madrob commented on a change in pull request #1769: URL: https://github.com/apache/lucene-solr/pull/1769#discussion_r487109759
########## File path: solr/docker/Docker-FAQ.md ########## @@ -0,0 +1,320 @@ + +Docker Solr FAQ +=============== + + +How do I persist Solr data and config? +-------------------------------------- + +Your data is persisted already, in your container's filesystem. +If you `docker run`, add data to Solr, then `docker stop` and later +`docker start`, then your data is still there. The same is true for +changes to configuration files. + +Equally, if you `docker commit` your container, you can later create a new +container from that image, and that will have your data in it. + +For some use-cases it is convenient to provide a modified `solr.in.sh` file to Solr. +For example to point Solr to a ZooKeeper host: + +``` +docker create --name my_solr -P solr +docker cp my_solr:/opt/solr/bin/solr.in.sh . +sed -i -e 's/#ZK_HOST=.*/ZK_HOST=cylon.lan:2181/' solr.in.sh +docker cp solr.in.sh my_solr:/opt/solr/bin/solr.in.sh +docker start my_solr +# With a browser go to http://cylon.lan:32873/solr/#/ and confirm "-DzkHost=cylon.lan:2181" in the JVM Args section. +``` + +But usually when people ask this question, what they are after is a way +to store Solr data and config in a separate [Docker Volume](https://docs.docker.com/userguide/dockervolumes/). +That is explained in the next two questions. + + +How can I mount a host directory as a data volume? +-------------------------------------------------- + +This is useful if you want to inspect or modify the data in the Docker host +when the container is not running, and later easily run new containers against that data. +This is indeed possible, but there are a few gotchas. + +Solr stores its core data in the `server/solr` directory, in sub-directories +for each core. The `server/solr` directory also contains configuration files +that are part of the Solr distribution. +Now, if we mounted volumes for each core individually, then that would +interfere with Solr trying to create those directories. If instead we make +the whole directory a volume, then we need to provide those configuration files +in our volume, which we can do by copying them from a temporary container. +For example: + +``` +# create a directory to store the server/solr directory +$ mkdir /home/docker-volumes/mysolr1 + +# make sure its host owner matches the container's solr user +$ sudo chown 8983:8983 /home/docker-volumes/mysolr1 + +# copy the solr directory from a temporary container to the volume +$ docker run -it --rm -v /home/docker-volumes/mysolr1:/target apache/solr cp -r server/solr /target/ + +# pass the solr directory to a new container running solr +$ SOLR_CONTAINER=$(docker run -d -P -v /home/docker-volumes/mysolr1/solr:/opt/solr/server/solr apache/solr) + +# create a new core +$ docker exec -it --user=solr $SOLR_CONTAINER solr create_core -c gettingstarted + +# check the volume on the host: +$ ls /home/docker-volumes/mysolr1/solr/ +configsets gettingstarted README.txt solr.xml zoo.cfg +``` + +Note that if you add or modify files in that directory from the host, you must `chown 8983:8983` them. + + +How can I use a Data Volume Container? +-------------------------------------- + +You can avoid the concerns about UID mismatches above, by using data volumes only from containers. +You can create a container with a volume, then point future containers at that same volume. +This can be handy if you want to modify the solr image, for example if you want to add a program. +By separating the data and the code, you can change the code and re-use the data. + +But there are pitfalls: + +- if you remove the container that owns the volume, then you lose your data. + Docker does not even warn you that a running container is dependent on it. +- if you point multiple solr containers at the same volume, you will have multiple instances + write to the same files, which will undoubtedly lead to corruption +- if you do want to remove that volume, you must do `docker rm -v containername`; + if you forget the `-v` there will be a dangling volume which you can not easily clean up. + +Here is an example: + +``` +# create a container with a volume on the path that solr uses to store data. +docker create -v /opt/solr/server/solr --name mysolr1data solr /bin/true + +# pass the volume to a new container running solr +SOLR_CONTAINER=$(docker run -d -P --volumes-from=mysolr1data apache/solr) + +# create a new core +$ docker exec -it --user=solr $SOLR_CONTAINER solr create_core -c gettingstarted + +# make a change to the config, using the config API +docker exec -it --user=solr $SOLR_CONTAINER curl http://localhost:8983/solr/gettingstarted/config -H 'Content-type:application/json' -d'{ + "set-property" : {"query.filterCache.autowarmCount":1000}, + "unset-property" :"query.filterCache.size"}' + +# verify the change took effect +docker exec -it --user=solr $SOLR_CONTAINER curl http://localhost:8983/solr/gettingstarted/config/overlay?omitHeader=true + +# stop the solr container +docker exec -it --user=solr $SOLR_CONTAINER bash -c 'cd server; java -DSTOP.PORT=7983 -DSTOP.KEY=solrrocks -jar start.jar --stop' + +# create a new container +SOLR_CONTAINER=$(docker run -d -P --volumes-from=mysolr1data apache/solr) + +# check our core is still there: +docker exec -it --user=solr $SOLR_CONTAINER ls server/solr/gettingstarted + +# check the config modification is still there: +docker exec -it --user=solr $SOLR_CONTAINER curl http://localhost:8983/solr/gettingstarted/config/overlay?omitHeader=true +``` + + +Can I use volumes with SOLR_HOME? +--------------------------------- + +Solr supports a SOLR_HOME environment variable to point to a non-standard location of the Solr home directory. +You can use this in Solr docker, in combination with volumes: + +``` +docker run -it -v $PWD/mysolrhome:/mysolrhome -e SOLR_HOME=/mysolrhome apache/solr +``` + +This does need a pre-configured directory at that location. + +To make this easier, Solr docker supports a INIT_SOLR_HOME setting, which copies the contents +from the default directory in the image to the SOLR_HOME (if it is empty). + +``` +mkdir mysolrhome +sudo chown 8983:8983 mysolrhome +docker run -it -v $PWD/mysolrhome:/mysolrhome -e SOLR_HOME=/mysolrhome -e INIT_SOLR_HOME=yes apache/solr +``` + +Note: If SOLR_HOME is set, the "solr-precreate" command will put the created core in the SOLR_HOME directory +rather than the "mycores" directory. + + +Can I run ZooKeeper and Solr clusters under Docker? +--------------------------------------------------- + +At the network level the ZooKeeper nodes need to be able to talk to eachother, +and the Solr nodes need to be able to talk to the ZooKeeper nodes and to each other. +At the application level, different nodes need to be able to identify and locate each other. +In ZooKeeper that is done with a configuration file that lists hostnames or IP addresses for each node. +In Solr that is done with a parameter that specifies a host or IP address, which is then stored in ZooKeeper. + +In typical clusters, those hostnames/IP addresses are pre-defined and remain static through the lifetime of the cluster. +In Docker, inter-container communication and multi-host networking can be facilitated by [Docker Networks](https://docs.docker.com/engine/userguide/networking/). +But, crucially, Docker does not normally guarantee that IP addresses of containers remain static during the lifetime of a container. +In non-networked Docker, the IP address seems to change everytime you stop/start. +In a networked Docker, containers can lose their IP address in certain sequences of starting/stopping, unless you take steps to prevent that. + +IP changes causes problems: + +- If you use hardcoded IP addresses in configuration, and the addresses of your containers change after a stops/start, then your cluster will stop working and may corrupt itself. +- If you use hostnames in configuration, and the addresses of your containers change, then you might run into problems with cached hostname lookups. +- And if you use hostnames there is another problem: the names are not defined until the respective container is running, +So when for example the first ZooKeeper node starts up, it will attempt a hostname lookup for the other nodes, and that will fail. +This is especially a problem for ZooKeeper 3.4.6; future versions are better at recovering. + +Docker 1.10 has a new `--ip` configuration option that allows you to specify an IP address for a container. +It also has a `--ip-range` option that allows you to specify the range that other containers get addresses from. +Used together, you can implement static addresses. See [this example](docs/docker-networking.md). + + +Can I run ZooKeeper and Solr with Docker Links? +----------------------------------------------- + +Docker's [Legacy container links](https://docs.docker.com/engine/userguide/networking/default_network/dockerlinks/) provide a way to +pass connection configuration between containers. It only works on a single machine, on the default bridge. +It provides no facilities for static IPs. +Note: this feature is expected to be deprecated and removed in a future release. +So really, see the "Can I run ZooKeeper and Solr clusters under Docker?" option above instead. + +But for some use-cases, such as quick demos or one-shot automated testing, it can be convenient. + +Run ZooKeeper, and define a name so we can link to it: + +```console +$ docker run --name zookeeper -d -p 2181:2181 -p 2888:2888 -p 3888:3888 jplock/zookeeper +``` + +Run two Solr nodes, linked to the zookeeper container: + +```console +$ docker run --name solr1 --link zookeeper:ZK -d -p 8983:8983 \ + apache/solr \ + bash -c 'solr start -f -z $ZK_PORT_2181_TCP_ADDR:$ZK_PORT_2181_TCP_PORT' + +$ docker run --name solr2 --link zookeeper:ZK -d -p 8984:8983 \ + apache/solr \ + bash -c 'solr start -f -z $ZK_PORT_2181_TCP_ADDR:$ZK_PORT_2181_TCP_PORT' +``` + +Create a collection: + +```console +$ docker exec -i -t solr1 solr create_collection \ + -c gettingstarted -shards 2 -p 8983 +``` + +Then go to `http://localhost:8983/solr/#/~cloud` (adjust the hostname for your docker host) to see the two shards and Solr nodes. + + +How can I run ZooKeeper and Solr with Docker Compose? +----------------------------------------------------- + +See the [docker compose example](docs/docker-compose.yml). + + +I'm confused about the different invocations of solr -- help? +------------------------------------------------------------- + +The different invocations of the Solr docker image can look confusing, because the name of the +image is "solr" and the Solr command is also "solr", and the image interprets various arguments in Review comment: should be `apache/solr` ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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