There are multiple ways to monitor Docker containers.
- Docker CLI provides the
docker container statsAPI that gives basic information about the running containers. - Docker Remote API provides more detailed information about the containers.
- Staring with Docker 1.13, there is an experimental feature with a Prometheus endpoint
- cAdvisor is an open source tool that provides last container usage and performance characteristics. This data can be stored in a time series database, such as InfluxDB. This data can then be shown in a fancy graph using a Kibana dashboard.
These options were covered in detail in an earlier blog.
There are other commercial options like Docker EE, Sysdig, Datadog, New Relic, App Dynamics and others. If you are running containers on AWS, then CloudWatch can provide integrated monitoring.
OSX is my primary development platform. But recently, I needed a way to monitor Docker containers using the Remote API (aka REST API) on a Windows machine. The output of the REST API is exactly same independent of the operating system. But the way to access the Docker REST API using curl is different on an OSX and a Windows machine. This blog will explain how to exactly access this API on these two operating systems.
Check out 1.27 swagger specification to learn more about the capabilities of the REST API. A nicer and a more readable version of the API can be seen using Swagger UI. This is broken until #32649 is fixed.
Complete details about how the REST API corresponds to different Docker versions is explained in Docker REST API Versioning.
We’ll dig into this a bit later but first let’s take a look on how this API can be accessed.
Docker Remote API on OSX
On OSX, curl connects using a Unix domain socket as shown:
1 | curl --unix-sock /var/run/docker.sock http://localhost/containers//stats |
A WildFly container can be started as:
1 | docker run --name web -d jboss/wildfly |
Stats can then be obtained using the command:
1 | curl --unix-socket /var/run/docker.sock http://localhost/containers/web/stats |
This will start printing stats as:
001 002 003 004 005 006 007 008 009 010 011 012 013 014 015 016 017 018 019 020 021 022 023 024 025 026 027 028 029 030 031 032 033 034 035 036 037 038 039 040 041 042 043 044 045 046 047 048 049 050 051 052 053 054 055 056 057 058 059 060 061 062 063 064 065 066 067 068 069 070 071 072 073 074 075 076 077 078 079 080 081 082 083 084 085 086 087 088 089 090 091 092 093 094 095 096 097 098 099 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 | { "read":"2017-04-16T21:25:06.99499178Z", "preread":"0001-01-01T00:00:00Z", "pids_stats":{ "current":40 }, "blkio_stats":{ "io_service_bytes_recursive":[ { "major":8, "minor":0, "op":"Read", "value":0 }, { "major":8, "minor":0, "op":"Write", "value":4096 }, { "major":8, "minor":0, "op":"Sync", "value":0 }, { "major":8, "minor":0, "op":"Async", "value":4096 }, { "major":8, "minor":0, "op":"Total", "value":4096 } ], "io_serviced_recursive":[ { "major":8, "minor":0, "op":"Read", "value":0 }, { "major":8, "minor":0, "op":"Write", "value":1 }, { "major":8, "minor":0, "op":"Sync", "value":0 }, { "major":8, "minor":0, "op":"Async", "value":1 }, { "major":8, "minor":0, "op":"Total", "value":1 } ], "io_queue_recursive":[ ], "io_service_time_recursive":[ ], "io_wait_time_recursive":[ ], "io_merged_recursive":[ ], "io_time_recursive":[ ], "sectors_recursive":[ ] }, "num_procs":0, "storage_stats":{ }, "cpu_stats":{ "cpu_usage":{ "total_usage":9569101779, "percpu_usage":[ 4920699125, 4648402654 ], "usage_in_kernelmode":1050000000, "usage_in_usermode":7730000000 }, "system_cpu_usage":5431500000000, "online_cpus":2, "throttling_data":{ "periods":0, "throttled_periods":0, "throttled_time":0 } }, "precpu_stats":{ "cpu_usage":{ "total_usage":0, "usage_in_kernelmode":0, "usage_in_usermode":0 }, "throttling_data":{ "periods":0, "throttled_periods":0, "throttled_time":0 } }, "memory_stats":{ "usage":266448896, "max_usage":285159424, "stats":{ "active_anon":241647616, "active_file":90112, "cache":225280, "dirty":20480, "hierarchical_memory_limit":9223372036854772000, "hierarchical_memsw_limit":9223372036854772000, "inactive_anon":20971520, "inactive_file":135168, "mapped_file":32768, "pgfault":81529, "pgmajfault":1, "pgpgin":76795, "pgpgout":12624, "rss":262619136, "rss_huge":0, "swap":57344, "total_active_anon":241647616, "total_active_file":90112, "total_cache":225280, "total_dirty":20480, "total_inactive_anon":20971520, "total_inactive_file":135168, "total_mapped_file":32768, "total_pgfault":81529, "total_pgmajfault":1, "total_pgpgin":76795, "total_pgpgout":12624, "total_rss":262619136, "total_rss_huge":0, "total_swap":57344, "total_unevictable":0, "total_writeback":0, "unevictable":0, "writeback":0 }, "limit":2096181248 }, "name":"/web", "id":"b6ad4af36f05ce100877d2d60c72e01b87f3627682e4492e7abe2a099b709953", "networks":{ "eth0":{ "rx_bytes":2764, "rx_packets":50, "rx_errors":0, "rx_dropped":0, "tx_bytes":0, "tx_packets":0, "tx_errors":0, "tx_dropped":0 } }} |
These stats are refreshed every second.
Any other REST API can be invoked very easily with this. This is simple and straight forward.
Install Docker on Windows
Docker installation on Windows depends on the flavor of your operating system.
Are you using Windows 10+ Pro 64-bit, then use Docker for Windows.
If using any older version of Windows, then you need to use Docker Toolbox.
Are you installing Windows in a virtual machine? Then Virtual Box cannot be used to create the VM. This is because Virtual Box does not support nested virtualization. This is required as Docker Toolbox uses Virtual Box to create and start Docker Machine. VMWare Fusion seems to work fine here though.
Now that you know that VMWare Fusion needs to be used, make sure you enable nested virtualization before starting the virtual machine.
Many thanks to Stefan Scherer (@stefscherer) for helping me understand the Windows configuration details.
Let’s see how the Docker REST API can now be invoked.
Docker Remote API on Windows 7/8
This section shows how to invoke the REST API using curl on Windows 7/8.
The REST API can be invoked using curl as shown:
1 | curl --cert <CERT> --cacert <CA_CERT> --key <KEY> https://localhost/containers/<name-or-id>/stats |
First of all, the REST API, /containers/<name-or-id>/stats, is exactly the same. The way this API can be invoked is a bit different.
There are four differences: The first three parameters specify security credentials for the Docker Machine generated by Docker Toolbox on your Windows box:
<CERT>is the SSL certificate for Docker Machine<CA_CERT>is the Certificate Authority certificate for the Docker Machine<KEY>is the key generated for the Docker Machine
The values of these configuration parameters is those generated by docker-machine CLI.
The last change is that the protocol is changed from http to https.
Here is the exact command that worked on Windows 7 VM:
1 | $ curl --cert /c/Users/Arun\ Gupta/.docker/machine/machines/default/cert.pem --cacert /c/Users/Arun\ Gupta/.docker/machine/machines/default/ca.pem --key /c/Users/Arun\ Gupta/.docker/machine/machines/default/key.pem https://192.168.99.100:2376/containers/web/stats |
This invocation will print the exact same stats output on Windows 7 VM.
Now that you know how to use this API on OSX and Windows, you can also this API to do everything that Docker CLI. This is because the Docker CLI is just a convenient wrapper over the REST API. So a docker container run command is invoking the appropriate REST API on the Docker Host.
Docker Remote API on Windows 10
If you are using Windows 10, then use Docker for Windows. After that, you need to figure out which curl command to be used. There are couple of options:
- Use Bash shell on Windows. It has
curlcommand that works like Unix command that we all know pretty well. In this case, the REST API can be invoked as:1curl http://localhost:2375/containers/web/statsDocker for Windows listens on port
2375on Windows. - If you are Powershell user, then install
curlcommand as:1chocoinstall-u curlNow the command to invoke the REST API is:
1curl.exe http://localhost:2375/containers/web/statsNote, there is a
curlalias in Powershell and that is an alias forInvoke-WebRequest. So make sure to usecurl.exeto invoke the REST API as this is the command installed using Chocolatey.
This blog provided different options of how to invoke the Docker Remote API using curl on Windows and OSX.
| Reference: | Docker Remote API on Windows and OSX from our JCG partner Arun Gupta at the Miles to go 3.0 … blog. |
