Dagr

Runs programs every day (in Norse mythology, Dagr is day personified).

Dagr monitors a specified git repository for programs (directories that contain a main executable) and ensures each of them is executed every day (or at any other frequency expressible in the Cron syntax). Program output (stderr and stdout) are captured and showed on a monitoring page. A program's exit code can be used to signal to Dagr whether a program succeeded (0) or failed (2), or whether it should be retried after a delay (1).

Running

$ cd $GOPATH
$ ./bin/dagr --http :8080 --repo git@github.com:uswitch/dagr-sample-programs --work /tmp/dagr-work --ui ./ui

Configuration

The scheduling of dagr programs can be controlled by an optional TOML file called dagr.toml in the same directory as main.

Scheduling programs

If dagr.toml contains a line in this format:

schedule = "CRON EXPRESSION"

the Cron expression gives the schedule on which to run the program.

Valid Cron expressions are those accepted by the robfig/cron library.

e.g.

schedule = "0 */5 * * * *"

would ensure the program would be run every five minutes.

If dagr.toml does not exist or the schedule line is not present, the schedule defaults to @daily (i.e. every day at midnight).

Running programs immediately on startup

If dagr.toml contains a line like this:

immediate = BOOLEAN

the program will be run immediately when dagr starts (as well as its usually scheduled times) if the boolean value is true.

i.e.

immediate = true

In any other case, the program will not be run immediately (i.e. it will run at scheduled times only)

Notify slack about job failures

Optional feature switched off by default. Can be configured with environment variables. To switch on set DAGR_SLACK_WEBHOOK_URL and DAGR_SLACK_ALERTS_ROOM to point to the slack incoming webhook and the slack room to be alerted. By default Dagr will notify the slack room for every failed job both with exit code 1 (retryable) or 2. By setting DAGR_SLACK_SILENCE_RETRYABLE slack will be only notifed if a job fails with exit code 2. The appearance of the message can be configured via setting DAGR_SLACK_USER_NAME (defaults to Dagr), DAGR_SLACK_ICON_EMOJI (defaults to :exclamation:) and DAGR_SLACK_ICON_URL (no default).

Naturally individual jobs can have their own warning logic, this is for an easy option to get basic monitoring on jobs for cheap.

Examples

For examples please see our sample programs repository.

Dagr Dashboard

The dashboard provides an overview of which programs are available to run, their most recent status and three counters showing how many programs succeeded or failed.

Execution Page

The execution page allows you to view stderr and stdout for a program- the state is updated via a websocket.

Build

Pre-requisites

• Go
• Zip
• Git

Dagr contains packages which are specified as github.com/uswitch/dagr/foo etc. When developing its helpful to ensure you pull the code using go get and build using the provided Makefile.

$ export PATH=$GOPATH/bin:$PATH
$ cd $GOPATH
$ go get github.com/uswitch/dagr
$ make -C src/github.com/uswitch/dagr deps
$ make -C src/github.com/uswitch/dagr

Docker

The Dockerfile requires that a RSA key be present that has read-only access to the github repo to be watched. The file should be named id_rsa and be copied into the same folder as the Dockerfile.

The command passed to the container would be the same as you would run from the command line.

Usage:

docker-compose build

#example usage
docker-compose ps
docker-compose run dagr --http :8080 --repo git@github.com:uswitch/dagr-sample-programs --work /tmp/dagr-work --ui ./ui