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Extract timeout from context in Prom client

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For vector and range queries, the Prometheus HTTP API takes a timeout
parameter.  Previously, we ignored this parameter.  Now, we check to see
if the context passed to the query contains a deadline, and if so,
compare that to the current time to calculate an appropriate timeout for
query evaulation.
This commit is contained in:
Solly Ross 2017-06-27 19:55:45 -04:00
parent d1d60f7f5e
commit 01755d5acb
2 changed files with 20 additions and 5 deletions
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21
pkg/client/api.go
View file

@ -25,6 +25,7 @@ import (
"net/http"
"net/url"
"path"
"time"
"github.com/golang/glog"
"github.com/prometheus/common/model"
@ -54,7 +55,6 @@ func (c *httpAPIClient) Do(ctx context.Context, verb, endpoint string, query url
u.RawQuery = query.Encode()
req, err := http.NewRequest(verb, u.String(), nil)
if err != nil {
// TODO: fix this to return Error?
return APIResponse{}, fmt.Errorf("error constructing HTTP request to Prometheus: %v", err)
}
req.WithContext(ctx)
@ -96,7 +96,6 @@ func (c *httpAPIClient) Do(ctx context.Context, verb, endpoint string, query url
var res APIResponse
if err = json.NewDecoder(body).Decode(&res); err != nil {
// TODO: return what the body actually was?
return APIResponse{}, &Error{
Type: ErrBadResponse,
Msg: err.Error(),
@ -174,7 +173,9 @@ func (h *queryClient) Query(ctx context.Context, t model.Time, query Selector) (
if t != 0 {
vals.Set("time", t.String())
}
// TODO: get timeout from context...
if timeout, hasTimeout := timeoutFromContext(ctx); hasTimeout {
vals.Set("timeout", model.Duration(timeout).String())
}
res, err := h.api.Do(ctx, "GET", queryURL, vals)
if err != nil {
@ -199,7 +200,9 @@ func (h *queryClient) QueryRange(ctx context.Context, r Range, query Selector) (
if r.Step != 0 {
vals.Set("step", model.Duration(r.Step).String())
}
// TODO: get timeout from context...
if timeout, hasTimeout := timeoutFromContext(ctx); hasTimeout {
vals.Set("timeout", model.Duration(timeout).String())
}
res, err := h.api.Do(ctx, "GET", queryRangeURL, vals)
if err != nil {
@ -210,3 +213,13 @@ func (h *queryClient) QueryRange(ctx context.Context, r Range, query Selector) (
err = json.Unmarshal(res.Data, &queryRes)
return queryRes, err
}
// timeoutFromContext checks the context for a deadline and calculates a "timeout" duration from it,
// when present
func timeoutFromContext(ctx context.Context) (time.Duration, bool) {
if deadline, hasDeadline := ctx.Deadline(); hasDeadline {
return time.Now().Sub(deadline), true
}
return time.Duration(0), false
}

4
pkg/client/interfaces.go
View file

@ -40,7 +40,9 @@ type Range struct {
Step time.Duration
}
// TODO: support timeout in the client?
// Client is a Prometheus client for the Prometheus HTTP API.
// The "timeout" parameter for the HTTP API is set based on the context's deadline,
// when present and applicable.
type Client interface {
// Series lists the time series matching the given series selectors
Series(ctx context.Context, interval model.Interval, selectors ...Selector) ([]Series, error)