GSE is a small standalone web app designed to help debugging the environment of orchestred containers, through a very small go app.
It can be be easly packaged into a < 3 MB docker image that will run with less than 20 Mo of ram, making it easly to deploy. See the image on dockerhub
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displays its env and the details of the http request it received
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usefull to understand what env and request your containers receive
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display its version in a single line of text
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healthcheck that can also be turned in ok or ko state through a simple http call
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usefull to play with your container orchestrator (kubernetes, nomad…) routing system.
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logger tonoutput what you want on the log output
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usefull to test your that log gathering system
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This was my first attempt as golang. Quick’n Dirty, but this tool has been proven usefull during our journey with Nomad or Kube… |
GSE offers 4 end points
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/gseendpoint can be queried through any HTTP method (GET, PUT, …). It will answer an HTTP 200 status, with an HTML content displaying information about the HTTP request received-
headers
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hostname
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path
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POST/PUT/… parameters
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note that this endpoint will write a one line log to stdout
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/gsecan be changed to another path via theGSE_BASEPATHpararameter. Other endpoints (version, healthcheck) will inherit this parameters.
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/gse/versionendpoint can be queried through any HTTP method (GET, PUT, …). It will answer an HTTP 200 status,with a single text line content made of program version and its stamp (if one has been specified, default stamp being empty) -
the "stamp" allows us to test rolling, blue/green, or canary update with our container orchestrator: the same docker image (=same version) can be run with a given stamp (see GSE_STAMP bellow) given as parameter by the orchestrator, so we can differenciate to deployments, exemple:
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with no stamp, the answer will be
3.0 -
with GSE_STAMP="A", the answer will be
3.0A
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/gse/healthis a endpoint to be used as healthcheck through an HTTPGETquery. Answer will be-
when healtcheck is on: HTTP 200 status, content will be the text string I’m alive
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when healthcheck is off: HTTP 503 status, content will be the text string I’m sick
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no log will be written to stdout
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healthcheck can be switched on/off (flip/flop) with an access with HTTP
POSTorPUTmethods:-
curl -X POST http://127.0.0.1:28657/gse/health -
curl -X PUT http://127.0.0.1:28657/gse/health -
note that
POSTorPUTaccess to this endpoint writes log to stdout:healthcheck has been switched to false healthcheck has been switched to true
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GSE accepts some parameters, either through command line flags or env vars.
| parameter | env var name | cli name | type | default value |
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path in the url (note: impacts all endpoints) |
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string |
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tcp port to listen to |
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int |
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stamp added to version endpoint |
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string |
empty |
set healthcheck answer to HTTP 200 or HTTP 503 |
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boolean |
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activate logger endpoint |
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boolean |
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$ ./gse -hSince we use https://github.com/namsral/flag to parse arguments, they can be fed either through command line or env vars.
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🔥
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flag parsing when value is /… seems to be bugged on windows. You cannot change the basepath on gse if you run on windows.
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Goal is to create a small but standalone binary to allow us to build a small container image.
$ CGO_ENABLED=0 GOOS=linux go build -a -tags netgo -ldflags "-s -w" .The resulting binary should be < 9 Mb.
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💡
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If that’s too big, you can use upx to reduce file size to ~ 2.5 Mb |
$ ./gsepoint your web browser to http://localhost:28657/gse
the following is a multi stage docker build. first we compile and compress executable in the builder stage, then we create an image `FROM scratch'
FROM devalias/upx:devel AS upx
FROM golang AS builder
COPY --from=upx /usr/bin/upx /usr/bin/upx
WORKDIR /go/src/github.com/DBuret/gse
RUN go get -d -v github.com/namsral/flag
COPY gse.go .
RUN CGO_ENABLED=0 GOOS=linux go build -a -tags netgo -ldflags "-s -w" .
RUN /usr/bin/upx --brute gse
FROM scratch
LABEL version="4.1"
LABEL link="https://github.com/DBuret/gse"
LABEL description="Go Show Env - micro HTTP service to help understanding container orchestrators environment"
WORKDIR /
COPY --from=builder /go/src/github.com/DBuret/gse .
ADD template.html .
CMD ["/gse"]$ sudo docker build -t gse .$ sudo docker run -p 28657:28657 gsepoint your web browser to http://localhost:28657/gse
$ sudo docker run -e GSE_BASEPATH=/foo -e GSE_PORT=2000 -e GSE_STAMP=A -e GSE_HEALTHCHECK=false -e GSE_LOGGER=true -p 2000:2000 gse$ curl -X PUT http://localhost:2000/foo/health
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gse will eat around 14 Mb of RAM (even if your file has been shrinked by upx, upon execution it will be uncompressed to RAM. Using upx just saves disk space and download time). When setting ressources quota to a gse container, allow 20 Mb of RAM to the container and you will be safe. |
$ ps -ef |grep gse
root 20034 17983 0 20:20 pts/0 00:00:00 sudo docker run -e GSE_BASEPATH=/foo -e GSE_PORT=2000 -e GSE_STAMP=A -e GSE_HEALTHCHECK=false -e GSE_LOGGER=true -p 2000:2000 gse
root 20035 20034 0 20:20 pts/0 00:00:00 /usr/bin/docker-current run -e GSE_BASEPATH=/foo -e GSE_PORT=2000 -e GSE_STAMP=A -e GSE_HEALTHCHECK=false -e GSE_LOGGER=true -p 2000:2000 gse
root 20068 20055 0 20:20 ? 00:00:00 /gse
$ sudo pmap -x 20068
20068: /gse
Address Kbytes RSS Dirty Mode Mapping
0000000000400000 3324 3324 3324 r-x-- [ anon ]
000000000073f000 3740 3740 3740 r---- [ anon ]
0000000000ae6000 372 280 280 rw--- [ anon ]
000000c000000000 65536 2048 2048 rw--- [ anon ]
00007f3397dc5000 35524 4216 4216 rw--- [ anon ]
00007fffa460b000 132 32 32 rw--- [ stack ]
00007fffa468f000 8 4 0 r-x-- [ anon ]
ffffffffff600000 4 0 0 r-x-- [ anon ]
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total kB 108640 13644 13640