Build and deploy Nextstrain


The nextstrain project is an attempt to make flexible informatic pipelines and visualization tools to track ongoing pathogen evolution as sequence data emerges. The nextstrain project derives from nextflu, which was specific to influenza evolution.

nextstrain is comprised of four components:

  • fauna: database and IO scripts for sequence and serological data
  • augur: informatic pipelines to conduct inferences from raw data
  • auspice: web app to visualize resulting inferences
  • janus: build and deploy scripts


Definition: Roman god of beginnings and passages.

This repo is intended to ease deployment of nextstrain instances. It's goal is to provide deploy scripts for augur builds.


Check out the code and branch.

git clone --recursive
cd janus
git submodule update --init --recursive

Or make sure to update to latest version.

git pull origin master
git submodule update

Install Python environment.


After this install the path to miniconda binaries (~/miniconda3/bin) needs to be added to PATH variable.


Set fauna environment variables (RETHINK_HOST and RETHINK_AUTH_KEY).

Download data.

./janus download --config filters="zika"

Run augur.

./janus --config filters="zika"

Inspect output in augur/builds/zika/auspice.

Environment configuration

Define database environment variables RETHINK_HOST, RETHINK_AUTH_KEY, and NCBI_EMAIL before trying to download data with fauna.

Define AWS credentials in the AWS_SECRET_ACCESS_KEY and AWS_ACCESS_KEY_ID environment variables before trying to push auspice results to S3.

Build configuration

Janus uses a JSON configuration file to define a list of one or more augur builds to run (e.g., zika, ebola, or flu_h3n2_ha_3y). The configuration file must provide a builds attribute with a corresponding list of one or more build definitions. The following is an example empty configuration.

    "builds": [

Builds are defined as dictionaries with two or more attributes. Each build requires a stem that specifies the names of the augur output files and a virus that corresponds to a virus supported by both fauna and augur. The virus attribute specifically enables running the appropriate augur scripts (e.g., builds/{virus}/{virus} For example, the following configuration defines a build instance for Zika that runs augur with default parameters.

    "builds": [
            "stem": "zika",
            "virus": "zika"

Builds can be defined as individual build instances, as shown above, or as build templates that Janus expands to one or more individual build instances. Build templates define variables with Python named string formatting in the stem and matching attributes in the build definition. Variable attributes provide lists of values to substitute in the stem and other optional non-list attributes. The following example defines one build template with a variable named virus and a list of two viruses to create individual build instances for.

    "builds": [
            "stem": "{virus}",
            "virus": ["zika", "ebola"]

Variables can be expanded into other non-list attributes of the build template to customize parameters for augur’s prepare and process commands. For example, the following build template uses the virus variable to specify which sequences should be included when running the augur prepare command.

    "builds": [
            "stem": "{virus}",
            "virus": ["zika", "ebola"],
            "prepare": "--sequences ../fauna/{virus}.fasta"

When multiple variables are defined in the stem, one build instance is created for each combination of variable values. For example, the following build template uses lineage and resolution variables to create all 12 possible combinations of lineages and resolutions for seasonal flu.

    "builds": [
            "stem": "flu_{lineage}_ha_{resolution}",
            "virus": "flu",
            "lineage": ["h3n2", "h1n1pdm", "vic", "yam"],
            "resolution": ["3y", "6y", "12y"],
            "segments": "ha",
            "prepare": "--sequences ../fauna/{lineage}.fasta"

As shown above, specific arguments can be passed directly to the augur prepare command with the prepare attribute. Similarly, specific arguments can be passed to the process command with a process attribute as shown below.

    "builds": [
            "stem": "zika",
            "virus": "zika",
            "process": "--no_raxml"

Users can define any additional attributes they need to parameterize their builds. For example, if a pathogen’s data are organized by serotype rather than lineage, the maintainer for that pathogen can include a serotype variable in the stem, assign a corresponding list of values to a serotype attribute in the build definition, and provide the necessary prepare and process arguments to run the build(s) correctly. The following configuration shows an example of this approach with dengue virus.

    "builds": [
            "stem": "dengue_{serotype}",
            "virus": "dengue",
            "serotype": ["denv1", "denv2", "denv3", "denv4"],
            "prepare": "--serotype {serotype}"

The complete set of attributes expected by Janus is listed below.

Required attributes:

  • stem: Name or name template for the build, used as the file prefix for augur outputs
  • virus: Name of a virus supported by fauna and augur

Optional attributes for augur prepare:

  • lineage: String or list of strings defining viral lineages to pass to the prepare script as --lineages {lineage}
  • segments: String or list of strings defining viral segments to pass to the prepare script as --segments {segments}
  • resolution: String or list of strings defining viral resolutions to pass to the prepare script as --resolution {resolution}
  • prepare: String of parameters to pass to the virus’s augur prepare command

Optional attributes for augur process:

  • process: String of parameters to pass to the virus’s augur process command

Optional attributes for fauna:

  • fauna: String of parameters to pass to fauna's script. Defaults to "--virus {virus} --sequences".

Other optional attributes:

  • description: String describing the build(s) represented by the build definition (e.g., “Flu builds for”)


Download all data (sequences, titers, etc.) for the viruses listed in the config.json file using fauna.

./janus download

The download command is required to be run before running the further commands below.

Dry run all builds defined in the config.json file, printing all rules that would be run without running them. Note that all janus arguments except -l are passed directly to the snakemake command.

./janus -n build

Run all builds on the cluster with no more than 4 cluster jobs at a time.

./janus -j 4 build

Run all builds locally with no more than 4 jobs at a time.

./janus -l -j 4 build

Run only H3N2 and Zika builds on the cluster. The filters configuration parameter supports a comma-delimited list of patterns to match in the complete list of build stems defined in the configuration file. Standard UNIX wildcards are supported through the fnmatch Python module.

./janus -j 4 build --config filters="flu_h3n2*,zika"

Filters also apply to all other rules including download, push, and clean. The following command will only download H3N2 data from fauna.

./janus download -j 4 --config filters="flu_h3n2*"

Run all builds defined in a custom configuration file.

./janus -j 4 build --configfile experimental_builds.json

Remove all augur outputs for all builds.

./janus clean

Alternately, force all existing augur outputs to be rebuilt.

./janus -j 4 build --forceall

Push all auspice JSON files to the S3 bucket defined in the s3_bucket attribute of the config.json dictionary.

./janus push

Push only flu JSONs to the S3 bucket.

./janus push --config filters="flu_*"

Debugging and benchmarking

Standard out and error from all rules are written to files in the log directory. Fauna downloads write to fauna_download.log. Prepare and process write to prepare_{stem}.log and process_{stem}.log, respectively. The S3 push script writes to s3_push.log.

Benchmark information from each rule is written to files in the benchmarks directory. File names follow the same patterns as logs except using the .txt extension instead of .log.

Cluster configuration

The janus script is a wrapper for Snakemake that submits jobs to a SLURM cluster using the DRMAA Python bindings. Job requirements (e.g., number of CPUs, memory, etc.) are defined in the cluster.json file as described in the Snakemake documentation.

To run builds on any other supported cluster, load the Janus Python 3 environment and run Snakemake directly. For example, the following command will run all builds on a Grid Engine-style cluster.

source activate janus_python3
snakemake -j 4 --cluster "qsub"

License and copyright

Copyright 2016-2017 Trevor Bedford.

Source code to nextstrain is made available under the terms of the GNU Affero General Public License (AGPL). nextstrain is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more details.