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Consulate provides a normalized HTTP endpoint that responds with 200 / non-200 according to Consul checks specified in the requested URL. This endpoint can then be composed with existing HTTP based monitoring tools, like AWS ELB health checks, to enable service monitoring based on Consul checks.

Building from source

To build Consulate from the source code yourself you need to have a working Go environment with version 1.9 or greater installed.

$ mkdir -p $GOPATH/src/github.com/kadaan
$ cd $GOPATH/src/github.com/kadaan
$ git clone https://github.com/kadaan/consulate.git
$ cd consulate
$ ./build.sh

Usage

Consulate provides a normalized HTTP endpoint that responds with
200 / non-200 according to Consul checks specified in the requested URL.
This endpoint can then be composed with existing HTTP based monitoring tools, like
AWS ELB health checks, to enable service monitoring based on Consul checks.

Usage:
  consulate [command]

Available Commands:
  help        Help about any command
  server      Runs the Consulate server
  version     Prints the Consulate version

Flags:
      --config string   config file (default is $HOME/.consulate.yaml)
  -h, --help            help for consulate

Use "consulate [command] --help" for more information about a command.

Version

Help
$ ./dist/consulate_darwin_amd64 help version
Prints the Consulate version

Usage:
  consulate version [flags]

Flags:
  -h, --help   help for version

Global Flags:
      --config string   config file (default is $HOME/.consulate.yaml)
Example
$ ./dist/consulate_darwin_amd64 version
Consulate, version 0.0.1 (branch: master, revision: 6b85aa3f65798fdaa7ed65f7b9a981c70bbd471b)
  build user:       user@computer.local
  build date:       2018-02-19T17:49:32Z
  go version:       go1.9.3

Server

Help
$ ./dist/consulate_darwin_amd64 help server
Starts the Consulate server and runs until an interrupt is received.

Usage:
  consulate server [flags]

Flags:
      --bad-request-status-code int              the status code returned when a request to Consulate could not be understood (default 400)
  -c, --consul-address string                    the Consul HTTP API address to query against (default "localhost:8500")
      --consul-cache-duration duration           the duration that Consul results will be cached (default 1s)
      --consul-navailable-status-code int        the status code returned when Consul did not respond promptly (default 504)
      --error-status-code int                    the status code returned when there are 1+ failing health checks (default 503)
  -h, --help                                     help for server
  -l, --listen-address string                    the listen address (default ":8080")
      --no-checks-status-code int                the status code returned when no Consul checks exist (default 404)
      --partial-success-status-code int          the status code returned when there are 1+ passing health checks and 1+ warning health checks (default 429)
      --query-idle-connection-timeout duration   is the maximum amount of time an idle (keep-alive) Consul HTTP API query connection will remain idle before closing itself (default 1m30s)
      --query-max-idle-connection-count int      the maximum number of idle (keep-alive) Consul HTTP API query connections (default 100)
      --query-timeout duration                   the maximum duration before timing out the Consul HTTP API query (default 5s)
      --read-timeout duration                    the maximum duration for reading the entire request (default 10s)
      --shutdown-timeout duration                the maximum duration before timing out the shutdown of the server (default 15s)
      --success-status-code int                  the status code returned when there are 1+ passing health checks, 0 warning health checks, and 0 failing health checks (default 200)
      --unprocessable-status-code int            the status code returned when Consulate could not parse the response from Consul (default 502)
      --warning-status-code int                  the status code returned when there are 0 passing health checks and 1+ warning health checks (default 503)
      --write-timeout duration                   the maximum duration before timing out writes of the response (default 10s)

Global Flags:
      --config string   config file (default is .consulate)
Example
$ ./dist/consulate_darwin_amd64 server
Press Ctrl-C to shutdown server
Started Consulate server on :8080

Routes

All routes respond to both GET and HEAD requests. They accept the following query string parameters:

  1. pretty: when present, pretty prints json responses
  2. verbose: when present, additional details are include in responses

/about

The /about route returns detailed version information about Consulate.

Request
curl -X GET http:/localhost:8080/about\?pretty
Response
HTTP/1.1 200 OK
Content-Type: application/json; charset=utf-8
...

{
    "Version": "0.0.1",
    "Revision": "c216c1294676cdaac0b018244be31ebb6e404b92",
    "Branch": "master",
    "BuildUser": "user@computer.local",
    "BuildDate": "2018-02-15T07:10:39Z",
    "GoVersion": "go1.9"
}
Status Codes
  • 200: Successful call
  • 500: Unexpected failure

/health

The /health route returns 200 if Consulate is running and able to communicate with Consul. Otherwise, a non-200 status code is returned.

Request
curl -X GET http:/localhost:8080/health\?pretty
Responses
Healthy
HTTP/1.1 200 OK
Content-Type: application/json; charset=utf-8
...

{
    "Status": "Ok"
}
Unhealthy
HTTP/1.1 503 Service Unavailable
Content-Type: application/json; charset=utf-8
...

{
    "Status": "Failed",
    "Detail": "Get http://localhost:8500/v1/agent/checks: dial tcp [::1]:8500: getsockopt: connection refused"
}
Status Codes
  • 200: Successful call
  • 500: Unexpected failure
  • 502: Could not parse the response from Consul
  • 504: Consul unavailable

/metrics

The /metrics route returns Prometheus metrics.

Request
curl -X GET http:/localhost:8080/metrics
Response
# HELP consulate_request_duration_seconds The HTTP request latencies in seconds.
# TYPE consulate_request_duration_seconds histogram
consulate_request_duration_seconds_bucket{code="200",method="GET",url="/about",le="0.5"} 1
consulate_request_duration_seconds_bucket{code="200",method="GET",url="/about",le="1"} 1
consulate_request_duration_seconds_bucket{code="200",method="GET",url="/about",le="2"} 1
consulate_request_duration_seconds_bucket{code="200",method="GET",url="/about",le="3"} 1
...
Status Codes
  • 200: Successful call
  • 500: Unexpected failure

Verify

Consulate verifies Consul checks by inspecting the status. The possible status values, in increasing severity are:

  • passing
  • maintenance
  • warning
  • critical

By default, verification will fail checks whose status is not passing.

This can be changed by specifying the status query string parameter like ?status=warning. Only checks whose status is worse than the specified value will cause a failure.

The following table shows all possible status query string parameter values and, as a result, which checks will be considered failing.

Status Query String Parameter Fails When Default?
Not specified or ?status=passing Check is not passing Yes
?status=maintenance Check is warning or critical No
?status=warning Check is critical No
?status=critical Never No

/verify/checks

The /verify/checks route returns 200 if all Consul checks ok. Otherwise, a non-200 status code is returned and the failing checks will be in the response.

Request
curl -X GET http:/localhost:8080/verify/checks\?pretty
Responses
Healthy
HTTP/1.1 200 OK
Content-Type: application/json; charset=utf-8
...

{
  "Status": "Ok"
}
Unhealthy
HTTP/1.1 503 Service Unavailable
Content-Type: application/json; charset=utf-8

{
    "Status": "Failed",
    "Counts": {
      "failed": 1,
      "passing": 0,
      "warning": 0
    },
    "Checks": {
        "check1b": {
            "Node": "computer.local",
            "CheckID": "check1b",
            "Name": "check 1",
            "Status": "critical",
            "Notes": "Check 1",
            "Output": "Timed out (1s) running check",
            "ServiceID": "service2",
            "ServiceName": "service2",
            "ServiceTags": [],
            "Definition": {
                "HTTP": "",
                "Header": null,
                "Method": "",
                "TLSSkipVerify": false,
                "TCP": "",
                "Interval": 0,
                "Timeout": 0,
                "DeregisterCriticalServiceAfter": 0
            },
            "CreateIndex": 0,
            "ModifyIndex": 0
        }
    }
}
Status Codes
  • 200: Successful call
  • 400: Request could not be understood
  • 404: No checks
  • 429: One or more Consul checks are passing and one or more Consul checks are warning
  • 500: Unexpected failure
  • 502: Could not parse the response from Consul
  • 503:
    • One or more Consul checks have failed
    • Zero Consul checks are passing and one or more Consul checks are warning
  • 504: Consul unavailable

/verify/checks/id/:checkId

The /verify/checks/id/:checkId route returns 200 if the specified Consul check is ok. Otherwise, a non-200 status code is returned and the failing check will be in the response.

Request
curl -X GET http:/localhost:8080/verify/checks/id/check1b\?pretty
Responses
Healthy
HTTP/1.1 200 OK
Content-Type: application/json; charset=utf-8
...

{
    "Status": "Ok"
}
Unhealthy
HTTP/1.1 503 Service Unavailable
Content-Type: application/json; charset=utf-8
...

{
    "Status": "Failed",
    "Counts": {
      "failed": 1,
      "passing": 0,
      "warning": 0
    },
    "Checks": {
        "check1b": {
            "Node": "computer.local",
            "CheckID": "check1b",
            "Name": "check 1",
            "Status": "critical",
            "Notes": "Check 1",
            "Output": "Timed out (1s) running check",
            "ServiceID": "service2",
            "ServiceName": "service2",
            "ServiceTags": [],
            "Definition": {
                "HTTP": "",
                "Header": null,
                "Method": "",
                "TLSSkipVerify": false,
                "TCP": "",
                "Interval": 0,
                "Timeout": 0,
                "DeregisterCriticalServiceAfter": 0
            },
            "CreateIndex": 0,
            "ModifyIndex": 0
        }
    }
}
Status Codes
  • 200: Successful call
  • 400: Request could not be understood
  • 404:
    • No checks
    • No checks matching specified CheckID
  • 429: One or more Consul checks are passing and one or more Consul checks are warning
  • 500: Unexpected failure
  • 502: Could not parse the response from Consul
  • 503:
    • One or more Consul checks have failed
    • Zero Consul checks are passing and one or more Consul checks are warning
  • 504: Consul unavailable

/verify/checks/id/:checkName

The /verify/checks/id/:checkName route returns 200 if the specified Consul check is ok. Otherwise, a non-200 status code is returned and the failing check will be in the response. More then one check will be verified if multiple checks share the same name.

Request
curl -X GET http:/localhost:8080/verify/checks/id/check%201\?pretty
Responses
Healthy
HTTP/1.1 200 OK
Content-Type: application/json; charset=utf-8
...

{
    "Status": "Ok"
}
Unhealthy
HTTP/1.1 503 Service Unavailable
Content-Type: application/json; charset=utf-8
...

{
    "Status": "Failed",
    "Counts": {
      "failed": 1,
      "passing": 0,
      "warning": 0
    },
    "Checks": {
        "check1b": {
            "Node": "computer.local",
            "CheckID": "check1b",
            "Name": "check 1",
            "Status": "critical",
            "Notes": "Check 1",
            "Output": "Timed out (1s) running check",
            "ServiceID": "service2",
            "ServiceName": "service2",
            "ServiceTags": [],
            "Definition": {
                "HTTP": "",
                "Header": null,
                "Method": "",
                "TLSSkipVerify": false,
                "TCP": "",
                "Interval": 0,
                "Timeout": 0,
                "DeregisterCriticalServiceAfter": 0
            },
            "CreateIndex": 0,
            "ModifyIndex": 0
        }
    }
}
Status Codes
  • 200: Successful call
  • 400: Request could not be understood
  • 404:
    • No checks
    • No checks matching specified CheckName
  • 429: One or more Consul checks are passing and one or more Consul checks are warning
  • 500: Unexpected failure
  • 502: Could not parse the response from Consul
  • 503:
    • One or more Consul checks have failed
    • Zero Consul checks are passing and one or more Consul checks are warning
  • 504: Consul unavailable

/verify/service/id/:serviceId

The /verify/service/id/:serviceId route returns 200 if all Consul checks for the specified service are ok. Otherwise, a non-200 status code is returned and the failing checks will be in the response.

Request
curl -X GET http:/localhost:8080/verify/service/id/service2\?pretty
Responses
Healthy
HTTP/1.1 200 OK
Content-Type: application/json; charset=utf-8
...

{
    "Status": "Ok"
}
Unhealthy
HTTP/1.1 503 Service Unavailable
Content-Type: application/json; charset=utf-8
...

{
    "Status": "Failed",
    "Counts": {
      "failed": 1,
      "passing": 0,
      "warning": 0
    },
    "Checks": {
        "check1b": {
            "Node": "computer.local",
            "CheckID": "check1b",
            "Name": "check 1",
            "Status": "critical",
            "Notes": "Check 1",
            "Output": "Timed out (1s) running check",
            "ServiceID": "service2",
            "ServiceName": "service 2",
            "ServiceTags": [],
            "Definition": {
                "HTTP": "",
                "Header": null,
                "Method": "",
                "TLSSkipVerify": false,
                "TCP": "",
                "Interval": 0,
                "Timeout": 0,
                "DeregisterCriticalServiceAfter": 0
            },
            "CreateIndex": 0,
            "ModifyIndex": 0
        }
    }
}
Status Codes
  • 200: Successful call
  • 400: Request could not be understood
  • 404:
    • No checks
    • No checks for services matching specified ServiceID
  • 429: One or more Consul checks are passing and one or more Consul checks are warning
  • 500: Unexpected failure
  • 502: Could not parse the response from Consul
  • 503:
    • One or more Consul checks have failed
    • Zero Consul checks are passing and one or more Consul checks are warning
  • 504: Consul unavailable

/verify/service/name/:serviceName

The /verify/service/name/:serviceName route returns 200 if all Consul checks for the specified service are ok. Otherwise, a non-200 status code is returned and the failing checks will be in the response. More than one service will be verified if multiple services share the same name.

Request
curl -X GET http:/localhost:8080/verify/service/name/service%202\?pretty
Responses
Healthy
HTTP/1.1 200 OK
Content-Type: application/json; charset=utf-8
...

{
    "Status": "Ok"
}
Unhealthy
HTTP/1.1 503 Service Unavailable
Content-Type: application/json; charset=utf-8
...

{
    "Status": "Failed",
    "Counts": {
      "failed": 1,
      "passing": 0,
      "warning": 0
    },
    "Checks": {
        "check1b": {
            "Node": "computer.local",
            "CheckID": "check1b",
            "Name": "check 1",
            "Status": "critical",
            "Notes": "Check 1",
            "Output": "Timed out (1s) running check",
            "ServiceID": "service2",
            "ServiceName": "service 2",
            "ServiceTags": [],
            "Definition": {
                "HTTP": "",
                "Header": null,
                "Method": "",
                "TLSSkipVerify": false,
                "TCP": "",
                "Interval": 0,
                "Timeout": 0,
                "DeregisterCriticalServiceAfter": 0
            },
            "CreateIndex": 0,
            "ModifyIndex": 0
        }
    }
}
Status Codes
  • 200: Successful call
  • 400: Request could not be understood
  • 404:
    • No checks
    • No checks for services matching specified ServiceName
  • 429: One or more Consul checks are passing and one or more Consul checks are warning
  • 500: Unexpected failure
  • 502: Could not parse the response from Consul
  • 503:
    • One or more Consul checks have failed
    • Zero Consul checks are passing and one or more Consul checks are warning
  • 504: Consul unavailable

Overhead

In it's standard configuration Consulate adds very little overhead to the system and to Consul. Caching is used to reduce the calls to Consul to one per second. The processing done in Consulate is CPU bound, but is not very intensive.

Performance testing was done with vegeta.

$ echo "GET http://localhost:8080/verify/checks" | vegeta attack -duration=5m | tee results.bin | vegeta report

Requests      [total, rate]            15000, 50.00
Duration      [total, attack, wait]    4m59.98055175s, 4m59.979999s, 552.75µs
Latencies     [mean, 50, 95, 99, max]  1.101265ms, 910.812µs, 1.761948ms, 1.958328ms, 249.418571ms
Bytes In      [total, mean]            225000, 15.00
Bytes Out     [total, mean]            0, 0.00
Success       [ratio]                  100.00%
Status Codes  [code:count]             200:15000
Error Set:

Changelog

0.0.5

  • Standardize metric naming, type, etc.

0.0.4

  • Adjust routing to support handling requests with trailing forward slash.

0.0.3

  • Add HEAD support for all methods.

0.0.2

  • Adjust status code semantics to follow Consul health check semantics. This results in some changes to the status codes returned.
  • Made all status code configurable.

0.0.1

  • Initial version

License

Apache License 2.0, see LICENSE.

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Consul check monitoring endpoint

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