOR
swh          11                  Swarm

~/swh-mirror$ docker service ls

ID             NAME                             MODE         REPLICAS   IMAGE                                       PORTS
tc93talbe2tg   swh_db-storage                   global       1/1        postgres:13
42q5jtxsh029   swh_db-web                       global       1/1        postgres:13
rtlz62ok6s96   swh_grafana                      replicated   1/1        grafana/grafana:latest
7hvn66um77wr   swh_graph-replayer               replicated   4/4        softwareheritage/replayer:20211022-121751
jao3rt0et17n   swh_memcache                     replicated   1/1        memcached:latest
rulxakqgu2ko   swh_nginx                        replicated   1/1        nginx:latest                                *:5081->5081/tcp
q560pvw3q3ls   swh_objstorage                   replicated   2/2        softwareheritage/base:20211022-121751
a2h3ltaqdt56   swh_prometheus                   global       1/1        prom/prometheus:latest
lm24et9gjn2k   swh_prometheus-statsd-exporter   replicated   1/1        prom/statsd-exporter:latest
gwqinrao5win   swh_storage                      replicated   2/2        softwareheritage/base:20211022-121751
7g46blmphfb4   swh_web                          replicated   1/1        softwareheritage/web:20211022-121751

If everything is OK, you should have your mirror filling. Check docker logs:

~/swh-mirror$ docker service logs swh_graph-replayer
[...]

or:

~/swh-mirror$ docker service logs --tail 100 --follow swh_graph-replayer
[...]

Content replayer#

Similarly, to run the content replayer:

~/swh-mirror$ cd conf
~/swh-mirror/conf$ cp content-replayer.yml.example content-replayer.yml
~/swh-mirror/conf$ # edit content-replayer.yml files
~/swh-mirror/conf$ cd ..

Once you have properly edited the conf/content-replayer.yml config file, you can start these services with:

~/swh-mirror$ docker-compose \
    -f base-services.yml \
    -f content-replayer-override.yml \
    config > content-replayer.yml
~/swh-mirror$ docker stack deploy \
    -c content-replayer.yml \
    swh
[...]

Full mirror#

Putting all together is just a matter of merging the 3 compose files:

~/swh-mirror$ docker-compose \
    -f base-services.yml \
    -f graph-replayer-override.yml \
    -f content-replayer-override.yml \
    config > mirror.yml
~/swh-mirror$ docker stack deploy \
    -c mirror.yml \
    swh
[...]

Getting your deployment production-ready#

docker-stack scaling#

In order to scale up a replayer service, you can use the docker scale command. For example:

~/swh-mirror$ docker service scale swh_graph-replayer=4
[...]

will start 4 copies of the graph replayer service.

Notes on the throughput of the mirroring process#

One graph replayer service requires a steady 500MB to 1GB of RAM to run, so make sure you have properly sized machines for running these replayer containers, and to monitor these.
The graph replayer containers will require sufficient network bandwidth for the kafka traffic (this can easily peak to several hundreds of megabits per second, and the total volume of data fetched will be multiple tens of terabytes).
The biggest kafka topics are directory, revision and content, and will take the longest to initially replay.

Operational concerns for the Storage database#

The overall throughput of the mirroring process will depend heavily on the swh_storage service, and on the performance of the underlying swh_db-storage database. You will need to make sure that your database is properly tuned.

You may also want to deploy your database directly to a bare-metal server rather than have it managed within the docker stack. To do so, you will have to:

modify the (merged) configuration of the docker stack to drop references to the db-storage service (itself, and as dependency for the storage service)
ensure that docker containers deployed in your swarm are able to connect to your external database server
override the environment variables of the storage service to reference the external database server and dbname