untilMongod

The untilMongod command attempts to connect to a MongoDB® server (mongod) or sharding front (mongos) for a maximum duration.

Its main use is as a way to start using a connection as soon as its server becomes available, without relying on manually adjusted timeouts.

Syntax

untilMongo -url mongodb://example.com:11117 -timeout 60

• -url is a typical MongoDB URL, defaulting to mongodb://localhost:27017

  • It supports the MongoDB driver Dial() URL options, which is necessary to support connecting to servers directly without reaching for the replica set, and other situations like authentication or pool tuning.

  • Specifically, to connect to a server started as part of a yet-unconfigured replica set, the URL must contain a directConnection=true query, like:

    untilMongo -url mongodb://example.com:11117?directConnection=true -timeout 60
    

• -timeout is the maximum delay (in seconds) the command will wait before aborting.
• -v will increase verbosity, outputting messages on stderr on each retry.

-connection-options

Exit codes

• 0: connection succeeded
• 1: connection could not be established, normal situation otherwise
• 2: another type of error occurred

Installing the command

Assuming a Go 1.22 or later toolchain is available, just do:

go install github.com/fgm/untilMongod@latest

This will install the untilMongod command in $GOPATH/bin, by default:

• $HOME/go/bin on UNIX-like systems (Linux, macOS)
• %USERPROFILE%\go\bin on Windows systems.

Running the Node.JS example

The examples/example.bash script show how to use untilMongo to run a Node.JS application only once the MongoDB server it tries to connect to has become available. The application itself is just an example showing the equivalent of the rs.Status() mongo shell command.

It assumes that:

• MongoDB Community has been installed
• Go is installed on the host

To run it:

cd examples
npm i
bash example.bash

Running tests

untilMongod uses the standard go testing package. Tests should pass, regardless of whether a mongod|mongos is available at the default mongodb://localhost:27017 URL, but they will only cover the successful connection path if an instance is available.

The recommended ways to run tests are:

# Running all tests and generating coverage.
go test -race -coverprofile coverage -covermode atomic ./...
go tool cover -html coverage

# Running only unit tests
go test -race -short ./...

# Running only integration tests
go test -race -run 'Integration$' ./...

IP information

• © 2018-2024 Frederic G. MARAND.
• Published under the General Public License, version 3 or later.
• MongoDB is a trademark of MongoDB, Inc.

License