rdkafka_consumer_example.c

/*
 * librdkafka - Apache Kafka C library
 *
 * Copyright (c) 2015, Magnus Edenhill
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met: 
 * 
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer. 
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution. 
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE 
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

/**
 * Apache Kafka high level consumer example program
 * using the Kafka driver from librdkafka
 * (https://github.com/edenhill/librdkafka)
 */

#include <ctype.h>
#include <signal.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <syslog.h>
#include <sys/time.h>
#include <errno.h>
#include <getopt.h>

/* Typical include path would be <librdkafka/rdkafka.h>, but this program
 * is builtin from within the librdkafka source tree and thus differs. */
#include "rdkafka.h"  /* for Kafka driver */


static int run = 1;
static rd_kafka_t *rk;
static int exit_eof = 0;
static int wait_eof = 0;  /* number of partitions awaiting EOF */
static int quiet = 0;
static 	enum {
	OUTPUT_HEXDUMP,
	OUTPUT_RAW,
} output = OUTPUT_HEXDUMP;

static void stop (int sig) {
        if (!run)
                exit(1);
	run = 0;
	fclose(stdin); /* abort fgets() */
}


static void hexdump (FILE *fp, const char *name, const void *ptr, size_t len) {
	const char *p = (const char *)ptr;
	unsigned int of = 0;


	if (name)
		fprintf(fp, "%s hexdump (%zd bytes):\n", name, len);

	for (of = 0 ; of < len ; of += 16) {
		char hexen[16*3+1];
		char charen[16+1];
		int hof = 0;

		int cof = 0;
		int i;

		for (i = of ; i < (int)of + 16 && i < (int)len ; i++) {
			hof += sprintf(hexen+hof, "%02x ", p[i] & 0xff);
			cof += sprintf(charen+cof, "%c",
				       isprint((int)p[i]) ? p[i] : '.');
		}
		fprintf(fp, "%08x: %-48s %-16s\n",
			of, hexen, charen);
	}
}

/**
 * Kafka logger callback (optional)
 */
static void logger (const rd_kafka_t *rk, int level,
		    const char *fac, const char *buf) {
	struct timeval tv;
	gettimeofday(&tv, NULL);
	fprintf(stdout, "%u.%03u RDKAFKA-%i-%s: %s: %s\n",
		(int)tv.tv_sec, (int)(tv.tv_usec / 1000),
		level, fac, rd_kafka_name(rk), buf);
}



/**
 * Handle and print a consumed message.
 * Internally crafted messages are also used to propagate state from
 * librdkafka to the application. The application needs to check
 * the `rkmessage->err` field for this purpose.
 */
static void msg_consume (rd_kafka_message_t *rkmessage) {
	if (rkmessage->err) {
		if (rkmessage->err == RD_KAFKA_RESP_ERR__PARTITION_EOF) {
			fprintf(stderr,
				"%% Consumer reached end of %s [%"PRId32"] "
			       "message queue at offset %"PRId64"\n",
			       rd_kafka_topic_name(rkmessage->rkt),
			       rkmessage->partition, rkmessage->offset);

			if (exit_eof && --wait_eof == 0) {
                                fprintf(stderr,
                                        "%% All partition(s) reached EOF: "
                                        "exiting\n");
				run = 0;
                        }

			return;
		}

                if (rkmessage->rkt)
                        fprintf(stderr, "%% Consume error for "
                                "topic \"%s\" [%"PRId32"] "
                                "offset %"PRId64": %s\n",
                                rd_kafka_topic_name(rkmessage->rkt),
                                rkmessage->partition,
                                rkmessage->offset,
                                rd_kafka_message_errstr(rkmessage));
                else
                        fprintf(stderr, "%% Consumer error: %s: %s\n",
                                rd_kafka_err2str(rkmessage->err),
                                rd_kafka_message_errstr(rkmessage));

                if (rkmessage->err == RD_KAFKA_RESP_ERR__UNKNOWN_PARTITION ||
                    rkmessage->err == RD_KAFKA_RESP_ERR__UNKNOWN_TOPIC)
                        run = 0;
		return;
	}

	if (!quiet)
		fprintf(stdout, "%% Message (topic %s [%"PRId32"], "
                        "offset %"PRId64", %zd bytes):\n",
                        rd_kafka_topic_name(rkmessage->rkt),
                        rkmessage->partition,
			rkmessage->offset, rkmessage->len);

	if (rkmessage->key_len) {
		if (output == OUTPUT_HEXDUMP)
			hexdump(stdout, "Message Key",
				rkmessage->key, rkmessage->key_len);
		else
			printf("Key: %.*s\n",
			       (int)rkmessage->key_len, (char *)rkmessage->key);
	}

	if (output == OUTPUT_HEXDUMP)
		hexdump(stdout, "Message Payload",
			rkmessage->payload, rkmessage->len);
	else
		printf("%.*s\n",
		       (int)rkmessage->len, (char *)rkmessage->payload);
}


static void print_partition_list (FILE *fp,
                                  const rd_kafka_topic_partition_list_t
                                  *partitions) {
        int i;
        for (i = 0 ; i < partitions->cnt ; i++) {
                fprintf(stderr, "%s %s [%"PRId32"] offset %"PRId64,
                        i > 0 ? ",":"",
                        partitions->elems[i].topic,
                        partitions->elems[i].partition,
			partitions->elems[i].offset);
        }
        fprintf(stderr, "\n");

}
static void rebalance_cb (rd_kafka_t *rk,
                          rd_kafka_resp_err_t err,
			  rd_kafka_topic_partition_list_t *partitions,
                          void *opaque) {

	fprintf(stderr, "%% Consumer group rebalanced: ");

	switch (err)
	{
	case RD_KAFKA_RESP_ERR__ASSIGN_PARTITIONS:
		fprintf(stderr, "assigned:\n");
		print_partition_list(stderr, partitions);
		rd_kafka_assign(rk, partitions);
		wait_eof += partitions->cnt;
		break;

	case RD_KAFKA_RESP_ERR__REVOKE_PARTITIONS:
		fprintf(stderr, "revoked:\n");
		print_partition_list(stderr, partitions);
		rd_kafka_assign(rk, NULL);
		wait_eof = 0;
		break;

	default:
		fprintf(stderr, "failed: %s\n",
                        rd_kafka_err2str(err));
                rd_kafka_assign(rk, NULL);
		break;
	}
}


static int describe_groups (rd_kafka_t *rk, const char *group) {
        rd_kafka_resp_err_t err;
        const struct rd_kafka_group_list *grplist;
        int i;

        err = rd_kafka_list_groups(rk, group, &grplist, 10000);

        if (err) {
                fprintf(stderr, "%% Failed to acquire group list: %s\n",
                        rd_kafka_err2str(err));
                return -1;
        }

        for (i = 0 ; i < grplist->group_cnt ; i++) {
                const struct rd_kafka_group_info *gi = &grplist->groups[i];
                int j;

                printf("Group \"%s\" in state %s on broker %d (%s:%d)\n",
                       gi->group, gi->state,
                       gi->broker.id, gi->broker.host, gi->broker.port);
                if (gi->err)
                        printf(" Error: %s\n", rd_kafka_err2str(gi->err));
                printf(" Protocol type \"%s\", protocol \"%s\", "
                       "with %d member(s):\n",
                       gi->protocol_type, gi->protocol, gi->member_cnt);

                for (j = 0 ; j < gi->member_cnt ; j++) {
                        const struct rd_kafka_group_member_info *mi;
                        mi = &gi->members[j];

                        printf("  \"%s\", client id \"%s\" on host %s\n",
                               mi->member_id, mi->client_id, mi->client_host);
                        printf("    metadata: %d bytes\n",
                               mi->member_metadata_size);
                        printf("    assignment: %d bytes\n",
                               mi->member_assignment_size);
                }
                printf("\n");
        }

        if (group && !grplist->group_cnt)
                fprintf(stderr, "%% No matching group (%s)\n", group);

        rd_kafka_group_list_destroy(grplist);

        return 0;
}



static void sig_usr1 (int sig) {
	rd_kafka_dump(stdout, rk);
}

int main (int argc, char **argv) {
        char mode = 'C';
	char *brokers = "localhost:9092";
	int opt;
	rd_kafka_conf_t *conf;
	rd_kafka_topic_conf_t *topic_conf;
	char errstr[512];
	const char *debug = NULL;
	int do_conf_dump = 0;
	char tmp[16];
        rd_kafka_resp_err_t err;
        char *group = NULL;
        rd_kafka_topic_partition_list_t *topics;
        int is_subscription;
        int i;

	quiet = !isatty(STDIN_FILENO);

	/* Kafka configuration */
	conf = rd_kafka_conf_new();

        /* Set logger */
        rd_kafka_conf_set_log_cb(conf, logger);

	/* Quick termination */
	snprintf(tmp, sizeof(tmp), "%i", SIGIO);
	rd_kafka_conf_set(conf, "internal.termination.signal", tmp, NULL, 0);

	/* Topic configuration */
	topic_conf = rd_kafka_topic_conf_new();

	while ((opt = getopt(argc, argv, "g:b:qd:eX:ADO")) != -1) {
		switch (opt) {
		case 'b':
			brokers = optarg;
			break;
                case 'g':
                        group = optarg;
                        break;
		case 'e':
			exit_eof = 1;
			break;
		case 'd':
			debug = optarg;
			break;
		case 'q':
			quiet = 1;
			break;
		case 'A':
			output = OUTPUT_RAW;
			break;
		case 'X':
		{
			char *name, *val;
			rd_kafka_conf_res_t res;

			if (!strcmp(optarg, "list") ||
			    !strcmp(optarg, "help")) {
				rd_kafka_conf_properties_show(stdout);
				exit(0);
			}

			if (!strcmp(optarg, "dump")) {
				do_conf_dump = 1;
				continue;
			}

			name = optarg;
			if (!(val = strchr(name, '='))) {
				fprintf(stderr, "%% Expected "
					"-X property=value, not %s\n", name);
				exit(1);
			}

			*val = '\0';
			val++;

			res = RD_KAFKA_CONF_UNKNOWN;
			/* Try "topic." prefixed properties on topic
			 * conf first, and then fall through to global if
			 * it didnt match a topic configuration property. */
			if (!strncmp(name, "topic.", strlen("topic.")))
				res = rd_kafka_topic_conf_set(topic_conf,
							      name+
							      strlen("topic."),
							      val,
							      errstr,
							      sizeof(errstr));

			if (res == RD_KAFKA_CONF_UNKNOWN)
				res = rd_kafka_conf_set(conf, name, val,
							errstr, sizeof(errstr));

			if (res != RD_KAFKA_CONF_OK) {
				fprintf(stderr, "%% %s\n", errstr);
				exit(1);
			}
		}
		break;

                case 'D':
                case 'O':
                        mode = opt;
                        break;

		default:
			goto usage;
		}
	}


	if (do_conf_dump) {
		const char **arr;
		size_t cnt;
		int pass;

		for (pass = 0 ; pass < 2 ; pass++) {
			if (pass == 0) {
				arr = rd_kafka_conf_dump(conf, &cnt);
				printf("# Global config\n");
			} else {
				printf("# Topic config\n");
				arr = rd_kafka_topic_conf_dump(topic_conf,
							       &cnt);
			}

			for (i = 0 ; i < (int)cnt ; i += 2)
				printf("%s = %s\n",
				       arr[i], arr[i+1]);

			printf("\n");

			rd_kafka_conf_dump_free(arr, cnt);
		}

		exit(0);
	}


	if (strchr("OC", mode) && optind == argc) {
	usage:
		fprintf(stderr,
			"Usage: %s [options] <topic[:part]> <topic[:part]>..\n"
			"\n"
			"librdkafka version %s (0x%08x)\n"
			"\n"
			" Options:\n"
                        "  -g <group>      Consumer group (%s)\n"
			"  -b <brokers>    Broker address (%s)\n"
			"  -e              Exit consumer when last message\n"
			"                  in partition has been received.\n"
                        "  -D              Describe group.\n"
                        "  -O              Get commmitted offset(s)\n"
			"  -d [facs..]     Enable debugging contexts:\n"
			"                  %s\n"
			"  -q              Be quiet\n"
			"  -A              Raw payload output (consumer)\n"
			"  -X <prop=name> Set arbitrary librdkafka "
			"configuration property\n"
			"               Properties prefixed with \"topic.\" "
			"will be set on topic object.\n"
			"               Use '-X list' to see the full list\n"
			"               of supported properties.\n"
			"\n"
                        "For balanced consumer groups use the 'topic1 topic2..'"
                        " format\n"
                        "and for static assignment use "
                        "'topic1:part1 topic1:part2 topic2:part1..'\n"
			"\n",
			argv[0],
			rd_kafka_version_str(), rd_kafka_version(),
                        group, brokers,
			RD_KAFKA_DEBUG_CONTEXTS);
		exit(1);
	}


	signal(SIGINT, stop);
	signal(SIGUSR1, sig_usr1);

	if (debug &&
	    rd_kafka_conf_set(conf, "debug", debug, errstr, sizeof(errstr)) !=
	    RD_KAFKA_CONF_OK) {
		fprintf(stderr, "%% Debug configuration failed: %s: %s\n",
			errstr, debug);
		exit(1);
	}

        /*
         * Client/Consumer group
         */

        if (strchr("CO", mode)) {
                /* Consumer groups require a group id */
                if (!group)
                        group = "rdkafka_consumer_example";
                if (rd_kafka_conf_set(conf, "group.id", group,
                                      errstr, sizeof(errstr)) !=
                    RD_KAFKA_CONF_OK) {
                        fprintf(stderr, "%% %s\n", errstr);
                        exit(1);
                }

                /* Consumer groups always use broker based offset storage */
                if (rd_kafka_topic_conf_set(topic_conf, "offset.store.method",
                                            "broker",
                                            errstr, sizeof(errstr)) !=
                    RD_KAFKA_CONF_OK) {
                        fprintf(stderr, "%% %s\n", errstr);
                        exit(1);
                }

                /* Set default topic config for pattern-matched topics. */
                rd_kafka_conf_set_default_topic_conf(conf, topic_conf);

                /* Callback called on partition assignment changes */
                rd_kafka_conf_set_rebalance_cb(conf, rebalance_cb);

                rd_kafka_conf_set(conf, "enable.partition.eof", "true",
                                  NULL, 0);
        }

        /* Create Kafka handle */
        if (!(rk = rd_kafka_new(RD_KAFKA_CONSUMER, conf,
                                errstr, sizeof(errstr)))) {
                fprintf(stderr,
                        "%% Failed to create new consumer: %s\n",
                        errstr);
                exit(1);
        }

        /* Add brokers */
        if (rd_kafka_brokers_add(rk, brokers) == 0) {
                fprintf(stderr, "%% No valid brokers specified\n");
                exit(1);
        }


        if (mode == 'D') {
                int r;
                /* Describe groups */
                r = describe_groups(rk, group);

                rd_kafka_destroy(rk);
                exit(r == -1 ? 1 : 0);
        }

        /* Redirect rd_kafka_poll() to consumer_poll() */
        rd_kafka_poll_set_consumer(rk);

        topics = rd_kafka_topic_partition_list_new(argc - optind);
        is_subscription = 1;
        for (i = optind ; i < argc ; i++) {
                /* Parse "topic[:part] */
                char *topic = argv[i];
                char *t;
                int32_t partition = -1;

                if ((t = strstr(topic, ":"))) {
                        *t = '\0';
                        partition = atoi(t+1);
                        is_subscription = 0; /* is assignment */
                        wait_eof++;
                }

                rd_kafka_topic_partition_list_add(topics, topic, partition);
        }

        if (mode == 'O') {
                /* Offset query */

                err = rd_kafka_committed(rk, topics, 5000);
                if (err) {
                        fprintf(stderr, "%% Failed to fetch offsets: %s\n",
                                rd_kafka_err2str(err));
                        exit(1);
                }

                for (i = 0 ; i < topics->cnt ; i++) {
                        rd_kafka_topic_partition_t *p = &topics->elems[i];
                        printf("Topic \"%s\" partition %"PRId32,
                               p->topic, p->partition);
                        if (p->err)
                                printf(" error %s",
                                       rd_kafka_err2str(p->err));
                        else {
                                printf(" offset %"PRId64"",
                                       p->offset);

                                if (p->metadata_size)
                                        printf(" (%d bytes of metadata)",
                                               (int)p->metadata_size);
                        }
                        printf("\n");
                }

                goto done;
        }


        if (is_subscription) {
                fprintf(stderr, "%% Subscribing to %d topics\n", topics->cnt);

                if ((err = rd_kafka_subscribe(rk, topics))) {
                        fprintf(stderr,
                                "%% Failed to start consuming topics: %s\n",
                                rd_kafka_err2str(err));
                        exit(1);
                }
        } else {
                fprintf(stderr, "%% Assigning %d partitions\n", topics->cnt);

                if ((err = rd_kafka_assign(rk, topics))) {
                        fprintf(stderr,
                                "%% Failed to assign partitions: %s\n",
                                rd_kafka_err2str(err));
                }
        }

        while (run) {
                rd_kafka_message_t *rkmessage;

                rkmessage = rd_kafka_consumer_poll(rk, 1000);
                if (rkmessage) {
                        msg_consume(rkmessage);
                        rd_kafka_message_destroy(rkmessage);
                }
        }

done:
        err = rd_kafka_consumer_close(rk);
        if (err)
                fprintf(stderr, "%% Failed to close consumer: %s\n",
                        rd_kafka_err2str(err));
        else
                fprintf(stderr, "%% Consumer closed\n");

        rd_kafka_topic_partition_list_destroy(topics);

        /* Destroy handle */
        rd_kafka_destroy(rk);

	/* Let background threads clean up and terminate cleanly. */
	run = 5;
	while (run-- > 0 && rd_kafka_wait_destroyed(1000) == -1)
		printf("Waiting for librdkafka to decommission\n");
	if (run <= 0)
		rd_kafka_dump(stdout, rk);

	return 0;
}