influxdb-c

A header-only C write client for InfluxDB.

• Supported versions:
  • InfluxDB v0.9 ~ v1.4
  • Check yourself while using other versions.

Why use influxdb-c?

• Exactly small:
  • Less than 300 lines and only about 10KB.
• Easy to use:
  • It's designed to be used without extra studies.
• Easy to assemble:
  • Only a tiny header file needs to be included.
• No dependencies:
  • Unless std C libraries.
• Under serious testing:
  • Uses gtest & mockcpp

Examples

Before using

• The very simple thing you should do before using is only:

  #include "influxdb.h"

Write example

• You should according to the write syntax while writing series(metrics).

  measurement[,tag-key=tag-value...] field-key=field-value[,field2-key=field2-value...] [unix-nano-timestamp]
  

• You can rapidly start writing series by using one of the following examples:

• Client configurations:

  influx_client_t c;
  c.host = strdup("127.0.0.1");
  c.port = 8086;
  c.db = strdup("db");
  c.usr = strdup("usr");
  c.pwd = strdup("pwd");

• Under C99, you can use:

  influx_client_t c = {
      .host = strdup("127.0.0.1"),
      .port = 8086,
      .db = strdup("db"),
      .usr = strdup("usr"),
      .pwd = strdup("pwd")
  };

• Then send out the series by calling post_http:

  post_http(&c,
      INFLUX_MEAS("foo"),
      INFLUX_TAG("k", "v"),
      INFLUX_TAG("x", "y"),
      INFLUX_F_INT("x", 10),
      INFLUX_F_FLT("y", 10.3, 2),
      INFLUX_F_FLT("z", 10.3456, 2),
      INFLUX_F_BOL("b", 10),
      INFLUX_TS(1512722735522840439),
      INFLUX_END);

  • NOTE:
    • 3rd parameter of INFLUX_F_FLT() is precision for floating point value.
    • usr and pwd is optional for authorization.
    • INFLUX_END is the delimiter for variable arguments list that should not be ommitted.

• The series sent is:

  foo,k=v,x=y x=10i,y=10.30,z=10.35,b=t 1512722735522840439
  

• You could change post_http to send_udp for UDP request. And only host and port are required for UDP operation.

  influx_client_t c = {strdup("127.0.0.1"), 8091, NULL, NULL, NULL};
  
  send_udp(&c,
      INFLUX_MEAS("foo"),
      INFLUX_TAG("k", "v"),
      INFLUX_F_INT("x", 10),
      INFLUX_END);

• Bulk/batch write is also supported:

  send_udp(&c,
      INFLUX_MEAS("foo"),  // series 1
      INFLUX_F_INT("x", 10),
  
      INFLUX_MEAS("foo"),  // series 2
      INFLUX_F_FLT("y", 10.3, 2),
  
      INFLUX_END);

• The series sent are:

  foo x=10i
  bar y=10.30
  

• If measurement data is sent from within a loop, but higher write performance is needed, one has to format each measurement separately, then at the end send the formatted line to the database. This example sends 10 measurements with a single http request:

  influx_client_t c = {strdup("127.0.0.1"), 8091, NULL, NULL, NULL};
  char *line = NULL;
  int len = 0;
  int used = 0;
  
  for (int i = 0; i < 10; ++i) {
      used = format_line(line, &len, used,
          INFLUX_MEAS("foo"),
          INFLUX_TAG("k", "v"),
          INFLUX_F_INT("x", i),
          INFLUX_END);
  }
  
  post_http_send_line(&c, line, used);

TODO

• Add more test cases for send functions.
• Supports DSN initializatin for influx_client_t.
• Add query function.
• Do not need to connect every time.

Misc

• Please feel free to use influxdb-c.
• Looking forward to your suggestions.
• If your project is using influxdb-c, you can show your project or company here by creating a issue or let me know.