[exporter/mezmo] Fix HTTP client settings usage (#15246)

Previously, the mezmoexporter was ignoring any settings provided by way of https://github.com/open-telemetry/opentelemetry-collector/tree/4d445807f9eca3af660bec2a3fb4ca3518cd255d/config/confighttp. This PR fixes that mistake.

.chloggen/mezmo_tls-config.yaml

@@ -0,0 +1,18 @@
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: bug_fix
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: mezmoexporter
+
+# A brief description of the change. Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Fix usage of HTTP client to honor settings
+
+# One or more tracking issues related to the change
+issues: [15246]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext: |
+ This change fixes mezmoexporter's usage of the user supplied HTTP client
+ settings. Previously, the settings were ignored for every request.

exporter/mezmoexporter/exporter.go

@@ -15,7 +15,6 @@
 package mezmoexporter // import "github.com/open-telemetry/opentelemetry-collector-contrib/exporter/mezmoexporter"
 
 import (
- "bytes"
  "context"
  "encoding/json"
  "fmt"
@@ -180,14 +179,14 @@ func (m *mezmoExporter) logDataToMezmo(ld plog.Logs) error {
 }
 
 func (m *mezmoExporter) sendLinesToMezmo(post string) (errs error) {
- req, _ := http.NewRequest("POST", m.config.IngestURL, bytes.NewBuffer([]byte(post)))
+ req, _ := http.NewRequest("POST", m.config.IngestURL, strings.NewReader(post))
  req.Header.Add("Accept", "application/json")
  req.Header.Add("Content-Type", "application/json")
  req.Header.Add("User-Agent", m.userAgentString)
  req.Header.Add("apikey", m.config.IngestKey)
 
  var res *http.Response
- if res, errs = http.DefaultClient.Do(req); errs != nil {
+ if res, errs = m.client.Do(req); errs != nil {
  return fmt.Errorf("failed to POST log to Mezmo: %w", errs)
  }
  if res.StatusCode >= 400 {