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Building mtail

mtail is implemented in Go.

You will need to install Go 1.7 or higher.

Go

Clone the source from GitHub into your $GOPATH. If you don't have a $GOPATH, see the next section.

cd $GOPATH/src
go get github.com/google/mtail
cd github.com/google/mtail
make

For Go First-Timers

An excellent starting guide for people new to Go entirely is here: https://github.com/alco/gostart

If you want to skip the guide, these two references are short but to the point on setting up the $GOPATH workspace:

Finally, https://golang.org/doc/code.html is the original Go project documentation for the philosophy on Go workspaces.

No Really, What is the TLDR

Put export GOPATH=$HOME/go in your ~/.profile.

export GOPATH=$HOME/go
mkdir -p $GOPATH/src

then back up to the Details above.

Building

Unlike the recommendation for Go projects, mtail uses a Makefile to build the source.

Having fetched the source, use make from the top of the source tree. This will install all the dependencies, and then build mtail. This assumes that your Go environment is already set up -- see above for hints on setting it up.

The resulting binary will be in $GOPATH/bin.

The unit tests can be run with make test, which invokes go test. The slower race-detector tests can be run with make testrace.

Cross-compilation

The Makefile has a crossbuild target for building on different platforms. By default it builds for a few amd64 targets:

% make crossbuild
mkdir -p build
gox --output="./build/mtail_v3.0.0-rc10_{{.OS}}_{{.Arch}}" -osarch="linux/amd64 windows/amd64 darwin/amd64" -ldflags "-X main.Version=v3.0.0-rc10-72-gcbea8a8 -X main.Revision=cbea8a810942be1129d58c37b27a55987a384776"
Number of parallel builds: 3

-->     linux/amd64: github.com/google/mtail
-->    darwin/amd64: github.com/google/mtail
-->   windows/amd64: github.com/google/mtail

but you can override it with the environment variable GOX_OSARCH like so:

% make GOX_OSARCX=linux/arm crossbuild
mkdir -p build
gox --output="./build/mtail_v3.0.0-rc10_{{.OS}}_{{.Arch}}" -osarch="linux/amd64 windows/amd64 darwin/amd64" -ldflags "-X main.Version=v3.0.0-rc10-72-gcbea8a8 -X main.Revision=cbea8a810942be1129d58c37b27a55987a384776"
Number of parallel builds: 3

-->    darwin/amd64: github.com/google/mtail
-->   windows/amd64: github.com/google/mtail
-->     linux/amd64: github.com/google/mtail

No Go

You can still build and develop mtail with Docker.

docker build -t mtail .
docker run -it --rm mtail --help

mtail is not much use without a configuration file or logs to parse, you will need to mount a path containing them into the container, like so:

docker run -it --rm -v examples/linecount.mtail:/progs/linecount.mtail -v /var/log:/logs mtail -logtostderr -one_shot -progs /progs/linecount.mtail -logs /logs/messages.log

Or, via Docker Compose, e.g. this docker-compose.yml snippet example:

service:
  mtail:
    image: mtail
    command:
      - -logtostderr
      - -one_shot
      - -progs
      - /progs/linecount.mtail
      - -logs
      - /logs/messages.log
    volume:
      - type: bind
        source: /var/log
        target: /logs
        readonly: true
      - type: bind
        source: examples/linecount.mtail
        target: /progs/linecount.mtail

Contributing

Please use gofmt to format your code before committing. Emacs' go-mode has a lovely gofmt-before-save function.

Troubleshooting

If make gives you the following error:

../github.com/google/mtail/vm/lexer.go:28: too many errors

Then run make in that dependency and run make again like such:

cd ../github.com/google/mtail
make
cd -
make