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advanced-usage.md

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Advanced Usage

Protocol v2 transition

During the transition to Babelfish v2 protocol and Semantic UAST client may choose either:

  1. Use existing client (protocol v1) and XPath queries. This should only be a temporary solution, since v1 will be deprecated.

  2. Use the latest Go client, set .Mode(Semantic) and change XPath to use the new Semantic UAST types. Requires v2 drivers (latest) and bblfshd >= 2.6.1. Note that v1 version of libuast used in the client to provide XPath does not support namespaces, as defined in the Semantic UAST spec. Thus, to query uast:Identifier the client should omit the namespace: //Identifier.

  3. Try the new UASTv2 representation by using Go client and the ParseRequestV2. This is not yet supported by all the clients, so check client's current status first.

Adding all drivers

In the previous section the bblfshctl command to install the drivers was shown with the --recommended switch. This will install all the drivers in beta stage or better and annotated UAST support. But if you're interested in installing all official language drivers, even the ones that have alpha status and only native AST support, you can use the --all switch instead:

$ docker exec -it bblfshd bblfshctl driver install --all

Adding drivers from the local Docker daemon

You can add a driver to the server using one stored in the local Docker daemon instead of the official ones at Dockerhub. This is especially useful when developing new drivers as it allows you to test versions of your driver integrated into the server.

If you want to do this, the Unix socket that Docker uses to communicate with the instance must be mounted in the bblfshd image, which you can do with the -v parameter like in the next example:

$ docker run -d -v /var/run/docker.sock:/var/run/docker.sock --name bblfshd --privileged -p 9432:9432 -v /var/lib/bblfshd:/var/lib/bblfshd bblfsh/bblfshd

Now you can add drivers from the local Docker using bblfshctl like this:

docker exec -it bblfshd bblfshctl driver install python docker-daemon:bblfsh/python-driver:dev-123321-dirty

Running a driver without the server

You can also directly run a driver's Docker image without a server. Like the bblfshd server, it will serve using the gRPC protocol on the 9432 port (through you can easily change it using the -p option to docker run).

Running a driver this way means that requests will be processed serially so no more than one request at a time will be served and of course no more than the driver's language can be parsed, through it can be convenient for some quick UAST extraction of specific files or quick tests since it skips the steps of running a server and managing its drivers.

To run a driver independently of the server run:

docker run --rm -p 9432:9432 bblfsh/python-driver

(change python-driver for the driver that you want to run).

Then you can send requests using any of the clients..