Compatibility Notes

libopenblas
cURL
Wget2
Nginx
iPerf 2
iPerf 3
etcd (distributed key-value store)
CTorrent and opentracker
http-server

libopenblas

libopenblas is a fairly low-level library, and can get pulled in transitively via dependencies. e.g., tgen uses libigraph, which links against liblapack, which links against blas.

libopenblas, when compiled with pthread support, uses busy-loops in its worker threads.

There are several known workarounds:

Use Shadow's --model-unblocked-syscall-latency feature. See busy-loops for details and caveats.
Use a different implementation of libblas. e.g. on Ubuntu, there are several alternative packages that can provide libblas. In particular, libblas3 doesn't have this issue.
Install libopenblas compiled without pthread support. e.g. on Ubuntu this can be obtained by installing libopenblas0-serial instead of libopenblas0-pthread.
Configure libopenblas to not use threads at runtime. This can be done by setting the environment variable OPENBLAS_NUM_THREADS=1, in the process's environment attribute in the Shadow config. Example: tor-minimal.yaml:109

cURL

Example

general:
  stop_time: 10s
  model_unblocked_syscall_latency: true

network:
  graph:
    type: 1_gbit_switch

hosts:
  server:
    network_node_id: 0
    processes:
    - path: python3
      args: -m http.server 80
      start_time: 0s
      expected_final_state: running
  client1: &client_host
    network_node_id: 0
    processes:
    - path: curl
      args: -s server
      start_time: 2s
  client2: *client_host
  client3: *client_host

rm -rf shadow.data; shadow shadow.yaml > shadow.log
cat shadow.data/hosts/client1/curl.1000.stdout

Notes

Older versions of cURL use a busy loop that is incompatible with Shadow and will cause Shadow to deadlock. model_unblocked_syscall_latency works around this (see busy-loops). Newer versions of cURL, such as the version provided in Ubuntu 20.04, don't have this issue. See issue #1794 for details.

Wget2

Example

general:
  stop_time: 10s

network:
  graph:
    type: 1_gbit_switch

hosts:
  server:
    network_node_id: 0
    processes:
    - path: python3
      args: -m http.server 80
      start_time: 0s
      expected_final_state: running
  client1: &client_host
    network_node_id: 0
    processes:
    - path: wget2
      args: --no-tcp-fastopen server
      start_time: 2s
  client2: *client_host
  client3: *client_host

rm -rf shadow.data; shadow shadow.yaml > shadow.log
cat shadow.data/hosts/client1/index.html

Notes

Shadow doesn't support TCP_FASTOPEN so you must run Wget2 using the --no-tcp-fastopen option.

Nginx

Example

`shadow.yaml`

general:
  stop_time: 10s

network:
  graph:
    type: 1_gbit_switch

hosts:
  server:
    network_node_id: 0
    processes:
    - path: nginx
      args: -c ../../../nginx.conf -p .
      start_time: 0s
      expected_final_state: running
  client1: &client_host
    network_node_id: 0
    processes:
    - path: curl
      args: -s server
      start_time: 2s
  client2: *client_host
  client3: *client_host

`nginx.conf`

error_log stderr;

# shadow wants to run nginx in the foreground
daemon off;

# shadow doesn't support some syscalls that nginx uses to set up and control
# worker child processes.
# https://github.com/shadow/shadow/issues/3174
master_process off;
worker_processes 0;

# don't use the system pid file
pid nginx.pid;

events {
  # we're not using any workers, so this is the maximum number
  # of simultaneous connections we can support
  worker_connections 1024;
}

http {
  include             /etc/nginx/mime.types;
  default_type        application/octet-stream;

  # shadow does not support sendfile()
  sendfile off;

  access_log off;

  server {
    listen 80;

    location / {
      root /var/www/html;
      index index.nginx-debian.html;
    }
  }
}

rm -rf shadow.data; shadow shadow.yaml > shadow.log
cat shadow.data/hosts/client1/curl.1000.stdout

Notes

Shadow currently doesn't support some syscalls that nginx uses to set up and control worker child processes, so you must disable additional processes using master_process off and worker_processes 0. See https://github.com/shadow/shadow/issues/3174.
Shadow doesn't support sendfile() so you must disable it using sendfile off.

iPerf 2

Example

general:
  stop_time: 10s

network:
  graph:
    type: 1_gbit_switch

hosts:
  server:
    network_node_id: 0
    processes:
    - path: iperf
      args: -s
      start_time: 0s
      expected_final_state: running
  client:
    network_node_id: 0
    processes:
    - path: iperf
      args: -c server -t 5
      start_time: 2s

rm -rf shadow.data; shadow shadow.yaml > shadow.log

Notes

You must use an iPerf 2 version >= 2.1.1. Older versions of iPerf have a no-syscall busy loop that is incompatible with Shadow.

iPerf 3

Example

general:
  stop_time: 10s
  model_unblocked_syscall_latency: true

network:
  graph:
    type: 1_gbit_switch

hosts:
  server:
    network_node_id: 0
    processes:
    - path: iperf3
      args: -s --bind 0.0.0.0
      start_time: 0s
      # Tell shadow to expect this process to still be running at the end of the
      # simulation.
      expected_final_state: running
  client:
    network_node_id: 0
    processes:
    - path: iperf3
      args: -c server -t 5
      start_time: 2s

rm -rf shadow.data; shadow shadow.yaml > shadow.log

Notes

By default iPerf 3 servers bind to an IPv6 address, but Shadow doesn't support IPv6. Instead you need to bind the server to an IPv4 address such as 0.0.0.0.
The iPerf 3 server exits with a non-zero error code and the message "unable to start listener for connections: Address already in use" after the client disconnects. This is likely due to Shadow not supporting the SO_REUSEADDR socket option.
iPerf 3 uses a busy loop that is incompatible with Shadow and will cause Shadow to deadlock. A workaround is to use the model_unblocked_syscall_latency option.

etcd (distributed key-value store)

Example

Example for etcd version 3.3.x.

general:
  stop_time: 30s

network:
  graph:
    type: gml
    inline: |
      graph [
        node [
          id 0
          host_bandwidth_down "20 Mbit"
          host_bandwidth_up "20 Mbit"
        ]
        edge [
          source 0
          target 0
          latency "150 ms"
          packet_loss 0.01
        ]
      ]

hosts:
  server1:
    network_node_id: 0
    processes:
    - path: etcd
      args:
        --name server1
        --log-output=stdout
        --initial-cluster-token etcd-cluster-1
        --initial-cluster 'server1=http://server1:2380,server2=http://server2:2380,server3=http://server3:2380'
        --listen-client-urls http://0.0.0.0:2379
        --advertise-client-urls http://server1:2379
        --listen-peer-urls http://0.0.0.0:2380
        --initial-advertise-peer-urls http://server1:2380
      expected_final_state: running
    - path: etcdctl
      args: set my-key my-value
      start_time: 10s
  server2:
    network_node_id: 0
    processes:
    - path: etcd
      # each etcd peer must have a different start time
      # https://github.com/shadow/shadow/issues/2858
      start_time: 1ms
      args:
        --name server2
        --log-output=stdout
        --initial-cluster-token etcd-cluster-1
        --initial-cluster 'server1=http://server1:2380,server2=http://server2:2380,server3=http://server3:2380'
        --listen-client-urls http://0.0.0.0:2379
        --advertise-client-urls http://server2:2379
        --listen-peer-urls http://0.0.0.0:2380
        --initial-advertise-peer-urls http://server2:2380
      expected_final_state: running
    - path: etcdctl
      args: get my-key
      start_time: 12s
  server3:
    network_node_id: 0
    processes:
    - path: etcd
      start_time: 2ms
      args:
        --name server3
        --log-output=stdout
        --initial-cluster-token etcd-cluster-1
        --initial-cluster 'server1=http://server1:2380,server2=http://server2:2380,server3=http://server3:2380'
        --listen-client-urls http://0.0.0.0:2379
        --advertise-client-urls http://server3:2379
        --listen-peer-urls http://0.0.0.0:2380
        --initial-advertise-peer-urls http://server3:2380
      expected_final_state: running
    - path: etcdctl
      args: get my-key
      start_time: 12s

rm -rf shadow.data; shadow shadow.yaml > shadow.log
cat shadow.data/hosts/*/etcdctl.*.stdout

Notes

The etcd binary must not be statically linked. You can build a dynamically linked version by replacing CGO_ENABLED=0 with CGO_ENABLED=1 in etcd's scripts/build.sh and scripts/build_lib.sh scripts. The etcd packages included in the Debian and Ubuntu APT repositories are dynamically linked, so they can be used directly.
Each etcd peer must be started at a different time since etcd uses the current time as an RNG seed. See issue #2858 for details.
If using etcd version greater than 3.5.4, you must build etcd from source and comment out the keepalive period assignment as Shadow does not support this.

CTorrent and opentracker

Example

general:
  stop_time: 60s

network:
  graph:
    type: 1_gbit_switch

hosts:
  tracker:
    network_node_id: 0
    processes:
    - path: opentracker
      # Tell shadow to expect this process to still be running at the end of the
      # simulation.
      expected_final_state: running
  uploader:
    network_node_id: 0
    processes:
    - path: cp
      args: ../../../foo .
      start_time: 10s
    # Create the torrent file
    - path: ctorrent
      args: -t foo -s example.torrent -u http://tracker:6969/announce
      start_time: 11s
    # Serve the torrent
    - path: ctorrent
      args: example.torrent
      start_time: 12s
      expected_final_state: running
  downloader1: &downloader_host
    network_node_id: 0
    processes:
    # Download and share the torrent
    - path: ctorrent
      args: ../uploader/example.torrent
      start_time: 30s
      expected_final_state: running
  downloader2: *downloader_host
  downloader3: *downloader_host
  downloader4: *downloader_host
  downloader5: *downloader_host

echo "bar" > foo
rm -rf shadow.data; shadow shadow.yaml > shadow.log
cat shadow.data/hosts/downloader1/foo

Notes

Shadow must be run as a non-root user since opentracker will attempt to drop privileges if it detects that the effective user is root.

http-server

Example

general:
  stop_time: 10s
  model_unblocked_syscall_latency: true

network:
  graph:
    type: 1_gbit_switch

hosts:
  server:
    network_node_id: 0
    processes:
    - path: node
      args: /usr/local/bin/http-server -p 80 -d
      start_time: 3s
      expected_final_state: running
  client:
    network_node_id: 0
    processes:
    - path: curl
      args: -s server
      start_time: 5s

rm -rf shadow.data; shadow shadow.yaml > shadow.log
cat shadow.data/hosts/client/curl.1000.stdout

Notes

Either the Node.js runtime or http-server uses a busy loop that is incompatible with Shadow and will cause Shadow to deadlock. model_unblocked_syscall_latency works around this (see busy-loops).

The Shadow Simulator